Archive for February, 2010
Dear Professor Pitman,
It would help me to understand your position if you were able to assist me in understanding this issue by answering some specific scientific questions.
Looking at the Hadley Centre’s global annual mean surface temperature anomalies since 1850, I notice that the data are stochastic, and yet with tantalizing indications of periodicity. Yet NOAA’s annual CO2 concentration anomalies appear to increase monotonically. Since absence of correlation is evident, and necessarily implies absence of causation, am I right in understanding that the monotonic increases in CO2 concentration over the period in question are not responsible for the considerable fluctuations in the surface temperature record over the period?
Looking at the same temperature record, I observe three supradecadal periods of marked warming, at a rate of approximately 0.16 Celsius degrees per decade: 1860-1880, 1910-1940, and 1975-1998. If I understand the IPCC’s rather diffuse documents correctly, it seems to be settled among all parties that humankind cannot have had any appreciable influence on temperature in the two earlier periods of rapid warming. The IPCC, however, states as its principal conclusion that, with 90% confidence, more than half of the warming since 1950 was anthropogenic. Nearly all of the warming since 1950 occurred in the 24 years 1975-1998: yet the rate of warming, at 0.16 C/decade, is not a whit greater than the rate of warming in the previous two periods. Have I understood this correctly?
The A2 scenario is the more conservative of the two IPCC scenarios that come closest to reflecting today’s actual global emissions of around 30 gigatons CO2. On that scenario, as best I can understand it, warming over the decades 2000-2020 is projected to be at a rate of 0.2 C/decade – appreciably higher than the highest supradecadal rate observed since 1850, which is 0.16 C/decade. Yet the real-world outturn since the year 2000 has been a warming rate vanishingly different from zero. Have I understood the facts correctly here?
If I were the IPCC, and I were trying to derive a reasonable central estimate of climate sensitivity to atmospheric greenhouse-gas enrichment, or to any other radiative perturbation of a presumed pre-existing equilibrium, I should wish to examine a sustained, supradecadal, generally-unidirectional period of statistically-significant warming or cooling, to identify the principal radiative forcings – if any – that can be detected by direct measurement. The only such period for which we have adequate satellite as well as terrestrial observations is 1983-2001, a period of warming substantial enough to give us some hope of overcoming mere statistical noise in our observations. Pinker et al. (2005), considering the ISCCP cloud records and the ERBE long-wave vs. short-wave outgoing-radiation datasets, concluded after a most meticulous intercalibration exercise between geostationary and polar-orbiting satellites that there was a sustained reduction in cloud cover over the period, which least-squares linear regression analysis shows to have represented a radiative forcing of 0.16 W/m2 for 19 years, or some 3.04 W/m2 in total. The radiative forcing from CO2 over the same period, using the function given in Myrhe (1998) and cited with approval by IPCC (2001, 2007), was 0.45 W/m2, and other anthropogenic forcings were 0.35 W/m2. Warming over the period was 0.45 K at most. From this, am I right to infer that the equilibrium temperature change to be expected from a doubling of CO2 concentration is represented approximately by the calculation below (subject, of course, to verification of Pinker’s results, and to identification of any significant negative forcings that he or I may have missed, and to action of very long-term feedbacks not reflected in the period)?
Delta-T = (5.35 ln 2)[0.45 / (3.04+0.45+0.35)] = 0.44 K
Am I right in recollecting that the IPCC, on the A2 scenario, predicts equilibrium warming of 3.26 K at CO2 doubling. It seems to me that, on the face of things, the IPCC’s central estimate of climate sensitivity is some 7.5 times larger than the result we have just reached above. In that event, Lord Monckton’s own theoretical determination of climate sensitivity 0.6 K at CO2 doubling (Monckton, 2008) may even be on the high side, when compared with the generally robust empirical result I have derived. Certainly, the IPCC’s central estimate of climate sensitivity seems insupportably excessive.
Would you care to comment?
Another thing which I found really interesting recently— a paper that strongly challenges the global warming claim that “global warming could trigger a collapse in temperatures across western Europe due to collapse of the Gulf Stream etc”
The main source of Europe’s mild climate is not the Gulf Stream as previously thought. The pacific ocean’s version of the gulf stream, the “Kuroshio current” does not reach as far as the northern latitiudes of Washington and British Columbia in north-west America. Yet the climate there is mild compared to similar latitudes in east asia on the west side of the pacific such as Vladivostok. So something other than the pacific gulf stream is keeping these latitidues in north america milder. It turns out the warmer climates on the east side of the atlantic and pacific are due to heat transfer from prevailing winds off the ocean, rather than the ocean currents themselves bringing in warm water ..This means we are not going to crash into an ice-age due to breakdown of the atlantic conveyor …
and popular and more reader friendly version of the above here:
The only thing I could think of that isn’t mentioned is the effect of the Jet Stream.