April 2003

CBO Releases Study on Economics of Climate Change

The Congressional Budget Office on April 25 released a new study on The Economics of Climate Change: a Primer, prepared by Robert Shackleton of the CBOs Macroeconomic Analysis Division. The study considers most of the issues involved in controlling greenhouse gas emissions, but reaches only tentative and general conclusions.

The study draws on a wide range of scholarship, but does not attempt to estimate the costs of various policies. It does conclude that pricing emissions through taxes or fixed-price permits is preferable in many ways to capping emissions through quotas.

One chapter considers climate science and the potential costs and benefits of global warming. Curiously, two graphs are displayed together that show a remarkable correlation between fluctuations in global temperature and in atmospheric carbon dioxide concentrations over the last 450 thousand years. Although the text does not claim that increasing carbon dioxide levels cause higher temperatures, the causal connection is implied by juxtaposing the two graphs.

Apparently the author is unaware that it has been observed and is now generally agreed that higher temperatures have preceded higher carbon dioxide levels. It has further been plausibly argued that temperature fluctuations cause carbon dioxide fluctuations through the atmosphere-ocean transfer of carbon dioxide. Oceans absorb carbon dioxide as temperatures cool and release carbon dioxide into the atmosphere as temperatures rise.

The study and a four-page issue brief based on it are posted at www.cbo.gov.

Emissions Drop Sharply in Britain

Carbon dioxide emissions in the United Kingdom dropped 3.5 per cent last year. The governments planned target of a 3.5 million ton reduction in emissions was exceeded by 10 million tons.

“The results of our agreements demonstrated real gains in energy efficiency, achieved in a cost-effective way,” claimed Lord Whitty, the government minister for sustainable energy, according to a Reuters story (April 9, 2003). Under the governments Climate Change Agreements, companies that fail to meet their targets can incur steep energy taxes.

Environment Minister Michael Meacher said that, “Todays figures are another boost for governments aim to cut carbon emissions by 60 per cent by 2050.”

The Independent of London explained the reason for the sharp decline in emissions in an April 8 article. “But the reductions in carbon dioxide output were principally due to falling steel production as Corus formerly British Steel struggled with severe operational difficulties, ministers admitted,” wrote technology editor Charles Arthur.

House Committee Will Take Up Sense of Congress Language on Climate

The House International Relations Committee is scheduled to take up the State Department Authorization bill (which has not yet been given a number) on May 7. Committee staff expect that Rep. Robert Menendez (D-N. J.) will offer sense of Congress on climate change language similar to that voted out of the Senate Foreign Relations Committee on April 9.

Last year, a similar amendment offered by Menendez was approved on a 23-20 vote. Republican Representative Chris Smith of New Jersey joined committee Democrats in voting for the amendment. Four Republicans missed the vote. The amendment was dropped in the House-Senate conference report on the bill.

This year, Menendezs amendment faces a more organized opposition. Chairman Henry Hydes (R-Ill.) committee staff are canvassing Republican members. The House majority leadership are united in opposing the amendment. A joint letter opposing the amendment from several trade associations led by the National Association of Manufacturers has been sent to committee members. Another joint letter from non-profit groups is being circulated by the Competitive Enterprise Institute for signatures.

The Senate has scheduled consideration of its State Department authorization bill, S. 925, for May 6. It is not known whether there will be an attempt to strip or replace the climate language. Among other things, the climate section calls on the administration to negotiate a new international treaty with binding commitments to reduce greenhouse gas emissions. For a more complete account of the Senate version, see the April 16 issue.

Senate Energy Bill Goes to Floor Without Climate Title

The Senate Energy and Natural Resources Committee completed work on comprehensive energy legislation on April 30 and sent the bill to the floor. The bill, S. 14, does not contain any climate policy provisions. Senator Jeff Bingamans (R-N.M.) amendment to add a renewable portfolio standard for electric utilities was also defeated.

