The issue of man induced climate change involves not the likelihood of
dangerous consequences, but rather their remote possibility.
The main areas of widespread agreement (namely that global mean temperature has risen rather irregularly about 0.6C over the past century, that atmospheric levels of carbon dioxide have increased about 30% over the past century, and that carbon dioxide by
virtue of its infrared absorption bands should contribute to warming) do not imply dangerous warming.
Indeed, we know that doubling carbon dioxide should lead to a heating of about 3.7 watts per square meter, and that man made greenhouse heating is already about 2.7 watts per
Thus, we have seen less warming than would be predicted by any model showing more than about 0.8 degrees C warming for a doubling of carbon dioxide.
This is consistent with independent identifications of negative feedbacks.
Alarming scenarios, on the other hand, are typically produced by models predicting 4 degrees C. After the fact, such models can only be made to simulate the observed warming by including numerous unknown factors which are chosen to cancel most of the warming to the present, while assuming that such cancellation will soon disappear.
Alarm is further promoted by such things as claiming that a warmer world will be stormier even though basic theory, observations, and even model outputs point to the opposite.
With respect to Kyoto, it is generally agreed that Kyoto will do virtually nothing about climate no matter what is assumed.
Given that projected increases in carbon dioxide will only add incrementally to the greenhouse warming already present, it seems foolish to speak of avoiding dangerous thresholds.
If one is concerned, the approach almost certainly is to maximize adaptability.
After spending years describing the physics of climate to audiences concerned with global warming, I came to the realization that I was speaking to people who were not aware of the basic premises of the issue.
The listeners were typically under the impression that the case for climate alarm was self-evident and strong, and that concern for the underlying physics constituted simply nit-picking in order to see if there were any remotely possible chinks in the otherwise solid case.
Given that most people (including scientists) can rarely follow 15 minute discussions of somewhat complex science, the conclusion of the listeners is that the objections are too obscure to challenge their basic prejudice.
I decided, therefore, to examine why people believed what they believed.
What I found was that they had been presented mainly three claims for which widespread scientific agreement existed. While these claims may be contested, they are indeed widely accepted.
The only problem is that these claims do not suggest alarm. Rather, upon careful analysis, they make clear that catastrophic implications are grossly unlikely, but cannot be rigorously disproved.
Thus, the real situation is that the supporters of alarm are the real skeptics who cling to alarm against widely accepted findings. The profound confusion pertaining to this situation is only reinforced by quibbling over the basic points of agreement.
Such quibbling merely convinces the public that the basic points of agreement must be tantamount to support for alarm.
We will begin by analyzing the popular consensus.
View the attached PDF for the full paper by:
RICHARD S. LINDZEN
Alfred P. Sloan Professor of Atmospheric Sciences
Massachusetts Institute of Technology