If warming continues at the present rate, it is may result in changes in ocean circulation, catastrophic global climate change, loss of biodiversity and irreversible damage to agriculture in those ecoregions most affected. In some regions, e.g. Western Europe, Bangladesh, damage is projected to be extreme, due to loss of Gulf Stream warming and global sea level rise respectively. More frequent bouts of destructive weather are also anticipated, and risk experts in the insurance industry have expressed very strong concerns, advocating a proactive approach based on the precautionary principle. Estimates accepted by the IPCC and by some insurance industry bodies estimate up to 3.5 billion people could be affected by rising disease, loss of fresh water supply, and other impacts.
In opposition stand the fossil fuel industry and its advocates, who have taken a strong stand in opposing most theories of human-caused global warming as well as action to mitigate Global Warming. They argue that crippling the energy industry to prevent an ecological catastrophe does not make "economic sense" - that healthy economies are required to fund technologically innovative "solutions." President G. W. Bush, made this argument in rejecting the Kyoto Protocol. Bush did not reject the science outright, and argued that the greenhouse gas control was a matter of voluntary restraint by industry. Many U.S. states have nonetheless put strong controls on greenhouse gases, rejecting this simple ideology.
This stark standoff between advocates of existing industries have made the scientific questions difficult to distinguish from political ones. While the scientific questions are clear, positions on them and appropriate tests of the theses advanced tend to be hopelessly mired in starting assumptions:
The proportion of scientists who support or oppose any of the various global warming theories is a matter of controversy in its own right. Environmentalists and their allies claim virtually unanimous support for the global warming theory from the scientific community. Opponents maintain that it is the other way around, claiming that the overwhelming majority of scientists either dismiss global warming altogether or merely consider it "unproven" (see global warming skepticism).
The hypothesis that a man-made increase in greenhouse gas concentration would lead to a higher global mean temperature was postulated in the late 19th century by Swedish chemist and 1903 Nobel Laureate Svante Arrhenius (see global warming hypothesis), although, his peers largely rejected that theory.
Some scientists point out that global warming correlates closely with natural factors, especially solar activity. The balance is attributed to the action of humans (see anthropogenic global warming). How much warming is natural or man-made has been hotly debated since the 1990s, by scientists, politicians and advocacy organizations (see global warming controversy).
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 degrees celsius. 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 (a very small minority), feel that up to 1.5 degrees Centrigade 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, rather than being optimistically driven by ideology or oil money.
Others go somewhat further and indicate that anyone who believes that to 'wait and see', potentially disadvantaging 3.5 billion people to seek narrow advantage in a few growing regions in developed nations, or wait for 'technological fixes', amounts to a declaration of war on the entire planet's population. They argue that long before any northern nation, e.g. Russia, Canada, would enjoy greater crop yields, the developed nations would be exterminated by biological warfare or other weapons of mass destruction launched by groups easily recruited from the most drastically affected world populations. This is of course a political not a scientific argument for action.
To add to the controversy, new findings - within the last 15 years - have indicated that the earth's climate system is inherently unstable, and that global warming could, counterintuitively, precipitate such non-linear, sudden climate shifts as have been discovered to have occurred within the earth's recent past. Ocean circulation, believed to be the key to such climate shifts, has been observed to be slowing, causing alarm among oceanographers. The National Academy Press of the US National Academy of Science issued a report on this phenomenon in 2002, titled Abrupt Climate Change - Inevitable Surprises.[1] "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."[2]
There is also some disagreement on the historical temperature record. Depending on what direct measurements and proxies are accepted, researchers have presented various scenarios: stable temperature followed by a sudden, steady rise in the 20th century vs. fluctuations of 1 or 2 degrees Centigrade, with near-stable temperature since 1940.
However, the US National Academy of Science, both in its 2002 report to President George W. Bush, and in its latest publications, has strongly endorsed evidence of an average global temperature increase in the 20th century and stated that human activity is heavily implicated in causing this increase.
Advocates of the global warming hypothesis who predict adverse consequences from as little as 1.5 degrees Centigrade of warming nearly all support the Kyoto Protocol as a countermeasure. Some researchers, politicians and businesses oppose it.