The Senate could begin floor debate on the bill as early as next week, although it is expected that there will be several weeks of intermittent debate before a final vote. Numerous amendments on climate policy may be offered. These include Titles 10, 11, and 13 from last years Senate energy bill; the McCain-Lieberman bill to cap greenhouse gas emissions, S. 139; and Senator Tom Carpers (D-Del.) Clean Air Planning Act, S. 843.

White House Denies Petition Using Data Quality Act

The White House Office on Science and Technology Policy on April 21 denied a petition to have the National Assessment on Climate Change corrected to comply with the Federal Data Quality Act.

OSTP legal counsel, in replying to the petition filed by Christopher C. Horner on behalf of the Competitive Enterprise Institute, claims that the National Assessment was produced by a federal advisory committee and is therefore exempted by the Federal Advisory Committee Act from meeting the Data Quality Acts requirements.

“Only a few problems stand between this claim and reality,” Horner commented.

“First, the statute authorizing the National Assessment expressly states that it will be produced by OSTP. Second, the National Assessments text acknowledges that it was produced by OSTP. Third, on numerous occasions the federal advisory committee charged with assisting OSTP acknowledges that the National Assessment itself will be a product of OSTP,” Horner continued.

“Furthermore, neither OSTPs guidelines nor the White House Office of Management and Budgets FDQA guidelines provide any exemption for FACA products,” said Horner, who is preparing an appeal on behalf of CEI.

The petition and the White Houses denial may be found at www.cei.org.

A study by Joel Schwartz challenges the scientific basis of both the Bush Administrations Clear Skies Initiative and Senator Jim Jeffordss (I-Vt.) Clean Power Act. The analysis has implications for climate policy because Jeffordss legislation includes regulation of carbon dioxide emissions and Bushs plan could serve as a proxy climate policy by forcing utilities to close coal-fired power plants in order to reach the limits on mercury emissions.

Clear Skies and Clean Power would impose tough new controls on power plants to reduce levels of fine particle (PM2.5) pollution, which both sides claim kills tens of thousands of people per year. Supporters of these bills promise substantial benefits from additional PM reductions.

Schwartzs new study, published by the Competitive Enterprise Institute, argues that Clear Skies and Clean Power rest on a weak scientific foundation. The U.S. Environmental Protection Agency (EPA) based its new annual fine PM (PM2.5) standard on a study known as the American Cancer Society (ACS) study of PM and mortality, which assessed the association between the risk of death between 1982 and 1998 with PM2.5 levels in dozens of American cities.

Although the ACS study reported an association between PM and mortality, some odd features of the ACS results suggest that PM is not the culprit. For example, higher PM levels increased mortality in men, but not women; in those with no more than a high school degree, but not those with at least some college; in former-smokers, but not current- or never-smokers; and in those who said they were moderately active, but not those who said they were very active or sedentary.

These odd variations in the relationship between PM2.5 and mortality seem biologically implausible. Even more surprising, the ACS study reported that higher PM2.5 levels were not associated with an increased risk of mortality due to respiratory disease; a surprising finding, given that PM would be expected to exert its effects through the respiratory system.

EPA also ignored the results of another epidemiological study that found no effect of PM2.5 on mortality in a cohort of veterans with high blood pressure, even though this relatively unhealthy cohort should have been more susceptible to the effects of pollution than the general population. The evidence therefore suggests that EPAs annual standard for PM2.5 is unnecessarily stringent. Attaining the standard will be expensive, but is unlikely to improve public health.

Air pollution has declined dramatically over the past 30 years, and will continue to decline, both because more recent vehicle models start out cleaner and stay cleaner as they age than earlier ones, and also because already-adopted standards for new vehicles and existing power plants will come into effect in the next few years.

If policymakers feel they must do something to speed up PM reductions, Schwartz advises they offer people tax incentives to scrap high-polluting older vehicles that account for a substantial portion of ambient PM levels in metropolitan areas. This flexible, cost-effective approach is more likely to result in net public health benefits than either Clear Skies or Clean Power.

