William Yeatman

Rainfall Variability Caused by Nature

One of the most widely cited “evidences” of global warming is the increase in “torrential” rainfall in the United States. A paper by Tom Karl of the National Climate Data Center, which appeared in 1995 in Nature magazine, had found a positive trend in heavy precipitation for much of the U.S., Canada and Europe in the last century. Specifically, Karls study found one additional day every two years that experiences rainfall of over 2 inches in a 24-hour period, but no increase in precipitation events of over 3 inches. Not much to get excited about.

A new study, which complicates the ability to link global warming and rainfall, appears in the May issue of Geophysical Research Letters. The researchers discovered a natural 65-80 year cycle in sea surface temperatures in the North Atlantic. Using sea surface temperatures from 1856 to 1999, they found a temperature fluctuation of 0.4 degrees C, which they dubbed the Atlantic Multidecadal Oscillation.

The warm phases occurred during 1860 to 1880 and 1940 to 1960 and the cool phases during 1905 to 1925 and 1970 to 1990. During the warm periods, the U.S. sees less than normal rainfall. We are currently in a warm period, which could mean “We may have once again entered a period such as 1930-1960,” said the studys lead author, David B. Enfield when the U.S. climate was much drier (Associated Press, May 14, 2001).

Enfield, an oceanographer with the National Oceanic and Atmospheric Administrations Atlantic Oceanographic and Meteorological Laboratory, said that this ocean cycle “could obfuscate our assessment of global warming response.”

Schneider Criticizes IPCC

Global warming projections coming from the Intergovernmental Panel on Climate Change had been steadily decreasing with each new iteration of its assessment report, suggesting that the more we learn about climate the less likely global warming will be a problem. The release of the Summary for Policymakers of the IPCCs Third Assessment Report shocked everyone by raising projections from a 1 to 3.5 degree C warming over the next 100 years to 1.4 to 5.8 degrees.

The new projections raised a lot of eyebrows, given that there has been no real change in scientific evidence or in our ability to detect manmade global warming. One of those who have expressed concerns over the presentation of the new scenarios is Stephen Schneider, a major booster of catastrophic global warming theory.

Schneider points out in an article in Nature (May 3, 2001), that “This sweeping revision depends on two factors that were not the handiwork of the modelers: smaller projected emissions of climate-cooling aerosols; and a few predictions containing particularly large CO₂ increases.”

Schneider asks, “How likely is it that the world will get 6 degrees C hotter by 2100?” That “depends on the likelihood of the assumptions underlying the projections.” According to Schneider, “the IPCC decided to prepare a special report on emissions scenarios (SRES) to produce a family of updated projections.” The group that met to make up these scenarios included academic scientists, environmental organizations, industrial scientists, engineers, economists, and systems analysts.

They decided to “create storylines about future worlds from which population, affluence and technology drivers could be inferred.” These storylines “gave rise to radically different families of emission profiles up to 2100 from below current CO₂ emissions to five times current emissions,” wrote Schneider.

Schneider says that he “strongly argued at the time that policy analysts needed probability estimates to assess the seriousness of the implied impacts,” but the group decided to express “no preference” for each scenario. The result has been the assumption that the higher bound is just as likely as the lower. “But this inference would be incorrect,” said Schneider, “because uncertainties compound through a series of modeling steps. Uncertainties in emissions scenarios feed into uncertainties in carbon-cycle modeling, which feed into uncertainties in climate modeling, which drive an even larger range of uncertain climate impacts. This cascade of uncertainties is compounded by the very wide range of emissions offered by the SRES authors.”

To get the final “dramatic revision upward in the IPCCs third assessment,” it combined the climate sensitivities of seven general circulation models (GCMs) with the “six illustrative scenarios from the special report” within a simple model to get 40 climate scenarios.

Schneider attempts to construct a probability distribution of these different temperature scenarios, finding that only 39 percent show a warming of 3.5 degrees or higher. Under a more comprehensive range of 108 scenarios using 18 GCMs, only 23 percent would result in a warming of over 3.5 degrees. Schneider “arbitrarily” assumes that temperature increases of 3.5 degrees C and over would have dangerous climate consequences.

Schneiders calculations broadly agree with an MIT study we reported on in our April 18 issue. It found that there is a “far less” than one percent chance that temperatures would rise to 5.8 degrees C or higher, the upper bound of the IPCCs projections, while there is a 17 percent chance the temperature rise would be lower than 1.4 degrees, the IPCCs lower bound.

