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Title: CHAPTER 7: Introduction to the Atmosphere - Causes of Climate Change
Source:
http://www.physicalgeography.net/
URL Source: http://www.physicalgeography.net/fundamentals/7y.html
Published: Feb 25, 2008
Author: michael.pidwirny@ubc.ca
Post Date: 2008-02-25 22:03:19 by robin
Keywords: None
Views: 714
Comments: 25
CHAPTER 7: Introduction to the Atmosphere Causes of Climate Change Figure 7y-1 illustrates the basic components that influence the state of the Earth's climatic system. Changes in the state of this system can occur externally (from extraterrestrial systems) or internally (from ocean, atmosphere and land systems) through any one of the described components. For example, an external change may involve a variation in the Sun's output which would externally vary the amount of solar radiation received by the Earth's atmosphere and surface. Internal variations in the Earth's climatic system may be caused by changes in the concentrations of atmospheric gases, mountain building, volcanic activity, and changes in surface or atmospheric albedo. Figure 7y-1: Factors that influence the Earth's climate. The work of climatologists has found evidence to suggest that only a limited number of factors are primarily responsible for most of the past episodes of climate change on the Earth. These factors include: Variations in the Earth's Orbital Characteristics The Milankovitch theory suggests that normal cyclical variations in three of the Earth's orbital characteristics is probably responsible for some past climatic change. The basic idea behind this theory assumes that over time these three cyclic events vary the amount of solar radiation that is received on the Earth's surface. The first cyclical variation, known as eccentricity, controls the shape of the Earth's orbit around the Sun. The orbit gradually changes from being elliptical to being nearly circular and then back to elliptical in a period of about 100,000 years. The greater the eccentricity of the orbit (i.e., the more elliptical it is), the greater the variation in solar energy received at the top of the atmosphere between the Earth's closest (perihelion) and farthest (aphelion) approach to the Sun. Currently, the Earth is experiencing a period of low eccentricity. The difference in the Earth's distance from the Sun between perihelion and aphelion (which is only about 3%) is responsible for approximately a 7% variation in the amount of solar energy received at the top of the atmosphere. When the difference in this distance is at its maximum (9%), the difference in solar energy received is about 20%. The second cyclical variation results from the fact that, as the Earth rotates on its polar axis, it wobbles like a spinning top changing the orbital timing of the equinoxes and solstices (see Figure 7y-2 below). This effect is known as the precession of the equinox. The precession of the equinox has a cycle of approximately 26,000 years. According to illustration A, the Earth is closer to the Sun in January (perihelion) and farther away in July (aphelion) at the present time. Because of precession, the reverse will be true in 13,000 years and the Earth will then be closer to the Sun in July (illustration B). This means, of course, that if everything else remains constant, 13,000 years from now seasonal variations in the Northern Hemisphere should be greater than at present (colder winters and warmer summers) because of the closer proximity of the Earth to the Sun. The third cyclical variation is related to the changes in the tilt (obliquity) of the Earth's axis of rotation over a 41,000 year period. During the 41,000 year cycle the tilt can deviate from approximately 22.5 to 24.5°. At the present time, the tilt of the Earth's axis is 23.5°. When the tilt is small there is less climatic variation between the summer and winter seasons in the middle and high latitudes. Winters tend to be milder and summers cooler. Warmer winters allow for more snow to fall in the high latitude regions. When the atmosphere is warmer it has a greater ability to hold water vapor and therefore more snow is produced at areas of frontal or orographic uplift. Cooler summers cause snow and ice to accumulate on the Earth's surface because less of this frozen water is melted. Thus, the net effect of a smaller tilt would be more extensive formation of glaciers in the polar latitudes. Periods of a larger tilt result in greater seasonal climatic variation in the middle and high latitudes. At these times, winters tend to be colder and summers warmer. Colder winters produce less snow because of lower atmospheric temperatures. As a result, less snow and ice accumulates on the ground surface. Moreover, the warmer summers produced by the larger tilt provide additional energy to melt and evaporate the snow that fell and accumulated during the winter months. In conclusion, glaciers in the polar regions should be generally receding, with other contributing factors constant, during this part of the obliquity cycle. Computer models and historical evidence suggest that the Milankovitch cycles exert their greatest cooling and warming influence when the troughs and peaks of all three cycles coincide with each other. Atmospheric Carbon Dioxide Variations Studies of long term climate change have discovered