"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 Policymnakers  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 95,  " The balance of the evidence suggests a discernible human influence on global climate "
To start with the "balance of the evidence" does not prove that humans influence the climate, nor does it show that there is an influence. All we have is  suggests, and 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.
The statement is meaningless, and certainly cannot be interpreted to mean that the IPCC have established a relationship between greenhouse gases and climate.
ALL the statements in the various "Summaries for Policymakers" are similarly obscure and non-committal. It is the price paid for consensus.
Climate Change 1990, the first 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 no mention of whether this additional warming was measurable, significant, or important.
Later, they 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 with the prediction of climate models you would find little broad consistency. 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 "broadly inconsistent". About the only thing they agree on is 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 by comparing similar curves, but they try to find a form of words which implies that you can. Broadly consistent is one way...
Even if "broad consistency" were to imply a cause and effect, 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 that it is because the weather station thermometers are more influenced by the extra heat from fuel combustion than by the greenhouse gases emitted.
Climate Change 01 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, 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 "human activities". Once more, no mention of greenhouse gases.
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.
It is clear that 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; that is. 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 01, 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 in CONSENSUS.
A meeting at Science House, Wellington, on Tuesday October 27th discussed New Zealand's contribution to the next IPCC Report, due to be published in 2007.
The objective will be to try and reduce the enormous bulk of these Reports by dealing only with updates and changes. We will believe it when we see it!
The Working Group 1 (Science) Report now proposes five Chapters out of 11 to deal with actual climate data, and the models take a back seat near the end. There are brave attempts to deal with uncertainties.
Anybody wishing to contribute should contact Andy Reisinger at
Vincent Gray
75 Silverstream Road
Crofton Downs
Wellington 6004
New Zealand
Phone/Fax (064) 4 9735939
"It's not the things you don't know that fool you.
It's the things you do know that ain't so"
Josh Billings