The Great Global Warming Swindle
has created a lot of buzz at sites like Samizdata
and (appropriately) Hot Air
The solar activity theory is especially noteworthy. Historical data on sunspot activity and cosmic radiation in the Earth's lower atmosphere suggest that as solar activity increases, solar wind incrases, thus "blowing" more cosmic radiation away from Earth. Less cosmic radiation means less cloud formation, and thus less water vapor, which is the most significant greenhouse gas. Thus the Earth warms.
As I was watching this segment, I started pondering the relevance of this theory to interplanetary colonization. If we ever discover the technology to reach another star system within a reasonable amount of time, presumably that will come after
we are able to study Earth-sized planets without leaving home. It makes sense that we shoudl find out some basic facts about foreign planets before we send out any colonization missions.
Most important is atmospheric content. Judging from the lack of heavy elements in the atmospheres of both Venus and Mars, each of which has a mass significantly less than that of Earth (.815 and ,107 Earths, respectively), it appears that planets will have to reach a certain mass before sustaining enough oxygen to support terrestrial life.
It also helps to know about long-term climate variation. By the time we can study terrestrial planets from long distance we'll be able to get direct temperature readings as well. But we'll only know about the present, and not that planet's past. If we can nail down the effect of solar activity on warming by study terrestrial and Martian core samples, we can get a good idea of the variability of that planet's climate. We would have to study extrasolar sunspot activity, if we're not doing that already. I suspect that stars within the same stellar classification
will have similar sunspot cycles.