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RESEARCH ON GLOBAL WARMING AND GREENHOUSE GASES
The world's most common greenhouse gases are:
water vapor
carbon dioxide
Atmospheric methane
nitrous oxide
ozone
chloroflorocarbons
water vapor, which contributes 36–72%
carbon dioxide, which contributes 9–26%
methane, which contributes 4–9%
ozone, which contributes 3–7%
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. Existence of the greenhouse effect as such is not disputed, even by those who do not agree that the recent temperature increase is attributable to human activity. The question is instead how the strength of the greenhouse effect changes when human activity increases the concentrations of greenhouse gases in the atmosphere.
Global warming
Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) between the start and the end of the 20th century. The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increase since the middle of the 20th century was very likely caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation. The IPCC also concludes that variations in natural phenomena such as solar radiation and volcanic eruptions had a small cooling effect after 1950. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of theProxy-Connection: keep-alive
Cache-Control: max-age=0
ajor industrialized countries.
Adaptation to Global warming
wide variety of measures have been suggested for adaptation to global warming, including: water conservation, water rationing, adaptive agricultural practices, including diversification, construction of flood defenses, changes to medical care, and interventions to protect threatened species. The capacity and potential for human systems to adapt is unevenly distributed across different regions and populations. The economic costs of adaptation are potentially large, but also largely unknown. Across the literature, there is wide agreement that adaptation will be more difficult for larger magnitudes and higher rates of climate change.
the scientific prediction come true
Scientists in the 1970s started to shift from the uncertain leanings in the 1960s to increasingly a prediction of future warming. A survey of the scientific literature from 1965 to 1979 found 7 articles predicting cooling and 44 predicting warming, with the warming articles also being cited much more often in subsequent scientific literature.
Several scientific panels from this time period concluded that more research was needed to determine whether warming or cooling was likely, indicating that the trend in the scientific literature had not yet become a consensus. On the other hand, the 1979 World Climate Conference of the World Meteorological Organization concluded "it appears plausible that an increased amount of carbon dioxide in the atmosphere can contribute to a gradual warming of the lower atmosphere, especially at higher latitudes....It is possible that some effects on a regional and global scale may be detectable before the end of this century and become significant before the middle of the next century."
The mainstream news media at the time did not reflect scientific opinion. In 1975, Newsweek magazine published a story that warned of "ominous signs that the Earth's weather patterns have begun to change," and reported "a drop of half a degree [Fahrenheit] in average ground temperatures in the Northern Hemisphere between 1945 and 1968." The article continued by stating that evidence of global cooling was so strong that meteorologists were having "a hard time keeping up with it." On October 23, 2006, Newsweek issued an update stating that it had been "spectacularly wrong about the near-term future".
Since about 1750 human activity has increased the concentration of carbon dioxide and other greenhouse gases. Measured atmospheric concentrations of carbon dioxide are currently 100 ppmv higher than pre-industrial levels. Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity, but over periods longer than a few years natural sources are closely balanced by natural sinks such as weathering of continental rocks and photosynthesis of carbon compounds by plants and marine plankton. As a result of this balance, the atmospheric concentration of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era.
In Asia, atmospheric levels of CO2 continue to rise, partly a sign of the industrial rise of Asian economies led by China. Over the 2000–2010 interval China is expected to increase its carbon dioxide emissions by 600 Mt, largely because of the rapid construction of old-fashioned power plants in poorer internal provinces.
potential global warming
The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale. Thus, if a gas has a high GWP on a short time scale (say 20 years) but has only a short lifetime, it will have a large GWP on a 20 year scale but a small one on a 100 year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase with the timescale considered.
Examples of the atmospheric lifetime and GWP for several greenhouse gases include:
Carbon dioxide has a variable atmospheric lifetime, and cannot be specified precisely. Recent work indicates that recovery from a large input of atmospheric CO2 from burning fossil fuels will result in an effective lifetime of tens of thousands of years.Carbon dioxide is defined to have a GWP of 1 over all time periods.
Methane has an atmospheric lifetime of 12 ± 3 years and a GWP of 72 over 20 years, 25 over 100 years and 7.6 over 500 years. The decrease in GWP at longer times is because methane is degraded to water and CO2 through chemical reactions in the atmosphere.
Nitrous oxide has an atmospheric lifetime of 114 years and a GWP of 289 over 20 years, 298 over 100 years and 153 over 500 years.
CFC-12 has an atmospheric lifetime of 100 years and a GWP of 11000 over 20 years, 10900 over 100 years and 5200 over 500 years.
HCFC-22 has an atmospheric lifetime of 12 years and a GWP of 5160 over 20 years, 1810 over 100 years and 549 over 500 years.
Tetrafluoromethane has an atmospheric lifetime of 50,000 years and a GWP of 5210 over 20 years, 7390 over 100 years and 11200 over 500 years.
Hexafluoroethane has an atmospheric lifetime of 10,000 years and a GWP of 8630 over 20 years, 12200 over 100 years and 18200 over 500 years.
Sulphur hexafluoride has an atmospheric lifetime of 3,200 years and a GWP of 16300 over 20 years, 22800 over 100 years and 32600 over 500 years.
