A popular denialist meme at the moment seems to be, “but it’s cold outside!” The Australian has printed an excerpt of a longer article by Christopher Booker, titled “2008 was the year man-made global warming was disproved”. Booker suggests that it has been so cold lately that:
This winter, with the whole of Canada and half the US under snow, looks likely to be even worse. After several years flatlining, global temperatures have dropped sharply enough to cancel out much of their net rise in the 20th century.
This is a silly argument. Transient weather events cannot be taken as evidence for or against long-term climate change. And it’s an argument that can’t endure – wait just a short while, and it can be countered with this:
+ Dallas hit 83 degrees, breaking its 2005 high temperature of 81.
+ In Iowa, the warm temperatures caused major visibility issues.
+ Madison, Wisconsin looked to hit a record high of 50 — followed by a cold front snapping temps back down.
+ In the Sierra Nevadas, it finally snowed on Dec 13 — weeks later than in years past. With an earlier melt, anxiety is on the rise.
+ Tennessee also looked forward to warm weather. The headline: Today’s forecast: Warm, wind advisory all day.
As Jed notes, relying on anecdote and cherry-picked weather events doesn’t prove or disprove anything. The only consolation is that time itself negates the argument. But perhaps the denialists who run such arguments are hoping that nobody will point out, and nobody will notice on their own, when the weather pattern runs against their argument.
Unfortunately, sometimes they reach too far back into the past and eviscerate their own claims. Take this recent National Review Online commentary by Deroy Murdock, in which he claims that:
the National Snow and Ice Data Center has found that the extent of Arctic sea ice has expanded by 13.2 percent over last year. This 270,000 square-mile growth in Arctic sea ice is just slightly larger than Texas’s 268,820 square miles.
Murdock links to a commentary on NSIDC data that was written back at the beginning of September. He neglects to note that “last year” was itself anomalous – 2007 saw the lowest level of Arctic sea ice coverage in recorded history, so regression to the mean can account for the 13.2% “expansion” – but even that doesn’t matter at this point. Because four months later, this is what the data looks like:
For the past week or two, the ice extent is identical to the same time in 2007.
Time passes, and climate change arguments based on isolated events fall apart. Of course, this is not only an issue for denialist arguments – as Wah notes, alarmist claims that attempt to link specific catastrophic events to climate change are just as dodgy. Reasonable and responsible science isn’t about these anecdotal claims and counter-claims – it’s a shame that this is what colours the public and political debate about climate change.