I would call myself of a skeptic of the most aggressive theories of Anthropogenic Global Warming (AGW). Upon hearing that, many people would assume that I have stuck my head in the sand - that I don’t believe, for instance, that global temperatures have increased, or that Arctic sea ice is disappearing, or that glaciers are retreating.
Nothing could be further from the truth. I do not dispute facts (although it is true that there are facts, and then there are other facts). In fact (ha ha), most thoughtful skeptics do not dispute facts. Facts are stubborn things, as Ronald Reagan used to say, so such a strategy would be a waste of time.
No, the beliefs of most skeptics are actually quite a bit more nuanced than your average bear is willing to admit. Mine, in fact (there he goes again), take quite a long time to explain, so I don’t often do it. However, I’ve wanted to catalog a short list of my AGW beliefs so that I can track them and see how they change as I continue to learn about the issue. So I’ve gone and done it here.
Some of the beliefs below are factual and some of them are just beliefs. It’s hard to organize them, but I’ve done the best I could. They do not constitute one long argument; they jump around a bit.
If you dispute any of the beliefs here, please feel free to post a response and I’ll try to engage in a civil debate. You score a point if you can educate me and get me to change one of my beliefs. If I educate myself and am forced to change a belief, I’ll post a blackline.
My Beliefs about Anthropogenic Global Warming
• Global temperatures have increased by approximately 0.4 -0.5C since 1979 (that's when the satellite record began)
• Global temperatures likely increased between the beginning of the thermometer record (1850s) and 1979, but the magnitude of that increase is more uncertain
• This temperature increase has been more severe in the Arctic than just about anywhere else; the Antarctic has shown very little, if any, temperature increase
• Atmospheric CO2 concentrations have increased in a manner highly correlated to man’s industrialization
• It is likely that the majority of the increase in global CO2 concentration is due to man, and particularly his emissions (watch out – I said nothing about temperature here)
• The land temperature record has been significantly corrupted by land-use changes and urban heat island (UHI) effects and requires adjustment to eliminate those effects
• Adjustments to the land-temperature record lack rigor, but may be approximately correct on average
• It is reasonable to conclude that a meaningful percentage of the increase of global temperatures since the mid-1800s may be entirely natural; after all, at the time we were still emerging from the Little Ice Age
• It is reasonable to conclude that a doubling of atmospheric CO2 concentration might result in a further rise in global temperatures of at least 1C; without taking into consideration feedback mechanisms, simple physics would seem to suggest such a result
• The science regarding climate feedback mechanisms, particularly cloud cover, are not well understood
• It is not reasonable to assume that virtually all important feedback mechanisms are positive
• Climate models are essentially useless without well-understood feedback mechanisms
• Virtually 100% of future climate predictions are based on advanced climate models
• Therefore, future climate predictions of a rise in temperatures of between 3-5C based on a doubling of CO2 concentration are highly uncertain
• It is certainly possible that a doubling of CO2 would result in an increase in global temperatures of between 3-5C, but as of today that conclusion is not proven
• Personally, I have no guess what temperature increase would result from a doubling of CO2
Considerations of the Hockey Stick and Paleo Reconstructions
• An important aspect in the argument for a link between the rise in CO2 and the rise in global temperatures is the contention that the current rise in temperatures is unprecedented
• Studies which purport to show unprecedented warming have largely been discredited; until the theory of AGW became de rigueur, scientists generally believed that the Medieval Warm Period (MWP) was warmer than today
• While the discrediting of paleo reconstructions has not disproven the theory of AGW – surely there is considerable other evidence – it has clearly affected the first argument above, and claims based on reconstructions should be removed from the literature
Other Important Considerations
• There are important benefits of increasing CO2 concentrations, including increasing crop yields and a more robust biosphere
• It is extremely important to study the benefits of increasing CO2 concentrations at the same time as we are studying their deleterious effects
• It is highly likely that aggressive AGW prevention strategies would have certain unintended consequences
• It is possible that aggressive AGW prevention strategies would have meaningful negative unintended consequences
Supremely Important But Highly Uncertain Conjectures and Conclusions
• The true cost of weaning ourselves off CO2 emissions is orders of magnitude larger than the assumptions of most proponents of aggressive AGW prevention strategies (with one exception mentioned below)
• Even if the theory of AGW is true (say, the midpoint of IPCC projections), the net present value of 100% of the costs (including loss of human life) of mitigating the effect of AGW are lower than the costs of preventing AGW starting now, even using very low discount rates
• Regardless of whether the theory of AGW is true as outlined by the IPCC, it is incumbent upon us to research mitigation strategies in addition to prevention strategies
• If we are to truly undertake aggressive prevention strategies, the laws of physics are too rigid: nuclear is our only option if we are to maintain global economic prosperity
A Few Assertions whose Logic Should Withstand Scrutiny
• The disappearance of Arctic sea ice may simply be due to the fact that it’s getting hotter in the Arctic (see above!) – this does not prove the theory of AGW – it only proves it’s getting hotter in the Arctic
• It is possible to believe in the fact of AGW but not necessarily the scope as outlined in the IPCC
• Being a "skeptic" is a good thing; that is why AGW proponents have changed their terminology to "deniers". There are undoubtedly "deniers" out there, but they're mostly quacks. Unfortunately, most AGW proponents do not take the time to distinguish who is a skeptic from who is a denier.