1732: Earth Temperature Timeline

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Earth Temperature Timeline

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Title text: [After setting your car on fire] Listen, your car's temperature has changed before.

Explanation

This comic is a timeline on how the temperature has changed from 20,000 BCE (Before Common Era) to the present day (2016), with three predictions for the rest of the 21st century depending on what actions are taken (or not taken) to stop CO₂ emission. This comic is a direct, but much more thorough, follow up on the previous global warming comic: 1379: 4.5 Degrees. By having readers scroll through millennia of slow-paced natural changes, Randall uses the comic to confront the rapid temperature rise in recent years.

Over the past 100 years, human action has produced a large amount of CO₂ emissions, which have caused a rise in average global temperature through the greenhouse effect. This is called global warming and is part of a climate change, a subject that has become a recurrent subject on xkcd. There are still many people who claim that this is not happening, or at least that it is not caused by any human actions, called climate change deniers. One argument of theirs is that global warming is happening for natural causes, summarized with the phrase "temperature has changed before".

This comic shows that while temperature changes have indeed occurred before, the speed of the current temperature rise is much, much faster than those measured for many previous thousands of years. The comic became so popular that Randall postponed the release of his next comic to keep this one on the front page one day longer.

The temperature curve is a dotted line most of the time, but from about 1850 to 2016 the measurement data is good enough to let the curve become a solid line indicating that this is not an estimate. Before 1850 the temperature is an estimate based on the sources given. And likewise into the future the three possible curves are also dotted to show that they are predictions, based on how seriously the population of Earth takes knowledge (and comics) like this.

Although this is a topic Randall obviously takes very seriously, and by far most of the facts fit with known history, he still includes several jokes in the comic. See also the table explaining each item in the comic.

The title text compares the saying that "the temperature has changed before" comparing temperature changes over thousands of years to the rapid global warming over the last century with saying that the "small" changes to the temperature a car experiences over the years of normal usage should not make you worried over the rapid temperature increase that happens when someone sets your car on fire. Randall previously used this joke in 1693: Oxidation and 1014: Car Problems.

Jokes in the comic

• By placing the invention of the internet at 1980 in the chart, just where the temperature curve starts its most rapid increase, Randall humorously implies that the internet caused the rise in temperature.
• At 13600 BCE a glacier is shown retreating from New York because of the warm up. It is disgusted by the new changes and proclaims: That’s it! I’m moving to Canada! This is a joke on an idiom said by US citizens to protest against changes in their country. As shown in the chart, the glacier takes 5000 years (13600-8400 BCE) to cross what would become the Canadian border (neither the United States nor Canada existed yet).^{[citation needed]} Also, glaciers don't speak English, or any language for that matter.^{[citation needed]}
• At 13400 BCE it is mentioned that humans domesticate dogs. Megan talks to a wolf about to be tamed making a deal with it, that it can eat and sleep with the humans as long as they can yell at it for pooping indoors. This sounds like a sweet deal for the wolf until Cueball mentions that they will breed it to be very small and then dress it up in small costumes. The wolf says wait, but it is already too late...
• The Pokémon reference at 9000 BCE about them going extinct in North America (although Megan, immediately underneath, does note that this is not a real fact). As the writing stated that Pokemon go extinct this can also be seen as a reference to a popular video game called Pokémon Go and hence also the comic 1705: Pokémon Go.
• At 4500 BCE, next to "Proto-Indo-European language develops", Ponytail gets the idea to develop the language heavily inflected to make it difficult to remember all the verb endings for future students. This is a direct reference to the comic 1709: Inflection.
• The reference to the 1984 mockumentary about the fake rock band This Is Spinal Tap in conjunction with Stonehenge at 2200 BCE. In the movie the band ordered a giant 18 feet Stonehenge megalith but a writing mistake gives them one that is only 18 inches high.
  • Another real band Nine Inch Nails is referenced 15000 BCE where Megan writes the band's stylized name NIИ on the wall next to Hairy who is in the process of painting the cave painting at Lascaux in France.
• Around the setting of the Iliad and the Odyssey (1200 BCE) a drawing of the Trojan Horse has writing on it that states: Not a trap.
• Just below the previous entry also at 1200 BCE is the mentioning of the invasion of the Sea Peoples. This sounds so much like a reference to mermaids, often called sea people that Randall feels the need to note that this invasion and these sea people is a real thing in a footnote. This is opposed to the Pokémon reference above where he notes that it is not a real fact. The sea people was a seafaring confederation of groups known to have attacked ancient Egypt and other Bronze age civilizations around this time. It is widely regarded to be one of the major causes of the Bronze Age Collapse.
• The reference at 450 BCE compares the Battle of Thermopylae (also known as 300 Spartans) with the dramatized 2007 movie 300, but in the real world the fighting of course occurred at regular speed and with more clothing.
• There are other minor jokes but this list mentions all the major jokes.

Table of all elements

• Here is table including all elements in the chart with explanations including reading off temperature and year for each event from the curve.
  • The year group is just an easy way to find the section.
  • Element is a description mainly taken from the transcript.
  • The actual year of an event has been read off more precisely on the chart.
    • The central part of the element has mainly been used.
    • Only rarely has ranges below 100 years been used but if a location is clearly midway between two hundred years intervals 50 year range has been used.
    • Only when there are several posts close to each other has smaller range been used a few times.
  • T (°C) is the number of degrees Celsius above or below the 1961-1990 average, which on this graph is set to zero, (i.e. not the number of physical degrees above or below this 0°C).
    • These have been read of to 0.1°C rounding up or down. Lines have been inserted over the chart, 10 for each degree, to make this as accurate as possible.
    • In a few cases where a maximum is reached 0.05°C has been used
  • Explanation of each element.

