Gordon Brown and his now-departed chief economist have both described global warming as the worst “market failure” ever. That loaded sound-bite suggests the “climate-change” scare is less about saving the planet than, as Jacques Chirac chillingly said in praise of the Kyoto treaty, “creating world government”. Politicians, scientists and bureaucrats have contrived a threat of Biblical floods, droughts, plagues and extinctions worthier of St. John the Divine than of science.

Nick Stern’s report on the economics of climate change says the debate is over. It is not. There are more greenhouse gases in the air than there were, so the world should warm a bit, but that is as far as the “consensus” goes. The Royal Society agrees with Stern, saying there is a worldwide scientific consensus. It brands Apocalypse-deniers as paid lackeys of coal and oil. There have been demands for the public execution of airline executives. Margaret Beckett, the Foreign Secretary, used an otherwise paralyzing speech on climate change recently to compare thermosceptics with advocates of Islamic terror. She said both should be denied access to the media.

In the US, Senators Rockefeller and Crowe have called on ExxonMobil to stop funding scientists who doubt whether climate change will be cataclysmic. Rockefeller inherited a fossil-fuel fortune made by Standard Oil, which became Esso, which became — well, ExxonMobil.

Fortunately, the Quarterly Economic Bulletin is still a free-speech zone, so I am allowed to say that Stern’s report is bad economics based on bad science. First, the science — such as it is.

The Science

In the hot summer of 1988 James Hansen, a climatologist, told Congress that temperature would rise 0.2 to 0.45C by the end of the century. It rose 0.06C. Hansen said sea level would rise several feet by 2100 (the UN is about to cut its high-end forecast for sea-level rise from 3 feet to just 17 inches). The UN set up a transnational bureaucracy, the Intergovernmental Panel on Climate Change. The UK taxpayer meets the entire cost of its scientific team, which, in 2001, produced the Third Assessment Report, a Bible-length document presenting apocalyptic conclusions well beyond previous reports.

Next year the fourth report will come out. Though the rhetoric of the final draft is still hysterical, the facts are forcing a rethink. Carbon dioxide concentrations are rising fast, but temperature has not risen at all since the last report. The sea has cooled in the past two years, losing a fifth of the heat it gained in the past 20 years (Lyman, 2006). The Antarctic and Greenland ice masses are growing. All the computer models on which the UN’s entire case shakily rests failed to predict either the stable temperature or the falling sea temperature, and most of them missed the growing ice-masses till after they had been observed and measured.

The scare is ingeniously constructed. First, the UN implied that carbon dioxide ended the last four ice ages. It displayed two 450,000-year graphs — a sawtooth curve of temperature and a sawtooth of airborne CO₂ scaled to look similar. Usually, similar curves are superimposed for comparison. The UN did not superimpose them. If it had, the truth would have shown: the changes in temperature preceded the changes in CO₂ levels, which acted as no more than a slight climate feedback boosting the rise in temperature each time it occurred (Petit et al., 1999; Indermuhle et al., 2000, Caillon et al., 2003).

Next, the UN abolished the mediaeval warm period. In 1995, David Deming, a geoscientist at the University of Oklahoma, had written an article reconstructing 150 years of North American temperatures from borehole data. He later wrote: “With the publication of the article in Science, I gained significant credibility in the community of scientists working on climate change. They thought I was one of them, someone who would pervert science in the service of social and political causes. One of them let his guard down. A major person working in the area of climate change and global warming sent me an astonishing email that said, ‘We have to get rid of the Mediaeval Warm Period.’”

The UN obliged. Its second assessment report, in 1996, had displayed a 1,000-year graph showing that temperature in the Middle Ages was warmer than today’s. But the 2001 report contained a new graph showing no mediaeval warm period, and wrongly concluded that the 20^th century was the warmest for 1,000 years. The graph looked like a hockey-stick. The incorrectly-flat 1000–1900AD temperature line was the shaft: the uptick from 1900 to 2000 was the blade.

The UN gave one technique for reconstructing pre-thermometer temperature 390 times more weight than any other, but did not say so. The overweighted technique was one which the UN’s 1996 report had said was unsafe: measurement of tree-rings from bristlecone pines. Tree-rings are wider in warmer years, but pine-rings are also wider when there is more carbon dioxide in the air. CO₂ is plant food. This carbon dioxide fertilization distorts the calculations.

