Climate Science Is Not Settled

We are very far from the knowledge needed to make good climate policy, writes leading scientist Steven E. Koonin

From the WSJ. Excerpts: 

"The crucial scientific question for policy isn't whether the climate is changing. That is a settled matter: The climate has always changed and always will."

"during the 20th century the Earth's global average surface temperature rose 1.4 degrees Fahrenheit."

"There is little doubt in the scientific community that continually growing amounts of greenhouse gases in the atmosphere, due largely to carbon-dioxide emissions from the conventional use of fossil fuels, are influencing the climate."

"The impact today of human activity appears to be comparable to the intrinsic, natural variability of the climate system itself.

Rather, the crucial, unsettled scientific question for policy is, "How will the climate change over the next century under both natural and human influences?"

"those questions are the hardest ones to answer."

"human additions to carbon dioxide in the atmosphere by the middle of the 21st century are expected to directly shift the atmosphere's natural greenhouse effect by only 1% to 2%."

"A second challenge to "knowing" future climate is today's poor understanding of the oceans."

"precise, comprehensive observations of the oceans are available only for the past few decades"

"A third fundamental challenge arises from feedbacks that can dramatically amplify or mute the climate's response to human and natural influences."

"feedbacks are uncertain. They depend on the details of processes such as evaporation and the flow of radiation through clouds. They cannot be determined confidently from the basic laws of physics and chemistry, so they must be verified by precise, detailed observations that are, in many cases, not yet available."

"computer models: While some parts of the models rely on well-tested physical laws, other parts involve technically informed estimation."

"In a given model, dozens of such assumptions must be adjusted ("tuned," in the jargon of modelers) to reproduce both current observations and imperfectly known historical records."

"as far as the computer models go, there isn't a useful consensus at the level of detail relevant to assessing human influences."

"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."

"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."

"Although the Earth's average surface temperature rose sharply by 0.9 degree Fahrenheit during the last quarter of the 20th century, it has increased much more slowly for the past 16 years, even as the human contribution to atmospheric carbon dioxide has risen by some 25%."

"the models famously fail to capture this slowing in the temperature rise."

"they fail to describe the comparable growth of Antarctic sea ice, which is now at a record high."

"the models do not account for the fact that the rate of global sea-level rise 70 years ago was as large as what we observe today"

"Today's best estimate of the sensitivity (between 2.7 degrees Fahrenheit and 8.1 degrees Fahrenheit) is no different, and no more certain, than it was 30 years ago. And this is despite an heroic research effort costing billions of dollars."

"They are not "minor" issues to be "cleaned up" by further research."

"a public official reading only the IPCC's "Summary for Policy Makers" would gain little sense of the extent or implications of these deficiencies."

"the field is not yet mature enough to usefully answer the difficult and important questions being asked of it."

"rigidly promulgating the idea that climate science is "settled" (or is a "hoax") demeans and chills the scientific enterprise, retarding its progress in these important matters."

"Individuals and countries can legitimately disagree about these matters"