Among climate scientists specializing in climate sensitivity there is a clear trend toward lower and lower estimates of it, as the chart below shows. Why? Because the empirical measurements of GAT have fallen so much lower than model-generated predictions.

In the chart, the dates are dates of publication (bottom axis) of peer-reviewed studies making estimates of climate sensitivity measured in degrees Celsius (left axis). ECS denotes “equilibrium climate sensitivity,” warming predicted in response to doubled atmospheric CO₂ concentration after all climate-system feedbacks are accounted for, a process that could take more than a century after CO₂ concentration has doubled. TCR denotes “transient climate response,” the temperature change at the time of CO₂ doubling but before all climate feedbacks have run their course. Generally the IPCC anticipates CO₂ will have doubled from pre-industrial times by late in this century (though this is not certain), so TCR would occur by then as well, and ECS a century or two later.

Those who charge people skeptical of claims of dangerous manmade warming (like us at the Cornwall Alliance) with being anti-science need to consider carefully: Who’s been trending right about how much warming comes from adding CO2 to the atmosphere—the alarmists, or the skeptics? (For in-depth discussion, see Nicholas Lewis, “Pitfalls in climate sensitivity estimation,” Part 1, Part 2, and Part 3.)

That’s a good reason to sign An Open Letter on Climate Change to the People, their Local Representatives, the State Legislatures and Governors, the Congress, and the President of the United States of America.