In a dramatic recent article on his blog, Clouds Dominate CO2 as a Climate Driver Since 2000, Roy Spencer sets out clear evidence for internally-forced changes in the climate system. An internal forcing is a feedback, as when a change in temperature causes some other change which itself also changes the temperature.
For example, when temperature rises, it may cause an increase in atmospheric water vapour; that water vapour may condense into clouds, which in turn, by reflecting the incoming sunlight back to space, may cause the temperature to drop.
Such a process might be termed a thermostat, a natural regulator, keeping the temperature within its natural bounds, much as it has done for half a billion years and more.
In our example, the forcing was a temperature increase and the feedback was a temperature decrease – a negative feedback, moving the temperature in the opposite direction from the forcing. A positive feedback would move the temperature in the same direction as the forcing.
To date, the IPCC assumes two vital things: that climate sensitivity is high and internal forcing (feedback) is positive.
I do not follow every detail that Dr Spencer describes, but, after challenging these two assumptions and showing them to be wrong, his conclusion pulls no punches.
Clouds Dominate CO2 as a Climate Driver Since 2000
Last year I posted an analysis of satellite observations of the 2007-08 global cooling event, showing evidence that it was due to a natural increase in low cloud cover. Here I will look at the bigger picture of how the satellite-observed variations in Earth’s radiative budget compare to those expected from increasing carbon dioxide. Is there something that we can say about the relative roles of nature versus humanity based upon the evidence?
What we will find is evidence consistent with natural cloud variations being the dominant source of climate variability since 2000. Continue Reading →
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