TCS Daily


The Climate "Consensus"

By Vincent Gray - April 8, 2004 12:00 AM

"Consensus is the process of abandoning all beliefs, principles, values and policies in search of something in which no one believes, but to which no one objects; the process of avoiding the very issues that have to be solved, merely because you cannot get agreement on the way ahead."

-- Margaret Thatcher "The Downing Street Years", page 167

The Summary for Policymakers that appears at the beginning of all Reports of the Intergovernmental Panel on Climate Change is agreed line-by-line by Government Representatives and senior scientists. It therefore represents a true consensus.

But, although it undoubtedly is a unanimous agreement, it also represents a compromise between opposing views, and it suffers from the drawbacks so clearly stated by Maggie.

For example, take the statement first made in Climate Change 1995 (published 1996),

"The balance of the evidence suggests a discernible human influence on global climate."

To start with, the "balance of the evidence" evidently does not prove that humans influence the climate, nor does it show that there is an influence. All we have is that it "suggests" an influence, which is merely "discernible." No scientific basis is given for this suggestion, or who it was that suggested it.

Then, there is no mention of greenhouse gases as one of the possible "human influences". It is evident that there must have been a significant number of participants who refused to include such an influence.

All scientists would agree, with the IPCC, that humans influence the climate, but the IPCC statement cannot be interpreted to mean that a relationship between greenhouse gases and climate has been established even if many have done so.

All the statements in the various "Summaries for Policymakers" are similarly non-committal. It is the price paid for consensus.

Climate Change (1990), the first IPCC science Report, in its first paragraph, claimed that the additional greenhouse gases would result

"on average in an additional warming of the earth's surface"

but they did not say whether this additional warming was measurable, significant, or important.

Later, the report said, referring to the combined weather station record,

"The size of the warming is broadly consistent with the prediction of climate models but is also of the same magnitude as natural climate variability."

Now, if you compared the combined weather station record they provided with the predictions of climate models, you would find little broad consistency between them. The weather station record showed a large rise from 1910 to 1940 when greenhouse gases were sparse, and a fall from 1945 to 1975, when they increased. The records are obviously broadly inconsistent. About the only thing they agree on is that they both rise over the past century. But here we run into a persistent trick of the IPCC. They know that a cause/effect relationship cannot be established merely by comparing similar curves, but they try to find a form of words which implies that you can. Saying something is broadly consistent is one way.

Even if a cause and effect relationship were found, it might not involve greenhouse gases at all, since the climate models, based on greenhouse gases, are also an approximate model for energy from fossil fuels. Even if you get a good agreement between warming of weather stations and climate models based on greenhouse gases, it may be because the weather station thermometers are more influenced by the extra heat from fuel combustion than by the greenhouse gases emitted.

The latest IPCC Report, Climate Change 2001 (2001), made several similarly confusing statements.

"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."

"The last 50 years" is puzzling. The combined weather station record, which is heavily promoted by the IPCC as an indicator of global temperature change, does not show a warming for the past 50 years. For the first half, 1950-1975 the temperature fell. It showed a rise only for the last 25 years. But then, the satellite record, which is far more reliable than the weather station record, does not show a significant warming for the past 25 years.

Then what is meant by "attributable"? Yet another way of implying a forbidden cause and effect from a correlation?

And which "human activities" are meant? No mention of greenhouse gas emissions as one of them.

Then we have:

"...most of the warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations."

Yet another breach of the cause/effect rule; using "is likely" as a cover up, and this time, no mention of humans. The main greenhouse gas, after all, is water vapour and that could change without humans.

None of the IPCC "Summaries for Policymakers" claim that the enormous amount of scientific evidence has established a relationship between greenhouse gases and any climate parameter; apart from the beneficial additional plant, forest, and crop growth.

The true opinion of the IPCC scientists is to be found in Chapter 1 of Climate Change 2001, page 97:

"The fact that the global mean temperature has increased since the late 19th century and that other trends have been observed does not necessarily mean that an anthropogenic effect on the climate has been identified. Climate has always varied on all time-scales, so the observed change may be natural."

But this opinion got buried, thanks to the need for consensus.

Vincent Gray is the author of The Greenhouse Delusion. He has a PhD in Physical Chemistry from Cambridge University and is an expert reviewer for the Intergovernmental Panel on Climate Change. He lives in Wellington, New Zealand.

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