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June 9, 2014

#1379: 4.5 Degrees

4.5 Degrees

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


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!


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