Year group	Element	Year	T (°C)	Explanation
20000 BCE	[An arrow goes from the dotted line to the central line at 0°C (representing the 1961-1990 average). In the middle of the line there is a temperature label:] 4.3°C At the start of our timeline, 22,000 years ago, Earth is 4°C colder than during the late 20th century.	20000 BCE	-4.3	The scale here is relative, showing the magnitude of change rather than an absolute temperature reading. As a rule, climate changes are compared with a 30 year interval, and the 1961-1990 average was chosen for convenience as the "normal" to compare temperature changes with, but any other choice of baseline would show the exact same changes. The Last glacial period (aka ice age) reached its maximum extent approximately 22 to 24 thousand years ago.
	Boston is buried under almost a mile of ice, and the glaciers reach as far south as New York City. [The Statue of Liberty is shown in front of a glacier front. Knit Cap is seen in the snowy landscape. The skyline of Boston is shown under a half a mile of ice.]	19700 BCE	-4.3	This shows what a difference 4 degree in global temperature means (massive effect), as opposed to four degrees on a daily weather wise scale (trivial). The Boston image is directly taken from 1225: Ice Sheets about the ice age glacier coverage; it was also shown buried in ice in 1379: 4.5 Degrees.
19500 BCE	But the world is about to warm up.	19500 BCE	-4.3	The warming process actually takes thousands of years, which this comic will portray down thousands of pixels to come. This is not a fast warm up, especially not compared to the one we are currently experiencing (at the bottom of the chart).
	By this time, humans have already spread across Africa, Eurasia, and Australia.	19300 BCE	-4.3	Homo Sapiens successfully migrated out of Africa somewhere between 130,000 and 70,000 BCE.
	They’ve created painting, pottery, rope, and bows and arrows, but haven’t developed writing or farming.	19100 BCE	-4.3	The oldest known paintings date back to about 38,000 BCE. The oldest known pottery date back to about 20,000 BCE. The oldest known rope date back to about 26,000 BCE. The oldest known arrows date back to about 70,000 BCE, but Randall seems to be mistaken about the bows which seems to be at most 10,000 years old. Writing is mentioned again at 3500 BCE and farming at 10,000 BCE.
19000 BCE	Changes in the Earth’s orbit mean that more sunlight reaches the polar ice…	18600 BCE	-4.2	Milankovitch cycles are repeated climate variations on a timescale of tens of millennia caused by cyclic variations in eccentricity, axial tilt, and precession of the Earth's orbit, which thus then determined climatic patterns on Earth. The Milankovitch cycles are referenced again around 4700 BCE.
	[A line chart with a labeled Y-axis "Summer sun W/m2 at 60°N" with three labeled ticks ranging from 450-550. The curve starts up and then goes down five times and up four times ending down. There is one plateau towards the end compared to the rest of the curve where the ups and downs are quite alike.]	18600 BCE	-4.2	The chart shows the input of sun during summer time in the Northern hemisphere (at 60° northern latitude) as the effect (W) per square meter (m2) which fluctuated in the range from 450-550 during the time shown in the chart. There is, however, no scale for the time between the peaks. This chart relates to the text about increasing sun to the polar ice in the entry above.
18500 BCE	[A map of the world. At the top is a light gray area covering North America, Greenland and northern Europe and most of the northern part of Russia. A similar gray area covers Antarctica. The gray areas are labeled as ice.]	18300 BCE	-4.2	This map shows where the ice covered the northern hemisphere (and Antarctica) during the Last Glacial Maximum. The continents have not moved much since then, but the lower water level caused by the amount of water bound up in the ice, can clearly be seen in several locations. For instance, the British islands, Greenland, and Papua New Guinea are connected to their respective neighboring continents. Also Alaska and Russia are connected through the ice sheets covering the northern part of the Earth.
18000 BCE	…And the ice sheets start to melt.	17900 BCE	-4.1	This was a slow process that takes 10,000 years. The ice is mentioned again at 13,600 and 8400 BCE.
17500 BCE	Temperatures have been creeping upward, but around this point, CO2 levels start to climb…	17300 BCE	-4.1	Due to the release of gasses from various sources (dissolved in the ocean, trapped in permafrost, etc), atmospheric CO2 levels increased by 100 parts per million over a span of thousands of years. Modern civilization has added the same amount in a single century.
17000 BCE	…And then the warming speeds up.	16700 BCE	-4.1	It took 3000 years for the temperature to increase with one degree. So this sentence can be seen as sarcasm about the rate of natural climate change compared to modern anthropogenic (human caused) warming.
16500 BCE	[Cueball is standing with a spear just the right of the graph talking to a rabbit.] Cueball: Still pretty cold.	16200 BCE	-4.0	True, because although the temperature has risen with 0.3°C over the last 4000 years, it's still 4°C below the 1961-1990 average.
16000 BCE	[Megan touches the dotted line to the right of her, with Ponytail standing on the other side. The graph has finally passed the -4°C line below the 1961-1990 average.]	15600 BCE	-3.9	Megan is the first drawing on the left side of the curve. She seems to be pushing the temperature up.
	[In the right part of the chart is an explanation of the data. Below the first two lines there are four drawings each showing possible temperature swings in reality compared to the smoothed data that represents the dotted curve of the entire chart. The dotted curve is shown in all four drawings and a thin line is shown running along it but with much more fluctuation left and right on the first two, a large spike right on the third and a large bump way right on the fourth. Above these there are two labels. The first labels is inside a bracket that covers the first three, and the last label is for the last drawing. Below is a list of sources.] Limits of this data: Short warming or cooling spikes might be “smoothed out” by these reconstructions but only if they’re small or brief enough. Possible Unlikely Reconstructions are from Shakun (2012) and Marcott (2013), scaled to Annan + Hargreaves (2013) estimate for the last glacial period.	15600 BCE	-3.9	This is Randall's pre-emptive response to skepticism about the accuracy of prehistoric data. Ice cores and similar records might miss individual year-to-year variation, but should catch sustained changes lasting many decades, which is the time scale that matters for climate. See links to the sources below.
15500 BCE	In what is now France, humans paint murals on the walls of the Lascaux caves [Hairy paints three animals, two with horns, and two humans, Cueball holding hand with Hairy who has a spear. On the other side of the central line Megan writes three letters, the last of which is reversed:] NIИ	15200 BCE	-3.8	A reference to the industrial techno band Nine Inch Nails as Megan writes the bands stylized name NIИ on the wall next to Hairy who is in the process of painting part of the cave paintings at Lascaux in France.
15000 BCE	Ice sheets around Alaska shrink, exposing a land bridge between Asia and North America [From around the bottom if this section and down to 11500 BCE the dotted curve moved steadily to the right towards warmed temperature peaking close to 1.5°C below the 1961-1990 average. Before this the temperature had not moved much away from that at the start.]	14600 BCE	-3.5	This land bridge is known as Beringia. It is mentioned again at 8300 when it disappears due to the rising seas.
14500 BCE	[Cueball walks right looking back at the graph behind him. Megan walks in front of him pointing further right.] Cueball: Cool. Humans reach North America.	14200 BCE	-3.3	This is approximately when the humans from Asia crossed the land bridge mentioned in the previous entry, from what is now Siberia to what is now Alaska. Settlement of the Americas occurred around the time shown in the chart, although it's possible that earlier humans did so by boat prior to the formation of the land bridge. Cueball's comment is a double entendre; it was figuratively "cool" that early people migrated this far, and the climate was literally cool compared to modern times.
14000 BCE	The edge of the ice withdraws from New York City and retreats north.	13700 BCE	-3.1	Even though the ice began to melt 4000 years before (at 18,000 BCE in the chart) it is first now that New York City is free of ice.
	[A large glacier front speaks in a speech bubble with an arrow pointing at it. Behind is there are four peaks in the horizon and in front of it three small melting pools and some rocks on the ground.] Glacier: That’s it! I’m moving to Canada!	13600 BCE	-3.0	When US citizens are unhappy with changes in their country, they sometimes say they will move to Canada in protest. Here it is the glacier that is anthropomorphically unhappy with the climate changes. However this is a slow process; it crosses the Canadian border more than 5000 years later.
13500 BCE	Humans domesticate dogs (Date uncertain, may be much earlier)	13400 BCE	-3.0	See Origin of the domestic dog. This timeline event is not quite accurate. The first dogs differentiated from wolves about 23,500 years ago, but there was an event around 13500 BCE that increased the population size and may be attributable to domestication events. The early population migrating into the Americas brought domesticated dogs with them, so it must have occured beforehand within the precursor cultural populations.
	[Megan and Cueball is watching a wolf looking at them.] Megan: Okay, you can live in our homes and we’ll feed you, but we’ll still get mad if you poop on the floor. Wolf: Deal. Cueball: And we get to breed you to be tiny and dress you in little costumes. Wolf: …Wait.	13100 BCE	-2.8	Megan is making a deal with the wolf that it can eat and sleep with the humans as long as they can yell at it for pooping indoor. This sounds like a sweet deal for the wolf until Cueball mentions that they will breed it to be very small and then dress it up in small costumes. The wolf says wait, but it is already too late...
13000 BCE	Woolly Rhino goes extinct	12900 BCE	-2.7	Mainland woolly rhinos died in the Quaternary extinction event, but a small island population survived until around 8000 BCE. Woolly rhinos likely became extinct in part due to over-hunting. Randall's choice of species on this chart seems to focus on animals that were greatly affected by humans, for good or ill.
	Oregon is scoured by huge floods as glacial dams burst and lakes of meltwater flow to the sea	12600 BCE	-2.2	This is a reference to the Missoula Floods several cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge flooding much of eastern Washington and the Willamette Valley in western Oregon at the end of the last ice age. During the last deglaciation ice dams formed then burst several times between 13,000 and 11,000 BCE.
12500 BCE	Ice sheets withdraw from Chicago	12200 BCE	-1.8	The next step towards the Canadian border, after they left New York at 13,600 BCE.
12000 BCE	Humans settle Abu Hureyra in Syria	11550 BCE	-1.6	A well-preserved prehistoric village that existed from 11,000 to 7000 BCE (a little later than noted in the chart), allowing archaeologists to study how their culture developed.
11500 BCE	[An arrow on the left side of the dotted curve is pointing down along the dotted curve and to the left indicate temperature is declining again, meaning the dotted curve now moves left to colder temperatures. This only continues until 10500 BCE. It is only the second time something is noted on the left side after Megan at 16000 BCE] Temperatures start to decline, mainly in the Northern hemisphere This may be caused by changes in ocean circulation due to the floods of cold fresh meltwater flowing into the Atlantic as the North American ice sheet melts. This cooler period is called the Younger Dryas	11300 BCE	-1.6	In the Younger Dryas, the Earth cooled by almost one degree over 1000 years. There were several floods during the end of the ice age but the most famous is the one from Lake Agassiz. A similar but less global effect could occur if the ice on Greenland melts too quickly and causes a shutdown of thermohaline circulation. Without the Gulf Stream, hot water would remain in the Gulf of Mexico and the Caribbean instead of warming the North Atlantic and Europe. The movie The Day After Tomorrow dramatized a worse-than-worst-case version of this, happening in days instead of centuries.
11000 BCE	[This is the first text to the left of the dotted curve:] Humans reach Argentina	10900 BCE	-1.8	The earliest evidence of humans in Argentina. Finally the temperature graph has risen enough that there is space to write text on the left side of the curve.
10500 BCE	[An arrow pointing down along the right side of the dotted curve and to the right indicate temperature is increasing again, meaning the dotted curve now moves right to hotter temperatures. This continues until 8000 BCE where it levels out just above the 1961-1990 average.] Warming resumes	10500 BCE	-1.8	After 1000 years of slightly decreasing temperatures the warm up of Earth resumes. Over the next 3000 years the temperature increases 2.5°C, reaching a long plateau about 0.5°C above the 1961-1990 average around 7500 BCE.
	Human settlements at Jericho	10050 BCE	-1.4	The first permanent settlement on the site of Jericho occurred around 9500 BCE, but there is evidence of non permanent settlement during this period, when cold and drought made permanent habitation in that region difficult.
10000 BCE	First development of farming	9750 BCE	-1.1	This is now called the Neolithic Revolution, i.e. the wide-scale transition of many human cultures from a lifestyle of hunting and gathering to one of agriculture and settlement. The history of agriculture began independently in several locations with both domestication of animals and the farming of different cereals. One of the first regions to develop farming was the Fertile Crescent. This is also around this time that the last ice age is said to have ended.
9500 BCE	Saber-toothed cat goes extinct	9200 BCE	-0.3	Although one of these (Smilodon) was known as the saber-toothed tiger, most saber-toothed "cats" are not related to tigers, or any modern cats at all, but can be viewed as examples of convergent evolution. Smilodon became extinct around 8000 BCE, and the last Saber-toothed cat first became extinct around 7000 BCE, which does not fit very well with Randall's range. Indirectly humans may have caused the extinction of the Saber-toothed cat by over-hunting their megafauna prey, depriving the cats of food sources.
	Horses disappear from North America	9100 BCE	-0.2	The evolution of the horse began millions of years ago in North America; early species migrated across Beringia into Eurasia before their predecessors died out.
9000 BCE	Last North American Pokémon go extinct [Cueball with a spear and Megan is looking up at this last “fact”.] Megan: That is not a real fact.	8900 BCE	-0.1	Pokemon are not real [citation needed]. This faux-extinction is likely a reference to the Pokémon Go game, which Randall spoofed in 1705: Pokémon Go. Virtual Pokémon now thrive throughout the entire world, and are most commonly found near affluent first world neighborhoods.
	Temperatures reach modern levels	8800 BCE	0.0	It took 11,200 years for the temperature to increase 4.3°C. It's possible that human-created effects will produce an equal change in a few hundred years.
	Rising seas cut off the land bridge between North America and Asia	8700 BCE	0.1	Beringia was freed of ice in 15,000 BCE. This is an example of what happens when the temperature rises and glaciers melt. Sea levels are rising again as ice on Greenland and Antarctica continues to melt.
	Cattle domesticated	8500 BCE	0.2	Cattle feature prominently in the comic 1338: Land Mammals.
8500 BCE	Ice sheets retreat across the Canadian border	8400 BCE	0.3	Finally the glacier that began retreating from New York around 13,600 BCE succeeded in moving to Canada as it had threatened to do...
	Temperatures start to level out slightly above 1961-1990 levels	8050 BCE	0.4	The next 3000 years the temperature stays within 0.2°C degree of a temperature 0.5°C above the 1961-1990 average. A very long and stable period.
8000 BCE	[The above sentence breaks over the 8000 BCE line. From here a maximum in temperature on the chart is reached at 0.5°C above the 1961-1990 average, which will not be overtaken until 2000 CE. It stays almost constant here until 5000 BCE where a slight cooling begins.]	8000 BCE	0.4	This is the only five hundred year span with no events listed fully inside. Maybe because nothing happens with the temperature.
7500 BCE	This warm, stable period is called the Holocene Climate Optimum	7400 BCE	0.5	Some skeptics like to say "it was warmer in the Holocene." This is no longer true. Global temperature began encroaching Holocene levels in 1998, and has equaled or possibly exceeded them since 2014.
	Jiahu settled in China	7050 BCE	0.5	Jiahu is another prehistoric settlement, similar to Abu Hureyra (12000 BCE), that was extensively studied by archaeologists.
7000 BCE	Final collapse of the North American ice sheet leads to rapid 2-4m sea level rise…	6800 BCE	0.55	The temperature almost reached 0.6°C above the 1961-1990 average before this happened and caused the slight decrease in temperature mentioned below.
	[A small arrow points down and left to the right of the dotted curve. There is a small decrease in temperature but it is very small and would have been missed without the arrow and label.] …And a period of cooling in the Northern hemisphere	6550 BCE	0.5	A 0.05 degree decrease in 200 years again refers to the theme of slow natural climate change.
6500 BCE	As seas rise to near their modern levels, Britain is cut off from mainland Europe	6300 BCE	0.45	This is a reference to the flooding of Doggerland.
6000 BCE	Humans develop copper metalworking	5600 BCE	0.5	The copper age was relatively brief before humans discovered how to make bronze.
5500 BCE	Massive volcanic eruption in Oregon creates crater lake	5300 BCE	0.55	Crater Lake is the caldera at the top of Mount Mazama, a collapsed stratovolcano. If it erupted again, it could become a Somma volcano (see 1714: Volcano Types).
	Gold metalworking	5050 BCE	0.6	The temperature peaks here at just a bit more than 0.6°C above the 1961-1990 average. It will not rise above this level until the global warming sets in in the 1900s.
5000 BCE	Invention of the wheel	4900 BCE	0.6	Wheels are one of the most important inventions of humanity. They feature in many xkcd comics, such as 1075: Warning.
	[To the right of the dotted curve is an arrow pointing down and slightly left. From here temperature decreases very slowly but steadily from 0.5°C above the 1961-1990 average until 1000 BCE where a stable plateau is reached around the 1961-1990 average.] Earth begins to cool slowly mainly due to regular cycles in its orbit	4800 BCE	0.5	Again a reference to the Milankovitch cycles mentioned in detail at 18,600 BCE. Here they cause a cooling rather than a heating as they did back then.
4500 BCE	Proto-Indo-European language develops	4400 BCE	0.5	Most of the languages in Europe, the Middle East, and India share a surprising number of common roots. PIE is the theoretical ancestor from which they descend. Randall mentions this language family in many comics, such as 890: Etymology.
