I listened with interest to Kevin Trenberth on the latest Climate Show describing how the increased water vapour in the atmosphere resulting from human-caused global warming is leading to greater extremes in weather events. It sent me back to take another look at the section in James Hansenâ€™s book Storms of My Grandchildren where he explains the greatly increased strength of storms we can expect as the century unfolds, unless we leave most fossil carbon in the ground. I reviewed the book a while back on Hot Topic and thought it worth outlining more closely here, as an extension of my review, Hansenâ€™s argument in the ten pages where he specifically addresses the storms of which the bookâ€™s title speaks.
The extreme weather flavour of the moment is without doubt heavy rain and flooding. As I write, severe flooding has caused 132 deaths in southern China and 19 in Burma. The Var region in southern France is recovering from spectacular flash flooding that killed 25 people (watch the BBC video), Tennessee’s recovering from a 1000 year flood in May, and NZ hasn’t escaped. The Metservice blog reports that the flooding in Whakatane a few weeks ago was caused by rainfall of 89.8mm in one hour (with more heavy rain either side of that hour). As the blog notes, that’s tropical rain happening well outside the tropics. But what struck me at the time was a comment from a Whakatane resident included in the TV3 News coverage of that flooding. I can’t remember his precise words, but it was something along the lines of “should be a wake-up call for anyone who doesn’t think global warming’s an issue, because this is what global warming delivers…” Perceptive, I thought, because one of the more robust predictions of climate science is sometimes described as an intensification of the hydrological cycle.