“Global Warming: An Exclusive Look at James Hansen’s Scary New Math”
by Paul Tullis
Time, May 10, 2012
One of the inconvenient truths climate skeptics seize from science is that although climate
models predict more severe weather and more frequent severe-weather events, science can’t say that a particular weather event– be it a hurricane, tornado, snow storm or heat wave– is due to global warming.
That may be changing, says Jim Hansen.
In his presentation at a symposium on the challenges of getting back to 350 ppb atmospheric co2, Hansen said heat waves that are three standard deviations from the mean– what he dubbed the “three-sigma anomaly”– are almost certainly due to global warming. The last couple years have seen three-sigma anomalies in temperature readings in Russia, Texas-Oklahoma and elsewhere. Prior to 1990, temperature readings three sigmas from the mean occurred about 0.2 percent of the time. Now they happen between 9 and 10 percent of the time. The order-of- magnitude difference is so great, Hansen said, that when one occurs now there’s virtually no chance it’s not due to global warming.