	[To the right of the curve Ponytail holds up a hand towards Cueball.] Ponytail: Let’s make our language heavily inflected, so future students have to memorize a zillion verb endings! Cueball: Okay!	4400 BCE	0.5	Ponytail gets the idea to develop the language heavily inflected to make it difficult to remember all the verb endings for future students and Cueball is okay with that. This is a direct reference to the comic 1709: Inflection.
	Permanent settlements in the fertile crescent	4200 BCE	0.5	The Fertile Crescent is one of those things you're supposed to remember from grade school. A lot of historic milestones happened there, such as the pyramids of Giza, the code of Hammurabi, and the Abrahamic religions.
4000 BCE	Horses domesticated	3950 BCE	0.5	Horse riding was the greatest advance in land travel until the invention of engines. Horses appear in many xkcd comics, such as 936: Password Strength.
	Minoan culture arises on Crete	3700 BCE	0.5	Minoan culture invented many strange and wonderful things, such as the Labyrinth at Knossos and Bull-leaping.
3500 BCE	Egyptian mummification	3500 BCE	0.5	xkcd has discussed mummification in What If? 134: Space Burial.
	Rise of the Indus Valley civilization	3300 BCE	0.5	The largest bronze-age civilization.
	Invention of writing in Sumer “prehistory” ends, “history” begins	3200 BCE	0.5	Our knowledge of prehistoric events must rely on digging up artifacts and making inferences. After this time, it became possible to find descriptions of past people and events, which is the definition of history. (Old guy in Sumer: Kids these days with their new-fangled stone tablets, instead of using their memory...)
	Earliest human whose name we know (Pharaoh Iry-Hor in Egypt)	3100 BCE	0.5	The first named person we know of today! This was also mentioned as a "cool fact" in the title text of 1355: Airplane Message.
3000 BCE	Three Sovereigns and Five Emperors period in China	2800 BCE	0.4	The temperature has finally dropped below 0.5°C above the 1961-1990 average after almost 2000 years of cooling from 0.6°C above the 1961-1990 average.
	Gilgamesh	2700 BCE	0.4	Gilgamesh was probably a Sumerian king whose tales were exaggerated into mythology.
	Imhotep	2600 BCE	0.4	Imhotep was not a pharaoh, but a wise commoner who was elevated to chancellor, high priest, and post-mortem divinity.
	Mayan culture emerges	2600 BCE	0.4	Like the ancient Egyptians, Mayans are remembered for pyramids and logographs.
	Great Pyramid constructed	2650 BCE	0.4	xkcd has discussed pyramids in 1717: Pyramid Honey and What If? 95: Pryamid Energy.
2500 BCE	Corded Ware culture in Europe	2500 BCE	0.3	The term Corded Ware was invented by an archaeologist; no civilization actually called themselves that.
	[To the left of the curve two rock musicians with long hair and electrical guitars are standing on either side of a small gate made of three slabs of stone, one on top of the other two standing stones.] Stonehenge completed	2200	0.3	This is a reference to the 1984 mockumentary about the fake rock band This Is Spinal Tap. In the movie the band wanted a giant Stonehenge prop 18 feet high, but a writing mistake gives them one that is only 18 inches.
	Chariots developed	2000 BCE	0.3	But Chariots of Fire came much later.
2000 BCE	Alphabetic writing developed in Egypt	1750 BCE	0.2	Obligatory reference to xkcd 1069: Alphabet.
	Last mammoths on a tiny Siberian island go extinct	1650 BCE	0.2	Many of the Pleistocene megafauna died in the Quaternary extinction event. Like the woolly rhino (see 12900 BCE) these animals likely became extinct in part due to humans hunting them, which may be why Randall included them in the chart. Most of the mammoths died out before 8000 BCE but some survived in remote areas and the last known population died on Wrangel Island in the Arctic Ocean around 2000 BCE, slightly earlier than Randall shows here.
	Minoan eruption	1600 BCE	0.2	This volcano may have led to the downfall of Minoan civilization.
1500 BCE	Iron smelting	1400 BCE	0.1	The beginning of the Iron Age.
	Olmec civilization develops in Central America	1350 BCE	0.1	No, Maggie, not Aztec, Olmec.
	[A Trojan horse with two Cueball-like guys in front and a third standing on its back. Its back is at three Cueball’s height and its head rises to the level of the Cueball on its back. It stands on a platform with four wheel on the visible side. There is text on the horse] Setting of the Iliad and the Odyssey Text on horse: Not a trap	1250 BCE	0.1	A reference to the Trojan War qua the drawing of the Trojan Horse. The horse was a big trap letting the soldiers hidden inside it into Troy. This explains why it has Not a trap written on it. Else they would not have taken the giant wooden horse present from their sworn enemies into their city just like that... Note that the Trojan horse isn't mentioned in the Iliad, and only recalled in passing by the characters in the Odyssey.
	Invasion of the Sea peoples* * A real thing	1200 BCE	0.1	Sea people might sound like a reference to mythical mermaids, so Randall feels the need to footnote that this event was a real thing (as opposed to his Pokémon reference, which he notes is not a real fact). The sea peoples were a seafaring confederation of groups known to have attacked ancient Egypt around this time.
	Polynesians explore the Pacific Ocean	1000 BCE	0.1	Polynesian navigation was surprisingly widespread.
1000 BCE	[From 1000 BBC to 1000 CE the temperature is stable and very close to the 1961-1990 average.]	1000 BCE	0.1	The temperature has fallen from the Holocene Optimum by half a degree to just a bit above the 1961-1990 average. It will stay in this range for the next 2000 years.
	Solomon	1000 BCE	0.1	Solomon may have been a real historical king, but he probably did not threaten to chop a baby in half.
	Iliad and Odyssey composed	900 BCE	0.1	These classic myths were written more than 300 years after their supposed events. Archaeologists believe the city of Troy existed (and was destroyed by war around the right time period), but characters like Helen, Odysseus, and Achilles did not.
	Rise of Greek city-states	800 BCE	0.1	This is Sparta, along with Athens and several others.
	Neo-Assyrian Empire	800 BCE	0.1	Hi, you may remember us from such kings as Adad-nirari and Sennacherib.
	First Olympics	750 BCE	0.1	The first of the ancient Olympic Games is traditionally dated to 776 BC.
	Zapotec writing in modern Mexico	600 BCE	0.0	Another Central American culture that fell to the Spanish invasion.
	Confucius	550 BCE	0.0	"He who knows all the answers has not been asked all the questions."
500 BCE	The stuff in the movie 300, but regular speed and with more clothing	450 BCE	0.0	A reference to the Battle of Thermopylae by comparison with the 2007 movie 300 about this battle. The real Spartans wore armor, and real humans don't fly through the air in slow motion when struck.
	Buddha	450 BCE	0.0	Randall also mentions other religious figures like Jesus and Muhammad.
	Nazca Lines	350 BCE	0.0	These huge ancient drawings are difficult to see from ground level, leading some people to believe that they were intended for aliens.
	Alexander the Great	350 BCE	0.0	One of the most successful conquerors of the iron age, known for supposedly cutting the Gordian Knot.
	Mayan hieroglyphics	250 BCE	0.0	The Maya Calendar was probably created hundreds of years later.
	Ashoka the Great	250 BCE	0.0	The Edicts of Ashoka proselytized Buddhism across the continent.
	Paper invented	200 BCE	0.0	A significant step up from stone tablets or even papyrus.
	Asterix	100 BCE	0.0	Fictional main character in The Adventures of Asterix, a comic series set around 50 BCE when Julius Caesar conquered Gaul.
	Teotihuacán metropolis	100 BCE	0.0	Another ancient city much beloved by archaeologists, even though they don't know who built it.
	Julius Caesar	50 BCE	0.0	Aside from being a conqueror, dictator, and deity, Julius had a big impact on calendars. The month of Quintilis was renamed July to honor him, and he was famously assassinated on the ides (middle day) of March.
1 BCE 1 CE	[Instead of a zero, there are two numbers for each of the two scales before (1 BCE) and after Christ (1 CE)]	0 CE	-0.1	Originally the year range went directly from 1 BC to 1 AD. The year zero has since been added for ease of mathematical and astronomical calculations.
	Roman Empire	1 CE	-0.1	Julius never held the title "Emperor"; his adoptive son Augustus was the first to do so.
	Jesus	1 CE	-0.1	Randall also mentions other religious figures like Buddha and Muhammad.
	[To the left and erupting volcano.] Pompeii	100 CE	-0.1	The volcano is Mount Vesuvius which exploded in 79 CE and is famous for burying everyone in the close by city Pompeii preserving peoples bodies inside the huge amount of ash that swallowed the city very rapidly. Today it has given the archeologist lots of knowledge about the culture of that time.
	Three Kingdoms period	250 CE	-0.1	Not just a series of movies and video games, but an actual thing that happened in China.
	Gupta empire	700 CE	-0.1	Not as great as Ashoka, but still a pretty important time in the history of India.
	Various groups take turns sacking Rome	550 CE	-0.1	500 years is a pretty successful span for an empire.
	Attila the Hun	550 CE	-0.1	He probably would not mind being remembered as one of the most infamous barbarians in history.
500 CE	Muhammad	600 CE	0.0	Randall also mentions other religious figures like Buddha and Jesus
	Tang Dynasty	750 CE	0.0	A golden age in China, responsible for the development of printing, gunpowder, and many other advances.
	[An arrow to the right of the dotted curve pointing down, takes a swing far out from the curve and then bends back again. The text label next to it breaks into the next 500 period. The dotted curve stays stable at the 1961-1990 average along this arrow.] Medieval warm period in Europe and some northern regions (too regional to affect the global average much)	900 CE	0.0	Changes in ocean currents caused various regions to warm up while others cooled.
	Leif Eriksson	950 CE	0.0	Probably the first European explorer to reach North America.
1000 CE	[To the left a drawing of a compass with needle pointing the black end towards north east. There are labels for the four main directions (N, S, W, E) and a label next to it:] Magnetic compass navigation	1050 CE	0.0	It's much easier to sail to the Orient when you can orient yourself.
	[The dotted curve moves to the left towards lower temperature reaching a minimum around 1650 CE of about 0.6°C below the 1961-1990 average at the Little Ice Age.]	1150 CE	-0.1	This less than half a degree drop in temperature over 500 years was enough to cause the "Little Ice Age" which resulted in extended ice coverage in the winters in instance Europe. See more below at the entry for the Little Ice Age.
	Genghis Khan	1200 CE	-0.2	Mongol emperor. Gengar is not named after him, but Kangaskhan and the Khals are.
	Zheng He’s fleet explores Asia and Africa	1400 CE	-0.3	He explored farther than European contemporaries like Dias or de Gama.
	Aztec Alliance	1400 CE	-0.3	Aztec dominance only lasted a century until Cortes arrived, but their cultural legacy is indisputable.
	Printing press	1450 CE	-0.3	Johannes Gutenburg ushered in the Age of Enlightenment.
	Columbus	1490 CE	-0.3	The time given here references when Christopher Columbus reached the New World in 1492. The five events around 1500 CE lies very close together but it fits with Columbus fitted in just before 1500.
1500 CE	European Renaissance	1500 CE	-0.3	From here on, the chart has labels for each 100 year increment instead of 500, but the scale stays the same. Important events happens so much faster in these last five hundred years, there isn't enough space to write all of them, so Randall has had to be selective. He includes Isaac Newton but leaves out Albert Einstein, includes airplanes but leaves out cars, etc.
	Shakespeare	1600 CE	-0.4	xkcd references Shakespeare many times, such as 79: Iambic Pentameter and 1026: Compare and Contrast.
1600	Newton	1650 CE	-0.4	Isaac Newton appears in various xkcd comics, such as 626: Newton and Leibniz.
	[To the right of the dotted curve there is an arrow pointing down that makes a swing in towards the curve and then back out again. This is the coldest it has been since 9500 BCE. It is labeled:] ”Little Ice Age”	1650 CE	-0.4	This was not a true geologic Ice Age, just a slightly chilly period when the temperature fell a fraction of a degree, but still colder than it had been through 11,000 years of human civilization. In Europe the winters were so cold that the river Thames froze over hard enough to hold River Thames frost fairs between 1607 and 1814. And in 1658 Sweden crossed the Danish Straits on foot to invade Copenhagen in the March Across the Belts. It was only possible due to the harsh winters of the Little Ice Age, demonstrating how much half a degree of climate change can mean.
1700	Steam engines	1750 CE	-0.4	The Age of Steam heralded the upsurge of human CO2 emissions.
	Unites States Independence	1770 CE	-0.3	On July 4, 1776.
1800	Industrial Revolution	1825 CE	-0.3	Not to be confused with Industrial music such as Nine Inch Nails.
	Telegraphs	1830 CE	-0.3	-. --- .-- --..-- / - .... . / -- --- - .... . .-. / --- ..-. / ... .- -- ..- . .-.. / -- --- .-. ... . / .- .-.. .-- .- -.-- ... / ... . -. - / - .... . / .-.. .- -.. / --- ..- - / --- -. / .- / .... --- .-. ... .
	[After this the dotted curve becomes solid.]	1850 CE	-0.3	From 1850 weather records became sufficiently accurate and widespread to greatly improve the precision of climate measurements. Hence the curve stops being an estimate and thus also stops being a dotted curve and becomes solid.
1900	Airplanes	1900 CE	-0.3	xkcd discusses airplanes many times, such as 726: Seat Selection and 30: Interplanetary Cessna.
	World Wars	1930 CE	-0.2	Likewise, there are many xkcds on this topic, such as 261: Regarding Mussolini and 100: WWII Films.
	[The solid line takes a step to the right close to the 1961-1990 average. Over the rest of the 1900s it moves closer to the 1961-1990 average, crossing it before 2000 where it almost reaches the maximum temperature of 0.5 °C above the 1961-1990 average from earlier in 8000 BCE.]	1940 CE	-0.2	This is what the previous 14000 pixels of comic has been leading up to. After a laborious 20 millennia of gradual and meandering climate change, it should be clear that a full degree of warming in a single century is unprecedented in human history, and very unlikely to be natural variation.
	Fossil fuel CO2 emissions start rapidly increasing	1950 CE	-0.1	The infamous "hockey stick" starts around here.
	Nuclear weapons	1950 CE	-0.1	The Working Group on the 'Anthropocene' suggests dating the Anthropocene epoch from ~1950. The week after this comic 1736: Manhattan Project with a mushroom cloud was released.
	Internet	1980 CE	0.1	The origin of the internet dates back to 1960 but it began growing rapidly in 1980. By placing the invention of the internet at 1980 in the chart, just where the temperature curve starts its most rapid increase, Randall uses this correlation to humorously imply that the internet caused the rise in temperature. This is also where the temperature crosses the 1961-1990 average, which has to happen somewhere due to the Intermediate Value Theorem.
2000	Northwest Passage opens	2000 CE	0.4	This was dramatic evidence that the climate had changed. When global warming removes enough sea ice to create shipping routes that never existed before, then it is clear to people that something is changing, even if they disregard who/what is responsible for the change.
	[From here to present day the solid line increases rapidly and in 2016, present day, is almost reaches 1°C above the 1961-1990 average, with about 0.8°C above the 1961-1990 average.]	2016 CE	0.8	Notice: Warming did not stop in 1998.
2016	Present day	2016 CE	0.8	Today, just after the two hottest months ever measured since 1850 had ended (July and August 2016), this comic was released with the message displayed very clearly here below. Act now or fry...
	[From here the curve once again becomes dotted as this is the future. After one dot it splits in two and after the first two dots another split between them occurs forming three possible future dotted curves.]	2016 CE	0.8	Here stops the data and the projection into the future begins so the curve again becomes dotted. Three different scenarios are depicted.
	The first curve bending down before the others, and thus to the right of the other two reaches about 1.2°C above the 1961-1990 average and then goes straight down and stops at the 2100 line. An arrow points to it from the left and a label is written partly before and the rest after the 2100 line to the left of the curve:] Best-case scenario assuming immediate massive action to limit emissions	2100 CE	1.2	If humanity does all in its power to stop global warming we might be able to halt the global warming already before 2050 keeping the maximum temperature to just 1.2°C above the 1961-1990 average. Only 0.4°C above today's temperature. (Note that this is not, in fact, the absolute best-case scenario, as it assumes that no new greenhouse gasses are either added to or removed from the atmosphere in the future; the temperature rise could be kept to an even lower level if some or all of the already-emitted greenhouse gasses were removed from the atmosphere.)
2100	[The middle curve bends a little down after reaching 1.3°C above the 1961-1990 average, and then continues this path reaching 2°C above the 1961-1990 average in 2100. An arrow point from below to it and a label is written below the curve and below 2100 line:] Optimistic scenario	2100 CE	2.0	If all the current realistic preventions are implemented, which might not be so realistic, then we may not even stop the warming but slow it down so we "only" reach 2°C above the 1961-1990 average in 2100 CE but it would not stop there. This is half the temperature change experienced since the ice age, but the other way. This was directly referenced in the title text of 1379: 4.5 Degrees: That's only HALF an ice age unit (IAU), which is probably no big deal.
	[The last line continues along the path from the last 16 years of the solid line reaching 4.2°C above the 1961-1990 average at 2100, almost as far on the other side of the 1961-1990 average in 150 years as it took 14,000 years to move from the other side from the start of the chart. Another arrow point to this from below with a label below the curve and below 2100 line:] Current Path	2100 CE	4.2	In this last scary scenario Randall assumes the temperature keeps rising steadily by extrapolating along the slope of the last two to three years. Randall has warned about the hazards of Extrapolating, but this line is in fact below the worst case predictions. If this comes true we will reach a temperature increase taking us from the 1961-1990 average and in just 125 years to 4.2°C above this average. That is just as far above this average in that short time span as the ice age temperature was below. And it took more than 11,000 years for nature to reach such an increase. Randall already contemplated what this would be like in the +1 ice age unit (IAU) panel of 1379: 4.5 Degrees two years ago, as well as in 164: Playing Devil's Advocate to Win almost 10 years ago. He may get to enjoy quite a ride as he "wished" for back then. There is no reason to assume the temperature will not keep rising past 2100 CE, so the "Hothouse Earth" of the early Cretaceous period mentioned in the 4.5 degree comics +2 IAU panel might come to pass in future centuries if we continue on our current path. On the bright side, modern civilization might collapse if this trend keeps up, which would drastically cut our releases of carbon dioxide and other greenhouse gasses into the atmosphere. But then again, positive feedback from methane in melting permafrost might take over... Good luck Earth.

