Weather Extremes Now Clearly Due to Climate Change

By Michael Mountain, February 22, 2012

Top NASA scientists explains why they are no longer anomalies

On the way to James Hansen’s talk at the AAAS Meeting in Vancouver at 8.30 on Sunday morning, you passed by lots of big rooms with a seating capacity of several hundred people, most of them with a dozen-or-so people scattered around the room. Then, down a side passageway, you finally reached Room 214 – full to capacity, and with dozens of people crowded outside, straining forward to hear Hansen speak.

I managed to squeeze forward to hear some of what he was saying. The big takeaway:

• While scientists have been leery of attributing specific droughts, heat waves and other weather events to climate change, you can now definitely draw the connection. The big Texas and Oklahoma droughts, for example, are indeed a direct result of climate change.

Hansen is a star of climate science and the antithesis of what the climate denial lobbyists try to tell you about environmental “activists.” His science is rigorous, there’s no hype, he speaks quietly, and he was a regular visitor to the Bush White House to brief the administration on climate science. (Not that anyone there took any notice of what he said!)

He’s the chief NASA climate scientist and head of the NASA Goddard Institute for Space Studies. (What’s that got to do with the climate on Earth? Very simple: His early training was in understanding the atmosphere of Venus, the extreme model of what happens when greenhouse gases go berserk. Hansen began to apply his work on that overheated planet to understand what might happen here on Earth as a result of a major greenhouse effect.)

At the AAAS Meeting, Hansen was part of a panel on “Climate Solutions: the Challenges of Getting to 350.” The figure 350 refers to the amount of CO2 gases in the atmosphere (350 parts per million or ppm) beyond which you’ve gone over the tipping point. Two hundred years ago, the figure was 275. Right now it’s 392, way into the red zone, and rising at 2 ppm every year.

Hansen’s graphs and figures all point to major Earth changes in the coming years – changes that are already underway. To some extent, he says, we’re already over the tipping point. We can still slow down what’s happening and limit the effects, but not if we keep burning fossil fuels at the current rate.

You can watch an eight-minute video of Hansen’s AAAS presentation here. His main points:

• The climate on Earth has been relatively stable for the last 10,000 to 12,000 years – the period of human civilization. All of that is now undergoing rapid change.
• Both poles are melting at the rate of hundred of cubic kilometers per year. Oceans are currently rising at the rate of 3 millimeters per year. At this rate, we’re talking about 30 centimeters per century (and the rate is actually accelerating) – enough to seriously impact coastal cities around the planet. (Note: we misstated these levels in an earlier version of this post.)
• Two degrees of warming (Celsius) by the end of the century, which looks more and more likely, will push sea levels tens of meters higher (like, say 50 feet higher).
• We’re also now looking, by the end of the century, at the irreversible extinction of 20 to 50 percent of all spec