CO₂s Positive Effects Confirmed

Thousands of studies have been conducted to determine the effects of rising atmospheric CO₂ on plant growth. The overwhelming weight of evidence is that higher levels of CO₂ increase plant growth. More recently scientists have looked into effects of higher CO₂ concentrations on the quality, not just the quantity, of the food supply.

To get to the bottom of this research, Sherwood Idso of the U.S. Water Conservation Laboratory and Keith Idso of the Center for the Study of Carbon Dioxide and Global Change have reviewed over 250 peer-reviewed studies (Environmental and Experimental Botany, 45, 2001). They find “that the ongoing rise in the airs CO₂ content will continue to increase food production around the world, while maintaining the nutritive quality of that food and enhancing the production of certain disease-inhibiting plant compounds.”

Some research had suggested that CO₂ induced growth lowers nitrogen and protein concentrations in plants, possibly having a deleterious effect on animal and insect herbivores. But, said the Idsos, “Few solid conclusions can be drawn, however, in light of the fact that many CO₂ enrichment studies have not detected significant reductions in foliage nitrogen or protein concentrations.”

Moreover, “Nitrogen concentrations of all plants decline in response to increasing plant biomass, irrespective of the cause of the biomass increase.” This result is “highly dependent on nitrogen supply and virtually disappears when nitrogen is freely available to the roots.”

The paper looks at several other components of plant quality in relation to animal and human health and finds that higher CO₂ concentrations do not have a harmful effect and in many cases has a beneficial effect.

Etc.

• On June 19, 2001 Barrow, Alaska experienced a rare thunderstorm. The National Weather Service noted in a public advisory statement that it was only the third thunderstorm to occur in Barrow since 1978. From that point on, the story took on a life of its own. News stories around the world reported that it was Barrows first ever thunderstorm and that it signaled the arrival of global warming.

On May 2, the Senate Environment and Public Works Committee held a hearing on global warming. In his opening remarks, Senator Ted Stevens (R-Alaska) said that global warming has already revealed itself in Alaska. He said that several communities along Alaskas Arctic coast, including Barrow, would need to be relocated due to rising seas. The May 5 Nando Times story which reported on Stevenss comments again stated, “Last June, Barrow experienced its first-ever thunderstorm.”

John Daly (www.john-daly.com) decided to look into these claims of rising seas and relocations. As it turns out, there is a tide gauge 200 miles from Prudhoe Bay along the same stretch of coastline as Barrow. The tide gauge measurements show no increase in sea levels along Alaskas Arctic coast. The inundation of certain Alaskan villages is due to coastal erosion, not sea level rise. It also turns out that there are no plans to relocate Barrow as Senator Stevens claimed.

Announcements

• The Competitive Enterprise Institute has released a report on several new global warming studies published since the final draft of the IPCCs Third Assessment Report was approved in August 2000. The report, “Latest Global Warming Report Already Obsolete,” by CEI environmental policy analyst Paul Georgia, concludes that these new studies cast serious doubt on some of the IPCCs most basic assumptions, leaving its conclusions in shambles. The report can be obtained at www.cei.org.

Man Blamed for Rising Sea Temperatures

Recently the news was full of stories about new and stronger evidence that man is causing the planet to warm. The stories were based on two new studies appearing in the April 13 issues of Science. According to Sydney Levitus, lead author of one of the studies, “We think this is some of the strongest evidence to date that human-induced effects are changing our climate” (Associated Press, April 13, 2001).

A closer examination of the studies reveals, however, that the claims are overblown. The studies rely on climate models, which arent evidence at all, but merely artificial constructions of what some scientists believe about the climate.

The study by Tim Barnett, et al. attempts to predict the ocean heat content averaged from the surface to 3,000 feet below the surface, from 1955 to 2000, that would result from CO₂ forcing. The study claims that the match between the observed warming in the oceans and that produced by the model is very good, therefore suggesting that human activity is responsible for that warming.

To achieve this apparent match, however, the researchers “smoothed” the data by using the average value of each ten-year period rather than the raw data to fit it to the model results. But even the smoothed data does not fit well. Of the five oceans examined, all but one experienced a cooling from the mid-1970s to the mid-1980s not replicated by the models.

The fit between the data and the models is achieved by using ocean temperatures down to 3,000 feet. The model in fact does a terrible job of replicating temperature changes at the oceans surface where greenhouse gases have the most immediate effect, but does a very good job of replicating temperatures at depths of 1,500 feet to 3,000 feet, which are largely unaffected by greenhouse gases. The modelss poor performance is hidden by averaging ocean temperatures over 3,000 feet.