Sources

The image attributes climate data sources as "Shakun et al. (2012), Marcott et al. (2013), Annan and Hargreaves (2013), HadCRUT4, IPCC":

• Shakun, Jeremy D.; Clark, Peter U.; He, Feng; Marcott, Shaun A.; Mix, Alan C.; Liu, Zhengyu; Otto-Bliesner, Bette; Schmittner, Andreas; Bard, Edouard (2012-04-04). "Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation" (PDF). Nature. 484 (7392): 49–54. doi:10.1038/nature10915. ISSN 1476-4687. Archived from the original on 2016-05-20.
• Marcott, Shaun A.; Shakun, Jeremy D.; Clark, Peter U.; Mix, Alan C. (2013-03-08). "A Reconstruction of Regional and Global Temperature for the Past 11,300 Years" (PDF). Science. doi:10.1126/science.1228026. Archived from the original on 2013-04-12.
• Annan, J. D.; Hargreaves, J. C. (2013-02-13). "A new global reconstruction of temperature changes at the Last Glacial Maximum" (PDF). Climate of the Past. 9 (1): 367–376. doi:10.5194/cp-9-367-2013. ISSN 1814-9324. Archived from the original on 2020-07-28.
• HadCRUT (Hadley Centre/Climatic Research Unit Temperature) - Official site
• Intergovernmental Panel on Climate Change - Official site

Transcript

Note there are several spelling errors in the comic, so please do only correct spelling errors that are not part of the comic! See more in the trivia section.

[A large heading, followed by a sub-caption. Below that two lines with a statement in between:]

A timeline of Earth’s average temperature

since the last ice age glaciation

When people say “The climate has changed before,” these are the kinds of changes they’re talking about.

[A very long chart below the headings above is headed with a label for the scale of the X-axis above the chart. Below that a sub-caption. To the left an arrow down to the top of the chart pointing to the dotted curves starting point (at -4.3°C below the 1961-1990 average) with a label above the arrow. And arrow pointing left to the left of the center and another pointing right to the right of the center has labels. Below these is the temperature scale of the X-axis, with 9 ticks between the borders each with a label ranging from -4 to +4°C compared to the 1961-1990 average, but with another step in each direction not labeled towards to axis so the chart covers -5 to +5°C compared to the 1961-1990 average.]

