Friday, December 9, 2011

Some Pictures

To put the whole COP17 fiasco into perspective I thought a few pictures would talk louder than words. Play this movie, from NASA’s Goddard Institute for Space Studies (GISS) web site, which illustrates temperature changes from 1880 to 2010:
Can you see any difference in recent decades?

One thing that causes a lot of confusion is the differences in various temperature trends, particularly satellite versus ground-based measurements. Using different instruments measuring temperatures at different places may give different short-term measures, but the trend should be the same. A recent paper (by Foster and Rahmstorf) illustrates that much of the difference is in the extent to which short-term variations like El Niño are picked up by these very different forms of measurement. You’ll find more discussion on Tamino’s blog and on RealClimate. These short-term variations do not change the trend, but cause more ripples in shorter time-scales. Once these short-term effects are eliminated, the trends line up very nicely:
What’s more, rather than the alleged slowdown in warming since 1998, the trend remains remorselessly up. So why the alleged slowdown? Let’s look at what they’ve subtracted out of the raw data:
MEI is multivariate el Niño index, AOD is aerosol optical thickness data, representing mainly the cooling influence of volcanoes and TSI is total solar irradiance, representing variations in the sun.
Contrast the adjusted graph with one of the best-known temperature records, that produced by NASA GISS:

Here, the 2010 data point is no longer unequivocally a maximum. But it’s still one of the highest points on the chart despite the fact that the solar cycle is clearly a lot lower in 2010 than in 1998.

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