The Levitus, et al. study is also questionable. It looks at historical records of ocean temperatures from the surface to 10,000 feet from 1955 to 1996. This study also smooths the data to achieve a better fit, which washes out an important ocean temperature shift that occurred in 1976-77, known as “the great Pacific climate shift.”

There was no statistically significant ocean warming before or after the 1976-77 temperature shift. Such sudden shifts can hardly be attributed to gradual increases in greenhouse gas concentrations, but by averaging the data, Levitus, et al. were able to construct a gradual temperature rise consistent with global warming theory.

More detailed criticisms of the studies can be found at www.john-daly.com and www.greeningearthsociety.org/climate.

Deforestation Blamed for Cooling

A possible new culprit for global warming has emergedtrees. A study by researchers at the Lawrence Livermore Laboratory has found cooling temperatures can be linked to deforestation, according to an April 24 Associated Press story.

The study looked at the period between 1000 and 1900, when the Earths temperature dropped two degrees Fahrenheit. Researchers found the places that cooled the most also experienced the most deforestation. Thus if deforestation causes cooling, then is it also the case that reforestation, which has been going on at a rapid pace in the U.S. for decades, will cause warming?

Arctic Sea Ice Thickness and Wind

Several studies have been done to determine what changes, if any, have occurred in sea ice cover and sea ice thickness in the Arctic. Interest in Arctic ice is fueled by the belief that the signs of global warming would be observed there first.

A paper by Greg Holloway and Tessa Sou, with the Institute of Ocean Sciences, in Sidney British Columbia, Canada, delivered at the 3^rd annual Arctic Science Summit Week, an initiative of the International Arctic Science Committee, asks the question, “Is Arctic Sea Ice Rapidly Thinning?” The answer is “no.”

Detailed satellite observations from 1979 to 1999 show a decrease in sea ice cover of nearly 3 percent per decade. Observations of sea ice thickness have shown even more dramatic changes, but the data is sparse.

A study by Rothrock et al., which appeared in the Geophysical Research Letters, used U.S. military submarine cruise records from autumns of 1958, 1960, 1962, 1970 and 1976 and compared them to cruises in 1993, 1996, 1997. “Systematically over all the regions sampled by the submarines, thickness had markedly decreased from the earlier to the later period,” according to Holloway and Sou. There was an apparent decrease of thickness of 43 percent at the 29 locations where the records could be compared.

In earlier work, Holloway had constructed a “numerical ocean-ice-snow model to attempt to formulate a mutually consistent budget for freshwater and heat in the Arctic ocean-ice-snow system.” For the current study, the model was run from 1948 to 1999 and replicated the well-measured three percent per year reduction in ice cover consistent with observations. “However, model-estimated thinning was nothing like the rapid thinning reported from submarines,” a thinning of only 12 percent.

Holloway and Sou argue that the mismatch between the submarine measurements and model results suggest either problems with the model or inadequate data. They prefer the latter explanation due to the sparseness of the data.

The researchers suggest that, “The apparent ice loss was only a shifting of location of ice within the Arctic,” which the infrequent submarine sampling missed. How does the ice shift? “Large-scale wind patterns are ever-changing, and the Arctic ice pack is readily rearranged,” said Holloway and Sou. Moreover, the patterns of wind stress in the model resemble the pattern of thinning.

Holloway and Sou conclude “that the positions of submarine observations were exceptionally biased towards regions of thinning.”

“The actual results from the actual submarine surveys appear to be a fluke of timing coupled with the natural mode of Arctic sea ice variability,” said the researchers.

Climate Models: “Unchanging with Time”

Recent media accounts of the latest report from the Intergovernmental Panel on Climate Change give the distinct impression that climate models, the primary source of global warming concerns, are getting more accurate all the time. A news article in Science (April 13, 2001), however, sets the record straight.

According to the author, Richard A. Kerr, “But while new knowledge gathered since the IPCCs last report in 1995 has increased many researchers confidence in the models, in some vital areas, uncertainties have actually grown.” Gerald North of Texas A&M University in College Station said that, “Its extremely hard to tell whether the models have improved” since the last IPCC report. “The uncertainties are large.”

Peter Stone, an MIT climate modeler, said, “The major [climate prediction] uncertainties have not been reduced at all.” And cloud physicist Robert Charlson, professor emeritus at the University of Washington, Seattle, said, “To make it sound like we understand climate is not right.”

The three main areas of uncertainty are detection of global warming, attribution of warming to greenhouse gases, and projecting future warming, Kerr writes. Detection is probably the closest to being resolved of the three. The IPCC puts warming at 0.6 degrees 0.2 degrees centigrade with a 95 percent confidence level.