a connection between the concentration of carbon dioxide in the atmosphere and mean global temperature. Carbon dioxide is one of the more important gases responsible for the greenhouse effect. Certain atmospheric gases, like carbon dioxide, water vapor and methane, are able to alter the energy balance of the Earth by being able to absorb longwave radiation emitted from the Earth's surface. The net result of this process and the re-emission of longwave back to the Earth's surface increases the quantity of heat energy in the Earth's climatic system. Without the greenhouse effect, the average global temperature of the Earth would be a cold -18° Celsius rather than the present 15° Celsius. Researchers of the 1970s CLIMAP project found strong evidence in deep-ocean sediments of variations in the Earth's global temperature during the past several hundred thousand years of the Earth's history. Other subsequent studies have confirmed these findings and have discovered that these temperature variations were closely correlated to the concentration of carbon dioxide in the atmosphere and variations in solar radiation received by the planet as controlled by the Milankovitch cycles. Measurements indicated that atmospheric carbon dioxide levels were about 30% lower during colder glacial periods. It was also theorized that the oceans were a major store of carbon dioxide and that they controlled the movement of this gas to and from the atmosphere. The amount of carbon dioxide that can be held in oceans is a function of temperature. Carbon dioxide is released from the oceans when global temperatures become warmer and diffuses into the ocean when temperatures are cooler. Initial changes in global temperature were triggered by changes in received solar radiation by the Earth through the Milankovitch cycles. The increase in carbon dioxide then amplified the global warming by enhancing the greenhouse effect. Over the past three centuries, the concentration of carbon dioxide has been increasing in the Earth's atmosphere because of human influences (Figure 7y-3). Human activities like the burning of fossil fuels, conversion of natural prairie to farmland, and deforestation have caused the release of carbon dioxide into the atmosphere. From the early 1700s, carbon dioxide has increased from 280 parts per million to 380 parts per million in 2005. Many scientists believe that higher concentrations of carbon dioxide in the atmosphere will enhance the greenhouse effect making the planet warmer. Scientists believe we are already experiencing global warming due to an enhancement of the greenhouse effect. Most computer climate models suggest that the globe will warm up by 1.5 - 4.5° Celsius if carbon dioxide reaches the predicted level of 600 parts per million by the year 2050. Figure 7y-3: The following graph illustrates the rise in atmospheric carbon dioxide from 1744 to 2005. Note that the increase in carbon dioxide's concentration in the atmosphere has been exponential during the period examined. An extrapolation into the immediate future would suggest continued increases. (Source: Neftel, A., H. Friedli, E. Moore, H. Lotscher, H. Oeschger, U. Siegenthaler, and B. Stauffer. 1994. Historical carbon dioxide record from the Siple Station ice core. pp. 11-14. In T.A. Boden, D.P. Kaiser, R.J. Sepanski, and F.W. Stoss (eds.) Trends'93: A Compendium of Data on Global Change. ORNL/CDIAC-65. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn. U.S.A. and Volcanic Eruptions For many years, climatologists have noticed a connection between large explosive volcanic eruptions and short term climatic change (Figure 7y-4). For example, one of the coldest years in the last two centuries occurred the year following the Tambora volcanic eruption in 1815. Accounts of very cold weather were documented in the year following this eruption in a number of regions across the planet. Several other major volcanic events also show a pattern of cooler global temperatures lasting 1 to 3 years after their eruption. At first, scientists thought that the dust emitted into the atmosphere from large volcanic eruptions was responsible for the cooling by partially blocking the transmission of solar radiation to the Earth's surface. However, measurements indicate that most of the dust thrown in the atmosphere returned to the Earth's surface within six months. Recent stratospheric data suggests that large explosive volcanic eruptions also eject large quantities of sulfur dioxide gas which remains in the atmosphere for as long as three years. Atmospheric chemists have determined that the ejected sulfur dioxide gas reacts with water vapor commonly found in the stratosphere to form a dense optically bright haze layer that reduces the atmospheric transmission of some of the Sun's incoming radiation. In the last century, two significant climate modifying eruptions have occurred. El Chichon in Mexico erupted in April of 1982, and Mount Pinatubo went off in the Philippines during June, 1991 (Figure 7y-5). Of these two volcanic events, Mount Pinatubo had a greater effect on the Earth's climate and ejected about 20 million tons of sulfur dioxide into the stratosphere (Figure 7y-6). Researchers believe that the Pinatubo eruption was primarily responsible for the 0.8 degree Celsius drop in global average air temperature in 1992. The global