|The Week That Was
June 14, 2003
THE THEME OF THIS ISSUE OF TWTW IS CLIMATE SCIENCE
1. New on the Web: PAUL MARTIN LETTER. UPSET WITH THE SCIENTIFIC RATIONALE
BEHIND THE KYOTO ACCORD, A GROUP OF 46 INTERNATIONAL SCIENTISTS SENT PAUL
MARTIN THIS LETTER, published in the Financial Post (Toronto) on June
4, 2003. Martin is expected to become Prime Minister of Canada when Chretien
retires next year. He has expressed reservations over the Kyoto Protocol.
(By a happy coincidence David Anderson, the environment minister and chief force behind Kyoto in Canada, just had a letter to the editor in the Ottawa paper claiming the science is settled (according to the IPCC, of course). Nothing could be further from the truth, nor does the IPCC ever claim such a thing.)
2. CLIMATE MODELS ARE INADEQUATE IN SIMULATING THE IMPORTANT EFFECTS OF ATMOSPHERIC AEROSOLS. This throws doubt on claims that models can give reliable projections of future warming.
3. FORESTS EXPANDING INTO DESERT REGIONS, THANKS TO HIGHER LEVELS OF CO2
4. EARTH HAS BECOME GREENER IN THE PAST TWO DECADES - BY 6%, SATELLITE STUDIES SHOW
5. ATMOSPHERIC TEMPERATURES SHOW LITTLE IF ANY WARMING, A NEW ANALYSIS OF SATELLITE DATA CONFIRMS. CLIMATE MODELS INADEQUATE.
6. ANALYSIS OF GREENLAND ICE CORE SHOWS REGULAR ABRUPT TEMPERATURE CHANGES. But cause is still a puzzle.
7. Al-Gore-like, SENATOR MCCAIN PRESSURES WITNESS ON ABRUPT CLIMATE CHANGE
2. Climate models cannot account for the forcing effects of aerosols
"Anthropogenic aerosol emissions are believed to have counteracted the global-warming effect of greenhouse gases over the past century. However, the magnitude of this cooling effect is highly uncertain. In their Perspective, Anderson et al. argue that the magnitude and uncertainty of aerosol forcing may be larger than is usually considered in models. This would have important implications for the total climate forcing by anthropogenic emissions, and hence for predicting future global warming."
Despite extensive study, it is still highly uncertain just how big a
factor the negative forcing of aerosols is in the overall climate-change
picture. At issue is whether computer and mathematical models that use
a variety of factors to gauge climate change have properly accounted for
"That's fine as a best-guess scenario, but what if the high-magnitude negative aerosol forcing values turn out to be correct? That would mean current interpretations of 20th century warming would be erroneous, and so projections of future climate change might be in error as well. We need to at least consider this possibility," Anderson said.
He noted that if all climate forcing from outside factors so far has had a cumulative negative effect, then climate warming that already has occurred cannot be from human activity but rather must be the result of natural climate fluctuation. On the other hand, if the total forcing to date has been very small but still caused the observed warming, then the Earth's climate might be much more sensitive to forced change than climate models currently indicate.
Improved knowledge of climate forcing could radically alter the current understanding of climate change, the authors say. And that improved knowledge could be available in the near future from a new generation of aerosol-sensing satellites. A big step comes next year when the National Aeronautics and Space Administration and the French space agency launch a satellite called CALIPSO, which will provide detailed maps of the atmosphere's aerosol content. CALIPSO will fly in formation with other satellites measuring energy variations and other factors.
Ref: Anderson, Theodore L., Robert J. Charlson, Stephen E. Schwartz,
Reto Knutti, Olivier Boucher, Henning Rodhe, Jost Heintzenberg, 2003.
Climate Forcing by Aerosols--a Hazy Picture. Science (Perspective) Vol
300, pp. 1103-1104.
