FIGURES in the final draft of the UN’s fourth five-year report on climate change show that the previous report, in 2001, had overestimated the human influence on the climate since the Industrial Revolution by at least one-third.

Also, the UN, in its 2007 report, has cut its high-end best estimate of the rise in sea level by 2100 from 3 feet to less than 2 feet. It suggests that the rate of sea-level rise is up from 2mm/yr to 3mm/year – no more than one foot in a century.

UN scientists faced several problems their computer models had not predicted. Globally, temperature is not rising at all, and sea level is not rising anything like as fast as had been forecast. Concentrations of methane in the air are actually falling.

The Summary for Policymakers was issued February 2, 2007, but the report on which the Summary is based was not published until May. This strange separation of the publication dates has raised in some minds the possibility that the Summary (written by political representatives of governments) was taken as a basis for altering the science chapters (written by scientists, and supposedly finalized and closed in December 2006).

The text of the science chapters reveals that the tendency of computers to over-predict rises in temperature and sea level has forced a major rethink.

The report’s generally more cautiously-expressed projections confirm scientists’ warnings that the UN’s heavy reliance on computer models had exaggerated the temperature effect of greenhouse-gas emissions.

Previous reports in 1990, 1995 and 2001 had been progressively more alarmist. In the final draft of the new report there is a change in tone. Though carbon dioxide in the air is increasing, global temperature is not.

Figures from the US National Climate Data Center show 2006 as about 0.03 degrees Celsius warmer worldwide than 2001. Since that is within the range of measurement error, global temperature has not risen in a statistically significant sense since the UN’s last report in 2001.

Sources at the center of the drafting say that, though the now-traditional efforts are being made to sound alarmist and scientific at the same time, key projections are being quietly cut.

One says: “Stern is dead. The figures in the final draft of the UN’s Fourth Assessment Report makes the recent report of your Treasury’s chief economist on the cost of climate change look like childish panic.”

The UN’s 2001 report showed that our greenhouse-gas emissions since 1750 had caused a “radiative forcing” of 2.43 watts per square metre. Our other effects on climate were shown as broadly self-cancelling.

In the current draft, the UN has cut its estimate of our net effect on climate by more than a third, to 1.6 watts per square metre. It now thinks pollutant particles reflecting sunlight back to space have a very strong cooling effect.

As a deterrent to direct comparisons between the two reports, the key table of “radiative forcings” – the list of human influences on the amount of heat-energy in the atmosphere – has been rotated by 90 degrees compared with the 2001 table.

The UN also uses a 90% “confidence interval” rather than the 95% interval that is normal statistical usage. This has the effect of giving the UN’s projections a misleading appearance of greater certainty.

The UN’s best estimate of projected temperature increase in response to CO₂ reaching 560 parts per million, twice the level in 1750, was 3.5C in the 2001 report. Now it is down to 3C.

The 2007 draft concludes that it is very likely that we caused most of the rise in temperatures since 1940. It does not point out that for half that period, from 1940 to 1975, temperature actually fell even though carbon dioxide rose monotonically – higher every year than the previous year.

Of the UN’s six modeled scenarios, three are extreme exaggerations. Two assume that population will reach 15bn by 2100, though demographers say population will peak at 10bn in 40 years and then plummet. The UN’s high-end temperature projection to 2100, up from 5.8C to 6C, is based on these extreme and unrealistic scenarios.

The new report confirms the finding of the 2001 report that global warming will have little effect on the number of typhoons or hurricanes, though it may increase the intensity of some storms a little. However, updated research shows that wind-shear effects largely cancel this intensity.

Computer models heavily relied on by the UN did not predict the considerable cooling of the oceans that has occurred since 2003 – a cooling which demonstrates that neither the frequency nor the intensity of the hurricanes in the year of Katrina was attributable to “global warming”.

The UN’s models also failed to predict the halt to the rise in methane concentrations in the air that began in 2001. And they did not predict the timing or size of the El Nino which hiked temperature in 1998. Without it, the satellite record shows little or no greenhouse warming. Land-based temperature records may accordingly overstate the problem.

Likewise the UN’s models have recently been found to have over-projected the observed rise in sea temperatures, which has had to be corrected downward to allow for over-reading by incorrectly-calibrated instrumentation.

The UN’s draft Summary for Policymakers contains no apology for the defective and discredited “hockey-stick” graph that erroneously abolished the warm climate of the Middle Ages, arousing in some minds the suspicion that the intellectual honesty of the IPCC process is deficient.

Ambiguities in the report, and considerable discrepancies between it and its predecessor, show that there is no scientific consensus on many points for which consensus is often claimed. Overall, however, the report is drafted so as to allow environmental extremists to cite its high-end projections as evidence of the need for urgent action.

The ambiguities, together with the conspicuous failure to apologize for the discredited “hockey-stick” graph, fully justify the decision of fast-developing third-world countries such as China and India not to yield to pressure from the EU at the recent Nairobi climate summit to cut their greenhouse-gas emissions.

China, with 30,000 coal mines, is opening a new pit every week and a new coal-fired power station every five days until 2012. Well before then, China will overtake the US as the world’s largest emitter of greenhouse gases.

Even if a country the size of Britain were to shut down and cease using energy or cars altogether, the growth in carbon emissions in China would more than make up for our sacrifice long before the Kyoto agreement expires in 2012.

Even if the US were to shut down its entire economy, growth in emissions from fast-emerging new polluters such as China, India, Indonesia, Russia, and Brazil would replace the US emissions within the next quarter of a century.

The Intergovernmental Panel on Climate Change of the UN approved the complete report for publication at its 36^th session, in Bangkok, Thailand, in May 2007.

In the meantime, there will be continuing pressure from a small but vociferous body of politicized scientists, bureaucrats, and lobby groups to suggest that the 2007 report is more alarming than its predecessors. However, the sharp downward revisions in the values of the two central variables – the human contribution to warming compared with 1750 and the projected rise in sea level to 2100 – indicates that the UN has come to appreciate the dangers that would have arisen if it were to have persisted in its former exaggerations.

The “consensus” clique are displeased at the UN’s new-found moderation, particularly in its slashing of its upper-bound projection of the rise in sea level to 2100. But it was they who formerly insisted that the UN, with 2,000 participating scientists, represented the very heart of the “consensus”. Accordingly they find themselves unable convincingly to repudiate the findings of a body whose work they have hitherto represented to us as sacrosanct.

Though the mass media are now well-programmed to focus on the more alarmist aspects of the report, the halving of the sea-level projection is in effect a declaration, from the heart of the “consensus”, that the consequences of warmer worldwide weather will be minor and may be beneficial, that the worst scenarios are no longer probable, and that the panic is officially over.