Scientific Statements Made by a Climate Change Skeptic

A recent op-ed in the Wall Street Journal concludes that "Climate Science Is Not Settled", contrary to activists' and scientists' claims that there is no longer even a debate.

The article, written by Steven Koonin, includes a number of interesting statements and is worth a read in its entirety. Unfortunately, responses to the article have not addressed many of his factual claims, so I wanted to list a few of them here.

Please feel free to comment or link to research that addresses or refutes these statements:

1) "For example, 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%. Since the climate system is highly variable on its own, that smallness sets a very high bar for confidently projecting the consequences of human influences."

2) "But 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."

3) "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%. This surprising fact demonstrates directly that natural influences and variability are powerful enough to counteract the present warming influence exerted by human activity."

4) "Even though the human influence on climate was much smaller in the past, 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—about one foot per century."

5) "[these model discrepancies] are not "minor" issues to be "cleaned up" by further research. Rather, they are deficiencies that erode confidence in the computer projections."