climatic effects of the eruption of Mount Pinatubo are believed to have peaked in late 1993. Satellite data confirmed the connection between the Mount Pinatubo eruption and the global temperature decrease in 1992 and 1993. The satellite data indicated that the sulfur dioxide plume from the eruption caused a several percent increase in the amount of sunlight reflected by the Earth's atmosphere back to space causing the surface of the planet to cool. Variations in Solar Output Until recently, many scientists thought that the Sun's output of radiation only varied by a fraction of a percent over many years. However, measurements made by satellites equipped with radiometers in the 1980s and 1990s suggested that the Sun's energy output may be more variable than was once thought (Figure 7y-7). Measurements made during the early 1980s showed a decrease of 0.1 percent in the total amount of solar energy reaching the Earth over just an 18 month time period. If this trend were to extend over several decades, it could influence global climate. Numerical climatic models predict that a change in solar output of only 1 percent per century would alter the Earth's average temperature by between 0.5 to 1.0° Celsius. Scientists have long tried to also link sunspots to climatic change (also see the link www.sunspotcycle.com). Sunspots are huge magnetic storms that are seen as dark (cooler) areas on the Sun's surface. The number and size of sunspots show cyclical patterns, reaching a maximum about every 11, 90, and 180 years. The decrease in solar energy observed in the early 1980s correspond to a period of maximum sunspot activity based on the 11 year cycle. In addition, measurements made with a solar telescope from 1976 to 1980 showed that during this period, as the number and size of sunspots increased, the Sun's surface cooled by about 6° Celsius. Apparently, the sunspots prevented some of the Sun's energy from leaving its surface. However, these findings tend to contradict observations made on longer times scales. Observations of the Sun during the middle of the Little Ice Age (1650 to 1750) indicated that very little sunspot activity was occurring on the Sun's surface. The Little Ice Age was a time of a much cooler global climate and some scientists correlate this occurrence with a reduction in solar activity over a period of 90 or 180 years. Measurements have shown that these 90 and 180 year cycles influence the amplitude of the 11 year sunspot cycle. It is hypothesized that during times of low amplitude, like the Maunder Minimum, the Sun's output of radiation is reduced. Observations by astronomers during this period (1645 to 1715) noticed very little sunspot activity occurring on the Sun. During periods of maximum sunspot activity, the Sun's magnetic field is strong. When sunspot activity is low, the Sun's magnetic field weakens. The magnetic field of the Sun also reverses every 22 years, during a sunspot minimum. Some scientists believe that the periodic droughts on the Great Plains of the United States are in someway correlated with this 22 year cycle.
(7 images) 
Figure 7y-2: Modification of the timing of aphelion and perihelion over time (A = today; B = 13,000 years into the future). 
Figure 7y-4: Explosive volcanic eruptions have been shown to have a short-term cooling effect on the atmosphere if they eject large quantities of sulfur dioxide into the stratosphere. This image shows the eruption of Mount St. Helens on May 18, 1980 which had a local effect on climate because of ash reducing the reception of solar radiation on the Earth's surface. Mount St. Helens had very minimal global effect on the climate because the eruption occurred at an oblique angle putting little sulfur dioxide into the stratosphere. (Source: U.S. Geological Survey, photograph by Austin Post). 
Figure 7y-5: Ash column generated by the eruption of Mount Pinatubo on June 12, 1991. The strongest eruption of Mount Pinatubo occurred three days later on June 15, 1991. (Source: US Geological Survey). 
Figure 7y-6: The following satellite image shows the distribution of Mount Pinatubo's sulfur dioxide and dust aerosol plume (red and yellow areas) between June 14 and July 26, 1991. Approximately 45 days after the eruption, the aerosol plume completely circled the Earth around the equator forming a band 20 to 50° of latitude wide. Areas outside this band were clear of volcanic aerosols. Within a year, the sulfur dioxide continued to migrate towards the North and South Pole until it covered the entire Earth because of the dominant poleward flow of stratospheric winds (stratospheric winds circulate from the equator to the polar vortices at the North and South Poles). These observed patterns of aerosol movement suggest that tropical explosive volcanic eruptions probably have the greatest effect on the Earth's climate. Diffusion of aerosols by stratospheric winds from a tropical source results in the greatest latitudinal coverage of the sulfur dioxide across both the Northern and Southern Hemispheres. (Source: SAGE II Satellite Project - NASA). 
Figure 7y-7: The Sun as seen at sunset. The Sun is essentially the only source of energy for running the Earth's climate. Thus any change in its output will result in changes in the reception of insolation and the generation of heat energy which drives the climate system.
