Abstract

It is often said that there is a scientific “consensus” to the effect that climate change will be “catastrophic” and that, on this question, “the debate is over”. The present paper will demonstrate that the claim of unanimous scientific “consensus” was false, and known to be false, when it was first made; that the trend of opinion in the peer-reviewed journals and even in the UN’s reports on climate is moving rapidly away from alarmism; that, among climate scientists, the debate on the causes and extent of climate change is by no means over; and that the evidence in the peer-reviewed literature conclusively demonstrates that, to the extent that there is a “consensus”, that “consensus” does not endorse the notion of “catastrophic” climate change.

David Miliband, the Environment Minister of the United Kingdom, was greeted by cries of “Rubbish!” when he told a conference on climate change at the Holy See in the spring of 2007 that the science of climate and carbon dioxide was simple and settled. Yet Miliband was merely reciting a mantra that has been widely peddled by politicians such as Al Gore and political news media such as the BBC, which has long since abandoned its constitutional obligation of objectivity on this as on most political subjects, and has adopted a policy of not allowing equal air-time to opponents of the imagined “consensus”.

The claim of “consensus” rests almost entirely on an inaccurate and now-outdated single-page comment in the journal Science entitled The Scientific Consensus on Climate Change (Oreskes, 2004). In this less than impressive “head-count” essay, Naomi Oreskes, a historian of science with no qualifications in climatology, defined the “consensus” in a very limited sense, quoting as follows from IPCC (2001) –

“Human activities … are modifying the concentration of atmospheric constituents … that absorb or scatter radiant energy. … most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations.”

The limited definition of “consensus”

Oreskes’ definition of “consensus” falls into two parts. First, she states that humankind is altering the composition of the atmosphere. This statement is uncontroversial: for measurement has established that the concentration of carbon dioxide in the atmosphere has risen over the past 250 years to such an extent that CO2 now constitutes almost 0.01 per cent more of the atmosphere than in the pre-industrial era. However, on the question whether that alteration has any detrimental climatic significance, there is no consensus, and Oreskes does not state that there is.

The second part of Oreskes’ definition of the “consensus” is likewise limited in its scope. Since global temperatures have risen by about 0.4C in the past 50 years, humankind – according to Oreskes’ definition of “consensus” – may have accounted for more than 0.2C.

Applying that rate of increase over the present century, and raising it by half to allow for the impact of fast-polluting developing countries such as China, temperature may rise by 0.6C in the present century, much as it did in the past century, always provided that the unprecedented (and now-declining) solar activity of the past 70 years ceases to decline and instead continues at its recent record level.

There is indeed a consensus that humankind is putting large quantities of greenhouse gases into the atmosphere; that some warming has resulted; and that some further warming can be expected. However, there is less of a consensus about whether most of the past half-century’s warming is anthropogenic, which is why, rightly, Oreskes is cautious enough to circumscribe her definition of the “consensus” about the anthropogenic contribution to warming over the past half-century with the qualifying adjective “likely”.

There is no scientific consensus on how much the world has warmed or will warm; how much of the warming is natural; how much impact greenhouse gases have had or will have on temperature; how sea level, storms, droughts, floods, flora, and fauna will respond to warmer temperature; what mitigative steps – if any – we should take; whether (if at all) such steps would have sufficient (or any) climatic effect; or even whether we should take any steps at all.

Campaigners for climate alarm state or imply that there is a scientific consensus on all of these things, when in fact there is none. They imply that Oreskes’ essay proves the consensus on all of these things. Al Gore, for instance, devoted a long segment of his film An Inconvenient Truth to predicting the imminent meltdown of the Greenland and West Antarctic ice-sheets, with a consequent global increase of 20 feet (6 m) in sea level that would flood Manhattan, Shanghai, Bangladesh, and other coastal settlements. He quoted Oreskes’ essay as proving that all credible climate scientists were agreed on the supposed threat from climate change. He did not point out, however, that Oreskes’ definition of the “consensus” on climate change did not encompass, still less justify, his alarmist notions.

Let us take just one example. The UN’s latest report on climate change, which is claimed as representing and summarizing the state of the scientific “consensus” insofar as there is one, says that the total contribution of ice-melt from Greenland and Antarctica to the rise in sea level over the whole of the coming century will not be the 20 feet luridly illustrated by Al Gore in his movie, but just 2 inches.

Gore’s film does not represent the “consensus” at all. Indeed, he exaggerates the supposed effects of ice-melt by some 12,000 per cent. The UN, on the other hand, estimates the probability that humankind has had any influence on sea level at little better than 50:50. The BBC, of course, has not headlined, or even reported, the UN’s “counter-consensual” findings. Every time the BBC mentions “climate change”, it shows the same tired footage of a glacier calving into the sea – which is what glaciers do every summer.

What Oreskes said

Oreskes (2004) said she had analyzed –

“928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords ‘climate change’.”

She concluded that 75% of the papers either explicitly or implicitly accepted the “consensus” view; 25% took no position, being concerned with palaeoclimate rather than today’s climate; and –