The Council of the American Physical Society (APS) has adopted on April 18, 2010 a "Climate Change Commentary" to append to their definitive and "incontrovertible" 2007 policy statement
on climate change. The commentary
allows considerable backpedaling from the prior policy while appearing to save face. The commentary removes the word incontrovertible
because such words are "rarely used in science because by its very nature science questions prevailing ideas." The statement "While there are factors driving the natural variability of climate (e.g., volcanoes, solar variability, oceanic oscillations), no known natural mechanisms have been proposed that explain all of the observed warming in the past century.
" is added, and while not true since there are a number of papers which show that ocean oscillations and solar variability can explain all of the 0.7 degree warming of the past century, it is a step in the right direction from the 2007 policy which makes no mention of natural forcing and blames climate change on man-made emissions of CO2.
For the first time there is acknowledgement of the uncertainties associated with models, including the statement "These models have uncertainties associated with radiative response functions, especially clouds and water vapor. However, the models show that water vapor has a net positive feedback effect (in addition to CO2 and other gases) on global temperatures. The impact of clouds is less certain because of their dual role as scatterers of incoming solar radiation and as greenhouse contributors."
While it is true the models show net positive feedback, that is only because that is how they were programmed, and no mention is made of the empirical satellite and weather balloon data
which show the net feedback is actually negative. At least, the commentary
begins to indicate large uncertainties with climate modeling.
The commentary adds "The uncertainty in the estimates from various climate models for doubling CO2-equivalent concentration is in the range of 1°C to 3°C with the probability distributions having long tails out to much larger temperature changes.
", without mentioning that 1°
C global warming is what is expected from the no feedback model and even less from the negative feedback model as supported by data, which is likely to be beneficial and is hardly cause for alarm or cap & tax schemes. As Richard Lindzen and Roy Spencer have repeatedly pointed out, the real issue to be determined is the sensitivity of the climate to changes in CO2, for which all the empirical data show the models have greatly overestimated sensitivity. If there is low sensitivity, there is no cause for alarm.
Here is the original 2007 policy, followed by the new Commentary: