Where Has Global Warming Gone?
For the last 15 years, according to the conventional way of measuring global warming, the planet does not seem to have become any hotter. But the reason is not that our greenhouse-gas emissions are no longer changing the earth’s climate, it is that surface temperature is a poor measure of human-induced warming.
SEATTLE – For the last quarter of the twentieth century, the average temperature at the surface of the earth edged inexorably upward. Then, to the surprise even of scientists, it stopped. The concentration of carbon dioxide in the earth’s atmosphere continued to rise; indeed, it is higher today than it has been for centuries. And yet, for the last 15 years, according to the conventional way of measuring global warming, the planet does not seem to have become any hotter.
What explains this unexpected turn of events, and what does it mean for future climate policy?
The pause in the rise of surface temperatures is real. It can be observed in surveys of the surface of the sea and in satellite measurements of the troposphere. But the reason it has occurred is not that our greenhouse-gas emissions are no longer changing the earth’s climate; it is that surface temperature is a poor metric for human-induced warming. Indeed, what scientists have figured out is that, instead of warming the surface, the excess heat that is being generated has gone to the deeper oceans.
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