In recent comments submitted to EPA, University of Alabama in Huntsville atmospheric scientist John Christy challenges the physical science basis of the agency’s Clean Power Plan.
EPA assumes that anthropogenic emissions of greenhouse gases, especially carbon dioxide (CO2) from energy use, are the driving force behind recent climate change. It thus further assumes that regulating CO2 emissions can mitigate future climate change, providing substantial health benefits to the American people.
Christy does not dispute the reality of climate change. The climate is always changing on multiple time scales. However, the Earth has experienced climatic “fluctuations in the past centuries similar to and even greater than what has occurred in the past 50 years.” Scientific instruments measure what the climate is doing; they don’t tell us why it behaves as it does.
To understand what drives climate change, scientists must test hypotheses against data. EPA assumes CO2 emissions are the chief driver because that’s what state-of-the-art IPCC climate models assume.
But, Christy points out, data from six independent global temperature monitoring systems “demonstrate that the models do not yet have the ability to discern ‘why’ a climate variation may have occurred simply because they cannot even reproduce ‘what’ has occurred.” The chart below compares climate model projections with observed temperatures over 35 years in the tropical troposphere, the portion of the atmosphere where models project a “highly consistent and significant” warming response to rising CO2 concentrations.













