Glenn Reynolds highlighted this item from the Mars Global Surveyor project:

[F]or three Mars summers in a row, deposits of frozen carbon dioxide near Mars' south pole have shrunk from the previous year's size, suggesting a climate change in progress.

While it is theoretically possible for human and animal activities to affect the climate on Earth, the main factor causing fluctuations in temperatures on this planet, as on Mars, is variability in energy output from the Sun. The Mars Global Surveyor data suggest what I think would be a relatively simple experiment: Why not place thermometers in a few locations on Mars, equipped with radio transmitters that would send temperature data to Earth or to a spacecraft? You'd have to take into account the two planets' different atmospheres, of course; the atmosphere on Mars is thin, but consists almost entirely of carbon dioxide. In time--it would take more than a few years' observations, obviously--such an experiment would settle once and for all the question whether human activities are making a significant contribution to climate variations on Earth. And I don't think the experiment would be very hard to conduct. The main catch I can see is that figuring out how to account for the planets' different atmospheres might recreate the debates that are now going on about how to properly model the Earth's weather system.

On the other hand, if it were that easy, maybe it already would have been done. Readers, what do you think?

UPDATE: They don't think much of my idea, evidently. For one thing, there are easier ways to measure the variation in energy output from the Sun directly. For another, calculating overall temperature changes on Mars would take more than a handful of thermometers; how, exactly, to do it would replicate one of the major debates now going on over temperature changes on Earth.

Still, it seems to me that even a rough estimate of the extent to which increasing solar output is raising temperatures on Mars would be a useful reality check on the "global warming" claims being made here on Earth.

Posted by John at 07:59 AM  |    |