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Does global warming diminish when measured accurately? Part 4
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We noted earlier in this series that surface temperature measurements over land may not be reliable for measuring the extent of global warming. (See here, here, and here.) But we've been measuring temperatures using satellites for 30 years. Why not use them?
It's a bit curious that the Goddard Institute for Space Studies (GISS), run by NASA, does not use satellite measurements for their analyses. I've never seen an explanation of why, although I've spent a lot of time on their website. James Hansen of GISS (yes, that James Hansen) developed his own software program for managing the ground measurement data set, and that may have something to do with it.
Satellite measurements in theory should be more accurate--they don't really measure temperatures, but radiance, and then analysts compute temperatures from that. But they cover all of the globe except the poles, and it doesn't suffer from the problem of having a road built up next to a measurement station.
But early measurements that failed to show global warming were in part due to orbital decay of the satellites which was not accounted for, and that may also be a cause for the reluctance to be completely reliant upon them. The other factor is that the 30 years covered by satellite measurements is very short, in comparison to the geologic records available from ice cores and other paleo-climatic sources of information.
However, satellite measurements show less warming (and indeed show recent tapering off in temperatures). As in theory satellites should be more accurate, this is one of a hundred sources of controversy between AGW proponents and skeptics.
GISS is headed up by James Hansen, who uses his own proprietary software program to analyse surface temperatures. They show continued, inexorable warming. One of the analyst teams for satellite data, which shows lower warming and recent cooling, is at the University of Alabama at Huntsville, led by Drs. Roy Spencer and John Christy, both confirmed skeptics. This has stirred the cauldron of controversy.
And the reason it's important is that, according to satellite measurements, the recent decline in temperatures indicates that right now, the world's mean temperature is pretty much where it was in 1979, right when all the fuss started. See the chart here.
Obviously, proponents of anthropogenically caused global warming will say that it's just the low end of a sawtooth shape trend that is continuously rising. Just as obviously, skeptics will say that we are now where we were 30 years ago--is this what the fuss was about? So how we discuss this matters a lot.
First, there is no question that if you look at the chart you will see lots of ups and downs. Over the past few decades, the trend has been for temperatures to rise. But skeptics say that this will eventually stop. Clouds will compensate for much of the additional CO2 and temperatures will decline. And they might be right.
We'll know soon enough. Well, soon enough in geological terms--30 years will answer the question. The question is whether we can wait 30 years before acting. And that's where the politics comes in.
For what it's worth, I think that we can act without panicking, but that we should act. We should invest in alternative energy generation, make carbon cost something, and help the poorest third of the planet get access to cleaner energy than wood and dung. But we should do that even if we're entering the next Ice Age, so I will get no props from AGW proponents for that. And as I keep repeating, what we really need to do now is to get accurate measurements and agree on definitions for analysis.
Because a system open to charges of bias on both sides is not solving the problem.
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