Since there has been a lot of discussion about Monckton here and elsewhere, I’ve offered him the opportunity to present his views here. – Anthony
Guest post by Christopher Monckton of Brenchley
At www.scienceandpublicpolicy.org I publish a widely-circulated and vigorously-debated Monthly CO2 Report, including graphs showing changes in CO2 concentration and in global mean surface temperature since 1980, when the satellites went on weather watch and the NOAA first published its global CO2 concentration series. Since some commenters here at Wattsup have queried some of our findings, I have asked Anthony to allow me to contribute this short discussion.
We were among the first to show that CO2 concentration is not rising at the fast, exponential rate that current anthropogenic emissions would lead the IPCC to expect, and that global temperature has scarcely changed since the turn of the millennium on 1 January 2001.
CO2 concentration: On emissions reduction, the international community has talked the talk, but – not least because China, India, Indonesia, Russia, Brazil, and South Africa are growing so quickly – it has not walked the walk. Accordingly, carbon emissions are at the high end of the IPCC’s projections, close to the A2 (“business as usual”) emissions scenario, which projects that atmospheric CO2 will grow at an exponential rate between now and 2100 in the absence of global cuts in emissions:
Exponential increase in CO2 concentration from 2000-2100 is projected by the IPCC on its A2 emissions scenario, which comes closest to today’s CO2 emissions. On the SPPI CO2-concentration graph, this projection is implemented by way of an exponential function that generates the projection zone. This IPCC graph has been enlarged, its ordinate and abscissa labeled, and its aspect ratio altered to provide a comparison with the landscape format of the SPPI graph.
On the A2 emissions scenario, the IPCC foresees CO2 rising from a measured 368 ppmv in 2000 (NOAA global CO2 dataset) to a projected 836[730, 1020] ppmv by 2100. However, reality is not obliging. The rate of increase in CO2 concentration has been slowing in recent years: an exponential curve cannot behave thus. In fact, the the NOAA’s deseasonalized CO2 concentration curve is very close to linear:
CO2 concentration change from 2000-2010 (upper panel) and projected to 2100 (lower panel). The least-squares linear-regression trend on the data shows CO2 concentration rising to just 570 ppmv by 2100, well below the IPCC’s least estimate of 730 ppmv on the A2 emissions scenario.
The IPCC projection zone on the SPPI graphs has its origin at the left-hand end of the linear-regression trend on the NOAA data, and the exponential curves are calculated from that point so that they reach the IPCC’s projected concentrations in 2100.
We present the graph thus to show the crucial point: that the CO2 concentration trend is well below the least IPCC estimate. Some have criticized our approach on the ground that over a short enough distance a linear and an exponential trend may be near-coincident. This objection is more theoretical than real.
First, the fit of the dark-blue deseasonalized NOAA data to the underlying linear-regression trend line (light blue) is very much closer than it is even to the IPCC’s least projection on scenario A2. If CO2 were now in fact rising at a merely linear rate, and if that rate were to continue, concentration would reach only 570 ppmv by 2100.
Secondly, the exponential curve most closely fitting the NOAA data would be barely supra-linear, reaching just 614 ppmv by 2100, rather than the linear 570 ppmv. In practice, the substantial shortfall between prediction and outturn is important, as we now demonstrate. The equation for the IPCC’s central estimate of equilibrium warming from a given rise in CO2 concentration is:
∆T = 4.7 ln(C/C0),
where the bracketed term represents a proportionate increase in CO2 concentration. Thus, at CO2 doubling, the IPCC would expect 4.7 ln 2 = 3.26 K warming – or around 5.9 F° (IPCC, 2007, ch.10, p.798, box 10.2). On the A2 scenario, CO2 is projected to increase by more than double: equilibrium warming would be 3.86 K, and transient warming would be <0.5 K less, at 3.4 K.
