Introduction to greenhouse effect
Greenhouse gases are transparent to shortwave radiation from the sun, the main source of heat on the Earth. However, they absorb some of the longer infrared radiation emitted by the Earth, thereby reducing radiational cooling and hence raising the temperature of the Earth.
The atmospheric concentrations of carbon dioxide and methane have increased by 31% and 149% respectively above pre-industrial levels since 1750. This is considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that carbon dioxide values this high were last attained 40 million years ago. About three-quarters of the anthropogenic (man-made) emissions of carbon dioxide to the atmosphere during the past 20 years are due to fossil fuel burning. The rest of the anthropogenic emissions are predominantly due to land-use change, especially deforestation.
Methane, the primary constituent of natural gas, enters the atmosphere both from biological production and leaks from natural gas pipelines and other infrastructure. Some biological sources are natural, such as termites or forests, but others have been increased or created by agricultural activities such as the cultivation of rice paddies. Recent evidence indicates that methane concentrations have begun to stabilize, perhaps due to reductions in leakage from fuel transmission and storage facilities.
Future carbon dioxide levels are expected to continue rising due to ongoing fossil fuel usage. The rate of rise will depend on uncertain economic, sociological, technological, and natural developments. The IPCC Special Report on Emissions Scenarios gives a wide range of future carbon dioxide scenarios, ranging from 541 to 970 parts per million by the year 2100. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal and tar sands are extensively used.
Carbon sink ecosystems (forests and oceans) are being degraded by pollutants. Degradation of major carbon sinks results in higher atmospheric carbon dioxide levels.
Anthropogenic emission of greenhouse gases broken down by sector for the year 2000.Globally, the majority of anthropogenic greenhouse gas emissions arise from fuel combustion. The remainder is accounted for largely by "fugitive fuel" (fuel consumed in the production and transport of fuel), emissions from industrial processes (excluding fuel combustion), and agriculture: these contributed 5.8%, 5.2% and 3.3% respectively in 1990. Current figures are broadly comparable. Around 17% of emissions are accounted for by the combustion of fuel for the generation of electricity. A small percentage of emissions come from natural and anthropogenic biological sources, with approximately 6.3% derived from agriculturally produced methane and nitrous oxide.
'Smoking gun' report to say global warming here
"The smoking gun is definitely lying on the table as we speak," said top U.S. climate scientist Jerry Mahlman, who reviewed all 1,600 pages of the first segment of a giant four-part report. "The evidence ... is compelling."
Andrew Weaver, a Canadian climate scientist and study co-author, went even further: "This isn't a smoking gun; climate is a batallion of intergalactic smoking missiles."
The first phase of the Intergovernmental Panel on Climate Change is being released in Paris next week.
This segment, written by more than 600 scientists and reviewed by another 600 experts and edited by bureaucrats from 154 countries, includes "a significantly expanded discussion of observation on the climate," said co-chair Susan Solomon a senior scientist for the U.S. National Oceanic and Atmospheric Administration.
She and other scientists held a telephone briefing on the report Monday.
That report will feature an "explosion of new data" on observations of current global warming, Solomon said.
Solomon and others wouldn't go into specifics about what the report says.
They said that the 12-page summary for policymakers will be edited in secret word-by-word by governments officials for several days next week and released to the public on February 2. The rest of that first report from scientists will come out months later.
The full report will be issued in four phases over the year, as was the case with the last IPCC report, issued in 2001.
Global warming is "happening now, it's very obvious," said Mahlman, a former director of NOAA's Geophysical Fluid Dynamics Lab. "When you look at the temperature of the Earth, it's pretty much a no-brainer."
Look for an "iconic statement" -- a simple but strong and unequivocal summary -- on how global warming is now occurring, said one of the authors, Kevin Trenberth, director of climate analysis at the National Center for Atmospheric Research, also in Boulder.
The February report will have "much stronger evidence now of human actions on the change in climate that's taken place," Rajendra K. Pachauri told the AP in November. Pachauri, an Indian climatologist, is the head of the international climate change panel.
An early version of the ever-changing draft report said "observations
Greenhouse effect
Atmospheric scientists first used the term 'greenhouse effect' in the early 1800s. At that time, it was used to describe the naturally occurring functions of trace gases in the atmosphere and did not have any negative connotations. It was not until the mid-1950s that the term greenhouse effect was coupled with concern over climate change. And in recent decades, we often hear about the greenhouse effect in somewhat negative terms. The negative concerns are related to the possible impacts of an enhanced greenhouse effect. This is covered in more detail in the Global Climate Change section of this Web site. It is important to remember that without the greenhouse effect, life on earth as we know it would not be possible.While the earth's temperature is dependent upon the greenhouse-like action of the atmosphere, the amount of heating and cooling are strongly influenced by several factors just as greenhouses are affected by various factors.
In the atmospheric greenhouse effect, the type of surface that sunlight first encounters is the most important factor. Forests, grasslands, ocean surfaces, ice caps, deserts, and cities all absorb, reflect, and radiate radiation differently. Sunlight falling on a white glacier surface strongly reflects back into space, resulting in minimal heating of the surface and lower atmosphere. Sunlight falling on a dark desert soil is strongly absorbed, on the other hand, and contributes to significant heating of the surface and lower atmosphere. Cloud cover also affects greenhouse warming by both reducing the amount of solar radiation reaching the earth's surface and by reducing the amount of radiation energy emitted into space.
Scientists use the term albedo to define the percentage of solar energy reflected back by a surface. Understanding local, regional, and global albedo effects is critical to predicting global climate change.
Great Stuff on eBay
Fetching new data from eBay now... please stand by
by multia
I am an university student who is interestend in global warming and I hope that I will get someone else interested too.
(more)Explore related pages
The Cult of Global Warming- The world's polar ice caps are melting? Are you sure about this. . . ?
Green Living Made Easy- Welcome! Have you thought about living green but just don't know where to start?...
The Earth Shop- It IS easy being green! Earth-friendly products have come a long way. You can li...
Global Warming- Global Warming is a threat to earth, say some - is just a term to scare us, say...
Christians and the Environment- Environmental stewardship is undergoing a huge revival in the Church these days,...
Warming signs in our changing climate- A spotlight on the current physical effects of climate change. The ea...