The UN’s scientists said they had included 24 datasets going back to 1400.  Without saying so, they left out the set showing the mediaeval warm period, tucking it into a folder marked “CENSORED DATA.”  They used a computer model to draw the graph from the data, but McIntyre & McKitrick (2005) later found that the model almost always drew hockey-sticks even if they fed in random, electronic “red noise”.

The large, full-colour “hockey-stick” was the key graph in the UN’s 2001 report, and the only one to appear six times. The Canadian Government copied it to every household. Four years passed before a leading scientific journal would publish the truth about the graph. Did Kofi or Ottawa apologize? No. The UN still uses the graph in its publications.

After the graph was exposed, several scientific papers apparently confirming its abolition of the mediaeval warm period appeared. The US Congress asked independent statisticians to investigate. They found that the graph was unmeritorious, and that known associates of the scientists who had compiled it had written many of the later papers supporting its conclusion. Later the US National Academy of Sciences said the statistical method used by the UN had a “validation skill not significantly different from zero” — i.e. it was useless.

The UN, echoed by Stern, says the graph is not important, and fails to apologize for it in the draft of its forthcoming report. Yet the mediaeval warm period is key. Scores of scientific papers show that it was real, global and up to 3C warmer than now. There are usually no glaciers in the tropical Andes, except on the very highest peaks: today they are there. There were Viking farms in Greenland: now some of them are under permafrost. Data from thousands of boreholes worldwide show global temperatures were higher in the Middle Ages than now. And the snows of Kilimanjaro are vanishing not because summit temperature is rising (it is unchanged) but because post-colonial deforestation has dried the air.

In some places it was also warmer than now in the Bronze Age and in Roman times. In the interglacial, 125,000 years ago, the temperature was at least 5C warmer than now: yet CO₂ concentrations were lower than today. It was not carbon dioxide that caused those warm periods. It was the Sun. So the UN adjusted the math and all but extinguished the Sun’s role in today’s warming. It dated its list of “forcings” — influences on temperature — from 1750, when the Sun was almost as warm as now. But its start-date for the increase in world temperature was 1900, when the Sun was cooler.

Every “forcing” produces “climate feedbacks” making temperature rise faster. For instance, as temperature rises in response to a forcing, the air carries more water vapour, the most important greenhouse gas; and polar ice melts, reducing the Earth’s albedo. Up goes the temperature again. The UN more than doubled the base forcings from greenhouse gases to allow for climate feedbacks. Its latest report will be compelled to revise the impact of both forcings and feedbacks sharply downward: yet it still says that a doubling of atmospheric CO2 concentrations since 1750 — which will perhaps occur between 2050 and 2100 — will cause temperature to rise by 3C. My calculations, using the latest data from the UN, suggest that “climate sensitivity” — the temperature response to a CO₂ doubling — will be about 0.6C.

Two centuries ago, the astronomer William Herschel was reading Adam Smith’s Wealth of Nations when he noticed that quoted grain prices fell when the number of sunspots rose. Gales of laughter ensued, but he was right. At solar maxima, when the Sun was at its hottest and sunspots showed, temperature was warmer, grain grew faster and prices fell. Such observations show that even small solar changes affect climate detectably. But recent solar changes have been big.

Solanki et al. (2005) report that in the past half-century the Sun has been warmer, for longer, than at any time in at least the past 11,400 years, contributing up to a third of the past century’s warming. The UN expresses its heat-energy forcings in watts per square metre. It estimates that the Sun caused just 0.12 watts of forcing since 1750. Begin in 1900 to match the temperature start-date, and the base solar forcing more than doubles to at least 0.3 watts. Multiply by 2.7, which Houghton (2006) suggests is the UN’s current factor for climate feedbacks, and you get 0.8 watts — more than six and a half times the UN’s figure. The entire 20^th-century warming from all sources was 1.72 watts. The Sun could have caused almost half of it.

Next, the UN slashed the natural greenhouse effect by 40% from 33C in the climate-physics textbooks to 20C, making the man-made enhancement appear bigger (Houghton, 2006).

Then the UN chose the biggest 20^th-century temperature increase it could find, and expressed surprise at how fast the world had warm. Stern wrote: “As anticipated by scientists, global mean surface temperatures have risen over the past century.” As anticipated? Only 30 years ago, when temperature had fallen for 35 years notwithstanding the monotonic rise in CO₂, a new Ice Age was widely predicted. Books called The Cooling were best-sellers. Sir Crispin Charles Cervantes Tickell, an eco-diplomatist, called for State subsidy to keep people warm. Now, unblushing, he calls for State subsidy for the opposite. Plus le climat change, plus c’est le meme Charles.