What is agreed, and what is still disputed, about ‘climate change’?

GWPF Background Paper

1. Matters where we agree with the dominant scientific establishment and can quantify the outcome
   1. The greenhouse effect is real and CO2 is a greenhouse gas.
   2. CO2 has increased in the atmosphere from approximately 0.029% to 0.039% over the past 50 years.
   3. CO2’s greenhouse warming potential follows a logarithmic curve with diminishing returns to higher concentrations.
   4. Absent feedbacks, and other things being equal, a doubling of carbon dioxide from pre-industrial levels would warm the atmosphere by approximately 1.1C.
   5. Since 1980 global temperatures have increased at an average rate of about 0.1C per decade. This is significantly slower than forecast by the vast majority of GCMs.
2. Matters where we agree with the scientific consensus but cannot quantify the outcome.
   1. Positive feedbacks from water vapour and soot, negative feedback from clouds and aerosols, and other factors, mean that actual climate sensitivity is a matter of vigorous scientific debate.
   2. Natural variability caused by ocean oscillations, amplified solar variations and other factors also act to increase or decrease temperature change. Thus overall temperature prediction is doubly uncertain.
   3. Arctic summer sea ice has decreased, but Antarctic sea ice has increased; this is more consistent with regional albedo changes due to soot than with global temperature changes due to greenhouse warming.
   4. There is no consensus that recent climate change has affected the variability of weather or the frequency of extreme weather events.
   5. Economists generally agree that net economic damage will occur above 2C of warming, net economic benefit below that level, but this cannot be certain.

C. Matters on which we think the evidence does not support the scientific consensus

1. There has been no net increase in global temperatures for about 16 years, a period about the same length as the warming period that preceded it.
2. Paleo-climate proxies agree that worldwide temperatures were higher and changed faster during other periods of climate change about 1,000, 2,000, 4,000, 8,000 and 12,000 years ago.
3. Predictions of increasing humidity and temperature in the tropical troposphere, a key prediction of rapid greenhouse warming, have been falsified by experimental data casting doubt on whether the warming of 1980-2000 was man-made.
4. Ice core data clearly show carbon dioxide responding to temperature change, rather than preceding them during glaciation and deglaciation episodes.
5. Satellite evidence confirms that vegetation has increased in density, in natural as well as agricultural ecosystems, probably as a result partly of carbon dioxide increases.

D. Why alarm is not secure [warranted?]

1. All sides of scientific debates have vested interests and display confirmation bias. Science keeps itself honest not by expecting unrealistic self-criticism by scientists but by encouraging challenge, and diverse interpretations of data, rather than trying to enforce a single “consensus”.
2. Forecasting of all kinds is extremely unreliable and predictions of ecological disaster have an especially poor track record.
3. Policies to decarbonize the economy using today’s technology are likely to be harmful to human welfare and natural ecology.
4. Integrity, openness and objectivity need to be introduced to the conduct of the scientific debate to restore the damage done by the Climategate, Hockey Stick, Gleick, Gergis, Lewandowsky and Marcott episodes.
5. Exaggerated alarmism is not harmless and is not scientific.

I have left the text unedited, with one exception, since it was not clear to me what ‘secure’ meant in the D heading. The GWPF went on to set out its position, which is as follows:

1.  Policy needs to take account of uncertainty.

2.  Policy needs to be subjected to thorough cost-benefit analysis.

3.  An enforceable global agreement on emissions reduction is unrealistic.

4.  Adaptation may be a cheaper and less harmful policy than mitigation.

5.  Public funding should support open debate, not one-sided advocacy.

I do not agree wholeheartedly with everything in this paper (or, rather, I would have written it rather differently), but it is a first-class summary of where I think the current debate is at the moment. What is plain from it is that, notwithstanding what the passionate warmists say, the science is not settled at all, and shouldn’t be. There is a good deal of agreement about some things, less about others, and strong disagreement about a third set.

Julia Gillard’s remark in Parliament, which I quoted yesterday, to the effect that ‘[I do] not believe that it is possible for a person of reason to have any other view’ than to believe in ‘the science’ shows how far from a real understanding of the scientific situation her view is. And of course she is not alone, alas.