SEPP Comment: Current climate models, with perhaps one exception, use woefully inadequate aerosol forcing. Even though it is admitted that the indirect effects that lead to the formation of clouds are much larger than the direct ones, models don't know how to handle the problem.
3. More on the expansion of forests into desert regions (see also TWTW of May 24)
For most plant species, higher CO2 concentrations increase efficiency of water use and permit afforestation into drier regions. Expanding into regions of sparse shrubs and C4 grasses could lead to significant carbon sequestration - providing a negative feedback.
In addition, as the investigators point out (Grunzweig, Yakir et al in Global Change Biol. 9:791, 2003), low-latitude forests would be out of phase with the main NH forests at high latitudes and thus be exposed to a winter concentration of CO2 that is about 10 ppm higher than summer.
4. Earth has become greener in the past two decades - by 6%, satellite studies show
(CNN) -- The Earth has become significantly greener over the past two decades, the result of climate changes that have furnished plants with more heat, light, water and carbon dioxide, according to a new Science magazine report.
The overall plant bulk went up about 6 percent over much of the planet, with spikes in the tropics and high latitudes of the Northern Hemisphere accounting for 80 percent of the gains, researchers said.
The years since 1980 included two of the warmest decades on record, producing changes that have boosted growth ingredients in regions where they might otherwise have been scarce.
A 9.3 percent increase in the greenhouse gas carbon dioxide, a de facto fertilizer, was significant, but not enough to produce by itself the kind of vegetative growth, the study found.
Not everywhere has become more vegetated. About 7 percent of the studied landmasses experienced drops in plant productivity.
"The biggest winners [becoming more green] seem to be India, Brazil and Canada," said lead author Ramakrishna Nemani. "Losers are parts of Mexico and northern Siberia [drying and cooling, respectively]."
The Amazon rain forest alone was responsible for more than 40 percent of the plant growth, mostly due to reduced cloud cover that let in more sunshine.
"The most surprising result is that of the Amazon," said Nemani, a forestry professor at the University of Montana in Missoula.
The South American rain forest has suffered from deforestation on the
edges in recent decades, but the interior sections have grown vigorously,
he said. The study, funded by NASA and the Department of Energy, includes
decades worth of satellite and ground data, which the research team studied
for nearly a year and a half to determine plant productivity.
Whether humans have contributed much to the greening trend remains unknown,
but co-author Ranga Myneni cautions that we should hold off on congratulating
ourselves on our green thumbs. "[Plant] productivity may have increased
6 percent in the last 18 years, but human population has increased by
over 35 percent over that same time," the Boston University geographer
5. Satellite data show climate models inadequate
-- John Christy is professor of atmospheric science and director of
the Earth System Science Center at the University of Alabama at Huntsville.
This commentary is excerpted from his May 13, 2003 testimony to the House
Climate models attempt to describe the ocean/atmospheric system with equations that approximate the processes of nature. No model is perfect because the natural system is incredibly complex. One modest goal of model simulations is to describe and predict the evolution of the ocean/atmospheric system in a way that is useful to discover possible environmental hazards that lie ahead. The goal is not to achieve a perfect forecast for every type of weather in every unique geographic region, but to provide information on changes in large-scale features. If in testing models one finds conflict with even the observed large-scale features, this would suggest that at least some fundamental processes, for example heat transfer, are not adequately described in the models.
A common feature of climate model projections with CO2 increases is a rise in the global surface temperature as well as an even more rapid rise in the layer up to 30,000 feet, called the troposphere.
Over the past 24-plus years various analyses of surface temperature indeed show a rise of about 0.7 °F. This is roughly half of the total rise observed since the 19th century. In the lower troposphere, however, various estimates which include the satellite data Dr. Roy Spencer of [University of Alabama at Huntsville (UAH)] and I produce, show much less warming, about 0.3 °F -- an amount less than half that observed at the surface. The real world shows less warming in the atmosphere -- not more, as models predict. Are these data reliable?
