The New York Times exposes an internal document (PDF) from the Global Climate Coalition, a group funded by the oil and auto industries, that shows that their own scientists were confirming the reality of human-caused global warming and the effects of greenhouse gasses as early as 15 years ago even while publicly trying to dispute that reality.
The document is from 1995 and it was a “primer” on the various issues being sent around to the auto companies for approval. It essentially admits that global warming is real and human-caused, that many of the counter-arguments are false and that we don’t yet have good enough predictive technology to know the full effects, especially in local areas. It begins by saying:
The scientific basis for the Greenhouse Effect and the potential impact of human emissions of greenhouse gases such as CO2 on climate is well established and cannot be denied.
It further says:
Are there alternate explanations for the climate change which has occurred over the last 120 years?
Explanations based on solar variability, anomalies in the temperature record, etc. are valid to the extent they are used to argue against a conclusion that we understand current climate or can detect a human component in the change in climate that has occurred over the past 120 years. However, these alternative hypotheses do not address what would happen if concentrations of greenhouse gases continue to rise at projected rates.
The section of the document on what it calls “contrarian theories” to explain the rise in global temperatures as resulting from something other than human activity is particularly interesting. For example, in considering the argument that sunspots is the real cause, the document says:
Direct measures of the intensity of solar radiation over the past 15 years indicate a maximum variability of less than 0.1%, sufficient to account for no more than 0.1DC temperature change. This period of direct measurement included one complete 11 year sun spot cycle, which allowed the development of a correlation between solar intensity and the fraction of the Sun’s surface covered by sun spots. Applying this correlation to sun spot data for the past 120 years indicates a maximum variability on solar intensity of 0.1%, corresponding to a maximum temperature change of0.1DC, one-fifth of the temperature change observed during that period.
If solar variability has accounted for 0.1DC temperature increase in the last 120 years, it
is an interesting finding, but it does not allay concerns about future warming which could
result from greenhouse gas emissions. Whatever contribution solar variability makes to climate change should be additive to the effect of greenhouse gas emissions.
The conclusion of the section on such alternative explanations:
The contrarian theories raise interesting questions about our total understanding of climate processes, but they do not offer convincing arguments against the conventional model of greenhouse gas emission-induced climate change. Jastrow’s hypothesis about the role of solar variability and Michaels’ questions about the temperature record are not convincing arguments against any conclusion that we are currently experiencing warming as the result of greenhouse gas emissions.
Sounds a lot like the tobacco industry’s claims for decades that smoking doesn’t cause lung cancer.