SCIENCE NEWS, Vol 147, Page 362, June 10, 1995
In recent months an iceberg nearly as large as Rhode Island broke off an Antarctic ice shelf, apparently because of rising temperatures there. A statistician declared that the seasons had slipped sync with the calendar, perhaps because of greenhouse gas pollution. And just in time for a climate summit in Berlin 2 months ago, a German research team reported finding an abnormal pattern of change in climate records that does not correspond to any natural causes.
Although the annual average global temperature has risen by about 0.5 degrees C since the late 19th century, investigators have had difficulty determining whether natural forces or human actions deserve the blame. But in late February, Klaus Hasselmann, director of the prestigious Max-Planck Institute for Meteorology in Hamburg, Germany, stepped forward to point a finger.
The Max-Planck researchers find it highly improbable—only 1 chance in 20—that natural forces caused the temperature rise during the last century.
Greenpeace International polled 400 climate scientists during December 1991 and January '92. The sample included all scientists involved in the 1990 study of the Intergovernmental Panel on Climate Change, and others who have published on issues relevant to climate change in `Science' or `Nature' during 1991. Scientists were asked whether they thought there would be a point of no return at some time in the future, if emissions continued at their present rate. By the end of January 1992, 113 had replied, in the following way: probably - 15 (13%), possibly - 36 (32%), probably not - 53 (47%). In other words, 45% believe the runaway greenhouse effect to be possible. [ http://www.greenpeace.org/~climate/database/records/zgpz0638.html ]
The main argument of one of the chief sceptics of the IPCC's conclusions, Professor Richard Lindzen, is negated. The role of water vapour in global warming is crucial. The climate models assume that as the oceans and atmosphere warm, so evaporation increases, and more water vapour accumulates in the atmosphere. Water vapour is itself a greenhouse gas, and of course it is present in far greater concentrations than the trace gases like carbon dioxide and methane. Linzen has advanced the idea that what will happen when the world warms is that increased convection will actually dry the middle and upper troposphere by a compensatory subsidence of air: that the increased vigour of circulation will effectivel y wring water vapour back out of the atmosphere. This means, Lindzen argues, that the GCMs have completely overestimated the water vapour feedback, and are hence strong overestimations of the warming that will ensue from human- enhancement of the greenhouse effect. A team of NASA and NOAA scientists now write in Nature: "we use some new satellite- generated water vapour data to investigate this question. From a comparison of summer and winter moisture values in regions of the middle and upper troposphere that have previously been difficult to observe with confidence, we find that, as the hemispheres warm, increased convection leads to increased water vapour above 500 mbar in approximate quantitative agreement with the results from the current climate models. The same conclusion is reached by comparing the tropical western and eastern Pacific regions. Thus, we conclude that the water vapour feedback is not overestimated in models and should amplify the climate response to increased trace-gas concentrations." The instrument used is the SAGE II (Stratospheric Aerosol and Gas Experiment) aboard the Earth Radiation Budget Experiment satellite.
(D. Rind, E. W. Chiou, W. Chu, J. Larsen, S. Oltmans, J. Lerner, M. P. McCormick, and L. McMaster, "Positive water vapour feedback in climate models confirmed by satellite data," Nature, v. 349, p. 500 - 503, 7 February 1993).
NOTES: The GCMs suggest that effective doubling of carbon dioxide will give a 1.2 oC warming. The water vapour feedback brings 1.7 oC on top of that. The ice-albedo feedback, according to their favoured GCM, is 0.4 oC. The authors conclude "given that potential impact of a 3-4 oC warming on droughts and ecosystems, our results re-emphasize the importance of reducing trace gas emissions." [ http://www.greenpeace.org/~climate/database/records/zgpz0830.html ]
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 from natural gas fields and gas hydrates during a period of extreme insolation.
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 depths that 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. 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."
(E. Nisbet, "Climate change and methane," Nature, v. 347, p. 23, September 1990). [ http://www.greenpeace.org/~climate/database/records/zgpz0687.html ]
A study finds that changes in vegetation and soil type that cause emission of carbon dioxide, such as those engendered by wildfires, could significantly increase carbon dioxide concentrations in a warming world. Such transient responses to warming, two environmental scientists from the University of Virginia argue, could overwhelm any tendency of in the carbon cycle for more carbon sequestration (such as species migration or soil formation). Estimates for the extent to which carbon might be added to the atmosphere based on two GCMs suggest that warming caused by a doubling of carbon dioxide could within 50-100 years provide an additional source equivalent to one third the present atmospheric concentrations of carbon dioxide.