Temperature

Compared to the 1961-1990 average

Start

Colder

Warmer

-4°C -3°C -2°C -1°C 0°C +1°C +2°C +3°C +4°C

[To the right of the chart is a gray text standing on the side down along the outer boarder of the chart with the sources for the chart:]

Source: Shakun et. al. (2012) , Marcott et. al. (2013), Annan and Hargreaves (2013) , HadCRUT₄, IPCC

[The chart is split in 10 columns by the temperature scale and the borders. The two central columns are white, and then from there to the left the background becomes a faded color that changes from light blue to blue at the edge in four steps. Similarly to the right the color changes from light red to red. To the left there is a time scale taking 500 years leaps from 20,000 BCE all the way to year 1, where there are two years, one for BBC and one for CE. The 500 year leaps continue until 1500 CE and from there the steps are down to 100 years until 2100 with also present day 2016 labeled. After 1500 the CE is omitted. The labels stop there, but there is space below covering down to 2200 CE. There is clearly visible division line across the chart on the level of each of the 500 step, and fainter lines for each of the 100 steps all the way even though only the last 5 of these 100 steps are labeled. There is a similar clear line at 2016. Below each step on the Y-axis is noted, and then any text starting before the next step is noted below indented. If there are extra image belonging to text this is indented once more. The graph that the whole chart is about is a dotted line that begins at the “start” point mentioned above at -4.3°C and then begins to go straight down. It will change left and right all the way down. To being with all text and most drawings are to right of the dotted curve. Whenever something is to the left it will be noted. When it says to the left above something, and then nothing over the next, then the next will be to the right. Only at the very bottom are there more entries to the left than right. ]

20000 BCE

[An arrow goes from the dotted line to the central line at 0°C. In the middle of the line there is a temperature label:]

4.3°C

At the start of our timeline, 22,000 years ago, Earth is 4°C colder than during the late 20^th century.

Boston is buried under almost a mile of ice, and the glaciers reach as far south as New York City.

[The Statue of Liberty is shown in front of a glacier front. A very tiny Cueball is on top of the glacier. The drawing is labeled and so is also the glacier.]

New York

Ice

[Cueball (wearing a knit cap with a pom-pom is seen walking in a snowy landscape leaving black footprints behind him. He walks through the white central part of the chart.]

[The skyline of Boston is shown with two clear buildings among all the other. Above it is a line and in between this area has been filled with thin lines. The drawing is labeled and so is this area. Also the skyline has an arrow pointing at it with a label:]

Boston

Ice

Modern skyline

19500 BCE

But the world is about to warm up.

By this time, humans have already spread across Africa, Eurasia, and Australia.

They’ve created painting, pottery, rope, and bows and arrows, but haven’t developed writing or farming.

19000 BCE

Changes in the Earth’s orbit mean that more sunlight reaches the polar ice…

[A line chart with a labeled Y-axis with three labeled ticks. The curve starts up and then goes down five times and up four times ending down. There is one plateau towards the end compared to the rest of the curve where the ups and downs are quite alike.]

Summer sun W/m² at 60°N

550

500

450

18500 BCE

[A map of the world. At the top is a light gray area covering North America, Greenland and northern Europe and most of the northern part of Russia. A similar gray area covers Antarctica. There are two labels in the gray area above and one in the gray area below:]

Ice Ice

Ice

18000 BCE

…And the ice sheets start to melt.

17500 BCE

Temperatures have been creeping upward, but around this point, CO₂ levels start to climb…

17000 BCE

…And then the warming speeds up.

16500 BCE

[Cueball is standing with a spear just the right of the graph talking to a rabbit.]

Cueball: Still pretty cold.

16000 BCE

[Megan points to the graph to the right of her and between her and Ponytail standing on the other side. Mean is the first drawing on the left side of the dotted curve, which has hardly moved since the beginning, only to just on the other side of 4°C.]

[In the right part of the chart is an explanation of the data. Below the first two lines there are four drawings each showing possible temperature swings in reality compared to the smoothed data that represents the dotted curve of the entire chart. The dotted curve is shown in all four drawings and a thin line is shown running along it but with much more fluctuation left and right on the first two, a large spike right on the third and a large bump way right on the fourth. Above these there are two labels. The first labels is inside a bracket that covers the first three, and the last label is for the last drawing. Below is a list of sources.]

Limits of this data:

Short warming or cooling spikes might be “smoothed out” by these reconstructions but only if they’re small or brief enough.

Possible Unlikely

Reconstructions are from Shakun (2012) and Marcott (2013), scaled to Annan + Hargreaves (2013) estimate for the last glacial period.

15500 BCE

In what is now France, humans paint murals on the walls of the Lascaux caves

[Hairy paints three animals, two with horns, and two humans, Cueball holding hand with Hairy who has a spear. On the other side of the central line Megan writes three letters, the last of which is reversed.]

NIИ

15000 BCE

Ice sheets around Alaska shrink, exposing a land bridge between Asia and North America

[From around the bottom if this section and down to 11500 BCE the dotted curve moved steadily to the right towards warmed temperature peaking close to -1.5°C. Before this the temperature had not moved much away from that at the start.]

14500 BCE

[Cueball walks right looking back at the graph behind him. Megan walks in front of him pointing further right.]

Cueball: Cool.

Humans reach North America.

14000 BCE

The edge of the ice withdraws from New York City and retreats North.

[A large glacier front speaks in a speech bubble with an arrow pointing at it. Behind is there are four peaks in the horizon and in front of it three small melting pools and some rocks on the ground.]

Glacier: That’s it! I’m moving to Canada!

13500 BCE

Humans domesticate dogs

(Date uncertain, may be much earlier)

[Megan and Cueball is watching a wolf looking at them.]

Megan: Okay, you can live in our homes and we’ll feed you, but we’ll still get mad f you poop on the floor.

Wolf: Deal.

Cueball: And we get to breed you to be tiny and dress you in little costumes.

Wolf: …Wait.

13000 BCE

[Randall did not use the normal spelling for Woolly Rhino, but this is an accepted alternative spelling:]

Wooly Rhino goes extinct

Oregon is scoured by huge floods as glacial dams burst and lakes of meltwater flow to the sea

12500 BCE

Ice sheets withdraw from Chicago

12000 BCE

Humans settle Abu Hureyra in Syria

11500 BCE

[An arrow on the left side of the dotted curve is pointing down along the dotted curve and to the left indicate temperature is declining again, meaning the dotted curve now moves left to colder temperatures. This only continues until 10500 BCE. It is only the second time something is noted on the left side after Megan at 16000 BCE]

Temperatures start to decline, mainly in the Northern hemisphere

This may be caused by changes in ocean circulation due to the floods of cold fresh meltwater flowing into the Atlantic as the North American ice sheet melts.

This cooler period is called the Younger Dryas

11000 BCE

[This is the first text to the left of the dotted curve:]

Humans reach Argentina

10500 BCE

[An arrow pointing down along the right side of the dotted curve and to the right indicate temperature is increasing again, meaning the dotted curve now moves right to hotter temperatures. This continues until 8000 BCE where it levels out just above 0°C.]

Warming resumes

Human settlements at Jericho

10000 BCE

First development of farming

9500 BCE

Saber-toothed cat goes extinct

[To the left:]

Horses disappear from North America

9000 BCE

[To the left, Randall spelled Pokémon wrong:]

Last North American Pokemon go extinct

[Cueball with a speak and Megan is looking up at this last “fact”.]

Megan: That is not a real fact.

Temperatures reach modern levels

Rising seas cut off the land bridge between North America and Asia

Cattle domesticated

8500 BCE

Ice sheets retreat across the Canadian border

Temperatures start to level out slightly above 1961-1990 levels

8000 BCE

[The above sentence breaks over the 8000 BCE line. From here a maximum in temperature on the chart is reached at 0.5°C which will not be overtaken until 2000 CE. It stays almost constant here until 5000 BCE where a slight cooling begins.]

7500 BCE

[To the left:]

This warm, stable period is called the Holocene Climate Optimum

[To the left:]

Jiahu settled in China

7000 BCE

Final collapse of the North American ice sheet leads to rapid 2-4m sea level rise…

[A small arrow points down and left to the right of the dotted curve. There is a small decrease in temperature but it is very small and would have been missed without the arrow and label.]

…And a period of cooling in the Northern hemisphere

6500 BCE

[To the left:]

As seas rise to near their modern levels, Britain is cut off from mainland Europe

6000 BCE

Humans develop copper metalworking

5500 BCE

[To the left:]

Massive volcanic eruption in Oregon creates crater lake

Gold metalworking

5000 BCE

[To the left:]

Invention of the wheel

[To the left. To the right of the dotted curve is an arrow pointing down and slightly left. From here temperature decreases very slowly but steadily from 0.5°C until 1000 BCE where a stable plateau is reached around 0°C.]

Earth begins to cool slowly mainly due to regular cycles in its orbit

4500 BCE

[To the left:]

Proto-Indo-European language develops

[To the right of the curve Ponytail holds up a hand towards Cueball.]

Ponytail: Let’s make our language heavily inflected, so future students have to memorize a zillion verb endings!

Cueball: Okay!

[To the left:]

Permanent settlements in the fertile crescent

4000 BCE

Horses domesticated

[To the left:]

Minoan culture arises on Crete

3500 BCE

Egyptian mummification

Rise of the Indus Valley civilization

[To the left:]

Invention of writing in Sumer “prehistory” ends, “history” begins

Earliest human whose name we know

(Pharaoh Iry-Hor in Egypt)

3000 BCE

Three Sovereigns and five emperors period in China

Gilgamesh

[To the left:]

Imhotep

Mayan culture emerges

[To the left:]

Great Pyramid constructed

2500 BCE

Corded Ware culture in Europe

[To the left of the curve two rock musicians with long hair and electrical guitars are standing on either side of a small gate made of three slabs of stone, one on top of the other two standing stones.]

Stonehenge completed

Chariots developed

2000 BCE

[To the left:]

Alphabetic writing developed in Egypt

Last mammoths on a tiny Siberian island go extinct

[To the left:]

Minoan eruption

1500 BCE

[To the left:]

Iron smelting

Olmec civilization develops in Central America

[A Trojan horse with two Cueball-like guys in front and a third standing on its back. Its back is at three Cueball’s height and its head rises to the level of the Cueball on its back. It stands on a platform with four wheel on the visible side. There is text on the horse]

Setting of the Iliad and the Odyssey

Text on horse: Not a trap

[To the left:]

Invasion of the Sea peoples*

* A real thing

Polynesians explore the Pacific Ocean

1000 BCE

[From 1000 BBC to 1000 CE the temperature is stable and very close to 0°C.]

[To the left:]

Solomon

Illiad [sic] and Odyssey composed

[To the left:]

Rise of Greek city-states

Neo-Assyrian empire

[To the left:]

First Olympics

Zapotec writing in modern Mexico

[To the left:]

Confucius

500 BCE

[To the left:]

The stuff in the 300 (film)|movie 300, but regular speed and with more clothing

Buddha

Nazca Lines

[To the left:]

Alexander the Great

[To the left:]

Mayan hieroglyphics

Ashoka the Great

[To the left:]

Paper invented

[To the left:]

Asterix

Teotihuacán metropolis

[To the left:]

Julius Caesar

[At the year 0, there is instead two numbers for each of the two scales before and after Christ:]

1 BCE

1 CE

[To the left:]

Roman Empire

Jesus

[To the left and erupting volcano.]

