Articles by Andrew Dessler

Save the Martians!

GLOBAL WARMING ON MARS!

I just read the Nature paper entitled "Global warming and climate forcing by recent albedo changes on Mars," by Fenton et al.

I suspect it will make the rounds in the blogosphere in fairly short order, so here are a few things to remember about the paper.

The innerworkings of it all

Those opposed to action on climate change are compelled to attack the Intergovernmental Panel on Climate Change (IPCC) and its reports. Not doing so would cede the scientific high-ground of the argument and essentially doom their preferred do-nothing policy approach.

One way to attack the IPCC is to describe it as a nameless bureaucracy pursuing its own political agenda, and entirely disconnected from the scientific community. For example, a report from the Fraser Institute makes this argument explicitly:

[A] compelling problem is that the Summary for Policymakers, attached to the IPCC Report, is produced, not by the scientific writers and reviewers, but by a process of negotiation among unnamed bureaucratic delegates from sponsoring governments. Their selection of material need not and may not reflect the priorities and intentions of the scientific community itself.

This argument is transparently false on several counts. First, the authors are not nameless, but are listed prominently on the first page of the Summary. In addition, they are not bureaucrats, but all have scientific credentials in the arena of climate change.

How can 3 percent be important?

Consider this argument often made by climate skeptics:

Water vapor is the most important gas, contributing 97 percent of the greenhouse effect. Carbon dioxide is only small percentage. Therefore, regulating carbon dioxide will have no impact on our climate.

WhileEven if these numbers are generally correct, there are lots of problems with this argument. For example, it disregards the fact that climate forcing by water is really a feedback, and that changes in carbon dioxide are amplified by the water vapor feedback.

Then there's this problem: the argument includes an implicit assumption that a small fractional change of any quantity is intrinsically unimportant. It might make intuitive sense: carbon dioxide is only 3 percent of total forcing, and how can 3 percent of anything be important?

If a single new result clashes with the consensus, it’s wise to doubt it

Science is a collective, multi-layered process consisting of three steps. First is the individual scientist testing hypotheses according to the norms of their field. Second, the results of the individual scientist undergo peer-review and are published for the community to evaluate. At this point a result may be considered preliminary, but not proven.

Third, important claims are then re-tested in the "crucible of science" -- they are either reproduced by independent scientific groups or they have their implications tested to insure consistency with the existing body of scientific knowledge. After enough tests/reproductions, a consensus emerges that the idea is correct.