(T. M. Smith and H. H. Shugart, "The transient response of terrestrial carbon storage to a perturbed climate," Nature, v. 361, p. 523 - 526, 11 February 1993). [ http://www.greenpeace.org/~climate/database/records/zgpz0459.html ]
The Declaration from an October 1993 meeting of IPCC experts at Woods Hole, Massachusetts, reads: "...the negative feedback mechanism of carbon dioxide fertilisation is likely to diminish in relative importance as carbon dioxide concentrations increase further and the positive feedback mechanisms of temperature enhancing rates of respiration (as well as production of methane and nitrous oxide) are likely to become more important as the Earth warms. The result of these consistent directional changes is that at the very least, the biosphere will become less effective at sequestering anthropogenically emitted carbon dioxide and other heat trapping gases, and at the worst, the biosphere may become a growing contributor to atmospheric accumulations of these gases." [ http://www.greenpeace.org/~climate/database/records/zgpz0552.html ]
Carbon dioxide is transported to the deep ocean by downwelling currents and may be retained in the depths for centuries. An important area of downwelling is in the Greenland Sea where northward moving warm and relatively saline water from the Gulf Stream sinks and cools. Scientists suggest that during the past decade, "the formation of North Atlantic deep water in the Greenland Sea apparently stopped." (P. Schosser, et. al. Reduction of Deepwater Formation in the Greenland Sea during the 1980's: Evidence from tracer Data," Science, v. 251, p. 1054-1056).
This shutdown would become a major positive feedback not currently included in the General Circulation Models, if it causes the ocean to cease serving as a carbon dioxide sink. (W.W.Kellogg, "The Arctic as a Source of Global Change Surprises," paper presented at AAAS Arctic Science Conference on Environmental Change in Valdez, Alaska, 8-12 September 1992). [ http://www.greenpeace.org/~climate/database/records/zgpz0726.html ]
From The Electronic Telegraph - Thursday, October 9th, 1997
Alaska meltdown as global warming thaws permafrost By Aisling Irwin, Science Correspondent, and Hugh Davies in Washington
FROZEN soil that underpins much of Alaska is melting, causing roads to collapse and landslides, and revealing that the United States may be suffering one of the first tangible consequences of global warming.
Researchers from the University of California and the US Forest Service, measuring the amount of carbon dioxide flowing into and out of Alaskan tundra over five summers, now publish the first evidence of significant net emission. They calculate that if their results apply to the entire high latitude belt, the tundra emitted 0.19 billion tonnes of carbon in 1990, some three percent of all the carbon emitted from fossil-fuel burning that year.
This is a significant positive feedback, and this process could well accelerate as the tundra warms further. (W. C. Oechel et al, "Recent change of Arctic tundra ecosystems from a net carbon dioxide sink to a source," Nature, 361, p 520-523, 11 February 1993).
"The recent climate patterns may be part of the normal climate variation or an early indication of greenhouse warming. In either case, it is clear that they have affected the current carbon flux from the arctic ecosystem, and that arctic and boreal forest ecosystems could provide a strong positive feedback on atmospheric carbon dioxide concentration." W. C. Oechel et al [ http://www.greenpeace.org/~climate/database/records/zgpz0461.html ]
FOR RELEASE AT 1:30 p.m. (PST) on SUNDAY, DECEMBER 15, 1996.
Contact: Sally Pobojewski
University of Michigan
Arctic Tundra Now Pumping More Carbon Into Atmosphere, Says U-M Scientist. Lakes And Streams Are Major Carbon Transfer Point.
EDITORS: Color slides and prints of scientists working in Alaska's Kuparuk River basin during the Summer of 1996 are available on request.
SAN FRANCISCO—The arctic tundra's vast carbon reservoir has sprung a leak. Recent experiments on Alaska's North Slope show that carbon molecules have started moving out of the tundra and into the atmosphere via a network of lakes, streams and rivers in larger amounts than ever before.
"Our latest data show that the arctic is no longer a strong sink for carbon," said George W. Kling, University of Michigan assistant professor of biology. "In some years, the tundra is adding as much or more carbon to the atmosphere than it removes, although the total amount of carbon released to the atmosphere is still quite small.
"However, the amount of carbon stored in arctic tundra equals almost one-third of the total carbon in Earth's atmosphere," Kling added. "The concern is what will happen in the future as global warming increases and melting permafrost exposes more of this buried carbon to be respired and released into the atmosphere."
Kling is one of several scientists working on the Gas Flux Study, part of the National Science Foundation's Arctic System Science (ARCSS) Program. Kling's research team studies how carbon dioxide and methane move between land, water and the atmosphere in the Kuparuk River Basin—an 8,100-square-kilometer area of Alaska's North Slope extending from the Brooks Range to the Arctic Ocean.
Kling and other scientists involved in the ARCSS Program presented data from this summer's field research during a special session of the American Geophysical Union meeting held here today.
"We have known for some time that arctic lakes and streams are supersaturated with carbon dioxide and methane, and that this excess gas diffuses into the atmosphere," Kling said. "What we didn't know is just how much carbon is entering the atmosphere through contact with surface waters."
