Has there been a “warming pause” since 1997?

The upcoming IPCC report is likely to show a slower rate of warming in the last 15 years than in the previous 15. That’s not disputed by anyone. But is that proof that warming has “stopped”, as the sceptics would like you to believe?

No, for the following reasons:

Around 1997-98, the pacific decadal oscillation, which produces El Ninos and La Ninas, moved from a warm period (producing frequent El Ninos) to a cool period (with cooler, wet La Ninas).  The decadal pacific oscillation is always going to produce a wave-like pattern of rising and falling temperatures, but the long-term trend is upwards. To pick only a “down” period is simply bad science – or deliberately misleading.

The production of aerosol pollutants, such as soot in the atmosphere, seems to have a cooling effect, estimated to be as high as 1C, which may be masking temperature rises.

Most (90 per cent) of the extra heat caused by the greenhouse effect goes into the oceans. When you factor in ocean temperatures, warming hasn’t slowed since 1998. Looking only at atmosphereric temperatures is thus misleading.

The bottom line? Most scientists still believe human-generated greenhouse gases are warming the planet at an alarming rate.

More, as always, at Skeptical Science.


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