James Hansen at UNC Chapel Hill

James Hansen, director of the NASA Goddard Institute for Space Studies, spoke at UNC Chapel Hill earlier this evening. As he put it himself, he is not a communicator, but a scientist who feels compelled to speak out because the gap between what is known by climate scientists and what is understood by a seeming majority of the public is very large and growing.

That he feels so compelled may be the most significant story, but it is not one that I want to tell.

I want to relate the important science story that he told.

He spoke of the inertia in a climate system that encompasses the entire planet. Estimates suggest that we have experienced about half of the warming expected based on the increases in atmospheric carbon dioxide since it was 280 ppm. That means if we immediately reduced our carbon emissions to the point where the atmospheric concentration rose no higher than it is today, we would continue to experience climate change and global warming for some time to come, and about double what has occurred thus far.

Dr. Hansen also spoke about tipping points, moments in time where the climate system may begin to change in ways and at rates over which we will have no control. These tipping points have most to do with positive feedbacks that may begin to operate. There are two big ones according to Hansen. First - melting ice sheets resulting in decreased surface albedo or reflectivity causing more absorption of sunlight and more heating, melting more ice sheets in a spiraling of warming.

Second, the danger of warming oceans allowing methane hydrates on the floor of the shallow areas of the oceans to "thaw" and bubble up to the surface and enter the atmosphere. Methane's greenhouse gas efficiency is more than 20 times that of carbon dioxide. More methane means more heating, meaning warmer oceans, causing the release of more ocean floor methane in a runaway greenhouse scenario. A 2009 story I summarized a while back goes into a little more detail on this feedback loop's scary possibilities.

There were a few other key concepts that will have to wait for a later posting. For now, the take home lesson is that Opa Hansen wants to remind us that global climate change's big losers have either only recently arrived on planet Earth, or have not yet even been born. The decisions we make in the next couple of decades will shape the face of this planet, and strongly influence the quality of life for our grandchildren, great grandchildren, and great great grandchildren.