Pompeii

Three Kingdoms period

[To the left:]

Gupta empire

[To the left:]

Various groups take turns sacking Rome

Attila the Hun

500 CE

Muhammad

[To the left:]

Tang Dynasty

[An arrow to the right of the dotted curve pointing down, takes a swing far out from the curve and then bends back again. The text label next to it breaks into the next 500 period. The dotted curve stays stable at 0°C along this arrow.]

Medieval warm period in Europe and some northern regions (too regional to affect the global average much)

[To the left:]

Leif Eriksson

1000 CE

[The dotted curve moves to the left towards lower temperature reaching a minimum around 1650 of about -0.6°C at the Little Ice Age.]

[To the left a drawing of a compass with needle pointing the black end towards north east. There are labels for the four main directions and a label next to it:]

N

W E

S

Magnetic compass navigation

[To the left:]

Ghengis [sic] Khan

Zheng He’s fleet explores Asia and Africa

[To the left:]

Aztec Alliance

[To the left:]

Printing press

[To the left:]

Columbus

1500 CE

European Renaissance

[To the left:]

Shakespeare

1600

[To the left:]

Newton

[To the right of the dotted curve there is an arrow pointing down that makes a swing in towards the curve and then back out again. At -0.6°C this is the coldest it has been since 9500 BCE. It is labeled:]

”Little Ice Age”

1700

Steam engines

[To the left:]

Unites States Independence

1800

Industrial Revolution

[To the left:]

Telegraphs

[After this the dotted curve becomes solid.]

1900

[To the left, and on the line for 1900:]

Airplanes

[To the left:]

World Wars

[The solid line takes a step to the right close to 0°C. Over the rest of the 1900s it moves closer to 0°C crossing it before 2000 where it almost reaches the maximum temperature of 0.5 °C from earlier in 8000 BCE.]

Fossil fuel CO₂ emissions start rapidly increasing

[To the left:]

Nuclear weapons

[To the left:]

Internet

2000

Northwest Passage opens

[From here to present day the solid line increases rapidly and in 2016 present day is almost reaches 1°C, with about 0.8°C.]

2016

[To the left on the line for 2016:]

Present day

[From here the curve once again becomes dotted as this is the future. After one dot it splits in two and after the first two dots another split between them occurs forming three possible future dotted curves. The first curve bending down before the others, and thus to the right of the other two reaches about 1.2°C and then goes straight down and stops at the 2100 line. An arrow points to it from the left and a label is written patly before and the rest after the 2100 line to the left of the curve:]

Best-case scenario assuming immediate massive action to limit emissions

2100

[The middle curve bends a little down after reaching 1.3°C and then continues this path reaching 2°C in 2100. An arrow point from below to it and a label is written below the curve and below 2100 line:]

Optimistic scenario

[The last line continues along the path from the last 16 years of the solid line reaching 4.2°C at 2100, almost as far on the other side of 0°C in 150 years as it took 14000 years to move from the other side from the start of the chart. Another arrow point to this from below with a label below the curve and below 2100 line:]

Current Path

Trivia

• There have been several large drawings in the history of xkcd, some of which are bigger than this one (for instance 1110: Click and Drag).
  • Among those that can be viewed in one go, without downloading a larger file or moving around, this is by far the longest.
• The timeline starts at 20,000 BCE (22,000 years ago) and ends at 2100 CE, thus covering 22,100 years.
• There are several spelling mistakes.
  • Most obvious is the second time Randall wrote the word "Iliad," because he just spelled it correctly at 1500 BCE and then spelled it Illiad at 1000 BCE with two Ls.
  • Attila the Hun was initially misspelt Atilla the Hun with one T and two Ls, but this was corrected at some point.
  • Genghis Khan is misspelt as Ghengis Khan (a common error).
  • Pokémon is spelled Pokemon, but then again, that is not so strange for Randall (see 1647: Diacritics). Despite that, he usually spells it correctly, as in 1705: Pokémon Go.
  • Note that the fact that woolly rhinoceros becomes Wooly rhino with only one l is not a spelling mistake but an alternative spelling of the word.
• The following notable facts are absent
  • 1850: methodical temperature record begins. However, this fact is indirectly indicated when the temperature curve becomes solid around 1850 and until present day.
  • The entire swing period between 20 and 200 thousand years prior to now would depict temperature swings with increasing frequency and amplitude (ref geological record). But of course, this could not be included in a comic that only goes back to 20,000 BCE.
  • During much of the 300 million years prior to that, the Earth was significantly warmer than now. However, the data's temporal precision decreases with age; seemingly abrupt changes millions of years ago might have happened over centuries or millennia. Hence, the older data is not usable to compare rates of change.

Popularity of comic

This comic received attention from a much broader audience than most xkcd comics. It was discussed admiringly by news sites such as Popular Science, Reason, Slate, Smithsonian, Forbes, Vox, NPR, Quartz, Science Alert and Climate Central. It was promoted by famous individuals such as Elon Musk and even twitted by the UN council on Climate Change, and obviously hated on by vocal climate change deniers and cranks such as Anthony Watts^debunked and Joanne Nova^debunked

For more rationalist critiques of this chart not driven by the agenda of pushing pseudoscientific beliefs which are against the worldwide consensus, see the following articles:

• Climate Change, Explained in One Simple Comic
• Send Around This XKCD Climate Change Web Cartoon, But Really Look at It First
• Epic Climate Cartoon Goes Viral, But It Has One Key Problem
• Everybody Always Gets This Wrong, Even Smart People

Due to the increased level of interest in this comic, Randall made some changes to the site and the week's release schedule:

• xkcd normally releases new comics on Monday, Wednesday, and Friday. This comic was released on Monday, but given the amount of attention it was receiving, Randall decided to release the next comic 1733: Solar Spectrum on Thursday.
• He replaced the default header of xkcd.com with an explanatory note, which remained until noon (EST) on Thursday:
  

Note: Since a lot of new people are here looking for this chart today, I'll be posting Wednesday's comic on Thursday instead.

• On the day of the release of this comic, the warning that had been on the site for over 10 years, along with the previous footnote, were both removed. While a new footnote was added 22 days later, the warning never came back.
• On March 1, 2019, this comic became one of the six footer comics featured in the bottom segment of xkcd.com.

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Discussion

As this is a controversial topic, there may be several denialist trolls lurking below. Beware of feeding them.

Well, never mind then. Oh well. -- JayRulesXKCD (talk) 1:02, 12 September 2016

I acknowledge that the picture is WAY too long, so I added a "skip to explanation" bar, to speed things up. --JayRulesXKCD (talk) 17:32, 12 September 2016 (UTC)

Thank you Run, you clever boy (talk)

Is it just me or does the picture not render all the way down in full resolution on firefox? I found it worked on Chrome and explorer... And Wauw, just after I had created the new Category:Climate change... Was also just watched a QandA program yesterday where Brian Cox tried to convince some Australian politician about global warming, but the other one just cried conspiracy... Will take some time to make this one complete I guess? Great ;-) --Kynde (talk) 17:53, 12 September 2016 (UTC)

That's the thing with this kind of stuff. It takes a LONG time to make it just right. --JayRulesXKCD (talk) 19:08, 12 September 2016 (UTC)

Please delete the ridiculous trivia

• The colors used to represent temperature vary from blue (the perceived hue of a black body at 20000K) to pale red (perceived at 2200K).

108.162.221.139 19:44, 12 September 2016 (UTC)

Of course you can pretty much ignore the part of the diagram that is in dotted line, you can't rely on that data. 108.162.246.119 20:40, 12 September 2016 (UTC)

Note that even if we ignore the extrapolated future, the warming in the past century is already a vastly more abrupt climate shift than anything that happened in the preceding 219 centuries. - Frankie (talk) 21:15, 12 September 2016 (UTC)

Actually we don't know what the shifts were on that scale in the past. The dotted line before modern measurement is a very limited estimate. We have no idea what the year to year changes were in the past, at best we can work out an average. I am reminded of a house mouse(life span of about 1 year) looking at the leaves fall from the tress and saying "Surely this is the end of the world". 108.162.246.119 14:44, 13 September 2016 (UTC)

Randall explicitly addresses your specious complaint at 15900 BCE. Year-to-year fluctuations are not the same as the current century-long surge. Either show scientific evidence or go away, Mr Troll from Seattle Cloudflare. - Frankie (talk) 16:11, 13 September 2016 (UTC)

I should have known better to enter into a religious debate on the internet. 108.162.246.119 00:17, 14 September 2016 (UTC)

No it is not that which is the problem, but that you try to disqualify the data without even bothering to look through them. Aa mentioned Randall tries to let us know that such a high fluctuation as we have in these last 100 years would not be hidden in the old data. As mentioned by Fankie this is explained between 16000 and 15500 BCE... --Kynde (talk) 14:30, 14 September 2016 (UTC)

I refuse to debate a matter of faith with you. Note that 15500-16000 is 500 years, perhaps when we have 500 years of accurate temperature measurements we will know more. 108.162.246.119 03:54, 15 September 2016 (UTC)

I'm not surprised that you can't even read a chart. 16000-15500 BCE is where the explanation is placed on the chart. The fluctuations he shows that would not register are small fluctuations over a decade or two. A fluctuation of a century would "unlikely" be smoothed out. The examples are even drawn to scale... 3rd grade level stuff here. 108.162.221.145 17:28, 16 September 2016 (UTC)

Why even bring your faith into this? 108.162.212.92 16:29, 15 September 2016 (UTC)

I call Troll. Talking about the significance of where the subchart/Legend/footnote lies? Like what years it's next to actually has any significance? Either he's too dim to actually look, or he's trolling. The standard recommendation is "Don't feed the trolls". :) - NiceGuy1 108.162.218.118 02:55, 16 September 2016 (UTC) I finally signed up! This comment is mine. (Heh, seems I was right, looks like the troll stopped after I called him out) :) NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

Frankie, funny how the nonaveraged plots [and even the averaged plot] linked to below invalidates Randall's plot, "Hence the comparison is not comparing like with like and is scientifically invalid." The temperature rate between 1859 (coincident with America's discovery of petroleum and the Carrington Event) and today does not exceed that within the past 2,000, 20,000, or 100,000s of years. The present surge (the tip of the "hockey stick") concerns not 100 years but almost 40 years (36 years in Randall's plot) which does not successfully meet the three fluctuation disclaimers. As mentioned in the Wikimedia discussion the temperature resolution is about 300 years; therefore it should take another 150 years to see whether this slope corrects itself. Lysdexia (talk) 13:04, 5 January 2019 (UTC)

Have you read the referenced papers? Well you fit well with the people he refers to between the two lines at the top. ;-) We are heading for troublesome times :-( 164: Playing Devil's Advocate to Win... --Kynde (talk) 21:22, 12 September 2016 (UTC)