Nitrogen trifluoride has an atmospheric lifetime of 740 years and a GWP of 12300 over 20 years, 17200 over 100 years and 20700 over 500 years.
carbon dioxide, which contributes 9–26%
methane, which contributes 4–9%
ozone, which contributes 3–7%
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. Existence of the greenhouse effect as such is not disputed, even by those who do not agree that the recent temperature increase is attributable to human activity. The question is instead how the strength of the greenhouse effect changes when human activity increases the concentrations of greenhouse gases in the atmosphere.
Global warming
Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) between the start and the end of the 20th century. The Intergovernmental Panel on Climate Change (IPCC) concludes that most of the observed temperature increase since the middle of the 20th century was very likely caused by increasing concentrations of greenhouse gases resulting from human activity such as fossil fuel burning and deforestation. The IPCC also concludes that variations in natural phenomena such as solar radiation and volcanic eruptions had a small cooling effect after 1950. These basic conclusions have been endorsed by more than 40 scientific societies and academies of science, including all of the national academies of science of theProxy-Connection: keep-alive
Cache-Control: max-age=0
ajor industrialized countries.
Adaptation to Global warming
wide variety of measures have been suggested for adaptation to global warming, including: water conservation, water rationing, adaptive agricultural practices, including diversification, construction of flood defenses, changes to medical care, and interventions to protect threatened species. The capacity and potential for human systems to adapt is unevenly distributed across different regions and populations. The economic costs of adaptation are potentially large, but also largely unknown. Across the literature, there is wide agreement that adaptation will be more difficult for larger magnitudes and higher rates of climate change.
the scientific prediction come true
Scientists in the 1970s started to shift from the uncertain leanings in the 1960s to increasingly a prediction of future warming. A survey of the scientific literature from 1965 to 1979 found 7 articles predicting cooling and 44 predicting warming, with the warming articles also being cited much more often in subsequent scientific literature.
Several scientific panels from this time period concluded that more research was needed to determine whether warming or cooling was likely, indicating that the trend in the scientific literature had not yet become a consensus. On the other hand, the 1979 World Climate Conference of the World Meteorological Organization concluded "it appears plausible that an increased amount of carbon dioxide in the atmosphere can contribute to a gradual warming of the lower atmosphere, especially at higher latitudes....It is possible that some effects on a regional and global scale may be detectable before the end of this century and become significant before the middle of the next century."
The mainstream news media at the time did not reflect scientific opinion. In 1975, Newsweek magazine published a story that warned of "ominous signs that the Earth's weather patterns have begun to change," and reported "a drop of half a degree [Fahrenheit] in average ground temperatures in the Northern Hemisphere between 1945 and 1968." The article continued by stating that evidence of global cooling was so strong that meteorologists were having "a hard time keeping up with it." On October 23, 2006, Newsweek issued an update stating that it had been "spectacularly wrong about the near-term future".
Since about 1750 human activity has increased the concentration of carbon dioxide and other greenhouse gases. Measured atmospheric concentrations of carbon dioxide are currently 100 ppmv higher than pre-industrial levels. Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity, but over periods longer than a few years natural sources are closely balanced by natural sinks such as weathering of continental rocks and photosynthesis of carbon compounds by plants and marine plankton. As a result of this balance, the atmospheric concentration of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era.
In Asia, atmospheric levels of CO2 continue to rise, partly a sign of the industrial rise of Asian economies led by China. Over the 2000–2010 interval China is expected to increase its carbon dioxide emissions by 600 Mt, largely because of the rapid construction of old-fashioned power plants in poorer internal provinces.
potential global warming
The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale. Thus, if a gas has a high GWP on a short time scale (say 20 years) but has only a short lifetime, it will have a large GWP on a 20 year scale but a small one on a 100 year scale. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase with the timescale considered.
Examples of the atmospheric lifetime and GWP for several greenhouse gases include:
Carbon dioxide has a variable atmospheric lifetime, and cannot be specified precisely. Recent work indicates that recovery from a large input of atmospheric CO2 from burning fossil fuels will result in an effective lifetime of tens of thousands of years.Carbon dioxide is defined to have a GWP of 1 over all time periods.
Methane has an atmospheric lifetime of 12 ± 3 years and a GWP of 72 over 20 years, 25 over 100 years and 7.6 over 500 years. The decrease in GWP at longer times is because methane is degraded to water and CO2 through chemical reactions in the atmosphere.
Nitrous oxide has an atmospheric lifetime of 114 years and a GWP of 289 over 20 years, 298 over 100 years and 153 over 500 years.
CFC-12 has an atmospheric lifetime of 100 years and a GWP of 11000 over 20 years, 10900 over 100 years and 5200 over 500 years.
HCFC-22 has an atmospheric lifetime of 12 years and a GWP of 5160 over 20 years, 1810 over 100 years and 549 over 500 years.
Tetrafluoromethane has an atmospheric lifetime of 50,000 years and a GWP of 5210 over 20 years, 7390 over 100 years and 11200 over 500 years.
Hexafluoroethane has an atmospheric lifetime of 10,000 years and a GWP of 8630 over 20 years, 12200 over 100 years and 18200 over 500 years.
Sulphur hexafluoride has an atmospheric lifetime of 3,200 years and a GWP of 16300 over 20 years, 22800 over 100 years and 32600 over 500 years.
Nitrogen trifluoride has an atmospheric lifetime of 740 years and a GWP of 12300 over 20 years, 17200 over 100 years and 20700 over 500 years.
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