13 Jan 2009 by ssattri
Global warming is here and humans are “very likely” the blame, an international group of scientists meeting in Paris, France, announced Friday.
The group of climate experts unanimously linked — with “90 percent” certainty — the increase of average global temperatures since the mid-20th century to the increase of manmade greenhouse gases in the atmosphere. ossil fuels like methane and carbon dioxide trap heat near the surface, a process known as the greenhouse effect. The greenhouse effect is a natural phenomenon, but human activities, like the burning of fossil fuels, can pour enormous volumes of these gases into the atmosphere, raising the planet’s temperature and destabilizing the climate.
The report found it was “likely” — “more likely than not” in some cases — that manmade greenhouse gases have contributed to hotter days and nights, and more of them, more killer heat waves than before, heavier rainfall more often, major droughts in more regions, stronger and more frequent cyclones and “increased incidence” of extremely high sea levels.
Greenhouse Effect: – What is that ?
The greenhouse effect is responsible for the Earth’s warm, livable atmosphere. Gases like methane and carbon dioxide trap heat near the surface, keeping the Earth about 33 C (60 F) warmer than it would be without its natural blanket of protective gas. The greenhouse effect is a natural phenomenon, but human activity can enhance its effect and destabilize the climate.
Water vapor, methane, carbon dioxide, CFCs, ozone and nitrous oxide are all greenhouse gases (GHGs). Carbon dioxide (CO2) is the most important, followed in descending order by methane, CFCs, ozone and nitrous oxide.
Climate scientists say human activities that pour enormous volumes of these gases into the atmosphere are raising the planet’s temperature.
The sun sends energy toward Earth in the form of light and radiation. We experience solar radiation as light and warmth on a sunny day
When the sun’s rays strike the atmosphere, some of the radiation is immediately reflected into space.
The radiation that gets through the atmosphere heads toward the Earth’s surface.
Solar radiation that passes through the Earth’s clear atmosphere is absorbed by the ground, water, plants and other objects. As the sun warms objects, they emit infrared radiation. This is the energy we know as heat.
A portion of the solar radiation that reaches the Earth’s surface — particularly areas covered by ice, snow or the ocean — also bounces back into space, where its heat energy dissipates.
6. Heat and gases
Molecules of greenhouse gases in the atmosphere absorb infrared radiation and release heat, which raises the temperature of the ground and air and warms the Earth’s surface.
Infrared radiation has a longer wavelength than visible light, so it is easier for molecules like carbon dioxide and water vapor to absorb energy and trap the sun’s energy beneath Earth’s atmosphere.
7. Into space
Some infrared radiation continues on its path out of the atmosphere and into space.
The energy the sun sends to the entire Earth averaged over a whole year is roughly 343 watts per square meter. When that energy hits the Earth’s surface, some of it is absorbed and some of it is reflected back into the atmosphere.The net outgoing energy — that is, radiation that goes back into space — is 240 of the original 343 watts per square meter.