Temperature predictions
Conventional predictions of future temperature rises depend on estimates of future GHG emissions (see SRES) and the climate sensitivity. Models referenced by the Intergovernmental Panel on Climate Change (IPCC) predict that global temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. Others have proposed that temperature increases may be higher than IPCC estimates. One theory is that the climate may reach a "tipping point" where positive feedback effects lead to runaway global warming; such feedbacks include decreased reflection of solar radiation as sea ice melts, exposing darker seawater, and the potential release of large volumes of methane from thawing permafrost.[91]
Some scientists, such as David Orrell or Henk Tennekes, say that climate change cannot be accurately predicted. Orrell says that the range of future increase in temperature suggested by the IPCC rather represents a social consensus in the climate community, but adds that "we are having a dangerous effect on the climate".[92]
A 2007 study by David Douglass and coworkers concluded that the 22 most commonly used global climate models used by the IPCC were unable to accurately predict accelerated warming in the troposphere when tuned to match actual surface warming, concluding that "projections of future climate based on these models should be viewed with much caution." This result contrasts a similar study of 19 models which found that discrepancies between model predictions and actual temperature were likely due to measurement errors.[93]
Forecasts confidence
The IPCC states it has increased confidence in forecasts coming from General Circulation Models or GCMs. Chapter 8 of AR4 reads:
“ There is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above. This confidence comes from the foundation of the models in accepted physical principles and from their ability to reproduce observed features of current climate and past climate changes. Confidence in model estimates is higher for some climate variables (e.g., temperature) than for others (e.g., precipitation). Over several decades of development, models have consistently provided a robust and unambiguous picture of signifi cant climate warming in response to increasing greenhouse gases.[94] ”
Certain scientists, skeptics and otherwise, believe this confidence in the models’ ability to predict future climate is not earned.[95][96] A recent peer-reviewed article has assessed the performance of global climate models by comparing their outputs to historical time series on the local level and concludes "At the annual and the climatic (30-year) scales, GCM interpolated series are irrelevant to reality."[97]
Models vs empirical forcasts
A schematic for a global atmosperic model, the atomospher is divided into a three-dimentional grid and climate forcings are applied.Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To "run" a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. The atmospheric component of the model calculates winds, heat transfer, radiation, relative humidity, surface hydrology, and surface fluxes of heat and moisture within each grid and evaluates interactions with neighboring points. The ocean component calculates currents, heat content and salinity. The atmospheric and oceanic components interact, for example with evaporation from the oceans into the atmosphere and with atmospheric winds affecting ocean currents. Different models vary in such basics as grid size and therefore do not give the same results.
Kesten Green and J. Scott Armstrong have criticized the validity of model projections of future climate, arguing "Advocates of complex climate models claim that they are based on well-established laws of physics. But there is clearly much more to the models than physical laws, otherwise the models would all produce the same output, which they do not, and there would be no need for confidence estimates for model forecasts, which there certainly is. Climate models are, in effect, mathematical ways for experts to express their opinions."[98] Green and Armstrong contend that the possibility of accurate long-term climate forecasts has never been proven, and argue that simple methods always outperform more complex forecasting methods.[98] The work of Green and Armstrong has been criticized for showing insufficient domain knowledge to evaluate their own criteria and for failing to distinguish between forecasts based on past experience and projections based on physical models.[99][100]
Arctic shrinkage
Main article: Arctic shrinkage
Arctic Sea ice as of 2007 compared to 2005 and also compared to 1979-2000 average
Northern Hemisphere ice trendsOne unsettled question related to temperature rises is if or when the Arctic sea may become ice-free in the summer (winter sea ice remains in all scenarios). Arctic specialist Mark Serreze said, following the record low in 2007,[101] "If you asked me a couple of years ago when the Arctic could lose all of its ice then I would have said 2100, or 2070 maybe. But now I think that 2030 is a reasonable estimate."[102]
However, a 2003 paper in Nature claims that computer models predictions poorly represent observed changes in Arctic sea ice:[103]
“ The observed variability of Arctic sea ice thickness, which shows that the sea ice mass can change by up to 16% within one year, contrasts with the concept of a slowly dwindling ice pack, produced by greenhouse warming. ”
Roger A. Pielke claims melting Arctic sea ice is a result of regional warming and not global warming.[104]
“ However, in terms of relating to the global average lower tropospheric temperature changes, in June 2007 (which is the latest data posted), the global average anomaly is +0.22 after being as high recently as +0.51C in January. Thus, it is regional warming, not "global warming" that appears to be the reason for this melting (Indeed, if it were global warming, we should see a similar reduction in Antarctic sea ice coverage, which, however, is not occurring (see[105] and see[106]). ”
Antarctica cooling
Main article: Antarctica cooling controversy
