How big a change would 4.5 degrees celsius be?

By Michael Graham Richard (

Randall Munroe of the XKCD webcomic has tried to better visualize how what might seem to be relatively small temperature differences can lead to big changes on our planet. He uses 4.5 degrees celsius (8°F) as a unit of measurement, showing on the negative side how just 1 of those units was enough to create an ice age and burrow his neighborhood (he lives in Boston) under half a mile of ice. Minus 4 of those units and you reach snowball Earth, with ice from pole to pole. more ...

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