September 12, 2016
#1732: Earth Temperature Timeline explain
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|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 20th 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