Using new field measurements and computer models developed at the Ecosystems Center in Woods Hole, Mass., ARCSS scientists have been able to quantify for the first time the amount of carbon flux from the arctic tundra into the global ecosystem.
Kling's data show that for each square meter of tundra five grams of carbon are being lost from surface waters annually in the Kuparuk watershed. Of that amount, almost half of the carbon leaching out of the tundra into lakes and rivers is released directly to the atmosphere in the form of carbon dioxide or methane. Rivers carry the other half to the Arctic Ocean.
"Arctic plants are still taking in carbon dioxide from the atmosphere during photosynthesis," Kling explained. "But instead of much of that carbon remaining locked up in soil, more of it is being respired back to the atmosphere."
Kling added that scientists still have a great deal to learn about the complex biogeochemistry of the arctic ecosystem. For example, how will rising temperatures affect respiration rates in arctic soils? If the tundra starts to dry out, will that increase the amount of carbon dioxide released to surface waters or the atmosphere? What impact will increasing amounts of carbon dioxide and methane from arctic tundra have on global warming?
"As average global temperatures continue to increase, we expect to see the most dramatic changes occurring in the arctic. To prepare for these changes, we need to know a lot more about controls on the exchange of carbon between land, water and the atmosphere than we do now."
Other scientists working with Kling on his part of the NSF Gas Flux Study include John Hobbie and Ed Rastetter of the Ecosystems Center in Woods Hole, Mass., Terry Chapin of the University of California at Berkeley, and Walter Oechel of San Diego State University.
ENN Daily News -- July 13, 1995
Arctic ice cap shrinking faster, scientists say Norwegian scientists have detected an acceleration in the melting of the Arctic ice cap in what could be a sign of long-term global warming. "Microwave data suggest that over the period 1987-94 the rate of decrease in the extent of the Arctic sea ice has accelerated," Martin Miles and colleagues at the Nansen Environmental and Remote Sensing Center said in a letter to the journal Nature.
"It is too early to say, however, whether this represents a long-term trend." The scientists said climatological models had predicted the Arctic would start melting as the Earth's atmosphere warmed. This means ocean levels will rise, flooding lowland coastal areas. "We must continue to monitor global sea ice to ascertain whether these recent trends continue, especially given recent model results indicating that within the next two decades the greenhouse signal in global near-surface temperature should be detectable above natural variations," they wrote.
In the same issue of Nature, a team of European scientists reported that Siberia was warmer than it had ever been for the past thousand years. Keith Briffa of the University of East Anglia in Britain and colleagues used living and fossilized larch trees in the northern Ural mountains to track climatic changes in Siberia. "This record shows that the mean temperature of the 20th century (1901-90) is higher than during any similar period since AD 914," they wrote. They said this was consistent with the idea than humanity had prompted global warming. Source: Reuters
ENN Daily News -- May 28, 1997
Humans could trigger dramatic climate change "We are playing Russian roulette with our climate," one scientist told the opening session of GW8, the Eighth International Global Warming Conference and Exposition being held this week at Columbia University.
Annual precipitation shown in ice cores and pollen distribution from seafloor sediments show that Earth's climate is subject to extremely abrupt and dramatic changes, said Wallace Broecker, Newberry Professor of Earth and Environmental Sciences at Columbia and a well-known paleoclimatologist. Patterns of ocean currents can change, and climate temperatures can rise or drop by 15 degrees Fahrenheit or more.
Human activity—such as our dumping 6 billion tons of carbon dioxide into the atmosphere annually—could precipitate such a dramatic change, Professor Broecker said, and the fact that our climate is currently between major periods of glaciation means the climate could as easily turn colder as warmer.
"The Earth's climate system is an angry beast subject to unpredictable responses, and by adding carbon dioxide to the atmosphere we may be provoking the beast," he said.
Monday October 20 5:12 PM EDT
U.S. Reports 3.4 Pct Jump in Carbon Pollution
By Vicki Allen
WASHINGTON (Reuters) - The United States last year posted one of its biggest annual increases in heat-trapping industrial pollution, the government reported Monday.
U.S. carbon emissions from burning fossil fuels in 1996 jumped 3.4 percent above 1995, the Energy Information Administration said. That means the nation would have to cut emissions by 8.3 percent to reach the 1990 level frequently used as a benchmark in negotiations to fight climate change.
The new figures were released as world leaders were considering how to reduce the threat of global warming from industrial pollution.
President Clinton this week is expected to announce targets he will seek in a treaty to cut the world's output of carbon gases that trap heat, with potentially dire results of rising sea levels and more severe storms and droughts.
A negotiating session was underway this week in Bonn, and the talks were to conclude in December in Kyoto, Japan.
Already by far the world's biggest carbon emitter, the United States last year had its biggest rise in carbon pollution in recent years partly because of its booming economy and severe weather, the EIA said in it latest analysis.
See also An Example of the Catastrophic View: A Global Warming Scenario