Is global warming really all about burning fossil fuels or does deforestation play a significant role?

For some time now, I have been wondering whether deforestation may have been playing a bigger role in the so-called global warming process than the proponents of global warming have been willing to let on. Now there is sense a hint of a suggestion that my suspicion may be true. In the article in The New York Times by Elisabeth Rosenthal and Andrew Revkin titled "Science Panel Says Global Warming Is 'Unequivocal'", we read the following:

"Since 2001, there has been a torrent of new scientific evidence on the magnitude, human origins and growing impacts of the climatic changes that are under way," said Mr. Holdren, who is the president of the American Association for the Advancement of Science. "In overwhelming proportions, this evidence has been in the direction of showing faster change, more danger and greater confidence about the dominant role of fossil-fuel burning and tropical deforestation in causing the changes that are being observed."

There it is, a reference to the role of "tropical deforestation." Or I should say, the purported.role.

I have no idea whether a hard scientific link can be established between deforestation and global warming, or the relative roles of fossil-fuel burning and deforestation and other factors, but I would hope that scientists would think that it is worth their while to find out.

We are drowning in a flood of opinion and belief, and parched by a drought of hard science.

I just ran across this expression of uncertainty in a report (summary of the eventual report) that supposedly dispels all uncertainty:

Climate-carbon cycle coupling is expected to add carbon dioxide to the atmosphere as the climate system warms, but the magnitude of this feedback is uncertain. This increases the uncertainty in the trajectory of carbon dioxide emissions required to achieve a particular stabilisation level of atmospheric carbon dioxide concentration. Based on current understanding of climate carbon cycle feedback, model studies suggest that to stabilise at 450 ppm carbon dioxide, could require that cumulative emissions over the 21st century be reduced from an average of approximately 670 [630 to 710] GtC to approximately 490 [375 to 600] GtC. Similarly, to stabilise at 1000 ppm this feedback could require that cumulative emissions be reduced from a model average of approximately 1415 [1340 to 1490] GtC to approximately 1100 [980 to 1250] GtC. {7.3, 10.4} [Add GtCO2 numbers].

I'm seeing all these tentative phrasings such as:

• "... is expected ..."
• "... but the magnitude of this feedback is uncertain ..."
• "... This increases the uncertainty ..."
• "... Based on current understanding ..."
• "... model studies suggest ..."

Hey, I don't want to beat up the scientists for being honest and expressing their current perceptions of the many uncertainties in global climate research, but I do feel obligated to point out that the promoters of global warming, even at the level of the high level summarization of the IPCC report, are claiming a degree of certainty that really isn't there in the underlying science. Even worse, they are claiming certainty for projections, based on rudimentary models, many decades into the future. Claiming that such projections are "unequivocal", is not credible.

The fact that they felt the need to add the caveat "Based on current understanding" is very telling. I think the scientists have done an admirable job of trying to understand climate, and I do hope that they continue to dig deeper and keep expanding our knowledge, but we do need to recognize that it is unlikely that we really do have a handle on the totality of the processes at work in the evolution of our climate.

BTW, the term "deforestation" is not to be found at all in the IPCC summary. Incredible. The official title of the "report" is Climate Change 2007: The Physical Science Basis - Summary for Policymakers.

-- Jack Krupansky