Thursday, October 25, 2007

Global warming

This is a reply to a friend's confused email about S. Fred Singer's article "Global Warming: Man-Made or Natural?". Another friend's response to my email gave me the idea to post it here.


if i'm not mistaken, this is the same person hired by tobacco firms in the U.S. some years back to spread information against the emerging scientific and medical consensus on the link between lung cancer and secondhand smoke. the guy is really notorious for putting his scientific credentials behind such controversial positions. needless to say, he's making big bucks out of it.

just some notes regarding his claims on global warming:

1. that most of the IPCC panelists have no scientific credentials: this is false information. most, if not all, of the lead authors, contributing authors, editors and reviewers to the IPCC technical reports work for universities, monitoring stations, laboratories, research institutions, government bodies, and private scientific organizations in different countries. the names of these people and their institutions are listed in the appendices to the technical reports.

2. that some members of scientific bodies (like the American Meteorological Society) might not have had a say in the formulation of these groups' consensus statements, and that such statements are therefore not reflective of these groups' real positions on climate change: these are not true. the processes of drafting these reports and public statements involved a lot of opportunities for criticisms, comments, and revisions from the members of these professional societies.

the hypothesis that such processes may have downplayed dissenting opinions from the members was tested with a study done by naomi oreskes (department of history and science studies program, university of california at san diego, in science, 3 december 2004) on 928 abstracts published in refereed scientific journals between 1993 and 2003. the abstracts were searched in the ISI database using the keywords "climate change". 75% of the abstracts were categorized as explicitly or implicitly accepting the consensus view. 25% raised methodological or paleoclimatic issues (uncertainties about past climatic changes from evidences in glacial deposits, fossils, and sediments).

none of the papers disagreed with the consensus position. it might be argued that the authors belonging to the 25% group might believe that the current global warming is natural. however, none of the papers in this group argued that point. the conclusions: scientists publishing in the peer-reviewed literature agree with the IPCC, the National Academy of Sciences, and their professional societies; the impression that there is disagreement or discord among climate scientists, that some sectors are trying to spread, is incorrect.

3. that the creation of so-called "scientific consensus" is not science or how science is supposed to proceed: may be true, but is misleading in this case. first, even if there is a scientific consensus on climate change, there is nothing in the supporting arguments and evidences to say that the consensus can never be wrong. a healthy dose of skepticism has always been the hallmark of the scientific method, and this is not being abandoned with the current consensus on climate change and global warming.

second, i don't think there is any step or statement in any formulation of the scientific method which says that one can not act based on any contingent knowledge resulting from its application. as oreskes puts it: "if the history of science teaches anything, it is humility, and no one can be faulted for failing to act on what is not known. but our grandchildren will surely blame us if they find that we understood the reality of anthropogenic climate change and failed to do anything about it."

4. that the climate has not warmed in the past eight years, even though greenhouse gas levels have increased rapidly: this is misinformation. both surface air temperatures and subsurface ocean temperatures have been increasing during the past 50 years. global warming (based on surface temperatures) is about 0.65 degrees centigrade. much of this warming is due to the increasing concentration of greenhouse gases in the atmosphere. and most of the extra greenhouse gases came from human activities. these are some of the conclusions reached by the IPCC and the National Academy of Sciences in their public reports.

5. that the supposed disparity between observed and predicted warming indicates insignificant man-made greenhouse contribution to global temperature changes: is dubious logic from false information. current climate models that consider both natural factors and increased greenhouse gases and aerosols are able to reproduce the observed global temperature changes. models which consider only natural factors are unable to reproduce such observed data. thus, at the very least, the disparity between observed global temperature data and predicted global warming based on existing climate models tend toward the contrary conclusion: that warming is unlikely to be entirely natural.

i won't go anymore to the claims regarding possible natural causes of global warming. these factors (like solar variations, feedback effects of water vapor, etc.) have been adequately covered in recent IPCC reports and are subjects of continuing studies by experts. there is really no reason to believe that their contribution to the present global warming can not be ascertained with better instrumentation and more researches in the future (in much the same way as the heat signatures of urban centers were earlier ruled out as a possible factor in the observed temperature changes).

groups and individuals who wage a constant war on the current consensus on climate change harp on these complicating factors much like lawyers of accused criminals try to suggest alternative crime scenarios or plausible alibis for their clients. they seem to be working on the frame that any small doubt cast on the current consensus on climate change could easily invalidate the growing body of evidence on anthropogenic contributions to global warming. that's how lawyers and economists work. that's not how scientists work.


the martian

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