You will recall the article in the Wall Street Journal “No need to panic about global warming” (see here). Then came the response from the headbangers, swiftly dealt with by Pat Michaels here (“Wall Street Journal war of words continues”) and letter writers here (“WSJ: When you’re a hammer, everything looks like a nail”).
Now the original writers have responded in detail:
[…] an important gauge of scientific expertise is the ability to make successful predictions. When predictions fail, we say the theory is “falsified” and we should look for the reasons for the failure. Shown in the nearby graph is the measured annual temperature of the earth since 1989, just before the first report of the Intergovernmental Panel on Climate Change (IPCC). Also shown are the projections of the likely increase of temperature, as published in the Summaries of each of the four IPCC reports, the first in the year 1990 and the last in the year 2007.
These projections were based on IPCC computer models of how increased atmospheric CO2 should warm the earth. Some of the models predict higher or lower rates of warming, but the projections shown in the graph and their extensions into the distant future are the basis of most studies of environmental effects and mitigation policy options. Year-to-year fluctuations and discrepancies are unimportant; longer-term trends are significant.
From the graph it appears that the projections exaggerate, substantially, the response of the earth’s temperature to CO2 which increased by about 11% from 1989 through 2011. Furthermore, when one examines the historical temperature record throughout the 20th century and into the 21st, the data strongly suggest a much lower CO2 effect than almost all models calculate.
Read it here.