Does anyone still doubt whether humans are changing the climate? Well, unfortunately...

Last month the IPCC released the Summary for Policymakers (SPM) of their Fourth Assessment Report (AR4); the full report is due out this Spring. I was really struck by the change in tone of the media coverage in the wake of this document, coming on the heels of the Stern Report and the big audience response to Al Gore's film "An Inconvenient Truth." Up until this past month, a lot of media coverage of global warming fell victim to a "he said, she said" format where global warming proponents and deniers were given "equal time" in the interest of supposed "fairness." But after the release of the AR4, across the board I kept seeing media headlines saying that the debate is "finally over." Mind you, the scientists knew this some time before the media caught on; but at least now they have taken note.

Strikingly, both the Bush White House and Canada's Kyoto-defeatist minority Conservative government both went on the record as conceding that humans are changing the climate. Even John Howard's Kyoto-rejecting administration in Australia has given up questioning the human role: "I am not as fanatical about it as others," he said. But, "the accumulated evidence is undeniable ... we do have to reduce greenhouse gas emissions." [International Herald Tribune, January 25, 2007] link

All this is quite new. These were the last three G8 leaders who were playing both sides of the fence on the science until recently. Harper in particular got slammed after his recent epiphany on climate science, as the Liberal party found a copy of a fundraising letter he sent out in 2002 calling Kyoto a "socialist plot" and touting "tentative and contradictory scientific evidence about climate trends." But the opinion polls showed a strong surge in public concern over global warming, so Harper had to give ground.

Once the AR4 SPM was released, the media flashed the "debate is over" headline, then spent a good ten days summing up the science. The Globe and Mail ran a two-page centre spread with a map of Canada's projected climate by 2099 - the map showed isotherm lines of mean temperate rise, with Toronto inside a +6C contour. Wow.

I take this to mean that the scientific "debate" in the mainstream media can now be framed as settled, instead of "he said, she said." Journalists are in effect giving themselves permission to point to the IPCC as the received wisdom, instead of having to bracket it with opposing views. This will certainly save them time.

Looking around the internet over the past few weeks, it is starting to look like a lot of the deniers have not yet received the memo that the debate is "over." Blogs and discussion groups continue to roll with back and forth over such profound topics as a debate on whether the scientists of the IPCC (and the NAS, AAAS, Britain's Royal Society, Swedish Royal Academy, ...) can or cannot be called a "consensus." If they can, deniers next say that science "does not operate by consensus" (so, what? Now we have too many scientists in favour? Oy vey!) Perhaps they also claim the missing scientists on side B of the "debate" have been driven underground by the other scientists not being nice to them.

If you try to work through the logic of the greenhouse effect with some of the deniers, they may throw stones at every step in the chain of reasoning. A lot of times the exact same very specific debating points will turn up over and over from different people in many different forums. There's a great "taxonomy of skepticism" on the wonderful blog A Few Things Ill Considered. I'm afraid I've seen almost all these objections tossed out more than once - each one refutable, but there is such a litany of them.

A lot of these points have been hammered repeatedly in the op-ed pages of conservative newspapers like Canada's National Post. So I guess it's no surprise that I also encounter the "man in the street" following virtually the same script as the online debating club crowd. Last week I spoke to someone I hadn't seen in some time. When I mentioned I was taking a university course on global warming, he started posing a series of questions that could have come straight from the Ill-Considered skeptic's checklist. He was very polite, and I gave my best short responses to them one by one. After the seventh or eighth "but what about" question, I had to stop myself from asking what editorial page he had been reading. The deniers have been quite effective in getting their program of doubt across to the public.

So it looks like so far, the message has not reached all the foot soldiers in the trenches that the climate denial army has been forced to surrender. Should we be dropping leaflets, perhaps?

Of course, the end of one debate, over the science, leads inevitably into the start of another, over the politics: what shall we do now? That's the right place to be in the discussion. But for the deniers, they have a Plan B response that may startle you. As the "scientists can't agree" objection gets worn away, a lot of opponents are quickly switching their tune to "it's too late to stop global warming." Whew - that was QUICK, eh? Last week you said it wasn't even happening, and now suddenly it got away from us? In two weeks?

I've read a string of pieces by opponents of Kyoto this week arguing that climate change is now inevitable, and mitigation (lowering our CO2 emissions) sufficiently is impossible, so we all need to brace ourselves and start planning for how to cope - so called "adaptation."

The flaw in this argument is that we can't afford to give up on the mitigation front; however poorly you feel about our prospects for keeping CO2 levels from soaring, it's absurd to say we should not even try, and just sit back and prepare for all the consequences. The impact of CO2 is not just linear - there are good reasons to be concerned that as levels rise, new and more serious consequences come to bear.