When NASA’s top climatologist, James E. Hansen, was silenced because his research on global warming was at odds with Bush Administration policies, he became a cause célèbre for browbeaten scientists fed up with the government stranglehold on their research.
It’s fitting, then, that he was a last-minute addition to the recent Conference on Politics and Science, hosted by the journal Social Research at the New School, where leading scientists and policy experts discussed the politicization of science and the urgency to address the consequences of global climate change.
Hansen has largely ignored the media for the past fifteen years, slightly less than half his tenure at NASA. But after a presentation in December on global warming to the American Geophysical Union (AGU) in San Francisco, he began to feel an even greater restraint on the public dissemination of his research.
“I think the reason was that my talk was very wide-ranging, connecting the dots from emissions to climate change and to impacts and what you need to do if you want to get on a scenario that reduces climate change,” Hansen said. “The public affairs people just didn’t like that and started bouncing off the walls, as I’ve been told.”
Hansen’s current research explores the relationship between greenhouse gases and changes in temperature and sea level over the past 400,000 years. Climate scientists have looked for this sort of paleoclimate data for decades because it strengthens the argument that the earth’s current warming cycle is predominantly influenced by our carbon dioxide emissions.
He explained that records of atmospheric carbon dioxide, methane and temperature for the past 400,000 years, taken from Antarctic ice cores, revealed the difference between the warmest interglacial periods and the depths of the Ice Age to be about five degrees on global average.
This, along with detailed sea-level data, also from the past 400,000 years, can measure climate sensitivity. When applied to the present interglacial period, which is the warm period that has existed for the past 10,000 years, the interplay and necessary balance between ice and greenhouse gases becomes clear.
“If the planet were out of balance by even one watt per square meter for 1,000 years, it would melt all the ice on the planet or raise the ocean temperature an implausible amount,” Hansen said.
And that is exactly where the earth is headed: Current fossil fuel carbon dioxide emissions increase about 2 percent each year; if this continues, temperatures will increase between two to three degrees Celsius by the end of the century.
This last occurred about 3 million years ago, when the earth was a much different place. The East Coast, for instance, was nearly 100 kilometers inland; Florida was completely underwater.