Source: Juan Cole
The images from Houston and its environs are heart-breaking and we at IC wish all those affected a speedy and safe return to normality.
Extreme weather events are associated with climate change, and whenever they occur, they raise the question of their relationship to that process.
Human-induced climate change did not “cause” Hurricane Harvey. There have after all been hurricanes in the Gulf of Mexico all along, and some of them have been monstrous. So can we relate Hurricane Harvey to human pumping of carbon dioxide and methane into the atmosphere by driving cars, heating or cooling buildings, etc.?
The answer is “yes.” Climate change did not produce Harvey the Hurricane, but climate change made Harvey worse than it would otherwise be. Maybe 30% worse. That is, if Harvey dumps 4 feet of water on the Houston area in 2017, that suggests it would only have dumped 2.64 feet of rain if it had arisen in the 1749 hurricane season when Spanish settlers in Texas made peace with the Lipan Apache tribe.
That is because in 1749, there were 270 parts per million of carbon dioxide in the atmosphere and today there are 410 ppm of CO2. The parts per million of carbon dioxide in the atmosphere have fluctuated between 200 and 270 for the last 800,000 years . Homo Sapiens Sapiens is only about 200,000 years old, so this is the only climate we’ve ever known. Starting in the late 1700s, human beings started behaving like a global bank of super-volcanoes, spewing greenhouse gases into the atmosphere faster than had ever occurred in the history of the earth. Hundreds of billions of metric tons of carbon dioxide, through the burning of massive amounts of coal, as well as petroleum and natural gas. Ordinarily, going from 270 ppm of CO2 to over 400 would take millions of years of heightened vulcanism.