Dyson discusses the science and politics of climate
Physicists pride themselves in problem solving, and Freeman Dyson is a problem solver's problem solver. In his many years at the Institute for Advanced Study in Princeton there is no end to the variety of problems on which he has brought his talents to bear. The most recent, on which he spoke at the American Physical Society centennial meeting in Atlanta upon accepting the Joseph A. Burton Award from the Forum on Physics and Society on 25 March 1999, is "The Science and Politics of Climate."
Dyson began with the "facts," as he had ascertained them:
1. The carbon dioxide in Earth's atmosphere corresponds to biomass that would cover Earth's surface with a layer 0.2 inches thick.
2. Ten percent of atmospheric carbon dioxide is cycled through photosynthesis and respiration every year.
3. Earth's atmosphere contains 600 gigatonnes of carbon, Earth's land vegetation contains 800 gigatonnes of carbon, and Earth's topsoil contains 1500 gigatonnes of carbon.
4. The rate at which plant growth depends on atmospheric carbon dioxide concentration depends on the species.
5. Humans output nine gigatonnes of carbon to the atmosphere per year, seven from fossil fuel combustion, the remaining two from deforestation and erosion. This has held constant due to increased energy efficiency, but only 3.5 gigatonnes are detected, leaving 5.5 gigatonnes unaccounted for.
6. The rate at which oxygen is being depleted from the atmosphere would reflect carbon dioxide absorption by the ocean. It has been measured by Roger Keeling, but he wants to improve the reliability of his measurements before releasing them.
The public has been led to believe that the carbon dioxide has a single cause (fossil fuel combustion) and a single consequence (temperature increase), Dyson said. "We need to understand all the causes and all the consequences," he added. "The coupling of carbon in the atmosphere, land, vegetation, and the ocean is too strong to consider any of these in isolation."Among the measurements that have been made Dyson listed the following:1. radiation as a function of wavelength and altitude (Atmospheric Radiation Measurement -- ARM)
2. movement of carbon dioxide between the atmosphere and biosphere.
3. measurement of ocean temperature from acoustic measurements in the ocean. (Since oceans are Earth's major heat reservoir, measuring their temperature is an important indicator of global climate change.)
Dyson elaborated on the second of these three measurements, noting that the difference between upward and downward carbon dioxide flux in the atmosphere equals the flux going to trees. Measurements of temperate forests in Massachusetts, tropical forests in Brazil, and boreal forests in Canada, extrapolated to the entire world show that the temperate forests are absorbing five gigatonnes per year, while the absorption by tropical forests and emission by boreal forests of one gigatonne per year essentially cancel each other out. Other measurements in Sweden and Italy, Dyson added, confirm that temperate forests are the major carbon sink.
Dyson said that he places greater faith in observations than in climate models, which he accuses of replacing physics with fudge factors. Of twenty climate models, only one has predicted an El Ni–o event (as reported in Clearinghouse Update in our Fall 1998 issue), and none of them use the ARM data. "Don't believe the numbers just because they come out of a supercomputer," he concluded.More Freeman Dyson:
http://www.hup.harvard.edu/S97Books/S97.Catalog/imagined.worlds.html
http://spot.colorado.edu/~gamow/george/1991bio1.html
http://a-ten.com/alz/dyson.htm
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