Dr. Jeremy Leggett

(Part Three)

(From Earth Crash Earth Spirit Website)


The largest biological system on the planet is that of marine phytoplankton; it produces more biomass - 104 billion tons of carbon per year - than all terrestrial ecosystems combined, which generate 100 billion tons of carbon annually. Any reduction of photosynthetic activities in the phytoplankton could amplify global warming in two ways. First, it would suppress the photosynthetic sink that absorbs carbon dioxide, and second, it might provide less dimethyl sulfide, a gas which generates condensation nuclei for the formation of clouds.  

     We now know that marine phytoplankton in the northern hemisphere will be exposed to intense ultraviolet-B radiation in the spring, just when they are at their most productive. The depletion of the protective ozone layer above the Arctic as a result of chlorofluorocarbon (CFC) production is the culprit. A recent U.N. Environment Program (UNEP) report warns that since most phytoplankton organisms do not have ultraviolet radiation receptors, they cannot avoid deleterious radiation that "penetrates deeper into the water column than has been previously measured." The report, submitted as part of the scientific review process under the Montreal Protocol agreement to protect the ozone layer by limiting CFC use, adds that this radiation exposure causes massive inhibition of photosynthesis, as measured in both field and laboratory studies.  

      How big could this feedback be? We have no way of knowing. The UNEP report merely observes that "a hypothetical loss of 10 percent of the marine phytoplankton would reduce the oceanic annual uptake of carbon dioxide by about 5 billion tons - an amount equal to the annual emissions of carbon dioxide from fossil fuel consumption."  

      [ECES note: This article was written by Dr. Jeremy Leggett, who took his PhD in earth sciences at the University of Oxford in 1978, and joined the faculty at Imperial College of Science and Technology, where during an 11 year career he won two major awards for his research on the geological history of oceans, sat on several advisory committees for the UK government's Natural Environment Research Council, and consulted for the oil industry in the UK and Japan. During the mid 1980s, he became increasingly concerned about environmental issues in general, and global warming in particular, a process culminating in 1989 in his leaving academia to join the international environment group Greenpeace as Scientific Director of Greenpeace International's Climate Campaign (1990-1994) and Director of its Solar Initiative (1995-1996). Between 1993 and 1995 he also served as a guest lecturer at Cambridge University’s Centre for Global Security. During 1996, he served as a Visiting Fellow at Oxford University’s Green College Centre for Environmental Policy and Understanding, working under the UK Prime Minister’s environment advisor, Sir Crispin Tickell. In 1996, Leggett won the US Climate Institute’s Award for Advancing Understanding. He left Greenpeace at the end of 1996 to set up a private solar energy company.He is author-editor of the best-selling "Global Warming," (Oxford University Press, 1990, published in English, Japanese, German,                    French, Portuguese, Italian, Czech and Russian), and "Climate Change and the              Financial Sector" (Gerling Academy Verlag, 1996).]  

     (12/04/1995) Scientists confirm anthropogenic greenhouse gases as cause of global warming trend, worry positive feedback processes could lead to "runaway" global warming. The contents of the premier scientific journals in the months immediately following the Berlin Climate Summit in April 1995 reveal a pronounced decrease in the level of uncertainty top climate-change researchers were prepared to ascribe to the view that the warming in recent decades might be due to reasons other than greenhouse warming. On April 7, 1995, a researcher from AT&T's Bell Labs published a statistical treatment of the twentieth-century warming record showing correspondence between warming and a decreasing amplitude of the annual temperature cycle - the temperature difference between winter and summer. Had changes in incoming solar radiation been solely or largely responsible for observed warming, as greenhouse skeptics tend to argue, the reverse should have been the case. Solar variability, AT&T researcher David Thomson concluded, "is at most a minor factor." Thomson said "you almost have to invoke magic if it is not carbon dioxide. It's the only logical explanation."  

     On April 21, 1995, scientists at the US National Climatic Data Center reported they had found a pattern suggesting that the US climate has turned towards a greenhouse regime in the last 15 years. They compiled data on climatic extremes expected to arise under greenhouse warming, including higher-than-normal daily minimum temperatures, extreme or severe droughts in warm months, and much-above-normal precipitation in cool months. Using this data, they calculated a Greenhouse Climate Response Index in order to express any persistent trends. The index has been consistently high since the late 1970s, in marked contrast to the pattern in earlier decades. Thomas Karl, the lead researcher, concluded that the probability that this can be natural fluctuation in a stable climate is only about 5%.  

     In June 1995 came two other high-powered studies similarly dismissive of natural climatic variability as an explanation for the hot years of the 1980s and 1990s, this time in the global record. A team from Germany's leading climate lab, the Max Planck Institute for Meteorology, concluded that there is only one chance in forty that natural variability can explain the warming seen over the last 30 years. "At the moment there is no other convincing explanation than carbon dioxide for such a big change in temperature," a member of the German team, Gabriele Hegerl, reported.  

      A second team at the USA's Lawrenc Livermore Laboratory factored the cooling influence of sulphate aerosols (largely derived from coal burning) into the                    temperature record, leaving a clear greenhouse fingerprint since about 1950, when the growth of carbon dioxide emissions took off. Commenting on this in Science magazine, Thomas Karl said "you're seeing a shift in the overall scientific view".  