The study is available at http://www.cei.org/gencon/025,03452.cfm.


The Cooler Heads Coalition and the George C. Marshall Institute will host a congressional staff and media briefing on Friday, May 16, from Noon to 1:30 PM in Room G-50 of the Senate Dirksen Office Building. Dr. Willie Soon, a research physicist with the Harvard-Smithsonian Center for Astrophysics, will speak on, “Was the Twentieth Century Climate Unusual? Exploring the Lessons and Limits of Climate History.”

Lunch will be provided, and reservations are required. To register, please telephone the Marshall Institute at (202) 296-9655 or e-mail them at info@marshall.org.

Soons talk will be based on a recent major review article of which he was the lead author. See the April 16 issue for more details. The article has been posted on the web at http://cfa-www.harvard.edu/~wsoon/1000yrclimatehistory-d/. A less technical version is available on the Marshall Institutes web site at www.marshall.org/pdf/materials/136.pdf.

The New York Times is wringing its hands over lost opportunities for U.S. companies to trade in phony assets (April 10, 2003). According to the Times, the U.S., which was the major promoter of emissions trading at the Kyoto negotiations, is now being left out of a potentially lucrative market.

The paper also notes that the Europeans, who were very cool to the idea of trading when it was being pushed by the U.S., have now jumped on the market-based bandwagon. “When Bush pulled out in the cavalier way he did, he galvanized everyone around the world to make it work,” said David Doniger, a former Clinton administration Kyoto negotiator, now with the Natural Resources Defense Council. “The system is made in America, and the Americans arent part of it.”

Steve Drummond, managing director of a greenhouse gas brokerage in London called CO2e.com, told the Times that, “Now that the Americans are out, Europe can dominate the emissions trading market. It entitles the Europeans to write the rules for global trading.”

The Times laments the prospect of American-based multinationals being “forced to put in place two ways of accounting for carbon dioxide emissions, one for emissions inside the United States and one for emissions in nations that signed on to Kyoto.” What the Times omits is that the Kyoto Protocol still has not been ratified and gone into effect.

The real dynamic in operation here is the attempt to build a business constituency in favor of ratifying Kyoto and implementing mandatory caps. The Times is playing on the fears (or hopes) of businesses facing uncertainty regarding the future of carbon dioxide regulations, which would increase the cost of energy use and hurt the economy.

Some companies are rightly upset about the prospect of such controls, but are also mindful of the fact that globally imposed regulations might be cheaper than a hodgepodge of conflicting rules. Other companies see an opportunity to game the emissions trading system Enron-style to raise profits. Those companies play at voluntary emissions trading and hope to get credits for emissions reduction activities that they would have carried out anyway. Those companies are behind efforts for federally-mandated early action crediting schemes.

The Times quotes Bruce Braine, vice president for strategic planning and analysis at American Electric Power, who says that his company sees voluntary trading as “an insurance policy. If you ultimately have mandatory requirements, then this gives us first-mover advantages.” But the first-mover advantage isnt insurance so much as a move to become part of a future carbon cartel, in which companies like AEP will rake in massive rents from less-advantaged companies.

What they really fear is not being part of the cartel. “By not putting in place similar legislation for greenhouse gases, critics fear, the United States allows other countries to gain experience and win business in the field,” says the Times. “All were doing now is giving other countries a chance for remedial education,” said Doniger, “and it will cost us in the end.”

Climate Title Stripped from Senate Energy Bill

Senator Pete Domenici (R-N.M.), chairman of the Energy and Natural Resources Committee, decided to drop his draft climate title when it came time to mark it up on April 10. He noted during the committee meeting that he had discovered that no consensus existed among members of the committee on what climate policies should be included in his comprehensive energy legislation. However, he pledged to work toward a constructive compromise before the bill reached the Senate floor.