Antarctic Skin Temperature Trends between 1981 and 2007, based on thermal infrared observations made by a series of NOAA satellite sensors. Skin temperature trends do not necessarily reflect air temperature trends.The Antarctica cooling controversy relates to the question of whether or not current temperature trends in Antarctica contradict or cast doubt on the theory of global warming. Observations unambiguously show the Peninsula to be warming. The trends elsewhere show both warming and cooling but are smaller and dependent on season and the timespan over which the trend is computed.[107][108] Climate models predict that future trends in Antarctica are much smaller than in the Arctic.[109]
To the extent that a controversy exists it is confined to the popular press and blogs; there is no evidence of a related controversy within the scientific community. Various skeptics, most notably Michael Crichton,[110] have asserted the findings of Doran et al.[111] contradict global warming. Peter Doran, the lead author of the paper, stated that "... our results have been misused as "evidence" against global warming by Crichton in his novel 'State of Fear'..."[112] Others, for example RealClimate, agree there is no contradiction.[113]
Data archiving and sharing
Scientific journals and funding agencies generally require authors of peer-reviewed research to archive all of the data necessary to reproduce their research. If another scientist attempts to reproduce the research and needs additional data, authors are expected (with few exceptions) to provide the data, metadata, methods and source code that may be necessary.
Dr David Legates has claimed that Mann, Bradley and Hughes 1998, famous for its hockey stick shaped historic temperature reconstruction, serves as an example of climate scientists not abiding by these policies and suggested that legislators might ultimately take action to enforce them.[114]
Political
See also: Politics of global warming and Economics of global warming
Washington Monument illuminated with a message criticizing American environmental policyIn the U.S. global warming is often a partisan political issue. Republicans tend to oppose action against a threat that they regard as unproved, while Democrats tend to support actions that they believe will reduce global warming and its effects through the control of greenhouse gas emissions.[115][dead link] Recently, bipartisan measures have been introduced.[116]
Kevin E. Trenberth stated:
“ The SPM was approved line by line by governments[...] .The argument here is that the scientists determine what can be said, but the governments determine how it can best be said. Negotiations occur over wording to ensure accuracy, balance, clarity of message, and relevance to understanding and policy. The IPCC process is dependent on the good will of the participants in producing a balanced assessment. However, in Shanghai, it appeared that there were attempts to blunt, and perhaps obfuscate, the messages in the report, most notably by Saudi Arabia. This led to very protracted debates over wording on even bland and what should be uncontroversial text... The most contentious paragraph in the IPCC (2001) SPM was the concluding one on attribution. After much debate, the following was carefully crafted: "In the light of new evidence, and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse-gas concentrations.[117] ”
As more evidence has become available over the existence of global warming debate has moved to further controversial issues, including:
The social and environmental impacts
The appropriate response to climate change
Whether decisions require less uncertainty
The single largest issue is the importance of a few degrees rise in temperature:
“ Most people say, "A few degrees? So what? If I change my thermostat a few degrees, I'll live fine." ... [The] point is that one or two degrees is about the experience that we have had in the last 10,000 years, the era of human civilization. There haven't been--globally averaged, we're talking--fluctuations of more than a degree or so. So we're actually getting into uncharted territory from the point of view of the relatively benign climate of the last 10,000 years, if we warm up more than a degree or two. (Stephen H. Schneider[118]) ”
The other point that leads to major controversy—because it could have significant economic impacts—is whether action (usually, restrictions on the use of fossil fuels to reduce carbon-dioxide emissions) should be taken now, or in the near future; and whether those restrictions would have any meaningful effect on global temperature.[citation needed]
Due to the economic ramifications of such restrictions, there are those, including the Cato Institute, a libertarian think tank, who feel strongly that the negative economic effects of emission controls outweigh the environmental benefits.[119] They claim that even if global warming is caused solely by the burning of fossil fuels, restricting their use would have more damaging effects on the world economy than the increases in global temperature.[120]
“ The linkage between coal, electricity, and economic growth in the United States is as clear as it can be. And it is required for the way we live, the way we work, for our economic success, and for our future. Coal-fired electricity generation. It is necessary.(Fred Palmer, President of Western Fuels Association[120]) ”
Conversely, others feel strongly that early action to reduce emissions would help avoid much greater economic costs later, and would reduce the risk of catastrophic, irreversible change.[121] In his December 2006 book, Hell and High Water, energy technology expert Joseph J. Romm
“ discusses the urgency to act and the sad fact that America is refusing to do so.... Romm gives a name to those such as ExxonMobil who deny that global warming is occurring and are working to persuade others of this money-making myth: they are the Denyers and Delayers. They are better rhetoriticians than scientists are.... Romm gives us 10 years to change the way we live before it's too late to use existing technology to save the world. ...humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. The tragedy, then, as historians of the future will most certainly recount, is that we ruined their world not because we lacked the knowledge or the technology to save it but simply because we chose not to make the effort' (Hell and High Water, p. 25).[122] ”
Ultimately, however, a strictly economic argument for or against action on climate change is limited at best, failing to take into consideration other potential impacts of any change.