A new version of the microwave satellite data has been produced, but not yet published, by Remote Sensing Systems, or RSS, of California. On June 1, a paper was published in Science magazine's electronic edition that used a curious means of testing our UAH version against RSS. The paper cited climate-model results that agreed more with RSS, because RSS data showed about 0.4°F more warming than UAH's data for this same layer called the mid-troposphere. UAH's total warming for this layer was about 0.05°F. (This layer is higher in the atmosphere than the lower troposphere mentioned earlier with its 0.3°F warming.) The strong implication of the paper was that since RSS was more consistent with the model output, it was likely a more accurate dataset than ours.
That same week, with much less fanfare, my latest paper appeared in the Journal of Atmospheric and Oceanic Technology. Unlike the paper in Science magazine, I performed several rigorous tests to estimate the potential error of our UAH satellite data. I used real observations from balloon datasets created by independent organizations, some with data from as many as 400 different balloon stations. Our UAH satellite data and the balloon data corroborated each other with remarkable consistency, showing only a slow warming of the bulk of the atmosphere. This evidence indicates that the projected warming of the climate models had little consistency with the real world. This is important because the quantity examined here, lower tropospheric temperature, is not a minor aspect of the climate system. This represents most of the bulk mass of the atmosphere, and hence the climate system. The inability of climate models to achieve consistency on this scale is a serious shortcoming and suggests projections from such models be viewed with great skepticism.
Changes in surface temperature have also been a topic of controversy. The conclusion in [the Intergovernmental Panel on Climate Change 2001 report] that human induced global warming was clearly evident was partly based on a depiction of the Northern Hemisphere temperature since 1000 A.D. This depiction showed little change until about 1850, then contains a sharp upward rise, suggesting that recent warming was dramatic and linked to human effects. Since IPCC 2001, two important papers have shown something else. Using a wider range of information from new sources, these studies now indicate large temperature swings have been common in the past 1000 years and that temperatures warmer than today's were common in 50-year periods about 1000 years ago. These studies suggest that the climate we see today is not unusual at all.
6. Analysis of Greenland ice core shows regular abrupt temperature changes. But cause is still a puzzle.
A reanalysis of temperatures in a Greenland ice core finds 23 consecutive cases of abrupt [Dansgaard-Oeschger] warming events during the last ice age with a recurrence period of 1470 years, with a precision of about 12%. It points to an extraterrestrial cause rather than an internal oscillation as frequently suggested --e.g. by W. Broecker [Science 300, 1519-1522, 2003].
Ref: Rahmstorf, S., Timing of abrupt climate change: A precise clock, Geophys. Res. Lett., 30(10), 1510, doi:10.1029/2003GL017115, 2003.
7. Senator McCain pressures witness on abrupt climate change
At the May 7 hearing of his Committee on Commerce, Science and Transportation, Senator John McCain tried to get witnesses to help him make the case for significant climate legislation. [He and Lieberman have modified their proposed Climate Stewardship Act of 2003 (S. 139) into an amendment to the Senate energy bill.]
He complained about lack of definiteness: " It makes it a little more difficult for me to make my case and ask colleagues to vote on cap-and-trade initiatives [for CO2] when they say that scientists aren't sure yet."
However, witness Richard Alley (Penn State University) told the Committee: "I am never going to tell you I am certain." Alley, who chaired the NAS panel that issued "Abrupt Climate Change: Inevitable Surprises" (Feb. 25, 2003), then added that climate change is highly likely, is occurring, and "highly likely occurring because of human influence." But his NAS report does not say this anywhere - nor do we know of evidence to support this claim of human influence.
SEPP Comment: So-was Alley just being polite -- or intimidated "Al-Gore-like" -- by Chairman McCain? It is ironic to note also (see above) that climate instabilities were pronounced and large when the climate was cold, but relatively minor during the present warm interglacial period. Does this suggest that the climate may become even more stable if it should warm in the future?