Senator Jeff Bingaman (D-N.M.), the ranking Democratic member, announced that he had prepared two amendments, but would delay offering them until late April when committee mark-up is scheduled to resume. These amendments are a new version of the Byrd-Stevens bill that was included in last years Senate energy bill and proposals to improve greenhouse gas emissions monitoring and reporting. Senator Ron Wyden (D-Oreg.) also said that he had an amendment, based on the Craig-Wyden carbon sequestration bill, that he planned to offer.

The draft climate title, which was released for comment on March 26, aroused opposition from several committee Republicans and from conservative and free market public interest groups. Title XI would have created a White House Office of Climate Policy and climate czar, required the executive branch to produce a national strategy that “will stabilize and ultimately reduce net U. S. emissions of greenhouse gases” plus annual progress reports; and created a system to award credits for voluntary actions to cut emissions.

A joint letter criticizing the climate title was sent to Chairman Domenici on April 4. It was signed by leaders of 21 non-profit groups, including the Competitive Enterprise Institute, Coalitions for America, Americans for Tax Reform, 60 Plus Association, American Conservative Union, National Taxpayers Union, Christian Coalition, National Center for Public Policy Research, Small Business Survival Committee, American Policy Center, and Frontiers of Freedom. The letter states that the climate title would “in our view create the institutional and legal framework and the political incentives necessary eventually to force Kyoto-style energy rationing on the American people.” The text may be found online at http://www.cei.org/gencon/003,03434.cfm.

Foreign Relations Committee Speaks on Climate Change

On April 9, the Senate Foreign Relations Committee passed by voice vote a sense of the Senate resolution on climate change as part of the State Department re-authorization legislation. Senator Joe Bidens (D-Del.) amendment includes a finding that there is growing evidence that “increases in atmospheric concentrations of man-made greenhouse gases are contributing to global climate change.” The resolution enumerates several other irrelevant and false findings before stating that the U.S. should reduce the risks of climate change by:

(1) “taking responsible action to ensure significant and meaningful reductions in emissions of greenhouse gases from all sectors;

(2) “creating flexible international and domestic mechanisms, including joint implementation, technology deployment, tradable credits for emissions reductions and carbon sequestration projects that will reduce, avoid, and sequester greenhouse gas emissions; and

(3) “participating in international negotiations, including putting forth a proposal to the Conference of the Parties, with the objective of securing United States participation in a future binding climate change Treaty in a manner that is consistent with the environmental objectives of the UNFCCC, that protects the economic interests of the United States, and recognizes the shared international responsibility for addressing climate change, including developing country participation.”

House Approves Energy Bill, ANWR Exploration

On April 11, the House of Representative passed an omnibus energy bill by a vote of 247-175. The bill would open the Alaska National Wildlife Refuges coastal plain to oil and gas exploration. It also contains numerous subsidies and incentives for conventional and renewable energy production.

Amendments to remove the ANWR provision, electricity restructuring, and oil and natural gas royalty relief were defeated, as was an amendment that would have required automobile manufacturers to raise the Corporate Average Fuel Economy of their fleets to 30 miles per gallon by 2010. A provision that would have allowed the Department of the Interior to make a complete inventory of the nations offshore oil and natural gas supplies was stripped from the bill. (Greenwire, April 14, 2003).

Climate Change Skepticism on the Rise in Russia

Global warming skepticism seems to be increasing in Russia as that country wrestles with the decision of whether to ratify the Kyoto Protocol. Russia has become the lynchpin in the Kyoto debate. Failure to ratify on Russias part would prevent the treaty from coming into legal force.

The Moscow newspaper, Pravda, recently published a strongly worded article, entitled “Kyoto Protocol Is Not Worth a Thing,” which questioned the wisdom of ratification. Another Russian newspaper, Nezavisimaya Gazeta, published an article written by two Russian climate scientists, Sergey Dobrovolsky and Vyacheslav Naydenov, entitled “The Warming That Never Existed.”