Kyoto Protocol
Main article: Kyoto Protocol
The Kyoto protocol is the most prominent international agreement on climate change, and is also highly controversial. Some argue that it goes too far[123] or not nearly far enough[124] in restricting emissions of greenhouse gases. Another area of controversy is the fact that China and India, the world's two most populous countries, both ratified the protocol but are not required to reduce or even limit the growth of carbon emissions under the present agreement even though when listed by greenhouse gas emissions per capita, they have rankings of 121st largest per capita emitter at 3.9 Tonnes of CO2e and 162nd largest per capita emitter at 1.8 Tonnes of CO2e respectively, compared with for example the USA at position of the 14th largest per capita CO2e emitter at 22.9 Tonnes of CO2e. Nevertheless, China is the world's second largest producer of greenhouse gas emissions, and India 4th (see: countries by greenhouse emissions). Various predictions see China overtaking the US in total greenhouse emissions between late 2007 and 2010,[125][126][127] and according to many other estimates, this already occurred in 2006.[128][129][130]
Additionally, high costs of decreasing emissions may cause significant production to move to countries that are not covered under the treaty, such as India and China, claims Fred Singer.[131] As these countries are less energy efficient, this scenario is claimed to cause additional carbon emissions.
The only major developed nation which has signed but not ratified the Kyoto protocol is the USA (see signatories). The countries with no official position on Kyoto are mainly African countries with underdeveloped scientific infrastructure or are oil producers[citation needed].
Funding for partisans
Both sides of the controversy have alleged that access to funding has played a role in the willingness of credentialed experts to speak out.
Several skeptical scientists—Fred Singer, Fred Seitz and Patrick Michaels—have been linked to organizations funded by ExxonMobil and Philip Morris for the purpose of promoting global warming skepticism [132][133] (see section: Risks of passive smoking). Similarly, groups employing global warming skeptics, such as the George C. Marshall Institute, have been criticized for their ties to fossil fuel companies.[134]
On February 2, 2007, The Guardian stated[135][136] that Kenneth Green, a Visiting Scholar with AEI, had sent letters[137] to scientists in the UK and the U.S., offering US$10,000 plus travel expenses and other incidental payments in return for essays with the purpose of "highlight[ing] the strengths and weaknesses of the IPCC process," specifically regarding the IPCC Fourth Assessment Report.
