Global Warming: Eyeballing the Data

Looking at the temperature data for the past century, the obvious interpretation is the combination of an upward trend with a roughly sinusoidal term of comparable magnitude and a period of about sixty years. When the additional term is going up, temperature rises at about twice the long term trend. When it is going down, it roughly cancels the trend, giving you stable temperatures from 1950 to 1980 and again from about 2000 to the present. I do not know if the oceanic model recently proposed to explain the additional term is correct or not, but that's the pattern suggested by the data.

If my interpretation is correct, there are two implications. One is that estimates of the rate of warming based on a period when the two effects were reinforcing each other will be too high. If we take 1940-2000 as one full cycle, the increase is just under .6°C, giving a trend of about .1°C/decade. That's one third as fast as the rate estimated in the first IPCC report, about half the rate estimated in later reports. If it holds, total warming by the end of the century, about half of which has already occurred, will be slightly under two degrees.

The other implication is that the current pause does not mean global warming is not real. If the pattern holds, warming will start again in about another fifteen years.