article

The global warming controversy is an ongoing dispute about the effects of humans on the global climate and what, if any, policies should be followed to avoid future effects. A current scientific opinion on climate change is that recent warming is largely human-caused (e.g. American Geophysical Union, Joint Science Academies), although others differ.

This article is about that controversy. The description and scientific explanation of global warming is spread over several articles:

__TOC__

Controversy over the theory

Leaving the realm of scientific journals, the debate has spilled out into the public arena, with some politicians making the issue a component of their campaigns for high office. One example of this is 2000 U.S. presidential candidate Al Gore, author of Earth in the Balance. Global warming is a more central and sustained issue, however, for the EU. In fact, both 'global warming' and the more politically neutral 'climate change' were listed in the political buzzwords or catchphrases of 2005. *

While there is little debate among climate scientists, there is an ongoing debate about global warming theories in the popular media, particularly whether there exists a scientific consensus sufficient to justify concerted international action to attempt to ameliorate its effects (see Kyoto Protocol).

Proponents of global warming theory express a wide range of opinions. Some merely recognize the validity of the observed increases in temperature. Others support measures such as the Kyoto Protocol that are intended to have some near-future climate effects and to lead eventually to further measures. Others believe that the environmental damage will have such severe impact that immediate steps must be taken to reduce CO2 emissions, regardless of the economic costs to advanced nations such as the United States (which has the largest emissions of greenhouse gases of any country in absolute terms and the second largest emissions per capita after Australia *).

Critics of the global warming theory similarly offer a wide spectrum of opinions. Some, such as Patrick Michaels, propose that human influence has warmed the atmosphere yet dispute the conclusion of the IPCC TAR, which says "*here is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities". Others point out that observations of global temperatures over much larger time spans, thousands of years rather than decades, show global temperatures fluctuated wildly in the past long before the introduction of human industrial activity such as the industrial revolution. An additional assertion of many critics is that it is not possible to ascertain any definitive global temperature trend from the limited temperature record often cited. Other scientists theorize that global temperature change may be induced by natural causes, such as volcanism and solar activity.

The above paragraphs might give the impression that belief in the course of past climate change correlates strongly with advocacy for future actions: this is not necessarily so. It is possible, perhaps common, to study the past record and give no counsel on the future.

The controversy is made up of separate issues relating to global warming which are sometimes mixed together by proponents of one view or another.

  1. Whether the climate is changing beyond natural variations (historical temperature record).
  2. Whether human/industrial activity is responsible for the change (attribution of recent climate change) and if so, to what extent.
  3. How large future changes will be.
  4. What will be the consequences of climate change.

Scope of the controversy

The controversy over anthropogenic (man-made) global warming is multi-layered; at its most basic level, it is an argument about whether any of the observed warming of the earth's climate over the past 150 years is due to human activity, and if so, how much. Air pollution and production of greenhouse gases are cited as possible influences on global climate, as are factors such as Solar variation and natural cycles.

Since the earth's climate changes over time, scientists must try to understand not only whether the earth's atmosphere is warming, but how much of this is attributable to humans, how much natural events contribute to this, and how the climate will be affected in the future. There is controversy on virtually all of these points among climate and other scientists, especially about future climate modelling.

Kevin E. Trenberth provides evidence for the controversy that occurs when science meets the political arena:

The SPM was approved line by line by governments... The argument here is that the scientists determine what can 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." [http://www.cgd.ucar.edu/cas/GLOB_CHANGE/ipcc2001.html

The arguments over global warming are viewed differently in different parts of the world. In Europe for example the global warming theory has gained wider acceptance than in other parts of the world, most notably the United States.

Reasons given by supporters of the global warming theory

Supporters of the global warming theory assert that:

