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Published online 16 April 2008 | 452, 796 (2008) | doi:10.1038/452796b
News in Brief
Further reports announced by climate-change panel
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One wonders how the IPCC will deal with the sudden halt to global warming in the past decade, given that their previous models all predicted a continuous rise in global temperature in parallel with the rise in anthropogenic carbon dioxide.
Halt over the past decade? Please cite your sources, because I don't think that the data support your statement! Beware of confusing short, perhaps transient episodes with an overall and long-term trend. And don't ignore the mounting evidence of impacts, most notably accelerating ice movement and loss. This is far too serious of an issue to develop an opinion about without a proper basis and understanding.
The root, I think, of Mr. Nelson's confusion is that it is not true that the IPCC has predicted a "continuous" rise in global temperature. It has predicted a stochastic, irregular rise in global temperature. Its forecast lines are only smooth because the expected jumps and dips cannot be forecast. And those forecasts, over the relevant time scales, have been, so far, accurate (see the good summary by realclimate.org's climatologists, at http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/). It would be bizarre if global temperature _did_ start rising in a smooth, "continuous" fashion, without any multi-year dips. Unfortunately, the time scale on which human beings form opinions about climate change is much smaller than the time scale of the noise wiggles in the anthropogenic warming curve.
Hopefully, the next IPCC report will include a revision of the total CO2 from fossils fuels that it is possible to release into the atmosphere. To quote a comment I made a couple of weeks ago: The IPCC scenarios are almost certainly unachievable for a simple reason - the assumptions of how much carbon is available for release into the atmosphere are probably gross overestimates. Recent revisions of available coal reserves and Hubbert linearization analyses of coal production both indicate that coal use will peak far earlier than the IPCC assumes - probably before 2030. This is not to say that the worlds total carbon reserves are too small for the IPCC scenarios, just that the amount of carbon that is feasible to access at an energy profit (and hence release into the atmosphere) is insufficient. It amazes me that the much lauded IPCC has not seriously considered the reliability of the available carbon estimates upon which they based their work. See the following articles, lectures and commentary about limitations on coal use and the IPCC scenarios: Prof. Kjell Aleklett of Uppsala University, Sweden: http://www.onlineopinion.com.au/view.asp?article=5933 ; Prof. David Rutledge of Caltech, USA: http://rutledge.caltech.edu/ ; Energy Watch Group on revision of coal reserves: http://www.energywatchgroup.org/files/Coalreport.pdf ;Commentary in New Scientist on coal by David Strahan: http://www.davidstrahan.com/blog/?p=116 (Unfortunately, by 2014 the world will almost certainly be deep in an energy crisis that will have goverments scrambling to cope with widespread poverty and hunger and climate change considerations will have been forgotten as we desperately burn anything available to keep the lights on.)
Michael Lardelli certainly makes a strong case that fossil fuel use - at present causing concern over climate change - will soon morph into a far more urgent and painful energy crisis. But surely the two crises go hand in hand. Some fossil carbon sources are not now being converted into usable fuel because a large fraction of their mass is needed to power the extraction process - oil shale is one example. Alongside the "energy profit", there would also be an inordinate CO2 cost. If alternative energy sources are insufficient and fossil fuel prices continue to rise, who knows what longterm cost humanity will risk for the sake of shortterm survival?
There are many coal deposits in my own East Tennessee that are not being mined; I doubt very much that “peak coal� theorists have catalogued every coal seam of every quality. Unless we develop new energy sources and/or conservation measures we will find something to burn for many decades to come, even if we have to clearcut our national forests. Or Brazil’s. Furthermore, CO2 is not the only greenhouse gas. There is speculation that it may only be the fuse to set off the defrosting of massive methane hydrate deposits that will will release a far more potent greenhouse gas. And, of course, all the CO2 already in the atmosphere is not going to vanish any time soon.
A much neglected cause of climate change is the human impact on the natural water cycle. Humans are diverting water to 'dry' regions for cultivation, etc. as well as overharvesting our forests to change this balance. Instead of looking at the impact of climate change on water supply worldwide the IPCC should look at the human impact on the natural water cycle as a cause of climate change prior to recommending any action.