Anthropocene climate: The new (deadly) normal
A temperature increase of less than one degree has already disrupted the global climate system, and this is only the beginning. Will the Anthropocene bring a totally new climate regime?Part One:
HOW BAD CAN ONE DEGREE BE?
Climate negotiators have adopted 2°C as the maximum increase in the global average temperature. that can be permitted if dangerous consequences are to be avoided. Many scientists, and the governments of many small countries, argue that 2° is too high – that the limit should be 1.5°. But according to climate experts, if current trends continue, the average temperature by the end of this century will definitely be 3.5° degrees above pre-industrial levels, and there is a strong possibility that the increase will be more than 4 degrees.[1]
That doesn’t sound like much. When I woke on a recent August morning, the temperature outside was 19°, and by noon, it was 25°. That’s a six degree jump in five hours or so, a pretty common experience in summer in the part of the Northern Hemisphere where I live. So why would we worry about an increase of 2 or even 4 degrees by 2100? Mention that at a party in my neighborhood, and someone is sure to say that they’d be very happy if our Canadian winters were 4 degrees warmer!
It may be counter-intuitive, but 4 degrees averaged over the entire world is actually a big jump. During the last ice age, when kilometers of ice covered areas as far south as present-day Chicago, the average global temperature was only 5 degrees cooler than today.
It’s important to remember that average global temperatures conceal substantial variations in time and place. The atmosphere is consistently cooler over oceans, so to get a global average increase of 4 degrees, continental temperatures would have to would have go up by considerably more. And it’s been estimated that a 4 degree average increase would mean a 16 degree increase in the Arctic.
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