• the use unqualified of the words "still many people" is exactly the kind of weasely nonsense that this comic is designed to refute. there are "still many people" who claim the earth is flat, that they have been abducted by aliens, or that the MMR jab made their children autistic. those people are deluded or insincere. the difference with deniers of climate change is that there are in their ranks scientists who are clear-sighted but who have decided that funding at any price is better than none. this site should be better than that. --141.101.98.84

You're absolutely right, the ranks of climate deniers do indeed include a few scientists willing to sell their voices to the highest bidder (e.g. http://www.polluterwatch.com/heartland-institute ). But is that what you meant to say? - Frankie (talk) 11:50, 13 September 2016 (UTC)

that the wording be changed to reflect that. --141.101.98.84 11:59, 13 September 2016 (UTC)

For a large post like this, it's a wonder that we can all keep up and edit something like this all at once. Wow. --JayRulesXKCD (talk) 11:56, 13 September 2016 (UTC)

Also, anyone else notice that this was a top trending post on Facebook last night? I don't know if I could call it a milestone but it's still pretty cool. And WE edited it! :D --JayRulesXKCD (talk) 12:06, 13 September 2016 (UTC)

Very interesting, so it was explain xkcd and not xkcd that where the top trending post? Could you post a link to where you found this out? --Kynde (talk) 20:15, 13 September 2016 (UTC)

I can see you are right from the fact that Randall has chosen to postpone his next comic in order to keep this one on the front page for all the new visitors as has now been noted in the explanation and in the trivia section. --Kynde (talk) 14:30, 14 September 2016 (UTC)

Maybe someone should add the fact that the transcript may be a reference to oxidation?Transuranium (talk) 19:21, 13 September 2016 (UTC)Transuranium

I think you mean the "title text" not the transcript? And that you refer to the recent comic 1693: Oxidation which is indeed referened in the title text, then that has been written at the bottom of the main explanation and has been there already since the 12th edit less than 1½ hour after the comic came out... --Kynde (talk) 20:02, 13 September 2016 (UTC)

Is nobody else having a problem seeing the comic? Both here and on XKCD I get an "Image not found" icon, a blue question mark. I thought maybe this was an interactive comic that doesn't work on my iPad (like that garden thing, though that did nothing on my computer either). If I tap it on XKCD nothing happens, here it leads to the picture's Wiki page - also with the question mark - which says it's a PNG, which I know this iPad can show. It's 11pm EST, maybe night maintenance on XKCD? Or the file got renamed without updating the sites? - NiceGuy1 162.158.126.227 03:12, 14 September 2016 (UTC) I finally signed up! This comment is mine. NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

I had trouble seeing it on my own PC using Firefox but not the other browsers I have. See my early comment above. I guess the file is too big for your iPad as it is a very huge file. I tried to download it but it failed. --Kynde (talk) 14:07, 14 September 2016 (UTC)

It's weird that I got what is clearly an "Image not found" icon, though. Maybe my 1st Gen iPad's Safari saw the file, decided "No way I'm loading that!"(or "that size can't be right", LOL!) and chose to show the error icon instead. When I force the issue, by going directly to the image URL listed on XKCD, the first time Safari crashed rather than load the image (but it crashes on a regular basis, so that didn't deter me), the second time it crashed, the third time it actually loaded, and I was able to see it. After seeing mentions here of spelling errors (though I have to disagree on "Pokemon", generally only people connected to the show bother with the accent. Like how I'm the only one who spells Hallowe'en correctly, with the apostrophe), I thought maybe the comic was taken down to correct it, but guess not. LOL! - NiceGuy1 108.162.218.239 20:54, 14 September 2016 (UTC) So's this! NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

I feel that the missing bottom axis is a usability problem, so I fixed it. See it here. Hananc (talk) 10:42, 14 September 2016 (UTC)

Nice but I'm sure it was on purpose to indicate that time continues down,as well as a possible even worse temperature change. As shown in the previous global warming comic 1379 Earth has been 8 degree hotter than now... And apart from the last small segment (albeit a very important one) you either remember that white is normal and bluer is colder redder is warmer or else you cannot use the chart in between the top and bottom, and since this is the longest xkcd comic so far it would be a shame. :-) --Kynde (talk) 14:07, 14 September 2016 (UTC)

Okay, now that I've managed to SEE the damn thing, I have a question. There's no mention of why this is using "BCE" and "CE" instead of the standard "BC" and "AD", never mind what these stand for (thinking and thinking about it, my guess is "Before Christ Era" and "Christ Era"). This is the kind of thing that should be mentioned on ExplainXKCD, LOL! Fun fact: when I searched this page for "BCE", to confirm it wasn't explained, I got "Over 100 matches". :) Anyway, I figure maybe those are currently accepted scientific terminology, especially since "AD" is Latin, unlike "BC", but the average person still uses BC and AD. In fact, I think this is the first time I've ever seen BCE and CE (unless it's been on XKCD before and I just dismissed it as a typo or something. This time there are WAY too many for it to be a mistake every time, including here in the explanation!) - NiceGuy1108.162.218.239 21:20, 14 September 2016 (UTC) I finally signed up! This comment is mine. NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

It's "Before Common Era" and "Common Era", an alternative to BC/AD. Pretty common alternative, though I don't know why off-hand - probably to remove the religious connotations of "Christ" and "Year of our Lord". --108.162.215.236 23:23, 14 September 2016 (UTC)

Because they're the standards in the scientific community. The guy above assumed his way is standard, but that's inaccurate. 108.162.212.92 00:26, 15 September 2016 (UTC)

I assume nothing. My statements are completely accurate. I OBSERVE it is the standard, the only standard anybody (else) seems to use. BC/AD is the "standard" because it is standard practice to use it. For good reason, since I would estimate just about everybody knows what it means, while I am sure I am in the majority in having never heard BCE/CE. It is also not "my" way, I made no choice here, it is the established convention, it is the way accepted and adopted by society. While I would normally be more inclined towards terminology devoid of religion (as seems to be the point here, now that someone kindly clarified these acronyms for me), I feel this would be a losing fight, one it would be foolish to attempt, the classic terminology is too ingrained in society. Sorry. - NiceGuy1 108.162.218.118 02:44, 16 September 2016 (UTC) Also mine! NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

For the convenience of archeologists working in the Middle East. Wwoods (talk) 01:16, 15 September 2016 (UTC)

Thank you! Yes, it sounds to me like the point would be to remove the religious aspect. Personally, I don't really mind the religious terminology, I just see it as historical, keeping a record of where the names and numbering came from. - NiceGuy1 108.162.218.118 02:44, 16 September 2016 (UTC) Also mine! NiceGuy1 (talk) 11:03, 9 June 2017 (UTC)

Well, "it is the established convention" isn't quite correct either.. checking Wikipedia suggests to me that it's a large argument, and that people that aren't Christian or Muslim (i.e. just under half of all people) really never used the AD/BC notation in the first place. BCE/CE appears to have originated in Jewish European communities some point before the 1700s. 172.70.100.192 20:12, 5 April 2023 (UTC)

What this comic doesn't show is what kind of changes occurred in the previous interglacial period as opposed to the current one. Since the current one is not yet over there could still be a stage of an interglacial with rapid temperature rise which we are only now reaching, but has happened in previous interglacial periods. 108.162.219.54 02:32, 15 September 2016 (UTC)

Check out this 400k year comparison of temperature variations from two ice core projects in Antarctica, Lake Vostok and EPICA. https://commons.wikimedia.org/wiki/File:Ice_Age_Temperature.png (Note that Randall's timeline matches up pretty well with the last 20k years on the far right of the graph) 162.158.69.98 13:23, 16 September 2016 (UTC)

I think this would be first time where I see global thermonuclear war described as "best case scenario". There was and still is lot of discussion about how much is current warming caused by humans, but that's not important. Important question is "can we stop it?" and the answer is "not without literally billions of dead" (and even that might not suffice). Any money currently used for most plans to reduce CO2 (which usually fails to reduce CO2, not speaking about global warming, but succeed in their main goal, which is moving the money into pockets of their proponents) would be better spent on ADAPTING to the change. Only plans for reducing CO2 actually worth doing are the ones related to stopping burning fossil fuels, because we will soon need fossil fuels to make food (and other stuff) from. Oh, and also stop burning FOOD. So we should replace fossil fuel power plants with only viable alternative - NUCLEAR. So called renewable power sources like solar are good addition, but doesn't scale to the amount of power and stability we need. -- Hkmaly (talk) 14:12, 15 September 2016 (UTC)

So disappointing to see that Randall Hitler Munroe subscribes to the obviously false "global warming" religion. He should know better. 172.68.55.83 00:11, 16 September 2016 (UTC)

Troll troll trolly trolly troll troll troll 162.158.214.217 03:07, 16 September 2016 (UTC)

https://www.explainxkcd.com/wiki/index.php/261:_Regarding_Mussolini 141.101.98.126 (talk) (please sign your comments with ~~~~)

I understand the concept behind this comic, but why doesn't the graph include atmospheric CO2, sulfur aerosols, and solar 10.7cm radio flux for comparison? Also, for the person who suggested we look at previous interglacial periods, I may be wrong, but I believe a lot of that data comes from ice cores, that would make it hard to look at time periods before the present ice sheets existed. IIRC, there were periods not too long ago (geologically speaking) where Antarctica was covered in lakes, tundra, and sparse forests instead of ice sheets.172.68.65.127 05:08, 16 September 2016 (UTC)

The jump of 0.5 degrees from 2000 to 2016 has been shown to be false. It exists because "scientists" went back and changed (or "seasonally adjusted") their data to fit their preconceived conclusions. Just look at Al Gore's 'Inconvenient [Non]Truth', pretty much every doomsday scenario has not occurred. I expect better of XKCD.173.245.48.77 20:58, 15 September 2016 (UTC)

It would be very nice if they wouldn't spread climate change misinformation. 22,000 year Time line [20,000 BC to 2000 AD] versus 2.5 to 3 billion years of Evolution on a 4 Billion year old Planet

22,000 / 2,500,000,000 = 0.0000088 Using 0.00088 % of Evolutionary History do decide what the weather is supposed to look like. Now an atmospheric history lesson - Cambrian Oxygen 12.5% - Carbon Dioxide 0.45% - Average Temp. 21 °C - sea level 30 - 90 meters - Ordovician Oxygen 13.5% - Carbon Dioxide 0.42% - Average Temp. 16 °C - sea level 180 - 220 - 140 meters - Silurian Oxygen 14% - Carbon Dioxide 0.45% - Average Temp. 17 °C - sea level 180 meters - Devonian Oxygen 15% - Carbon Dioxide 0.22% - Average Temp. 20 °C - sea level 189 - 120 meters - Carboniferous Oxygen 32.5% - Carbon Dioxide 0.08% - Average Temp. 14 °C - sea level 120 - 0 - 80 meters - Permian Oxygen 23% - Carbon Dioxide 0.09% - Average Temp. 16 °C - sea level 60 - 0 - -20 meters - Triassic Oxygen 16% - Carbon Dioxide 0.1750% - Average Temp. 17 °C - sea level 0 meters - Jurassic Oxygen 26% - Carbon Dioxide 0.1950% - Average Temp. 16.5 °C - Cretaceous Oxygen 30% - Carbon Dioxide 0.17% - Average Temp. 18 °C - Paleogene Oxygen 26% - Carbon Dioxide 0.05% - Average Temp. 18 °C - Neogene Oxygen 21.5% - Carbon Dioxide 0.028% - Average Temp. 14 °C - Current Oxygen 20.9% - Carbon Dioxide 0.039% - Average Temp. 15 °C

