Global warming decreases...

Last week, the press made a big deal about a new study that supposedly had the 'smoking gun' to prove global warming. The real story is that the scientist in question, Jim Hansen from NASA, has lowered his estimate (for a second time) of the effects of carbon dioxide.

You would think that it would be big news when Hansen-the guy who started all this mess with his incendiary 1988 congressional testimony-lowers his estimate for the sensitivity to two-thirds of the value he used back then.

Hansen's most recent figure, just published in Sciencexpress, is that the surface temperature ultimately changes 0.67˚C per Watt per square meter (W/m2). In 1988 he said it was a full degree, and in 2001 he lowered it to 0.75.

The lower the climate sensitivity, the less that the global temperature will rise in the future (given the same amount atmospheric carbon dioxide) and the lower the threat of catastrophic climate change.

But the greenhouse emissions are also much lower than people expected. The standard modeling technique raises the carbon dioxide concentration of the atmosphere 1% per year, but the actual rate of increase for the last three decades has been around 0.45% per year. And, despite scary news stories, there's little evidence for any sharp upward change. There was a lot of press when the 2003 concentration of atmospheric carbon dioxide rose considerably, and virtually no coverage when it was balanced out by much smaller changes in 2004.

The United Nations Intergovernmental Panel on Climate Change (IPCC) assumes an average change of roughly 0.65% per year in carbon dioxide, or 41% greater than the observed, very constant rate.

Yet another topic that won't be properly debated in Canada.