To the Editor,
NASA climate modeller James Hansen introduces his August 5 op-ed (“Climate change is here–and worse than we thought”) by referring to his June 23, 1988 testimony on global warming to a joint House/Senate Committee, stating that he was “too optimistic” at that time. The opposite is true.
At that time, Hansen projected warming based upon two viable emissions scenarios–what he called “Business as Usual”, or his “Scenario A”, and another with emissions reductions (“Scenario B”). The warmings predicted by the two, between then and now, are, respectively, 1.26 and 1.21 degrees Fahrenheit. The observed warming, in his own somewhat controversial climate record, is 0.68 degrees.
Overpredicting warming by roughly 50% (given the obviously large margins of error in this data) means that warming has been much less than he thought.
Patrick J. Michaels
Director, Center for the Study of Science