The Pravda article highlighted the words of an ecologist who questioned global warming science. “This trouble is coming from the Russian Arkhangelsk region,” according to Pravda. “This region is celebrated for its implementation of the Kyoto protocol. There was a briefing held there recently to discuss climate questions. Young ecologist Alexander Shalarev dared to say [what] Moscow scientists are afraid to say. He declared that there was actually no [manmade] greenhouse effect at all. Shalarev added that the Kyoto protocol was simply a far-fetched idea, a political action that was meant to show the care for the climate of the Earth.”

Pravda also noted that Shalarev believes that the Kyoto protocol was signed without adequate scientific analysis and in order to satisfy the political goals of a Democratic administration (as it was back in those days). He said that the Clinton administration loved grand ecological schemes with the maximum federal involvement. When a Republican administration was elected, the U.S. backed away from the Kyoto protocol.

Dobrovolsky and Naydenov are equally dismissive of the Kyoto Protocol. “We would like to mention that the Kyoto protocol was formally based on the [work of the United Nations Intergovernmental Panel on Climate Change]. However, neither the conclusions of that research, nor science as it is can support the measures of the Kyoto protocol (Electricity Daily, April 14, 2003).”

Evidence Confirms Existence of Naturally-Occurring, Large-Scale Climate Change

A new study reviewing over 240 climate studies shows that the 20th century is neither the warmest century nor the century with the most extreme weather over the last 1000 years as has been argued by some scientists. Michael Mann and his collaborators, for example, have published studies using proxy data to reconstruct past global temperatures suggesting that the Medieval Warm Period never existed and that the Little Ice Age was not a global phenomenon. They also argued that the 20th century was the warmest in the last 1000 years. Their research and the resulting “hockey stick” graph showing significant and anomalous 20th century warming were featured prominently in the IPCCs Third Assessment Report.

The new study, conducted by Willie Soon and Sallie Baliunas with the Harvard-Smithsonian Center for Astrophysics, Craig and Sherwood Idso with the Center for the Study of Carbon Dioxide and Global Change, and David Legates with the Center for Climatic Research at the University of Delaware, sets out to answer three questions.

1) “Is there an objectively discernible climatic anomaly occurring during the Little Ice Age, defined as 1300-1900 A.D.?”

2) “Is there an objectively discernible climatic anomaly occurring during the Medieval Warm Period, defined as 800-1300 A.D.?”

3) “Is there an objectively discernible climatic anomaly occurring within the 20th century that may validly be considered the most extreme (i.e., the warmest) period in the record?”

To answer these questions, the researchers reviewed the extensive scientific literature on the available climate proxy data. “Many true research advances in reconstructing ancient climates have occurred over the past two decades,” said Soon, “so we felt it was time to pull together a large sample of recent studies from the last 5-10 years and look for patterns of variability and change.”

The researchers analyzed numerous climate indicators including: borehole data; cultural data; glacier advances or retreats; geomorphology; isotopic analyses from lake sediments or ice cores, tree or peat celluloses (carbohydrates), corals, stalagmite or biological fossils; net ice accumulation rates, including dust or chemical counts; lake fossils and sediments; river sediments; melt layers in ice cores; phenological (recurring natural phenomena in relation to climate) and paleontological fossils; pollen; seafloor sediments; luminescent analysis; tree ring growth, including either ring width or maximum late-wood density; and shifting tree line positions plus tree stumps in lakes, marshes and streams.

What they found from analyzing many more proxy records than did Mann flatly contradicts his conclusions. “Climate proxy research does yield an aggregate and broad perspective on questions regarding the reality of the Little Ice Age, the Medieval Warm Period and the 20th century surface thermometer global warming. The picture emerges from many localities that both the Little Ice Age and Medieval Warm Period are widespread…. [and] are worthy of their respective labels. Furthermore, thermometer warming of the 20th century across the world seems neither unusual nor unprecedented within the more extended view of the last 1000 years. Overall, the 20th century does not contain the warmest or most extreme anomaly of the past millennium in most of the proxy records” (Energy and Environment, March 2003).