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#2. To: robin, *Agriculture-Environment* (#0)
Belief and models, always the best way to do science. BTW, your article backs me up more than it did you.
* Atmospheric carbon dioxide variations. * Volcanic eruptions * Variations in solar output. This is from a science class at the University of British Columbia. It is the source I linked to in the other thread. But no one seems to ever check the links. #5. To: mirage (#4) I don't think the experts say sun spots have no impact, but that there is another factor at play now too. www.physicalgeography.net/fundamentals/7y.html 'He will make Cheney look like Gandhi.' U.S. conservative pundit Pat Buchanan, imagining presidential hopeful John McCain in the White House. robin posted on 2008-02-25 17:27:25 ET In this case, it seems you have not read all of chapter 7. It certainly addresses CO2 as one of the factors along with sunspots, (which was why I posted the link in the other thread). Exxon does not want people to understand the science of Global Climate Change. They want to distort the facts, as you have already attempted in this thread. The ice core sample article and timeline from NOVA support the growing evidence that CO2 levels have never been as high as they are today.
And I've given you two links that show otherwise. There are some serious flaws in the ice core data. I have a friend writing a paper on that now in relation to the Younger Dryas and there was another one he showed me I'll try and dig up.
One or two links by a handful or less of scientists who do not agree with the findings of the ice core samples, when the VAST MAJORITY OF SCIENTISTS DO! en.wikipedia.org/wiki/Ice_core There are thousands of links on the ice core samples and the CO2 findings. Why do you prefer to believe what one or two obscure scientists say over all the rest of science?
Why don't you show a study to back that up. Not a news report, not someone saying it is so. You keep making that claim with no evidence to back it up. BTW, there have been studies that disprove consensus.
I already have in the past: I also notice that you have refused to respond to the report by the Scientists I posted earlier (twice since you ignored it), that Exxon has spent millions to spread disinfo about Global Warming. So now I find your comments here three times as suspicious. The poll was whether or not Global Warming is man made or not. That's a reasonable question that we should all ponder. http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change There is a VERY LONG LIST here that I will post separately. If you have to ask me my position about 9/11 then that tells me you don't read many thread on this 4um. I post a great deal about that subject and I have stated my views many, many, many times. 9/11 was clearly an inside job, probably out of Cheney's office in cahoots with or directed by the likes of Dov Zakheim, Richard Perle, Elliott Abrams, Paul Wolfowitz, Douglas Feith and all the other dual-citizen ZioNazis and Traitors who have taken over our govt in a silent coup. What's more important is that the official govt line is a lie, and as I've posted many times, exactly how it was done is less important. Ron Paul for President - Join a Ron Paul Meetup group today! This is just too long to post, but there are very few dissenting voices. With the release of the revised statement by the American Association of Petroleum Geologists, no scientific bodies of national or international standing are known to reject the basic findings of human influence on recent climate. Ron Paul for President - Join a Ron Paul Meetup group today! ---------------------------------------------------------- You then chose to attack wikipedia, although wiki referenced it's list of scientists.
So to support you position of consensus you point to a wiki section on the IPCC? You do know that the IPCC mandate states from the start that man is causing global warming. That's what their charter says.
#17. To: farmfriend (#15)
Let's see, one guy named Hans disagrees but all these groups agree. Hmmm... [edit] Statements by concurring organizations In February 2007, the IPCC released a summary of the forthcoming Fourth Assessment Report. According to this summary, the Fourth Assessment Report finds that human actions are "very likely" the cause of global warming, meaning a 90% or greater probability.[2] The New York Times reports on the report: The Associated Press summarizes the position on sea level rise: In preparation for the 2007 G8 summit, the national science academies of the G8+5 nations issued a declaration referencing the position of the 2005 joint science academies' statement, and acknowledging the confirmation of their previous conclusion by recent research. Following the IPCC Fourth Assessment Report, the declaration states: In 2005 the national science academies of the G8 nations, plus Brazil, China and India, three of the largest emitters of greenhouse gases in the developing world, signed a statement on the global response to climate change. The statement stresses that the scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action[6], and explicitly endorsed the IPCC consensus. The eleven signatories were the science academies of Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom, and the United States. In 2001, following the publication of the IPCC Third Assessment Report, sixteen national science academies issued a joint statement explicitly acknowledging the IPCC position as representing the scientific consensus on climate change science. The sixteen science academies that issued the statement were those of Australia, Belgium, Brazil, Canada, the Caribbean, China, France, Germany, India, Indonesia, Ireland, Italy, Malaysia, New Zealand, Sweden, and the United Kingdom.