As you can see an atmosphere when healthy should have Oxygen 25 - 32% Carbon dioxide 0.1 - 0.15% Average Temperature 14 - 18 °C Sea level 60 - 180 meters and there should be no polar ice caps

our sea level is at extinction levels our carbon dioxide is almost too low for plants to survive and our oxygen level is almost suffocatingly low

Less Carbon Dioxide means less Plants Less plants means less Oxygen Less Oxygen means less Life108.162.246.112 07:24, 17 September 2016 (UTC)

I think the point of comics is that while there were changes in temperature before, they were never this rapid. Although I wouldn't be sure about THAT either ... granted, the previous rapid changes were accompanied with mass extinction ... -- Hkmaly (talk) 15:16, 17 September 2016 (UTC)

Yeah, the long sample intervals and best fit curves from pre-industrial temperature estimates tend to smooth out any rapid changes that may have occurred over the time period (Think of an ECG/EKG that took a single instantaneuos microvolt sample once every 15 minutes of your life from birth to death, the resulting deflection graph would not look like anything like a normal heart rhythm, but it could be interpreted as the average electrical activity of your heart over the course of a lifetime). It's true that the rapid climate shifts we are able see in geological records usually coincide with things like supervolcano eruptions and asteroid impacts. But those shifts are usually to the negative end from the nuclear winter effect. Idea for reversing global warming without affecting CO2 emissions, just send a couple of hypervelocity rods or a gravity-tractored asteroid into a dormant supervolcano caldera every few years and... instant winter. 173.245.51.75 02:38, 18 September 2016 (UTC)

Very interesting and important work.

Actually.... Solomon and Jesus are not historical figures. Outside the Old and the New Testament, there is no archaeological or other evidence for their existence. I suppose, Jesus has played a significant role in history. So, you may be justified to add an entry saying something like "Date that religious traditions hold as the date of birth of Jesus."

Then, if you mention, say, Shakespeare, then you should also mention the estimated composition of the Bible, an event with more important historical influences.

Roman empire was continued for more than thousand years (Eastern Roman Empire, today reffered as Byzantium).

Current scholarly wisdom is that the Homeric epics, (the Iliad and the Odussey) were composed at the second half of the 8th century, perhaps around 720 BCE. Konstantas (talk) 05:14, 19 September 2016 (UTC)

Except that no historical evidence has ever contradicted the Bible, and many archaeological discoveries were predicted by it.

According to proper scientific analysis, it is the most accurate historical document(s) in existence. 172.70.51.173 02:19, 11 August 2021 (UTC) Darryl

I wonder if it is getting to be a good time to make a followup, showing the further warming over the last several years and the rightward movement of the 'if we...' paths. 21-Feb-2020

~5000 BCE is higher slightly lower then now User:Squishmallow fan (talk) 01:47, 10 February 2011 2024 (UTC)

Actual best-case scenario

The actual best-case scenario is far better than Randall's depiction; please see. However, the URLs below in that linked Imgur gallery's first caption were rendered unclickable, probably for spam protection measures, so I reproduce them here:

Actual "best-case scenario assuming immediate massive action to limit emissions"

From https://www.theguardian.com/environment/2013/apr/17/why-cant-we-give-up-fossil-fuels

What will it take to get to this scenario? https://www.solveforx.com/explorations/foghorn/ with http://freenights.txu.com/ and http://co2-chemistry.eu/ for ocean carbonate-sourced plastic composite structural lumber allowing reforestation.

JSalsman (talk) 15:02, 22 September 2016 (UTC)

First, the Guardian is a newspaper, not a science journal. Second, that article is from 2013, before the latest upsurge. Third, even ignoring those things, the article doesn't say what you claim it does. The single most optimistic sentence I see is "If we are lucky, the impact of burning all that oil, coal and gas could turn out to be at the less severe end of the plausible spectrum." The rest of the article is quite pessimistic, such as "it is overwhelmingly likely that we would shoot well past 2C and towards 3C or even 4C of warming."

Please post exact quotes where your links talk about a better scenario. Please do not post URLs and expect us to figure out what you mean. You are making the claim, the burden of proof is on you. - Frankie (talk) 17:13, 5 October 2016 (UTC)

How do you expect me to quote from the graphs? I can't upload images, maybe I need more edits. Please ask any questions you like. JSalsman (talk) 06:14, 1 November 2016 (UTC)

please explain how the Guardian graph you posted on imgur has to do with better scenarios. The title: "Cuts required for 50% chance of not exceeding 2°C". The footer: "CO2 emissions since 1850 (red); exponential growth (blue); cuts to hit climate target (dashed)." It says that in order to possibly reach the "optimistic" +2° scenario (Randall's 2nd line, not the 1st one), we would need to cut anthropogenic CO2 to about 1/10th our current level, which is ridiculously unlikely to happen. The other graphs you posted are just hypothetical extrapolations about energy production that, even if they're trustworthy (which I doubt) don't reference any climate scenarios at all, much less ones better than the timeline. Until you can post a cogent explanation, I will assume you are trolling and undo your edits. - Frankie (talk) 17:19, 2 November 2016 (UTC)

If you extrapolate [1] to 2023-4, renewables dominate, right? Wind has been in competitive equilibrium with coal since 1995, and solar hit grid parity early this year and is expected to continue falling in price about as fast at least until 2035. Is there any reason to believe fossil fuels won't be abandoned by 2030? JSalsman (talk) 02:01, 3 November 2016 (UTC)

Exactly zero words in your explanation discuss how the linked graphs show the existence of a better scenario than the ones listed in the timeline. Your very first graph, from the Guardian, explicitly says 50% chance of not exceeding 2°C, which is Randall's middle scenario. That means it supports exactly what Randall is saying. It says absolutely nothing about a scenario better than the "best case" timeline. - Frankie (talk) 21:06, 3 November 2016 (UTC)

Do you understand the words that I am saying? The words that I have been saying from the start of this conversation? I don't f***ing care about pie in the sky energy projects. Even if your energy claims are correct, they don't say a single d**n thing about beating the +1.2°C curve.. - Frankie (talk) 21:13, 3 November 2016 (UTC)

I apologize. I confused the +1° mark with +2°. The labels are so far above at the top. You are correct. I will forgo uploading the graphs as we are now in agreement. JSalsman (talk) 22:23, 3 November 2016 (UTC)

Joanne Nova

• http://www.skepticalscience.com/How-Jo-Nova-doesnt-get-past-climate-change.html
• http://blog.hotwhopper.com/2014/03/almost-everything-we-know-about-fake.html
• http://skeptico.blogs.com/skeptico/2009/02/global-warming-denial.html
• http://www.desmogblog.com/joanne-nova-climate-skeptics-handbook
• http://rationalwiki.org/wiki/Joanne_Nova
• http://itsnotnova.wordpress.com/

- Frankie (talk) 23:41, 8 October 2016 (UTC)

Interesting Ways to Look at it.

Hey, I had a great time scrolling down and watching the earth heat up :).108.162.245.115 19:47, 17 October 2016 (UTC)

ICYMI, Cato provides an IPCC MAGICC climate model simulator for anyone to examine. FWIW, I side with Bjorn Lomborg, who famously champions a middle way in climate science for the sake of downtrodden peoples around the world. Should we reconsider this explanation in this light? Run, you clever boy (talk)

Fact checking the chart on Stack Exchange

I posted a question on Earth Sciences Stack Exchange about how the Younger Dryas fits into this comic: http://earthscience.stackexchange.com/q/9103/6973

There was also an existing question about the chart's general accuracy: http://earthscience.stackexchange.com/q/8746/6973

--Aaron Rotenberg (talk) 02:53, 14 November 2016 (UTC)

Translation of the Morse code message

The translation of the explanation in "Telegraph", written in Morse code, is: "Now, the mother of Samuel Morse always sent the lad out on a horse." Agusbou2015 (talk) 15:56, 28 May 2017 (UTC)

"Sad comics"

...So after the election of a climate change denier later in the year of this comic's release, several sad comics have been posted. Some of the reason could be that Randall no longer believes that even his worst fears (as expressed by the current path at the bottom) will hold up, when USA gets a president, who will on purpose act in a way that scientist claims will make the temperature rise even more. See more here.

I've mentioned this on the talk page for 2137: Text Entry, but I'll reiterate it here: this observation is not factual, not relevant to the explanation, and does not belong in the description of this comic. If you read it in context, you will see that it is also a non-sequitur, clumsily inserted after one or two factual sentences - it does not follow from anything prior in the discussion. It is poorly expressed and the point being made is unclear in any case.

While the user doing this may well have honest intentions, they are simply defacing articles with their own anti-Trump projections and spamming a link to their own, misleadingly-titled page (Sad comics) which has no clear meaning or explanatory value. Hawthorn (talk) 16:38, 26 April 2019 (UTC)

I have removed the offending paragraph. Hawthorn (talk) 21:20, 26 May 2019 (UTC)

The industrial revolution and its consequences have been a disaster for the human race, and this graph shows it.172.68.50.19

I agree that it has probably been a disaster (certainly a gamechanger) for the ecosystems, causing changes and challenges that are so much different to what everything else woupd have experienced without such a heavy hand of humans upon the planet. But for "the human race",vI wonder if there'd be so many billions of us if industrial (and post-malthusian) developments had never arisen. By a simplistic numbers game, we are (currently) ranking higher than it seems likely a more nature-tuned alternative 20th/21st-Century would have looked like.

A higher population doesn't guarantee "success", I know, and only hindsight will say for sure whether unprecedented growth leads to unprecedented decline in the same 'scoring' value (indicating that it isn't the best score to use long-term), but some would say this. (Not me, I'm just philosophising here.)

Beyond this, if only by entering the Industrial Age do we have the ability to foresee and forestall some asteroid impact..? Perhaps then the (somewhat damaged) ecosystem actually lives on 'better' (subjectively) from our flawed attempt to industrially improve the planet, to our own ends, the rediscovery of ecoprinciples and then the successful aversion of another planet-killing asteroid (or at least the development of "arks" to let the current biodiversity to ride out the problem, here or elsewhere). Unless you have the view that the post-now changes (like the post-dinosaur/etc changes) are themselves higher scoring on the nature-scale. (But then if an unaverted asteroid is equal to a prior one, then is our polluion of the world equal to when earlier organisms started to fill the atmosphere with deadly oxygen and convert the world to an entirely different phase of life?)

What can definitely be said is that we're doing something, but expect some people (who aren't actually full-on deniers) to suggest that it isn't really a bad thing. Which it probably is, of course. Or at least not the best thing, and there's probably better outcomes than the one we're tumbling into, by whatever measure. 172.70.86.31 09:03, 1 May 2023 (UTC)

<-- ...Sea Peoples * a real thing -->