      Then, on August 10, 1995, the results of the most sophisticated climate-model experiments yet performed were reported in Nature magazine. Researchers at the UK's Meteorological Office effectively  simulated past climate variations using a coupled model (one linking both the atmospheric and oceanic components of the climate system) which also factored in the sulphate aerosol effect. This breakthrough significantly boosted confidence in the accuracy of the models used for forecasting climate change in the future. Leading IPCC climatologist Tom Wigley wrote in a commentary that "these results mark a turning point both in our ability to understand past changes and predict the future".  

       The impression of a significant stiffening of scientific opinion on the question of "the signal" was reinforced at a conference of leading climatologists in Colorado, reported in Nature on August 24, 1995. Rapporteur Michael MacCracken, summarizing many presentations, concluded that the evidence for an anthropogenic signal was becoming "quite compelling. Although greenhouse gases and aerosols are not yet convicted beyond all reasonable doubt (in the warming of recent decades), the case is becoming steadily stronger". And at the same time, the drip of worrying evidence that the feedbacks may be preparing to kick in, stoking up an amplifying effect for future warming, did not abate. In Science magazine on August 25, 1995, a team of researchers at the US National Oceanographic and Atmospheric administration reported that they had found isotopic evidence for a large sink for carbon dioxide on land in the northern hemisphere during 1992 and 1993. "Because carbon storage on land is likely to be more transient and vulnerable to anthropogenic and climatic perturbations than storage in the oceans," they concluded, "the current partitioning of CO2 uptake between the oceans and the land biosphere may well have significant implications for future increases in atmospheric CO2".  

      Within a week, as though to abate hopes that even the oceanic sink would hold up, came evidence in Nature magazine that the oceans may be losing fixed nitrogen. Fixed nitrogen, as the nutrient nitrate, is a major control on the abundance of phytoplankton. Denitrification - the degradation of nitrate by bacteria in areas of oxygen-deficient surface waters in the oceans - converts fixed nitrogen to free nitrogen or nitrous oxide, of no use to most plants. Studying nitrogen balances, Canadian and American oceanographers found evidence that warmer oceans will lose nitrate, thereby depleting phytoplankton, which will in turn increase the amount of atmospheric carbon dioxide.  

      On September 10, 1995, the stiffening of scientific opinion reached the front page of the New York Times. The headline referred to a leaked draft copy of the IPCC's Second Assessment report, due to be published in December. It read: "Experts confirm human role on global warming."  

      Against the march of this kind of evidence and events, soon to be codified in the IPCC Second Assessment, the arguments of the small but vocal community of so-called "global warming skeptics" are beginning to look increasingly flimsy.                    (Sources)  

      (09/01/1990) Geologists fear Arctic warming could lead to release of vast              amounts of methane hydrates, leading to runaway global warming. One explanation of rapid climate change at the end of the last glaciation, argues Dr. Euan Nisbet of the University of Sakatchewan, is that it was initially driven by methane released from natural gas fields and gas hydrates during a period of extreme insolation. Methane is an even more potent greenhouse gas than carbon dioxide.  

      Methane hydrates are solids which lock methane gas up under pressure in an ice-like lattice of water molecules. They are present under the oceans and permafrost in vast quantities. In the offshore Arctic, the cold allows their formation at sufficiently shallow depthshat warming can reach them and destabilize them.  

      Nisbet is one of a number of geologists who fear methane hydrates as a                   potentially major positive feedback mechanism that could be released by global warming. He wrote in a 1989 paper that "any slight warming of the Arctic water will release hydrate from the sea floor almost immediately. A temperature change of a few degrees will liberate methane from the uppermost sea-floor sediments at this depth within a few years."  

      The worst-case analysis is grim indeed: "the danger of a thermal runaway caused by methane release from permafrost is minor, but real ... even if there is only a 1 per cent chance that such events will occur, the social implications are profound," says Nisbet. (Sources)  

      (10/29/1999) In research with potentially critical implications for current climate change study, scientists find that a catastrophic release of methane hydrate deposits due to warming oceans led to melting of the polar ice caps during the Cenozoic era and the mass extinction of species. Fifty-five million years ago, during the Cenozoic era, geologic evidence shows that Earth's polar ice caps did not exist. They had melted because the Earth was on average 4 to 6 degrees Celsius warmer than it is today, and temperatures at the poles may have been two times or more warmer than the global average at the time. But climatologists have had difficulty explaining that fact using models that rely solely on the effects of greenhouse gases. Now new research presented at the 1999 meeting of the Geological Society of America points to methane gas as a possible reason why the paleoclimate in the Cenozoic era was so warm.  

       Lisa Sloan, an Earth scientist at the University of California at Santa Cruz (UCSC), said new climate models she and her colleagues have generated indicate that the indirect effects of high concentrations of methane gas in the atmosphere probably played a major role in warming the Earth, particularly the polar regions.  

      An overly warm ocean triggered the methane release. When the ocean reached a certain temperature, a critical threshold was crossed that allowed a catastrophic release of methane hydrates in the sea floor.  

      The released methane, a byproduct of abundant bacteria thriving on an already warm and wet Earth between 50 and 60 million years ago, in turn produced stratospheric clouds of water vapor that can only form in the shadowy polar regions. This held in solar heat, warmed and melted ice at the poles and, in turn, warmed the Earth, Sloan said.  

      The 150,000-year-long epoch of climate warming during the Cenozoic era had profound effects on countless marine and terrestrial organisms, including the mass extinction of species, according to research by William C. Clyde of the Department of Earth Sciences at the University of New Hampshire. (Sources)