- The current report reduces the estimates of changes in sea level from previous reports.
- Recent rises in temperature fall within the range of error for the studies and do not match earlier predictions made on computer models.
- Other aspects of human activity may have a cooling effect on the planet, like the reflective qualities of particulates released into the atmosphere in vehicle and industrial exhaust.
We remain convinced that (a) carbon emissions probably do contribute to the fact that the earth is about one degree Celsius warmer than it was 100 years ago; (b) global warming, like any phenomenon in a complex system, has multiple causes, the contribution of any one of which is daunting to estimate; (c) humanly predicted apocalypses hardly ever happen; (d) while reductions in the use of fossil fuels would be salutary on multiple counts, enforcing reductions with draconian laws would create more harm than good.
So we'll affirm this conclusion from the good minds at WSJ:
While everyone concedes that the Earth is about a degree Celsius warmer than it was a century ago, the debate continues over the cause and consequences. We don't deny that carbon emissions may play a role, but we don't believe that the case is sufficiently proven to justify a revolution in global energy use. The economic dislocations of such an abrupt policy change could be far more severe than warming itself, especially if it reduces the growth and innovation that would help the world cope with, say, rising sea levels. There are also other problems--AIDS, malaria and clean drinking water, for example--whose claims on scarce resources are at least as urgent as climate change.
Update: George Will offers similar analysis in Newsweek:
We do not know how much we must change our economic activity to produce a particular reduction of warming. And we do not know whether warming is necessarily dangerous. Over the millennia, the planet has warmed and cooled for reasons that are unclear but clearly were unrelated to SUVs. Was live better when ice a mile think covered Chicago? Was it worse when Greenland was so warm that Vikings farmed there? Are we sure the climate at this particular moment is exactly right, and that it must be preserved, no matter the cost?
It could cost tens of trillions (in expenditures and foregone economic growth, here an in less-favored parts of the planet) to try to fine-tune the planet's temperature. We cannot know if these trillions would purchase benefits commensurate with the benefits that would have come from social wealth that was not produced.