4.5 Degrees
Permanent link to this comic: https://xkcd.com/1379/
Image URL (for hotlinking/embedding): https://imgs.xkcd.com/comics/4_5_degrees.png
Without prompt, aggressive limits on CO2 emissions, the Earth will likely warm by an average of 4°-5°C by the century's end. How big a change is that? [[The panel shows a temperature scale.]] In the coldest part of the last ice age, Earth's average temperature was 4.5°C below the 20th century norm. Let's call a 4.5°C difference one "Ice Age unit." ((These are along the time line, spaced out for clarity.)) -2 IAU <-- snowball Earth (-4 IAU) -1 IAU 20,000 years ago ((There's an inset panel, showing a picture of a glacier.)) My neighborhood: Half a mile of ice 0 Average during modern times ((Another inset panel.)) [[A character is in the foreground of a green field with a skyline in the distance.]] My neighborhood: Character: Hi! 0.20 Where we are today +1 IAU Where we'll be in 86 years ((Another inset panel.)) My neighborhood: ? +2 IAU Cretaceous hothouse +200m sea level rise No glaciers Palm trees at the poles {{Title text: The good news is that according to the latest IPCC report, if we enact aggressive emissions limits now, we could hold the warming to 2°C. That's only HALF an ice age unit, which is probably no big deal.}}
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