Urban Heat in Houston

The urban heat island (UHI) effect is a well known phenomenon that causes an upward bias in the temperature records used to determine whether the earth is warming up. Because concrete, asphalt and steel retain heat better than natural landscapes, cities are warmer than their surrounding areas. As cities grow this temperature bias grows also, making it difficult to determine whether global temperatures are increasing due to greenhouse gases or urbanization. Attempts have been made to account for these biases, but there is simply no way to know whether the methods used are adequate.

New research appearing in the March issue of Remote Sensing of Environment, suggests that the UHI can have a large influence on temperatures. David Streutker with the Department of Physics and Astronomy at Rice University, used satellite remote sensing to determine the effect of urban growth on temperatures in Houston, Texas. Data was collected from two discrete time periods, March 1985 to February 1987 and July 1999 to June 2001. Eighty-two relatively cloud free images were obtained from the first period and 125 were obtained for the second period.

What Streutker found upon analyzing the data is that the temperature from rural areas around Houston experienced no change in temperature. But for the Houston metropolitan area, “Over the course of 12 years, between 1987 and 1999, the mean nighttime surface temperature heat island of Houston increased 0.82 0.10 [degrees C] in magnitude.” This is a rather striking increase, especially when compared to the general belief that global temperatures have only risen about 0.6 degrees C over the last 100 years. Streutker also noted that, “The growth in UHI, both in magnitude and spatial extent, scales roughly with the increase in population, at approximately 30 percent.” World population has increased 280 percent over the last century.

Irrigation Blamed for Warming San Joaquin Valley

A new study funded by the National Science Foundation suggests that the warming experienced in the San Joaquin Valley in California is due to increasing amounts of irrigated land rather than carbon dioxide emissions. One of the researchers, John Christy, director of the Earth System Science Center at the University of Alabama in Huntsville, said that increases in humidity from irrigation may be the culprit in rising temperatures.

“One of the big issues right now is human-induced climate change from carbon dioxide,” said Christy. “Temperatures in the valley are used to assess climate change, and the typical view has been that if there is warming, it must be due to carbon dioxide, therefore we must reduce the use of fossil fuels. Actually, it appears temperature in the valley could be due to a different human factor, and that is irrigation.”

Night-time temperatures in the valley have risen by about 4 degrees over the past 70 years, according to Christy. The study area contains two million irrigated acres and the resulting increases in humidity may be preventing nighttime air from cooling off. “The evidence shows that if this were a large scale climate change caused by carbon dioxide, it would affect the valley, the foothills and the mountains. But we have not seen these changes in the higher elevations,” said Christy.

Environmentalists questioned the usefulness of the research. Bernadette Del Chiaro, a spokeswoman for Environment California worried that this might derail efforts to suppress energy usage. “There may be multiple factors causing climate change,” said Del Chiaro. “But regardless, there is still the larger problem, which is our dependence on fossil fuels.”

The majority staff of the Senate Energy and Natural Resources Committee on March 26 released comprehensive energy legislation in draft form. The bill includes significant global warming policy proposals in Title XI. The climate change title would create a White House Office of Climate Policy and climate czar, require the executive branch to produce a national strategy that “will stabilize and ultimately reduce net U. S. emissions of greenhouse gases” plus annual progress reports; and create a system administered by the Department of Energy to award credits for voluntary actions to cut emissions.

After taking comments through April 4, the committee staff plans to produce a “chairmans mark” for release on April 8. This would allow Chairman Pete Domenici (R-N.M.) to mark up the bill in committee on April 10. It is unlikely that action on the entire bill will be completed before the Easter recess, but sources told Cooler Heads that the chairman wanted to complete work on the climate title on the 10th.

The language in the climate provisions is mostly taken from Republican-sponsored amendments to the energy bill put together in the last Congress by then-Majority Leader Tom Daschle (D-S. D.), which was brought to the floor without being considered by the Energy Committee. Most of those amendments were offered in an attempt to water down what were considered by their sponsors to be the most objectionable parts of Daschles bill.