[7] In 2001 the Committee on the Science of Climate Change of the National Research Council published Climate Change Science: An Analysis of Some Key Questions [8]. This report explicitly endorses the IPCC view of attribution of recent climate change as representing the view of the scientific community: The American Meteorological Society (AMS) statement adopted by their council in 2003 said: The American Geophysical Union (AGU) statement [11] adopted by the society in 2003 and revised in 2007 affirms that rising levels of greenhouse gases have caused and will continue to cause the global surface temperature to be warmer: The Governing Board of the American Institute of Physics endorsed the AGU statement on human-induced climate change:[12] The American Astronomical Society has endorsed the AGU statement:[13] "Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes. "The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now."[14] On May 2, 2006, the Federal Climate Change Science Program commissioned by the Bush administration in 2002 released the first of 21 assessments. Though it did not state what percentage of climate change might be anthropogenic, the assessment concluded: The American Association for the Advancement of Science stated, "The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society."[16] The Stratigraphy Commission of the Geological Society of London stated, "We find that the evidence for human-induced climate change is now persuasive, and the need for direct action compelling."[17] "The Geological Society of America (GSA) supports the scientific conclusions that Earth’s climate is changing; the climate changes are due in part to human activities; and the probable consequences of the climate changes will be significant and blind to geopolitical boundaries. Furthermore, the potential implications of global climate change and the time scale over which such changes will likely occur require active, effective, long-term planning."[18] The American Chemical Society stated: "Engineers Australia believes that Australia must act swiftly and proactively in line with global expectations to address climate change as an economic, social and environmental risk... We believe that addressing the costs of atmospheric emissions will lead to increasing our competitive advantage by minimising risks and creating new economic opportunities. Engineers Australia believes the Australian Government should ratify the Kyoto Protocol."[20] "CMOS endorses the process of periodic climate science assessment carried out by the Intergovernmental Panel on Climate Change and supports the conclusion, in its Third Assessment Report, which states that the balance of evidence suggests a discernible human influence on global climate."[21] The 2001 statement from the American Association of State Climatologists noted the difficulties with predicting impacts due to climate change, while acknowledging that human activities are having an effect on climate: The American Association of Petroleum Geologists (AAPG) Position Statement on climate change states that "the AAPG membership is divided on the degree of influence that anthropogenic CO2 has on recent and potential global temperature increases ... Certain climate simulation models predict that the warming trend will continue, as reported through NAS, AGU, AAAS and AMS. AAPG respects these scientific opinions but wants to add that the current climate warming projections could fall within well-documented natural variations in past climate and observed temperature data. These data do not necessarily support the maximum case scenarios forecast in some models."[23] Prior to the adoption of this statement, the AAPG was the only major scientific organization that rejected the finding of significant human influence on recent climate, according to a statement by the Council of the American Quaternary Association.[24] The AAPG updated its statement in part because the previous statement was "not supported by a significant number of our members and prospective members".[25] With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate.[24] A question which frequently arises in conveying the scientific opinion to a broader audience is to what extent that opinion rises to the level of a consensus. Several scientific organizations have explicitly used the term "consensus" in their statements: Various surveys have been conducted to determine a scientific consensus on global warming. Few have been conducted within the last ten years. A 2004 article by geologist and historian of science Naomi Oreskes summarized a study of the scientific literature on climate change.[31] The essay concluded that there is a scientific consensus on the reality of anthropogenic climate change. The author analyzed 928 abstracts of papers from refereed scientific journals between 1993 and 2003, listed with the keywords "global climate change". Oreskes divided the abstracts into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. 75% of the abstracts were placed in the first three categories, thus either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, thus taking no position on current anthropogenic climate change; none of the abstracts disagreed with the consensus position, which the author found to be "remarkable". According to the report, "authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point." A survey was conducted in 2003 by Dennis Bray and Hans von Storch [32] [33] Bray's submission to Science on December 22, 2004 was rejected, but the survey's results were reported through non-scientific venues.