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)
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