The energy bill overall is much more pro-energy than last years Daschle bill. It contains provisions that would allow greater access to Americas energy resources and promote development of the nations energy infrastructure. It also jettisons several provisions that would limit energy supplies and raise prices, such as the Renewable Portfolio Standard for electric utilities.

The Competitive Enterprise Institute immediately came out against the climate title. A joint letter to Chairman Domenici was being circulated for signing by other non-profit groups. It states that the climate title would “in our view create the institutional and legal framework and the political incentives necessary eventually to force Kyoto-style energy rationing on the American people.” The letter will be posted at www.cei.org.

“The climate title looks more like a Kerry or Lieberman campaign document than something produced by a Republican committee staff. If this title is enacted, we wont need the rest of the energy bill,” said Myron Ebell, director of global warming policy at CEI (and editor of Cooler Heads).

Although committee staff initially spread the word that the Administration supported the climate title, Administration sources denied that they supported it or had been involved in its drafting. In fact, legislating a White House climate czar and office would undo the Bush Administrations decision in 2001 to abolish that Clinton-created office and position.

When the United Nations Intergovernmental Panel on Climate Change released its Third Assessment Report (TAR) in 2001, many were surprised that its projections for temperature increases had risen substantially. The IPCCs 1996 Second Assessment Report (SAR) predicted that the earths temperature could increase by as much as 0.9 to 3.5 degrees Celsius. The TAR, however predicted a rise of 1.4 to 5.8 degrees C. In a paper published in the Journal of Climate (October 15, 2002), Thomas Wigley with the National Center for Atmospheric Research and Sarah Raper with the Climatic Research Unit at the University of East Anglia, ask the question, “Why are the more recent projections so much larger?”

The authors attempt to quantify how much of the change in projections was due to the new emissions scenarios presented in the IPCCs Special Report on Emissions Scenarios, and how much was due to differences in the science used in the climate models. To determine this, the authors plugged the emissions scenarios responsible for the high and low ends of the temperature projections into the models used for the TAR, what Wigley and Raper call the “TAR science.”

For the TARs high end, coal-intensive scenario, the “CO2 concentrations are remarkably similar” to those used for the high-end scenario in the SAR. The biggest differences between the two high-end scenarios are the assumptions about sulfate aerosol concentrations, which are thought to offset warming. “The large aerosol forcing differences arise because the SRES scenarios account for likely policy responses to sulfur pollution…. This leads to substantially lower SO2 emissions than for the [SAR scenarios].” There are also some differences in methane forcing and tropospheric ozone forcing. This exercise revealed a difference in forcing from changes in the TAR greenhouse gas cycle from 0.5 Watts per meter squared (W/m2) at the low end to 2 W/m2 at the high end.

The differences in science between the two reports refer to changes in the way the models handle complex climate processes. So it is not so much a change in science as a change in modeling. To determine how these changes affect the projections, Wigley and Raper compare the low and high-end scenarios using SAR science and TAR science. What they found was that “the effects on concentration projections for any give emission scenario are relatively small.”

In fact, there was actually a reduction in CO2 forcing combined with increased warming. This was due primarily to two thingsa change in a parameter that defines the relationship between CO2 concentrations and forcing and a change in how the thermohaline circulation (THC) was modeled. A slowdown in the THC, for example, would offset some of the projected warming due to higher greenhouse gas concentrations. In the TAR, the THC will not slow down as much as assumed in the SAR.

The result of these exercises reveals that very little of the change in temperature projections is due to changes in scientific understanding or better modeling, but due almost entirely to different emissions scenarios. “At the low warming limit, TAR science inflates the 1990-2100 warming for the [low-end SAR scenario] by around 34 percent,” says Wigley and Raper. “At the high end, TAR science inflates the 1990-2100 warming for the [high-end SAR scenario] by around 4 percent.” The rest of the high-end alarmist projection comes from changes in the worst-case storyline, which has little basis in reality. A full 79 percent of the change at the high-end projection came from the changed assumptions about sulfate aerosols alone, about which we know very little.