|
|
Wednesday, 26 March 2008 |
|
The release of greenhouse gases and aerosols resulting from human activities are changing the amount of radiation coming into and leaving the atmosphere, likely contributing to changes in climate. Greenhouse Gases Greenhouse gas concentrations in the atmosphere have historically varied as a result of many natural processes (e.g. volcanic activity, changes in temperature, etc). However, since the Industrial Revolution humans have added a significant amount of greenhouse gases in the atmosphere by burning fossil fuels, cutting down forests and other activities. Because greenhouse gases absorb and emit heat, increasing their concentrations in the atmosphere will tend to have a warming effect. But the rate and amount of temperature increase is not known with absolute certainty. Changes in the atmospheric concentration of the major greenhouse gases are described below: 
Carbon dioxide (CO2) concentrations in the atmosphere increased from approximately 280 parts per million (ppm) in pre-industrial times to 382 ppm in 2006 according to the National Oceanic and Atmospheric Administration's (NOAA) Earth Systems Research Laboratory, a 36 percent increase. Almost all of the increase is due to human activities (IPCC, 2007). The current rate of increase in CO2 concentrations is about 1.9 ppmv/year. Present CO2 concentrations are higher than any time in at least the last 650,000 years (IPCC, 2007). See Figure 1 for a record of CO2 concentrations from about 420,000 years ago to present. For more information on the human and natural sources of CO2 emissions, see the Emissions section and for actions that can reduce these emissions, see the What You Can Do Section. |
|
Last Updated ( Thursday, 03 July 2008 )
|
|
Read more...
|
|
|
Tuesday, 18 March 2008 |
|
The Intergovernmental Panel on Climate Change and former US Vice-President Al Gore have been announced as the joint winners of the 2007 Nobel Peace Prize. They have certainly made a commendable effort in the field, but how does climate change affect the chance for peace? The Nobel Foundation Prizes for efforts and achievements in the fields of Physics, Chemistry, Physiology or Medicine, Literature and Peace, along with an additional prize for Economics, are awarded every year by the Swedish-based Nobel Foundation. The prizes are regarded as the most prestigious in their respective fields, with the winners receiving £750,000 cash, a medal and a diploma. Previous winners of the Nobel Peace Prize include Jimmy Carter, Kofi Annan, Desmond Tutu, Mother Teresa and Martin Luther King. The IPCC (Intergovernmental Panel on Climate Change), which is a part of the UN, and Al Gore share the 2007 prize "for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change". |
|
Last Updated ( Thursday, 03 July 2008 )
|
|
Read more...
|
|
|
Tuesday, 18 March 2008 |
|
Scientists have long agreed that climate change could have a profound impact on the planet; from melting ice sheets and withering rainforests, to flash floods and droughts.Now a team of climate experts has ranked the most fragile and vulnerable regions on the planet, and warned they are in danger of sudden and catastrophic collapse before the end of the century.In a comprehensive study published today, the scientists identify the nine areas that are in gravest danger of passing critical thresholds or "tipping points", beyond which they will not recover. Although the scientists cannot be sure precisely when each region will reach the point of no return, their assessment warns it may already be too late to save Arctic sea ice and the Greenland ice sheet, which they regard as the most immediately in peril. By some estimates, there will not be any sea ice in the summer months within 25 years. |
|
Last Updated ( Thursday, 03 July 2008 )
|
|
Read more...
|
|
|
Tuesday, 18 March 2008 |
|
the United Nations scientific panel studying climate change declared that the evidence of a warming trend is "unequivocal," and that human activity has "very likely" been the driving force in that change over the last 50 years. The last report by the group, the Intergovernmental Panel on Climate Change, in 2001, had found that humanity had "likely" played a role. The addition of that single word "very" did more than reflect mounting scientific evidence that the release of carbon dioxide and other heat-trapping gases from smokestacks, tailpipes and burning forests has played a central role in raising the average surface temperature of the earth by more than 1 degree Fahrenheit since 1900. It also added new momentum to a debate that now seems centered less over whether humans are warming the planet, but instead over what to do about it. In recent months, business groups have banded together to make unprecedented calls for federal regulation of greenhouse gases. The subject had a red-carpet moment when former Vice President Al Gore's documentary, "An Inconvenient Truth," was awarded an Oscar; and the Supreme Court made its first global warming-related decision, ruling 5 to 4 that the Environmental Protection Agency had not justified its position that it was not authorized to regulate carbon dioxide. |
|
Last Updated ( Thursday, 03 July 2008 )
|
|
Read more...
|
|
|
Tuesday, 18 March 2008 |
 The study was spurred in part by "The Great Global Warming Swindle," the TV documentary that featured a hypothesis that increased solar radiation may be causing global warming.
"All the graphs they showed stopped in 1980, and I knew why -- because things diverged after that," said researcher Mike Lockwood of the Rutherford-Appleton Laboratory in the United Kingdom. "[But] you can't just ignore bits of data that you don't like."
According to the cosmic ray hypothesis, increased solar radiation leads to a more powerful magnetic field, which blocks cosmic rays from reaching Earth. Because cosmic rays provide particles around which water vapor condenses to form clouds, a decrease in cosmic rays would thus lead to a drop in cloud cover. This means that more solar radiation would strike Earth, leading to warming.
But the current study showed that solar radiation has actually decreased, not increased, in the last 20 years. This same period corresponds to a rate of warming equal to or even greater than that of the rest of the century.
"This paper reinforces the fact that the warming in the last 20 to 40 years can't have been caused by solar activity," said Dr. Piers Forster, a professor at Leeds University and a significant contributor to the Intergovernmental Panel on Climate Change.
"I do think there is a cosmic ray effect on cloud cover," Lockwood said. "It works in clean maritime air where there isn't much else for water vapor to condense around. It might even have had a significant effect on pre-industrial climate, but you cannot apply it to what we're seeing now, because we're in a completely different ball game." |
|
Last Updated ( Thursday, 03 July 2008 )
|
|
|
|
<< Start < Prev 1 2 3 4 5 6 7 8 9 Next > End >>
|
| Results 55 - 63 of 81 |
Climate Change 
