Opinion: Ignore climate Cassandra at our peril

Daily Climate 6 August 2012.

James Hansen’s latest findings linking extreme weather to climate change is science society cannot afford to ignore.

The first scientist to alert Americans to the prospect that human-caused climate change and global warming was already upon us was NASA climatologist James Hansen. In a sweltering Senate hall during the hot, dry summer of 1988, Hansen announced that “it is time to stop waffling…. The evidence is pretty strong that the [human-amplified] greenhouse effect is here.”

Given the prescience of James Hansen’s science, we would be unwise to ignore his latest, more dire warning.

At the time, many scientists felt his announcement to be premature. I was among them.

I was a young graduate student researching the importance of natural – rather than human-caused – variations in temperature, and I felt that the “signal” of human-caused climate change had not yet emerged from the “noise” of natural, long-term climate variation. As I discuss in my book, The Hockey Stick and the Climate Wars, scientists by their very nature tend to be conservative, even reticent, when it comes to discussing findings and observations that lie at the forefront of our understanding and that aren’t yet part of the “accepted” body of scientific knowledge. ..

In a paper published today in the prestigious journal Proceedings of the National Academy of Sciences, Hansen and two colleagues argue convincingly that climate change is now not only upon us, but in fact we are fully immersed in it. Much of the extreme weather we have witnessed in recent years almost certainly contains a human-induced component.

Hansen, in his latest paper, shows that the increase in probability of hot summers due to global warming is such that what was once considered an unusually hot summer has now become typical, and what was once considered typical will soon become a thing of the past – a summer too improbably cool to anymore expect.