But if we were to take the best-fit exponential trend on the CO2 data over the past decade, equilibrium warming from 2000-2100 would be 4.7 ln(614/368) = 2.41 K, comfortably below the IPCC’s least estimate and a hefty 26% below its central estimate. Combining the IPCC’s apparent overestimate of CO2 concentration growth with the fact that use of the IPCC’s methods for determining climate sensitivity to observed increases in the concentration of CO2 and five other climate-relevant greenhouse gases over the 55 years 1950-2005 would project a transient warming 2.3 times greater than the observed 0.65 K, anthropogenic warming over the 21st century could be as little as 1 K (less than 2 F°), which would be harmless and beneficial.
Temperature: How, then, has observed, real-world global temperature responded?
The UAH satellite temperature record shows warming at a rate equivalent to 1.4 K/century over the past 30 years. However, the least-squared linear-regression trend is well below the lower bound of the IPCC projection zone.
The SPPI’s graph of the University of Alabama at Huntsville’s monthly global-temperature anomalies over the 30 years since 1 January 1980 shows warming at a rate equivalent to 1.4 K/century – almost double the rate for the 20th-century as a whole. However, most of the warming was attributable to a naturally-occurring reduction in cloud cover that allowed some 2.6 Watts per square meter of additional solar radiance to reach the Earth’s surface between 1981 and 2003 (Pinker et al., 2005; Wild et al., 2006; Boston, 2010, personal communication).
Even with this natural warming, the least-squares linear-regression trend on the UAH monthly global mean surface temperature anomalies is below the lower bound of the IPCC projection zone.
Some have said that the IPCC projection zone on our graphs should show exactly the values that the IPCC actually projects for the A2 scenario. However, as will soon become apparent, the IPCC’s “global-warming” projections for the early part of the present century appear to have been, in effect, artificially detuned to conform more closely to observation. In compiling our graphs, we decided not merely to accept the IPCC’s projections as being a true representation of the warming that using the IPCC’s own methods for determining climate sensitivity would lead us to expect, but to establish just how much warming the use of the IPCC’s methods would predict, and to take that warming as the basis for the definition of the IPCC projection zone.
Let us illustrate the problem with a concrete example. On the A2 scenario, the IPCC projects a warming of 0.2 K/decade for 2000-2020. However, given the IPCC’s projection that CO2 concentration will grow exponentially from 368 ppmv in 2000 towards 836 ppmv by 2100, CO2 should have been 368e(10/100) ln(836/368) = 399.5 ppmv in 2010, and equilibrium warming should thus have been 4.7 ln(399.5/368) = 0.39 K, which we reduce by one-fifth to yield transient warming of 0.31 K, more than half as much again as the IPCC’s 0.2 K. Of course, CO2 concentration in 2010 was only 388 ppmv, and, as the SPPI’s temperature graph shows (this time using the RSS satellite dataset), warming occurred at only 0.3 K/century: about a tenth of the transient warming that use of the IPCC’s methods would lead us to expect.
Barely significant warming: The RSS satellite data for the first decade of the 21st century show only a tenth of the warming that use of the IPCC’s methods would lead us to expect.
We make no apology, therefore, for labelling as “IPCC” a projection zone that is calculated on the basis of the methods described by the IPCC itself. Our intention in publishing these graphs is to provide a visual illustration of the extent to which the methods relied upon by the IPCC itself in determining climate sensitivity are reliable.
Some have also criticized us for displaying temperature records for as short a period as a decade. However, every month we also display the full 30-year satellite record, so as to place the current millennium’s temperature record in its proper context. And our detractors were somehow strangely silent when, not long ago, a US agency issued a statement that the past 13 months had been the warmest in the instrumental record, and drew inappropriate conclusions from it about catastrophic “global warming”.
We have made one adjustment to please our critics: the IPCC projection zone in the SPPI temperature graphs now shows transient rather than equilibrium warming.
One should not ignore the elephant in the room. Our CO2 graph shows one elephant: the failure of CO2 concentration over the past decade to follow the high trajectory projected by the IPCC on the basis of global emissions similar to today’s. As far as we can discover, no one but SPPI has pointed out this phenomenon. Our temperature graph shows another elephant: the 30-year warming trend – long enough to matter – is again well below what the IPCC’s methods would project. If either situation changes, followers of our monthly graphs will be among the first to know. As they say at Fox News, “We report: you decide.”