January 5th, 2007

New Tilley Hat

Consensus on Global Warming & Water Vapor as a "Greenhouse Gas"

At the New Years Party at cakmpls', I was discussing Global Warming (really non-caps: global warming) with ithildae. He raised two issues, common to global warming deniers: First, that there is no consensus among scientists that global warming even exists (without saying what plurality might convince him) and, second, that water vapor is a greenhouse gas (implying a dismissal of human influence on the environment). So I asked the family expert, my brother Joe, author of Hell and High Water: Global Warming--the Solution and the Politics--and What We Should Do. He pointed me to two urls, posts from RealClimate: Climate science from climate scientists:

Just what is this Consensus anyway? excerpt:
The consensus that exists is that of the IPCC reports, in particular the working group I report (there are three WG's. By "IPCC", people tend to mean WG I). Fortunately that report is available online for all to read at report. Its a good idea to realise that though the IPCC report contains the consensus, it didn't form it. The IPCC process was supposed to be - and is - a summary of the science (as available at the time). Because they did their job well, it really is a good review/summary/synthesis.

The main points that most would agree on as "the consensus" are:
  1. The earth is getting warmer (0.6 +/- 0.2 oC in the past century; 0.17 oC/decade over the last 30 years (see update)) [ch 2]
  2. People are causing this [ch 12] (see update)
  3. If GHG emissions continue, the warming will continue and indeed accelerate [ch 9]
  4. (This will be a problem and we ought to do something about it)
    The most recent (Jan. 3) entry also speaks to the subject: Consensus as the New Heresy, regarding a piece in the New York Times. The conservative news media, even those in the Science section of the paper, get it wrong. brief extracts:
    However, there is a big difference between really challenging the majority opinion and simply stating that you are.... In reading about the new 'heretics' then, one might have expected that associated with them would be statements that would contradict IPCC or that we (as mainstream scientists who do not claim to be heretics) would otherwise find objectionable. So let's consider the specific tenets of the 'new heresy' mentioned in the article [details]....The only substantial disagreement, then, is over a movie review. On all other points of substance the 'heresy' and the old orthodoxy are the same.
    On to the next question.

    Water vapour: feedback or forcing? excerpt:
    Whenever three or more contrarians are gathered together, one will inevitably claim that water vapour is being unjustly neglected by 'IPCC' scientists. "Why isn't water vapour acknowledged as a greenhouse gas?", "Why does anyone even care about the other greenhouse gases since water vapour is 98% of the effect?", "Why isn't water vapour included in climate models?", "Why isn't included on the forcings bar charts?" etc. Any mainstream scientist present will trot out the standard response that water vapour is indeed an important greenhouse gas, it is included in all climate models, but it is a feedback and not a forcing. From personal experience, I am aware that these distinctions are not clear to many, and so here is a more in-depth response [lengthy details follow]

    I hope this is sufficient proof for ithildae and others.