Attribution of global warming to anthropogenic emissions of greenhouse gases is much more difficult, however. The IPCC claims, “most of the observed warming over the last 50 years is likely [66 percent to 90 percent chance] to have been due to the increase of greenhouse gas concentrations.”

Some modelers, such as Jerry Mahlman with NOAA and John Mitchell at the UKs Hadley Centre for Climate Prediction and Research, think the models are getting better. The models are “getting quite a remarkable agreement,” with reality, said Mitchell.

“Thats stretching it a bit,” said John Christy of the University of Alabama at Huntsville. Stone argues that human attribution “may be right,” but, “I just know of no objective scientific basis for that.” Tim Barnett of Scripps Institution of Oceanography and Jeffrey Kiehl of the National Center for Atmospheric Research concur.

One of the primary means by which modelers have tweaked the models for better results is the inclusion of aerosols. But according to Kiehl, “The more we learn [about aerosols], the less we know.” Indeed, according to the IPCC report, “The uncertainties are so large that a best estimate with error bars of the indirect cloud effect of aerosols is still impossible.” Possible aerosol cloud effects now range from no effect to a near total masking of the alleged manmade greenhouse effect.

North argues that the “huge range of climate uncertainty among the models” is a serious problem. “There are so many adjustables in the models and there is a limited amount of observational data, so we can always bring the models into agreement with the data.”

According to Science, North explained that, “Models with sensitivities to CO₂ inputs at either extreme of the range can still simulate the warming of the 20^th century.”

Many of these scientists still think something should be done to slow down the emission of greenhouse gases. This, however, seems to be a reaction to change as much as a concern over whether there will be any ensuing harm. “The evidence for chemical change of the atmosphere is so overwhelming, we should do something about it,” said Charlson.

Quantifying the Uncertainties

Although most scientists are willing to admit that there are still large uncertainties in the predictions about rising global temperatures, there has been little effort to quantify those uncertainties. Uncertainties are important, however.

According to a new study by researchers at the Joint Program on the Science and Policy of Global Change at MIT, “Communicating uncertainty in climate projections provides essential information to decision makers, allowing them to evaluate how policies might reduce the risk of climate impacts.”

The Intergovernmental Panel on Climate Change does not provide these numbers, however. “The Third Assessment Report of the [IPCC] reports a range for global mean surface temperature rise by 2100 of 1.4 to 5.8 degrees centigrade but does not provide likelihood estimates for this key finding although it does for others,” says the study.

The researchers perform this calculation and conclude, “that there is far less than a 1 in 100 chance of a global mean surface temperature increase by 2100 as large as 5.8 degrees centigrade.” They also conclude, “there is a 17 percent chance that the temperature change of 2100 would be less than the IPCC lower estimate” (web.mit.edu/globalchange/www/).

Even though it is much more likely that the amount of warming over the next 100 years will be less than 1.4 degrees centigrade than 5.8 degrees centigrade or more, it is the higher number that is emphasized in news coverage of the issue. This is highly misleading if the MIT calculations are correct.

Ecosystem Effects of Global Warming

The anticipated effects of global warming are supposed to be horrific, according to environmental activists and the science politicos who populated the Clinton Administration. A short news item appearing in Nature (April 5, 2001) begins in the usual way, as a prelude to a horror story. “The first survey for a decade of animals and plants on Australias Heard Island, 4,000 kilometres southwest of Perth, has unearthed dramatic evidence of global warmings ecological impact,” said Nature.

What are these impacts? The usual stuff, such as glaciers that “have retreated by 12 percent since the first measurements were taken in 1947,” and “a rise in sea surface temperature of up to 1 degree C” The story then takes an odd turn. Global warming has also led to “rapid increases in flora and fauna” on the island.

Previously low vegetation areas are now “lush with large expanses of plant,” said Dana Bergstrom, an ecologist at the University of Queensland in Brisbane. “The number of king penguins has exploded from only three breeding pairs in 1947 to 25,000, while Heard Island cormorant, listed previously as vulnerable, has increased to 1,200 pairs. From near extinction, fur seals now number 28,000 adults and 1,000 pups,” noted Nature.

The changes on Heard Island, especially the retreating glaciers, are not likely due to global warming, according to John Daly, who maintains the Australian-based website, Still Waiting for Greenhouse (www.john-daly.com). The island, says Daly, has two volcanoes and the larger of the two has been very active in the past 120 years, including numerous eruptions and lava flows.