Historical temperature record Climate scientists generally agree that Earth has undergone several cycles of global warming and global cooling in the last 20 thousand years, with the average air temparature fluctuating within a range of about 3 Celsius degrees (5 Fahrenheit degrees), over this time period. During the Medieval Warm Period, for example, Vikings colonized Greenland, but the colonies were abandoned during the Little Ice Age that followed.
Evidence for a current warming period According to the IPCC, Earth has seen a significant increase in average global surface temperature over the last 150 years.
The main evidence for global warming comes from thermometer measurements from land stations since 1860. The data from these stations, particularly those located outside of the United States, show an average surface temperature increase of 0.4 to 0.8 Celsius degrees during the 20th century. Most of the warming occurred during two periods: 1910 to 1945 and 1976 to 2000. (Source: Intergovernmental Panel on Climate Change, the IPCC).
Secondary evidence comes from observed variations in the snow cover and ice extent, global average sea level, precipitation, cloud cover, El Niņo and extreme weather events during the 20th century.
For example, satellite data shows a 10% decrease of snow cover since the late 1960s, and the Northern Hemisphere spring and summer sea-ice extent has decreased by about 10% to 15% since the 1950s and there has been a widespread retreat of mountain glaciers in non-polar regions throughout the 20th century. (Source: IPCC).
Evidence against a current warming period In January 2002, scientists released data showing that the Antarctic ice cap had grown about 25%. Some editorial writers claimed that this contradicts the expectation that rising temperatures should cause the ice cap to shrink. However, the scientists studying the situation in the Antarctic who released this data point out that local cooling in some areas is consistent with an overall trend of global warming and insist that "the ice-sheet growth that we have documented in our study area has absolutely nothing to do with any recent climate trends."[3]
Weather balloons and satellites measuring the temperature of the atmosphere above the earth's surface show a smaller warming trend than the trend at the earth's surface. Nevertheless, a National Academy of Sciences panel that reviewed this apparent discrepancy concluded that "the warming trend in global-mean surface temperature observations during the past 20 years is undoubtedly real and is substantially greater than the average rate of warming during the twentieth century. The disparity between surface and upper air trends in no way invalidates the conclusion that surface temperature has been rising."[4][5]
Climate models Climate simulations show that the warming that occurred from 1910 to 1945 can be explained by variation in solar radiation (internal and natural forcing) only (see climate change). The models are used to estimate the relative importance of the various factors mentioned above. Most models show that warming occurring from 1976 to 2000 needs anthropogenic greenhouse gas emissions to be explained.
The IPCC (see below), a United Nations science and public policy organization, published a report saying that scientists believe that anthropogenic greenhouse gases "play an important role in global warming."
This conclusion depends on the accuracy of the models used and on the correct estimation of the external factors. The majority of scientists agree that important climate features are incorrectly accounted for by the climate models but don't think that better models would change the conclusion. (Source: IPCC)
Critics point out that there are flaws in the models and external factors not taken into consideration that could change the conclusion above. Some critics say that the climate simulations are unable to model the cooling effects of the particles, fitting the water vapor feedback, and handling clouds. Critics also point out that the sun may have a share of responsibility for the observed global warming greater than now thought by the majority of the scientific community. Some indirect solar effects may be very important and are not accounted for by the models. So, they argue, the share of global warming caused by anthropogenic greenhouse gases may be lower than thought. (Source: The Skeptical Environmentalist)
Potential Effects Many public policy organizations and government officials are concerned that the current warming has the potential for harm to the environment and agriculture.
This is a matter of considerable controversy, with environmentalist groups typically emphasizing the possible dangers and groups close to industry questioning the climate models and consequences of global warming - and funding scientists to do so.
Due to potential effects on human health and economy due to the impact on the environment, global warming is the cause of great concern. Some important environmental changes have been observed and linked to global warming.
The examples of secondary evidence cited above (lessened snow cover, rising sea levels, weather changes) are examples of consequences of global warming that may influence not only human activities but also the ecosystems. Increasing global temperature means that ecosystems may change; some species may be forced out of their habitats (possibly to extinction) because of changing conditions, while others may spread. Few of the terrestrial ecoregions on Earth could expect to be unaffected.
