SciAm Blog: Are You a Global Warming Skeptic? Part III

Scientific American's blog has a "summary of misgivings about whether global warming is occurring and whether it is caused by human activity." The list is extensive, so I am only going to include the main sections, but there is quite a bit of more detail in the original list. Also, in case anyone wants to participate, there is a poll on which arguments against global warming are the most compelling:

SciAm Blog: Are You a Global Warming Skeptic? Part III: As promised, here is the updated list of misgivings about whether global warming is occurring and whether it is caused by human activity. I've incorporated comments from the first and second threads and from private emails, and I've reshuffled some of the categories. I've done my best to be fair in representing the variety of opinion.

I think most people would agree that some of these arguments are stronger than others. What we need to do is find some way to rank them. As a start, I've set up a poll. After you take a look at the arguments, I invite you to go to the polling site and select which broad category you find the most persuasive. For completeness, I've included a response option for those who do think that anthropogenic warming is occurring, although I don't intend for this to be a broad survey of opinion. The poll is imperfect: for instance, the difference among categories II, III, and IV is a matter of degree. But I think it would help focus the discussion if we got a rough-and-ready sense of which line of argument is considered the most important.

View poll (The poll is a bit of a hack, so please bear with me. ...)

1. Warming may not actually be occurring. Most respondents seemed to agree that the global average temperature is rising, but some did not.
   
   1. This past winter was so cold. Where's the warming?
   2. Temperatures were higher 1,000 years ago in Western Europe.
   3. The global average temperature has been decreasing since 1998. This is the start of a cooling trend predicted by Theodore Landscheidt.
   4. Ground temperature readings are subject to systematic errors such as the urban heat island effect or localized natural temperature variation.
   5. Ground temperature readings contradict satellite measurements.
   6. Reports of changes in polar climate are anecdotal and could be localized effects.
      
2. The present warming could be a natural uptick. Respondents pointed out that climate conditions fluctuate because of volcanism, the obliquity cycle, changes in solar output, and internal (chaotic) variability. If pre-industrial fluctuations were natural, then industrial-age ones could be, too. One respondent put it this way: "Every time I read that we have had 'the hottest summer in 100 years' I wonder what caused that hot summer 100 years ago."
   
   1. It is not, in fact, historically anomalous. Evidence suggesting as much is shaky.
   2. It could be explained by any number of natural processes.
      
3. CO2 emissions cannot explain the warming. This is complementary to the previous category: instead of arguing for a natural cause, the respondents here argued against an anthropogenic one.
   
   1. The emissions are too puny.
   2. Historical climate data rule out a significant role for CO2.
   3. CO2 levels might be driven by temperature, rather than the other way around. For instance, warm oceans can hold less CO2.
   4. The physics of CO2 absorption is too poorly understood to blame it for warming.
      
4. Climate models are unconvincing. In this category, I put the argument that, whatever the inherent plausibility of anthropogenic global warming, climate scientists have yet to present a solid case.
   
   1. Models do not capture the complexity of the climate system.
   2. Proper application of the scientific method does not support anthropogenic warming.
      
5. Warming is a good thing, so we shouldn't try to stop it. It might be good in a absolute sense or in a relative one.
   
   1. It will increase humidity in tropical deserts and improve the lot of high-latitude regions.
   2. Higher CO2 levels encourage plant growth, and that's good.
   3. Historically, humanity has done better when the climate was warm, such as at the height of the Roman Empire, than when it was cold, such as the early medieval period.
   4. For most of its history, Earth has been warmer than today. Animals and plants seemed to do just fine in those periods of warm climate. One respondent wrote: "Our present chilly climate is the aberration when judged on a geological time scale."
   5. It staves off the next glaciation, which we're due for.
   6. Claims that global warming has worsened storm damage, or will do so, are overblown. If damage seems to have increased, it is simply because more people live in storm-prone regions and their plight is more widely publicized than before.
   7. Attempts to stop global warming would do more damage they than avert. Warming might be bad, but it is better than the alternative, be it Kyoto or some other mitigation strategy. The underlying assumption here is that the null strategy -- letting people move away from shorelines as sea levels gradually rise and adopt non-carbon energy sources as commodity prices dictate, without any explicit climate policy -- carries the least net costs.
      
6. Kyoto is useless, or worse. Many of the complaints were specific to the Kyoto Protocol, which has set up a cap-and-trade system for greenhouse gases. Although these comments don't really pertain to the science, I include them because some respondents linked their mistrust of climate science to their misgivings about Kyoto.
   
   1. It would bankrupt us. One correspondent said Kyoto mandates "a practically unlimited expenditure of effort (and money, naturally)."
   2. It may not bankrupt us per se, but it would divert resources from other, better-established priorities.
   3. It is an inefficient response to climate change. We are better off dealing with the consequences directly. For instance, an increased malarial threat could be handled by mosquito control measures.
   4. It reeks of social engineering: holier-than-thou environmentalists telling people how to lead their lives.
   5. It would reduce warming by 0.02 degrees C or a similarly meager amount.
   6. It exempts developing countries, whose emissions intensity and growth rates are much higher than those of developed countries. In effect, Kyoto lets developed countries outsource their emissions.
   7. It "demands that developed countries send money to Third World dictators for greenhouse gas credits."
   8. People may claim to support it, but their energy-wasting habits belie their true sentiments.
      
7. People who argue that human activity causes global warming can't be trusted. Now we get to what seems to be the single biggest complaint: doubts as to the competence or motivation of scientists and others who accept anthropogenic climate change. Many respondents perceive scientists as jumping to conclusions, haughtily dismissing doubters, refusing to take the time to explain things, and adopting absolutist positions. One respondent wrote: "What data would convince me? I don't know if data is the problem as much as needing to perceive an objective voice."
   
   1. Climate scientists have lost their credibility by making bad calls.
   2. Climate scientists behave unscientifically.
   3. Activists and journalists have gone overboard.

I should point out that the above taxonomy doesn't capture all the responses. Some people simply asked questions about climate science, proposed that other human activities be incorporated into models, or commented on the motivations of the skeptics themselves. We can return to these thoughts as the discussion unfolds.