  • gas bubbles trapped in ice cores give us a detailed record of atmospheric chemistry and temperature back more than four hundred thousand years, with the temperature record confirmed by other geologic evidence. This record tells us that carbon dioxide and temperature rise and fall tightly together. *
  • the recent rise in carbon dioxide and other greenhouse gases is greater than any in hundreds of thousands of years* and this is human-caused, shown by isotopic signature of CO2 from fossil fuels
  • we know carbon dioxide captures IR radiation and converts it to heat because we use these physics to measure carbon dioxide concentration
  • the historical temperature record shows a rise of 0.4–0.8 °C over the last 100 years.
  • the urban heat island effect makes no significant contribution.
  • the current warmth is unusual in the past 1000 years (see Temperature record of the past 1000 years).
  • the warming of the last 50 years is likely caused by human activity (see attribution of recent climate change), using analysis based on climate modeling; and that natural variability or solar variation cannot explain the recent change.
  • Carbon dioxide is a first order forcing on climate change—other effects such as water vapour greenhouse effects are either roughly constant over time, act as amplifiers, or do not have a large effect
  • humankind is performing a great geophysical experiment and if it turns out badly—however that is defined—we cannot undo it. We cannot even abruptly turn it off. Too many of the things we are doing now have long-term ramifications for centuries into the future *.
  • climate models can reproduce this trend, but only when using greenhouse gas forcing. *
  • climate models predict more warming, and other climate effects (sea level rise, more frequent and severe storms, drought and heat waves, etc) in the future. For instance, Atlantic hurricane trends have been recently linked to climate change, June 2006. *
  • action should be taken now to prevent or mitigate warming (see Precautionary principle).
  • the IPCC reports correctly summarise the state of climate science.
  • there is a scientific consensus behind all of the above.
  • Our existence is poised within a fluid-dynamic, ocean-atmosphere-biosphere system, where non-linear feedbacks are common and where climate states are only relatively stable (i.e., "metastable"). Unknown unknowns are likely to surprise us, particularly if they trigger a non-linear, positive feedback that flips climate to a new meta-stable state.

Proponents of global warming tend to support the IPCC position and thus represent a broadly unified viewpoint, though with considerable differences over what action should be taken. Optionally, supporters may go on to point out that there is a good chance that the future changes may be undesirable, and that planning to avoid or mitigate them would be a good idea. Only 2 of the 120 contributing authors to the IPCC TAR are known to have voiced any complaint.

Science Magazine analyzed 928 peer-reviewed scientific papers on global warming published between 1993 and 2003 (Oreskes, 2004). Not a single one challenged the scientific consensus the earth’s temperature is rising due to human activity.

Reasons given by opponents of the global warming theory

Some of the assertions made in opposition to the global warming theory include:

  • IPCC draws firm conclusions unjustified by the science, especially given the acknowledged weakness of cloud physics in the climate models. For example, even those who accept that there is a warming trend point out that there is a big difference between correlation and causality. In other words, just because temperatures have generally been rising since the beginning of the Industrial Revolution, that doesn't necessarily mean that the Industrial Revolution has caused the change in temperature (see post hoc, ergo propter hoc argument). On the other hand, the period since the beginning of the Industrial Revolution has indeed produced ever-growing "urban heat islands" (see below) that could be skewing temperature measurements that indicate the recent warming.
  • Using "consensus" as evidence is an appeal to the majority argument rather than scientific discussion (see consensus science). Ergo, because the issue has become so politicized, it is suspected that climatologists who disagree with the consensus as it is may be afraid to speak out for fear of losing their positions or funding.
  • Consensus is further compromised in this field of study due to students being attracted to the field by their belief that something should be done about global warming. They complete their education and add their voices to the consensus, which gives a perceived bias.
  • Earth's climate has been both colder and warmer than today, and these changes are adequately explained by mechanisms that do not involve human greenhouse gas emissions.
  • There is no significant global warming relative to the expected natural trends.
  • CO2 in the atmosphere is mainly volcanic in origin, accounting for 97% of the CO2 found in the atmosphere, most of which travels to the oceans. Estimates at CO2's effectiveness as a greenhouse gas vary, but are generally around 10-100 times lower than water weight for weight, leaving a "net" greenhouse effect of man-made CO2 emissions at less than 1% *
  • Climate science can not make definitive predictions yet, since the computer models used to make these predictions are still evolving and do not yet take into account recently discovered feedback mechanisms (see GIGO).
  • Climate models will not be able to predict the future climate until they can predict solar and volcanic activity.
  • Some global warming studies have errors or have not been reproduced.
  • Global temperatures are directly related to such factors as: sunspot activity (an 11-year cycle).
  • The concern about global warming is analogous to the concern about global cooling in the 1970s. The concern about global cooling was unnecessarily alarmist. The concern about global warming is equally alarmist.

Some opponents of global warming theory give more weight to data such as paleoclimatic studies, temperature measurements made from weather balloons, and satellites which they claim show less warming than surface land and sea records, though early balloon records have been shown to be possibly erroneous due to mechanical design flaws in the sensors.

