03 October, 2014

Global Warming-US Senior Official's Epiphany

Physicist Steven Koonin says climate science is far from settled and we are a long way from having good enough knowledge to make wise climate policy.
That view is not news to climate skeptics, but it may seem surprising coming from Koonin, who was undersecretary for science in the Obama administration’s Energy Department in the president’s first term.
Koonin says the crucial question isn’t whether climate is changing, which is a settled matter: It is changing and always will change. The crucial question – how will climate change over the next century as a result of both human and natural influences – is more complex and unsettled.
Although human activities could have a powerful effect on climate, they are and will be small in relation to the climate as a whole, Koonin argues. For instance, he notes human additions to atmospheric carbon dioxide will enhance the natural greenhouse effect by just 1 to 2 percent by the middle of this century.
In addition, he writes, ocean cycles and feedbacks can dramatically amplify or mute the climate’s response to human and natural influences, and we neither understand nor can model either of these factors well enough to trust our knowledge when forming public policy.
Concerning climate models, Koonin notes the IPCC uses 55 different models:
Although most of these models are tuned to reproduce the gross features of the Earth’s climate, the marked differences in their details and projections reflect all of the limitations that I have described. For example:
The models differ in their descriptions of the past century’s global average surface temperature by more than three times the entire warming recorded during that time. Such mismatches are also present in many other basic climate factors, including rainfall, which is fundamental to the atmosphere’s energy balance.
Whereas human CO2 emissions have risen 25 percent over the past 16 years, temperature has remained largely flat, a result none of the models predicts, Koonin notes. In addition, average sea level rise hasn’t changed from the level experienced more than 70 years ago, contra the models’ estimates.
Koonin says it will take decades before sufficient, accurate data are available to accurately assess human effects on climate and any dangers they might pose. Accordingly, society must make choices based on uncertain knowledge of future climate, meaning policy actions should be prudent, not radical. Modest, “no regrets” policies are reasonable, he argues. Large-scale, economy-changing policies could be more harmful to people than the climate changes they are meant to prevent, he notes.
“Our tolerance for risk and the priorities that we assign to economic development, poverty reduction, environmental quality, and intergenerational and geographical equity” must have greater influence on our policies than model-based climate prognostications, he argues.
Only by recognizing, rather than ignoring or trying to deny, the limits of our knowledge can society make productive decisions with regard to climate policy, Koonin concludes.
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