Another cause of great concern is sea level rise. Sea levels are rising 1 to 2 centimetres (around half an inch) per decade, and some small countries in the Pacific Ocean are expressing concerns that if this rise in sea level continues, they soon will be entirely under water. Global warming causes the sea level to rise mainly because sea water expands as it warms, but some scientists are concerned that in the future, the polar ice caps and glaciers may melt. As a consequence, the sea level could rise several metres. At the moment, scientists are not expecting any major ice melting in the next 100 years. (Sources: IPCC for the data and the mass media for the general perception that climate change is important.) Some researchers have found a negative correlation between sea level rise and average global temperature; water evaporates more quickly than it expands. (Source: Science and Environmental Policy Project)
As the climate gets hotter, evaporation will increase. This will cause heavier rainfall and more erosion. Many people think that it could result in more extreme weather as global warming progresses.
Global warming can also have other, less obvious effects. The North Atlantic drift, for instance, is driven by temperature changes. It seems as though it is diminishing as the climate grows warmer, and this means that areas like Scandinavia and Britain that are warmed by the drift might face a colder climate in spite of the general global warming. It is now feared that Global Warming may be able to trigger the type of abrupt massive temperature shifts which bracketed the Younger Dryas period.
However, global warming can also have positive effects, since higher temperatures and higher CO2 concentrations improve the ecosystems' productivity. Satellite data shows that the productivity of the Northern Hemisphere has increased since 1982. On the other hand, an increase in the total amount of biomass produced is not necessarily all good, since biodiversity can still decrease even though a small number of species are flourishing. Similarly, from the human economic viewpoint, an increase in total biomass but a decrease in crop harvests would be a net disadvantage. In addition, IPCC models predict that higher CO2 concentrations would only spur growth of flora up to a point; after that, though greenhouse effects and warming would continue there would be no compensatory increase in growth.
The Intergovernmental Panel on Climate Change Since it is such an important issue, governments need predictions of future trends in global change so they can take political decisions to avoid undesired impacts. Global warming is being studied by the Intergovernmental Panel on Climate Change (IPCC). In its last report, the IPCC made some predictions about future climate change. These predictions are the basis for current political and scientific discussion.
IPCC predictions are based on the same models used to establish the importance of the different factors in global warming. These models need data about anthropogenic emissions of greenhouse gases and aerosols. These data are predicted from economic models based on 35 different scenarios. Scenarios go from pessimistic to optimistic, and predictions of global warming depend on the kind of scenario considered. None of these scenarios consider any kind of measures to avoid global warming.
The models used are primarily based on surface temperature measurements but attempt to predict the temperature of the entire troposphere, not just surface temperatures.
However, a NASA report challenges the success of these models: "The IPCC's 1995 estimate of average global warming at the surface until the year 2100 is +0.18 °C/decade. Climate models suggest that the deep layer measured by the satellite and weather balloons should be warming about 30% faster than the surface (+0.23 °C/decade). None of the satellite or weather balloon estimates are near this value." (Source: NASA Science News 14 August 1998.) Note that "deep layer" refers to the entire troposphere, rather than just the surface.
Nevertheless, proponents of the IPCC assessment say that the current climate models are good in predicting surface temperatures and that this is significant. They furthermore argue that it is surface temperatures that will have the greatest and most direct effect on the environment, agriculture and the stability of polar ice.
The IPCC says that it has corrected the land station data to account for the urban heat island effect. To do: find and summarize their correction technique.
In its last report, IPCC stated that average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 metres over the same period.
IPCC predictions are supposedly the best predictions available but are nevertheless under strong scientific scrutiny. The IPCC concedes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved. Critics point out that the available data is not sufficient to determine the real importance of greenhouse gases in climate change. Sensitivity of climate to greenhouse gases may be overestimated because of some flaws in the models and because the importance of some external factors may be underestimated.
On the other hand, predictions are based on scenarios, and the IPCC did not assign any probability to the 35 scenarios used. Critics charge that some of the scenarios that predict the largest impacts are not realistic because they contradict "basic economic reasoning".