Opponents tend to define themselves in terms of opposition to the IPCC position. They generally believe that climate science is not yet able to provide us with solid answers to all the major questions about the global climate.

Opponents frequently characterise supporters arguments as alarmist and premature, so as to emphasise what they perceive as the lack of scientific evidence supporting global warming scenarios.

Opponents also say that if global warming is real and man-made, no action need be taken now because:

  • Future scientific advances or engineering projects will remedy the problem before it becomes serious and for less money.
  • A small amount of global warming would be benign or even beneficial, as increased carbon dioxide would benefit plant life, thus potentially becoming profitable for agriculture world-wide.
  • There is a distinct correlation between GDP growth and greenhouse gas emissions. A cutback in emissions might lead to a decrease in the rate of GDP growth.

Counting experts / Petitions and attacks on them

The proportion of scientists who support or oppose any of the global warming theories is a matter of controversy in its own right. Environmental groups, many governmental reports, and the non-US media often claim virtually unanimous support for the global warming theory from the scientific community. Some opponents maintain that it is the other way around, claiming that the majority of scientists either consider global warming "unproven" or even dismiss it altogether. Other opponents decry the dangers of consensus science, which appears to imply that they do believe there may actually be a consensus.

A 2004 essay in Science * surveyed abstracts of peer-reviewed research articles related to climate change. It concluded that a scientific consensus in favor of the global warming theory exists.

Global warming skeptics dispute the claim that (or relevance of) a consensus of scientists supports the view of global warming presented by the IPCC, and say that even the IPCC report authors do not all support the reports. However, of the 120 lead authors of the TAR, only two are known to have complained. In fact, they say, the consensus of those who expend the effort to comment is moving in the opposite direction. Others dispute this. To support this claim, the website of S. Fred Singer's Science and Environmental Policy Project (SEPP) lists four separate petitions:

  • The 1992 "Statement by Atmospheric Scientists on Greenhouse Warming" ("...Such policy initiatives concerning the Earth Summit is scheduled to convene in Brazil in June 1992 derive from highly uncertain scientific theories. They are based on the unsupported assumption that catastrophic global warming follows from the burning of fossil fuels and requires immediate action. We do not agree.") *
  • The "Heidelberg Appeal" (also from 1992)
  • Singer's own "Leipzig Declaration on Global Climate Change" (1995 and 1997)
  • The "Oregon Petition," which was circulated in 1998 by physicist Frederick Seitz.

According to SEPP associate Candace Crandall, these petitions show that "the number of scientists refuting global warming is growing." * However, people who have examined the petitions challenge that conclusion, pointing out that:

  1. The 1992 "Statement by Atmospheric Scientists" is more than a decade old and only has 46 signers.
  2. The Heidelberg Appeal actually does not say anything about global warming.
  3. Most of the signers of the Leipzig Declarations are non-scientists or lack credentials in the specific field of climate research.
  4. Many of the signers of the Oregon Petition are also non-scientists or lack relevant scientific backgrounds.

Global warming and carbon dioxide

One argument against anthropogenic global warming questions the contention that rising levels of carbon dioxide and other greenhouse gases (GHGs) correlate with—and thus have caused—global warming. Proponents of the view that greenhouse gases have caused recent global warming respond that correlation is not a significant part of the evidence. See attribution of recent climate change.
  • Correlation is not causation. Indeed, studies of ice age temperature variations show carbon dioxide levels increasing after warming rather than before. [http://cdiac.esd.ornl.gov/trends/co2/vostok.htm This however assumes that current climate change can be expected to be like past climate change. While it is generally agreed that past (ice age) variations are timed by astronomical forcing; the current variations, of whatever size, are claimed to be timed by anthropogenic releases of CO2 (thus returning the argument to the importance of human CO2 emissions).
  • Most warming during the past century took place before most carbon dioxide had been released.
  • Between 1940 and 1970, global temperatures went down even though carbon-dioxide levels went up.

As noted above, climate models are only able to simulate the temperature record of the past century when GHG forcing is included, which some insist strongly points to the importance of GHGs, as does attribution of recent climate change.

Urban heat islands

Global warming skeptics question the accuracy of the temperature records. They say if the monitoring stations are located in more populated areas, they must be influenced by the increased heat generated by the city as a whole (known as the "Urban heat island effect"). Those who believe in the accuracy of the records point out their consistency with the unaffected marine record; the lack of a difference between the warmings observed in urban and rural areas; and various studies which have examined the records and found no bias.

