The “Internal Variability” Fallback Argument
April 30, 2011 Leave a comment
One fallback argument used by AGW proponents is that the flat to declining temperatures since 1997 (or since the El Niño warming of 1998) is the result of an “offset” or masking of the AGW effect by internal variation. However, for consistency sake, they must allow for internal variability in the two PREVIOUS regimes that could have been affected by rising CO2 emissions (that is, the 1977-1998 warming and the 1944-1977 cooling).
To paraphrase Doug L. Hoffman, if a regime-shift from the ’77 to ’98 warming (0.13 ± 0.02°C per decade) changes to a practically flat trend for the next few decades (−0.02 ± 0.05°C per decade), increasing again with the assumption of continuous underlying warming, then the reduced trend is actually consistent with the LOW-END empirical estimates of climate sensitivity. (Approx. 0.2°C above present levels by 2100.)
Not only is this considerably lower than most IPCC projections (IPCC, 2007), but also fits in pretty well with a recovery from the Little Ice Age. In fact, if you take into account the 1880-1915 cooling and 1915-1944 warming —periods that could not have been influenced by rising levels of CO2— then the pattern of warming-cooling looks indistinguishable from natural fluctuations internal to the climate system itself! The point is that if there is an AGW effect, how could you tell the difference between what is natural and what is anthropogenic.
‘Stat Model Predicts Flat Temperatures Through 2050 by Doug L. Hoffman’
‘Structural break models of climatic regime-shifts: claims and forecasts (2009)’
31 December, 2010