The United Nations Framework Convention on Climate Change and the Kyoto Protocol Main article: Kyoto Protocol Even if there are some doubts about its importance, global warming is perceived by the general public, by many scientists, and by some political leaders as a potential threat to human health and economic prosperity. Reductions of the emissions of greenhouse gases by developed countries was proposed, with developing countries such as India and China being exempted from reductions. Since this problem is like the tragedy of the commons, only an international agreement could reduce the emissions of greenhouse gases; voluntary reductions would be avoided by individual countries. In light of this expectation, the global warming treaty will not take effect unless enough countries ratify it.
The United Nations Framework Convention on Climate Change (UNFCCC) establishes a process for developing an international response to the perceived global warming problem. Most of the countries in the world are parties to the UNFCCC, including all the major industrial nations. The UNFCCC, however, does not provide any binding emission targets.
Most of the parties to the UNFCCC, including all the major industrial nations, are party to the Kyoto Protocol to the UNFCCC, which proposes binding greenhouse gas limits for developed countries (developing countries are not subject to limits under the Protocol). The limits are based on the level of their emissions in 1990; most developed countries would be required to limit their emissions to a level below the 1990 level, although a few, such as Iceland, would be permitted to limit their emissions to a level higher than what they emitted in 1990.
The United States, responsible for one-third of the world-wide emissions of greenhouse gases, has signed but not ratified the Kyoto Protocol. During the Presidential administration of Bill Clinton, the United States Senate voted on a resolution against ratifying the protocol, with not a single Democratic Senator voting in favor of it. The current President, George W. Bush, has indicated that he does not intend to submit the treaty for ratification. This decision has resulted in internal and international controversy with major political and ideological ramifications.
References Every source has a point of view or a sponsor which might be a source of bias. If you discover evidence for bias or a major source of its funding, please include it in the site's description.
Scientific websites:
NASA's Global Hydrology and Climate Center National Oceanic and Atmospheric Administration - NOAA, US Department of Commerce United Nations websites:
http://www.ipcc.ch -- the Intergovernmental Panel on Climate Change (IPCC), established by WMO and UNEP (below) in 1988 http://www.wmo.ch -- the World Meteorological Organization (WMO) http://www.unep.org/ -- the United Nations Environment Programme http://unfccc.int/ -- the United Nations Framework Convention for Climate Change (UNFCCC) IPCC report: summary for policy makers, (2001) (pdf file) IPCC report: Climate Change 2001: The Scientific Basis -- Technical Summaries (pdf file) Environmentalist websites:
http://www.greenpeace.org/ -- Greenpeace http://www.panda.org/climate/ -- the Worldwide Wildlife Fund (WWF) http://www.worldwatch.org/about -- Worldwatch Institute Industry-sponsored (even in part):
http://www.cei.org -- the Competitive Enterprise Institute Access to Energy CO2 science magazine http://www.junkscience.com -- PR Watch says, "Steven Milloy's website is actually a good example of junk science itself, heaping adolescent insults on any and all scientists (ranging from Samuel Epstein to the New England Journal of Medicine) who fail to defend the corporate, anti-environmentalist worldview." (Source: [6]) Independent (or receives too little support to constitute "sponsorship"):
Bjorn Lomborg, author of The Skeptical environmentalist, (2001) ISBN 0521010683. After investigating his book and his other work, the Danish Committees on Scientific Dishonesty, a panel of eminent scientists, found him guilty of "scientific dishonesty."[7] The PR Plot to Overheat the Earth, analysis of industry efforts to discredit global warming science, by Bob Burton and Sheldon Rampton, published in the Earth Island Journal. Testimony of Richard S. Lindzen before the Senate Environment and Public Works Committee on 2 May 2001 -- Lindzen is a professor at MIT http://www.sepp.org/ -- the Science and Environmental Policy Project (SEPP) Other websites (viewpoint or sponsorship unknown):
http://www.greeningearthsociety.org http://www.globalwarming.org http://www.theclimate.info
See also: Global warming potential, Carbon sequestration, Impact of global climate changes on agriculture
wikipedia.org dumped 2003-03-17 with terodump