Global warming and solar activity

Another point of controversy regarding anthropogenic global warming is the investigation of temperature correlations with the solar variation. This subject is a point of controversy between supporters and opponents of anthropogenic global warming.

Beneficial or detrimental

There is also disagreement on whether the effects of global warming will be beneficial or detrimental. Many researchers predict disastrous consequences for a warming of 1.5 to 7 °C. The UN's Intergovernmental Panel on Climate Change (IPCC) predicts such a warming is likely within the 21st century, unless severe measures are taken (see Kyoto Protocol).

Other researchers feel that up to 1.5 °C of warming would increase crop yields and stabilize weather. Many of these doubt a larger warming is likely. In response, some advocates of strong early measures (well beyond Kyoto) note that the belief in beneficial effects and the doubt that a large warming is possible should be independent if these conclusions were in fact neutrally derived from scientific research.

An unstable world

Recent findings suggest that Earth's climate system is inherently unstable, and that global warming could thus precipitate non-linear sudden climate shifts, as have been discovered to have occurred within the earth's past. Ocean circulation, believed to be the key to such climate shifts, has been observed to be slowing, causing alarm among oceanographers. Some scientists fear that the Gulf Stream, which conveys warm water from the Caribbean Sea across the Atlantic Ocean and is partly responsible for the relative mildness of northern Europe's climate (though other factors also predominate: *), could be reduced or stopped altogether by the decreased salt content of sea water resulting from global warming. This could cause temperatures in northern Europe to drop.

The US National Academy of Sciences issued a report on this phenomenon in 2002, titled Abrupt Climate Change - Inevitable Surprises. * "It is important not to be fatalistic about the threats posed by abrupt climate change," it stated. "Societies have faced both gradual and abrupt climate changes for millennia and have learned to adapt through various mechanisms, such as moving indoors, developing irrigation for crops, and migrating away from inhospitable regions. Nevertheless, because climate change will likely continue in the coming decades, denying the likelihood or downplaying the relevance of past abrupt events could be costly."

Relevant paradigms

The evaluation of importance of influences is affected by several paradigms being used, with some specialties using some concepts as having more influence than others. Many of the apparent contradictions can be resolved by noting that different specialties may use different time and amplitude scales for various influences and concepts.
  • The climate system has been in a steady state (e.g., during the Holocene, i.e., the last 10 kyr).
  • The climate system has had large variations (canonically, ice ages).
  • The climate system is dominated by internal processes.
  • Large influences tend to have large effects.
  • The climate response to forcing is largely linear.
  • Internal processes exist which amplify otherwise small influences.
  • Conditions now are significantly different from those in the past.

Supporters of the global warming theory

Organisations that support the global warming theory (or at least that have issued supportive declarations) include:

Opponents of the global warming theory

Some of the most vocal opponents of the global warming theory from within the climate/scientific community have been:

Some prominent opponents from outside the climate/science community have been:

Some organisations were formed to further the opponents' views:

Controversy about responses to global warming

Even among those who agree that global warming is real there are further controversial issues:

  1. What are the best responses to climate change.
  2. Whether decisions require less uncertainty.

Much of the discussion centers on the effect of emissions of carbon dioxide related to human activity ranging from burning fossil-fuels to industrial activity (see above). But this alone would be a scientific argument confined to the scientific press. The 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.

Because of the economic ramifications of such restrictions, there are those who feel strongly 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. In contrast, 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.

Kyoto Protocol

The Kyoto protocol is the most prominent international agreement on climate change and also highly controversial. It has been argued both that it goes too far in restricting emissions of greenhouse gases and also that the cuts in emissions it would introduce are far too small. Other areas of controversy are the fact that India and China, which have ratified the protocol, are not required to reduce carbon emissions under the present agreement. Furthermore it has also been argued that it would cause more damage to the economy of the US than those of other countries and so it would provide an unfair economic advantage to some countries. Additionally, the 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. As these countries are less energy efficient, this could cause additional carbon emissions.

Political Pressure on Scientists

American climate scientists have accused the Bush adminstration of systematically changing scientific reports on global warming NASA climate scientist Dr. James E. Hansen has complained *.

See also

External links

Politics

Science

Climate change assessment and attribution | Debates | Controversies | Global warming skeptics

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Global warming controversy".

Home Page • arts • business • computers • games • health • hospitals • home • kids & teens • news • physicians • recreation• reference • regional • science • shopping • society • sports • world