A furor was raised when it was revealed that the Intermountain Rural Electric Association (an energy cooperative that draws a significant portion of its electricity from coal-burning plants) donated $100,000 to Patrick Michaels and his group, New Hope Environmental Services, and solicited additional private donations from its members.[138][139][140]
The Union of Concerned Scientists have produced a report titled 'Smoke, Mirrors & Hot Air',[141] that criticizes ExxonMobil for "underwriting the most sophisticated and most successful disinformation campaign since the tobacco industry" and for "funnelling about $16 million between 1998 and 2005 to a network of ideological and advocacy organizations that manufacture uncertainty on the issue." In 2006 Exxon claimed that it was no longer going to fund these groups[142] though that claim has been challenged by Greenpeace.[143]
The Center for the Study of Carbon Dioxide and Global Change, a skeptic group, when confronted about the funding of a video they put together ($250,000 for "The Greening of Planet Earth" from an oil company) stated, "We applaud Western Fuels for their willingness to publicize a side of the story that we believe to be far more correct than what at one time was 'generally accepted.' But does this mean that they fund The Center? Maybe it means that we fund them!"[144]
Donald Kennedy, editor-in-chief of Science, has said that skeptics such as Michaels are lobbyists more than researchers, and that "I don't think it's unethical any more than most lobbying is unethical," he said. He said donations to skeptics amounts to "trying to get a political message across."[145]
A number of global warming skeptics, such as the following, assert that grant money is given preferentially to supporters of global warming theory. Atmospheric scientist Reid Bryson said in June 2007 that "There is a lot of money to be made in this... If you want to be an eminent scientist you have to have a lot of grad students and a lot of grants. You can't get grants unless you say, 'Oh global warming, yes, yes, carbon dioxide.'"[146] Similar claims have been advanced by climatologist Marcel Leroux,[147] NASA's Roy Spencer, climatologist and IPCC contributor John Christy, University of London biogeographer Philip Stott,[148] and Accuracy in Media.[149]
Richard Lindzen, the Alfred P. Sloan Professor of Meteorology at MIT, makes the specific claim that "[in] the winter of 1989 Reginald Newell, a professor of meteorology [at MIT], lost National Science Foundation funding for data analyses that were failing to show net warming over the past century." Lindzen also suggests four other scientists "apparently" lost their funding or positions after questioning the scientific underpinnings of global warming.[150] Lindzen himself, however, has been the recipient of money from energy interests such as OPEC and the Western Fuels Association, including "$2,500 a day for his consulting services",[151] as well as funding from federal sources including the National Science Foundation, the Department of Energy, and NASA.[152]
Changing positions of skeptics
In recent years some skeptics have changed their positions regarding anthropogenic global warming. Ronald Bailey, author of Global Warming and Other Eco-Myths (published by the Competitive Enterprise Institute in 2002), stated in 2005, "Anyone still holding onto the idea that there is no global warming ought to hang it up".[153] By 2007, he wrote "Details like sea level rise will continue to be debated by researchers, but if the debate over whether or not humanity is contributing to global warming wasn't over before, it is now.... as the new IPCC Summary makes clear, climate change Pollyannaism is no longer looking very tenable".[154] Others have shifted from claims that global warming is unproven to advocating adaptation, sometimes also calling for more data, rather than take immediate action on mitigation through consumption/emissions reduction of fossil fuels. "Despite our intuition that we need to do something drastic about global warming, we are in danger of implementing a cure that is more costly than the original affliction: economic analyses clearly show that it will be far more expensive to cut carbon dioxide emissions radically than to pay the costs of adaptation to the increased temperatures," says Danish academic Bjørn Lomborg.[155] Lomborg has been severely questioned by groups in Denmark.[156] Nordhaus and Schellenberger[157] present similar, more sophisticated, arguments in favor of adaption.
"There are alternatives to its [(the climate-change crusade's)] insistence that the only appropriate policy response is steep and immediate emissions reductions.... a greenhouse-gas-emissions cap ultimately would constrain energy production. A sensible climate policy would emphasize building resilience into our capacity to adapt to climate changes.... we should consider strategies of adaptation to a changing climate. A rise in the sea level need not be the end of the world, as the Dutch have taught us." says Steven F. Hayward of American Enterprise Institute, a conservative think-tank.[158] Hayward also advocates the use of "orbiting mirrors to rebalance the amounts of solar radiation different parts of the earth receive"—an example of so-called geoengineering.
In 2001 Richard Lindzen in response to the question, "Kyoto aside for a moment, should we be trying to reduce carbon dioxide emissions? Do our concerns about global warming require action?" said "We should prioritize our responses. You can't just say, "No matter what the cost, and no matter how little the benefit, we'll do this." If we truly believe in warming, then we've already decided we're going to adjust...The reason we adjust to things far better than Bangladesh is that we're richer. Wouldn't you think it makes sense to make sure we're as robust and wealthy as possible? And that the poor of the world are also as robust and wealthy as possible?"[159]
Others argue that if developing nations reach the wealth level of the United States this could greatly increase CO2 emissions and consumption of fossil fuels. Large developing nations such as India and China are predicted to be major emitters of greenhouse gases in the next few decades as their economies grow.[160][161]
The conservative National Center for Policy Analysis whose "Environmental Task |
