Guest essay by Christopher Monckton
As soon as the BBC/Maslowski forecast of no sea ice in the Arctic summer by 2013 has been disproven (see countdown on right sidebar), WUWT will need another countdown. May I propose the Santer countdown?
On November 17, 2011, Ben Santer and numerous colleagues, including researchers from Remote Sensing Systems (RSS), published a paper in the Journal of Geophysical Research (Atmospheres) that, as his press release said,
“shows that climate models can and do simulate short, 10- to 12-year “hiatus periods” with minimal warming, even when the models are run with historical increases in greenhouse gases and sulfate aerosol particles. … tropospheric temperature records must be at least 17 years long to discriminate between internal climate noise and the signal of human-caused changes in the chemical composition of the atmosphere.”
In an earlier posting I demonstrated that for more than 17 years (now 17 years 7 months) the HadCRUt4 monthly global mean surface temperature anomaly dataset had shown no global warming distinguishable from the combined 2 σ measurement, coverage, and bias uncertainties published together with the data themselves.
However, there were those who said that, nevertheless, the HadCRUt4 data appeared to show some warming (albeit less than 1 Cº/century). Well, the first of the five principal datasets to show no warming at all for 17 years is likely to be the RSS dataset of Santer’s own colleagues. Today the data for August 2013 were made available:
The least-squares linear-regression trend on the data from the RSS satellites since November 1996 shows there has been no global warming at all for 202 months (16 years 10 months). In a few more months, unless an el Niño comes along in January, its favorite month, RSS may be the first dataset to show 17 full years with a zero global warming trend.
The NOAA’s 2008 State of the Climate report said 15 or more years without global warming would indicate what was delicately described as a “discrepancy” between prediction and observation.
Fifteen years without warming duly came and went: indeed, Professor Jones of the University of East Anglia was the first to admit this, in response to a question I had suggested to Roger Harrabin of the BBC (who had thought I was daft to suggest that there had been no statistically-significant warming for as much as a decade and a half).
So Santer moved the goalposts.
Taking the mean of all five principal global-temperature datasets (GISS, HadCRUt4, NCDC, RSS, and UAH), since the new millennium began on 1 January 2001 there has been no global warming at all for 152 months (12 years 8 months):
Therefore, those who are anxious to believe that the long pause in global warming is what the models expected, or at least allowed for, can take a crumb of comfort from that.
Two important caveats. First, linear trends are not predictions. They are only one way of representing the trend (if any) that has already occurred over a chosen period in a stochastic dataset such as the global mean surface or lower-troposphere temperature anomalies.
Secondly, a strong el Niño, or a resumption of stronger solar activity, or simply some hitherto-unexplained factor in natural climate variability, could cause a resumption of global warming at any time. The central consideration, then, is not whether there have been x years without global warming, vexing though this embarrassing statistic is to the true-believers and their models. It is the extent and the persistence of the discrepancy between predicted and observed global warming.
The monthly Global Warming Prediction Index keeps track of this discrepancy. The index number for September 2013, published today, is 0.22 Cº. That is how much the IPCC’s central projection of global warming over the 8 years 8 months from January 2005 to August 2013 has overshot the observed temperature trend.
Today’s index graph shows 34 models’ projections of global warming since January 2005 in the IPCC’s Fifth Assessment Report as an orange region. The IPCC’s central projection, the thick red line, is that the world should have warmed by 0.20 Cº (equivalent to 2.33 Cº/century) since that starting date.
The mean of the RSS and UAH satellite measurements, in dark blue over the bright blue trend-line, shows global cooling of 0.02 Cº (–0.22 Cº/century). The models have thus over-predicted warming since January 2005 by 0.22 Cº (2.55 Cº/century).
The 18 ppmv (202 ppmv/century) rise in the trend on the gray dogtooth CO2 concentration curve, plus other ghg increases, should have caused 0.1 Cº warming, with the remaining 0.1 ºC from previous CO2 increases. No warming has occurred.
On its own, the CO2 increase since 2005 should have caused a radiative forcing of 0.24 Watts per square meter, or 0.34 W m–2 after including the influence of all other greenhouse gases. Even without temperature feedbacks, according to the IPCC’s methods this forcing should have caused 0.1 Cº warming. Adding in the IPCC’s temperature estimates of temperature feedbacks and of previously-committed global warming should have caused up to 0.3 Cº warming since January 2005. None has occurred.
Note how the temperature has failed to rise since 2005, notwithstanding that the CO2 concentration has risen quite rapidly. The usual suspects like to display what they call an “escalator graph” with many of Santer’s “hiatus periods” of 10-12 years without any global warming, but an overall rising trend nonetheless.
However, previous periods free of global warming did not occur while Man was putting more CO2 in the air anything like as rapidly as he is today. Now that CO2 concentration is rising, so should temperature be rising, if the IPCC were correct about how much warming we should expect as CO2 concentration increases.
The “escalator graph”, then, is meaningless, except to the extent that the frequency with which the “hiatus periods” occurs suggests that the probability of seeing anything like the 2.8 Cº warming this century that is the IPCC’s central projection is not very great.
Though the IPCC projects that the world should have warmed by 0.20 Cº (2.33 Cº/century) since 2005, the mean of the RSS and UAH satellite datasets shows cooling of 0.02 Cº (0.22 Cº/century). The predicted and actual trends are visibly diverging. Solar physicists expect significant cooling in the coming decades. If they are right, the divergence will become more than merely embarrassing.
Even as things stand, if the IPCC overshoot over the past 104 months were to continue for 100 years the IPCC’s prediction would exceed the measured trend by more than 2.5 Cº.
If Jeffrey Patterson’s harmonic decomposition of the past 113 years’ temperature records is correct, the world may actually be cooler in 2100 than in 2000.
A shame we shall not be there to see the baffled faces of the profiteers of doom.