[34][35] The survey received 530 responses from 27 different countries. One of the questions asked was "To what extent do you agree or disagree that climate change is mostly the result of anthropogenic causes?", with a value of 1 indicating strongly agree and a value of 7 indicating strongly disagree. The results showed a mean of 3.62, with 50 responses (9.4%) indicating "strongly agree" and 54 responses (9.7%) indicating "strongly disagree". The same survey indicates a 72% to 20% endorsement of the IPCC reports as accurate, and a 15% to 80% rejection of the thesis that "there is enough uncertainty about the phenomenon of global warming that there is no need for immediate policy decisions." The survey has been criticized on the grounds that it was performed on the web with no means to verify that the respondents were climate scientists or to prevent multiple submissions. The survey required entry of a username and password, but this information was circulated to a climate skeptics mailing list and elsewhere on the internet.[36][37]. Bray and von Storch have recently defended their results[38] and accused climate change skeptics of interpreting the results with bias. In 1997, the conservative think tank Citizens for a Sound Economy surveyed America's 48 state climatologists on questions related to climate change[39]. Of the 36 respondents, 44% considered global warming to be a largely natural phenomenon, compared to 17% who considered warming to be largely man-made. The survey further found that 58% disagreed or somewhat disagreed with then-President Clinton's assertion that "the overwhelming balance of evidence and scientific opinion is that it is no longer a theory, but now fact, that global warming is for real". Eighty-nine percent agreed that "current science is unable to isolate and measure variations in global temperatures caused ONLY by man-made factors," and 61% said that historical data do not indicate "that fluctuations in global temperatures are attributable to human influences such as burning fossil fuels." Sixty percent of the respondents said that reducing man-made CO2 emissions by 15% below 1990 levels would not prevent global temperatures from rising, and 86% said that reducing emissions to 1990 levels would not prevent rising temperatures. Thirty nine percent agreed and 33% disagreed that "evidence exists to suggest that the earth is headed for another glacial period,"[40] though the time scale for the next glacial period was not specified. In 1996, Dennis Bray and Hans von Storch undertook a survey of climate scientists on attitudes towards global warming and related matters. The results were subsequently published in the Bulletin of the American Meteorological Society.[41] The paper addressed the views of climate scientists, with a response rate of 40% from a mail survey questionnaire to 1000 scientists in Germany, the USA and Canada. Most of the scientists believed that global warming was occurring and appropriate policy action should be taken, but there was wide disagreement about the likely effects on society and almost all agreed that the predictive ability of currently existing models was limited. The abstract says: The survey was extensive, and asked numerous questions on many aspects of climate science, model formulation, and utility, and science/public/policy interactions. To pick out some of the more vital topics, from the body of the paper: Note that the following surveys are over 15 years old. The state of climate science and the beliefs of climate scientists have changed radically since their time, as demonstrated by the reviews cited above.
Top • Page Up • Full Thread • Page Down • Bottom/LatestMany scientists believe that higher concentrations of carbon dioxide in the atmosphere will enhance the greenhouse effect making the planet warmer. Scientists believe we are already experiencing global warming due to an enhancement of the greenhouse effect. Most computer climate models suggest that the globe will warm up by 1.5 - 4.5° Celsius if carbon dioxide reaches the predicted level of 600 parts per million by the year 2050.
#4. To: farmfriend (#2)
* Variations in the Earth's orbital characteristics.
#5. To: robin (#4)
The ice core sample article and timeline from NOVA support the growing evidence that CO2 levels have never been as high as they are today.
#7. To: farmfriend (#5)
#9. To: robin (#7)
when the VAST MAJORITY OF SCIENTISTS DO!
#11. To: farmfriend (#9)
http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change
#15. To: robin (#11)
Replies to Comment # 15. [edit] Intergovernmental Panel on Climate Change (IPCC) 2007
[edit] Joint science academies’ statement 2007
[edit] Joint science academies’ statement 2005
[edit] Joint science academies’ statement 2001
[edit] U.S. National Research Council, 2001
[edit] American Meteorological Society
[edit] American Geophysical Union
[edit] American Institute of Physics
[edit] American Astronomical Society
[edit] American Physical Society
[edit] Federal Climate Change Science Program, 2006
[edit] American Association for the Advancement of Science
[edit] Stratigraphy Commission of the Geological Society of London
[edit] Geological Society of America
[edit] American Chemical Society
[edit] Engineers Australia (The Institution of Engineers Australia)
[edit] The Canadian Meteorological and Oceanographic Society
[edit] Noncommittal statements
[edit] American Association of State Climatologists
[edit] American Association of Petroleum Geologists (AAPG)
[edit] Statements by dissenting organizations
[edit] Scientific consensus
[edit] Surveys of scientists and scientific literature
[edit] Oreskes, 2004
[edit] Bray and von Storch, 2003
[edit] Survey of U.S. state climatologists 1997
[edit] Bray and von Storch, 1996
[edit] Other older surveys of scientists
End Trace Mode for Comment # 15.