DISAGREEMENT ON HUMAN-CAUSED
CLIMATE CHANGE

The global warming controversy is an ongoing dispute about the effects of humans on global climate and about what policies, if any, should be implemented to avoid possible undesirable effects of climate change.

The current scientific consensus on climate change is that recent warming indicates a fairly stable long-term trend, that the trend is largely human-caused, and that serious damage may result at some future date if steps are not taken to halt the trend. However, there is also a small but vocal number of scientists in climate and climate-related fields that disagree with the consensus view.

Opposition from politicians and business to climate change

There has been considerable opposition from parts of the political and business communities both to the conclusion that humans are causing climate change, and to the need to take action to reduce human effects on climate. Chiefly, opposition arose because of claims that these actions would cause enormous expense and disruption to the current geopolitical and economic situation, with no obvious recognizable short-term benefits. As of 2007, this opposition has been very muted as more evidence has accumulated about the human causes of climate change,.

This is a public and political debate. Political and economic effects of both global warming and reduction strategies are more difficult to quantify. As an example, in asking whether the costs of reducing fossil fuel dependency compare with the costs of not taking action, one is confronted by the fact that it is difficult to anticipate social or technological changes that affect such costs.

Controversy over the global warming theory

While there is little debate on the existence of global warming amongst mainstream published climate scientists, there is an ongoing debate about human-caused global warming theories in the popular media and on a policy level.

Non-scientists debate whether there is a scientific consensus on the existence of global warming, and in particular whether there is sufficient evidence to justify action to attempt to ameliorate its effects. Those who believe such a consensus exists express a wide range of opinions: some merely recognize the validity of the observed increases in temperature, while 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.

Still others believe that environmental damage will be so severe that immediate steps must be taken to reduce CO2 emissions, even if the immediate economic costs of doing so are substantial. An example of the latter is the Sierra Club, which has sued the U.S. government over failure to raise automobile fuel efficiency standards and thereby decrease carbon dioxide emissions.

Critics of the global warming theory similarly express a wide spectrum of opinions. Some, such as Patrick Michaels, accept that human influence has warmed the atmosphere but dispute the conclusion 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 long before the industrial revolution. Some critics assert that it is not possible to ascertain any definitive global temperature trend from the limited temperature record often cited. Others theorize that global temperature change may be induced by natural causes such as volcanism and solar activity.

Four main issues in the global warming controversy

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

• Whether the climate is changing beyond natural variations over history
• Whether human/industrial activity is responsible for the change and to what extent
• How large future changes will be
• What the consequences of climate change will be.

Opponents tend to define themselves in terms of opposition to the Intergovernmental Panel Climate Change (IPCC) position which states humans have caused much of the global warming recently. 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 often characterize supporters’ arguments as alarmist and premature, emphasizing what they perceive as the lack of scientific evidence supporting global warming scenarios.

Many 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
• A small amount of global warming could be benign or even beneficial
• A cutback in emissions might lead to a decrease in the rate of GDP growth.

Assertions by opponents of the global warming theory

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

• The IPCC draws firm conclusions unjustified by the science
• Temperature rises since the Industrial Revolution doesn’t mean that was the cause
• "Urban heat islands” could be skewing temperature measurements
• Some global warming studies have errors or have not been reproduced
• Using “consensus” as evidence is an appeal to the majority argument

• Global warming is so politicized we are no longer being scientific
• Climate models won't work until they can predict solar and volcanic activity.
• Climate science predictions don't involve recently discovered feedback mechanisms
• Global temperatures are directly related to such factors as sunspot activity
• Global warming is largely a result of reduced low-altitude cloud cover
• Global warming is similar to unfounded alarm over global cooling in the 1970s

• Satellite temperature records show less warming than surface land and sea records.

Many opponents also point to the Medieval warm period, a period lasting from the 10th to the 14th century that shows an above average temperature for at least Western Europe, and possibly the whole Earth. This period was followed by the Little Ice Age, which lasted until the 19th century, when the Earth began to heat up again. Also, the relationship between historic temperatures and CO2 levels, based on ice core samples, shows carbon dioxide increases have always followed a rise in temperature rather than the other way around.

response by supporters of the global warming theory

It should be noted that questioning and challenging of a theory is an essential part of the scientific process, whether it be evolution, a flat Earth versus a round Earth or climate change. Scientists who support the global warming theory usually incorporate these challenges to develop a better hypothesis to explain the environmental data.

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.

Correlation does not imply causation. Indeed, studies of ice age temperature variations show carbon dioxide levels increasing after warming rather than before. This 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 mostly 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).
Between 1940 and 1970, global temperatures went down slightly even though carbon-dioxide levels went up. This is largely attributed to the cooling effect of sulphate aerosols.

The amount of carbon dioxide in the atmosphere is small, accounting for 0.0381% of Earth’s atmosphere. Also, the Earth has been in an ice age with a much higher level of CO2. The Ordovician period of the Paleozoic era, the earth was in an ice age with atmospheric CO2 estimated at 4400ppm (or .44% of the atmosphere). However, a recent study may have explained this occurrence.

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.

Is solar activity the main cause of global warming?

Another point of controversy regarding anthropogenic global warming is the investigation of temperature correlations with the solar variation. According to the Stanford Solar Center, at most 25% of recent global temperature variations can be attributed to solar irradiance. When the 11 year sun cycle is accounted for, there still remains a significant .75 degree Celsius increase in recorded global temperatures.

Will global warming actually benefit us?

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.

Other researchers feel that up to 1.5 °C of warming would increase crop yields and stabilize weather in non-tropical areas, which would benefit developed nations more. Developing nations near the equator would unfortunately be affected adversely.

Many researchers doubt a larger warming than 1.5 °C 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.”

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This information is licensed under the GNU Free Documentation. It is derivative of articles on Climate Change, Global Warming and related environmental issues at http://en.wikipedia.org