Greenhouse gases are several chemical species present in the atmosphere which have the property of trapping much of the solar radiation reflected from the Earth . When irradiated by incoming solar radiation,the atmosphere permits entry of most of the impinging energy of the solar electromagnetic spectrum; however, the spectrum of reflected sunlight is altered and has a higher fraction of long wave radiation, which is preferentially absorbed by greenhouse gases. Thus the net effect of higher concentrations of greenhouse gases is to encourage net heat buildup of the Earth’s atmosphere. Through normal heat exchange processes between the atmosphere and Earth’s surface, the temperature at the Earth’s surface is correspondingly elevated.
The steady increase in atmospheric concentrations of the three main greenhouse gases to which humans make notable contributions – carbon dioxide, methane, and nitrous oxide– is clear from the data sets for these gases over the last 420,000 years. Since the Industrial Revolution, concentrations of carbon dioxide, methane, and nitrous oxide have all risen sharply. Intensification of agriculture, fossil fuel combustion, land cover alteration to peatlands and wetlands have been the primary causes for these changes; however, all of these drivers are underlain by a root cause of the expanding global human population.
The analysis of greenhouse gas impacts on climate is the object of intense study, but is extremely complex due to the interactions of ocean currents and the diversity of carbon dioxide and methane sinks, which include forests, surface waters, peatlands and tundra. The situation is also complex since methane levels are rising faster percentagewise than carbon dioxide, and methane has approximately 30 times the greenhouse potency of carbon dioxide. The issue would be relatively simple, if all greenhouse gas emissions were merely the result of combustion processes, but production of methane is preponderantly from livestock grazing, rice farming and other non-point sources that are often linked to livelihoods of people in developing countries.
The seas in which corals and other calcifying species dwell are turning acidic, their pH slowly dropping as Earth's oceans acidify in response to increased carbon dioxide...
AnthropoceneLast Updated on 2013-09-03 12:23:40
The Anthropocene defines Earth's most recent geologic time period as being human-influenced, or anthropogenic, based on overwhelming global evidence that atmospheric, geologic, hydrologic, biospheric and other earth system processes are now altered by humans. The word combines the root "anthropo", meaning "human" with the root "-cene", the standard suffix for "epoch" in geologic time. The Anthropocene is distinguished as a new period either after or within the Holocene, the current epoch, which began approximately 10,000 years ago (about 8000 BC) with the end of the last glacial period.
Anthropocene is a new term, proposed in 2000 by Nobel Prize winning scientist Paul Crutzen. A similar term, Anthrocene, was coined by Andrew Revkin in his 1992 book Global Warming: Understanding the Forecast, but was not adopted by scientists.... More »
Tracking the Global Carbon CycleLast Updated on 2013-07-11 09:56:26
Carbon dioxide (CO2) is the primary anthropogenic (man-made) greenhouse gas in terms of concentration and effect. It is responsible for about one-third of the global warming that derives from human activities.  Concentrations of CO2 in the atmosphere depend on the global carbon cycle that accounts for the fluxes of carbon among various storage pools. The vast majority of carbon on Earth is part of limestone and other sedimentary rocks. The decomposition of rocks, called weathering, as well as the high temperatures used during cement production, release CO2 from limestone and enters the atmosphere or dissolves in bodies of water.
Photosynthetic organisms absorb CO2 from the atmosphere or bodies of water and then use solar radiation to convert this low-energy carbon into the high-energy carbon in organic compounds. This process reverses when organisms breathe in and out (respire) or... More »
Ocean acidification troublesLast Updated on 2012-08-09 00:00:00
The seas in which corals and other calcifying species dwell are turning acidic, their pH slowly dropping as Earth's oceans acidify in response to increased carbon dioxide in the atmosphere.
Trouble in Paradise:
Ocean Acidification This Way Comes
Sustainability of tropical corals in question, but some species developing survival mechanisms
The following Discovery article is part two in a series on the National Science Foundation's Science, Engineering and Education for Sustainability (SEES) investment. Visit parts one, three, four, five, six and seven in this series.
The following is part five in a series on the National Science Foundation's Long-Term Ecological Research (LTER) Network. Visit parts one, two, three, four, six, seven, eight and nine in this series.
Double, double toil and trouble;
Fire burn, and caldron bubble.
—Shakespeare,... More »
Atmospheric scienceLast Updated on 2012-03-27 00:00:00
Atmospheric science is the umbrella term for the study of the atmosphere — the blanket of air covering the Earth. It is a relatively new discipline that is concerned with the composition, structure and evolution of the atmosphere as well as its processes and how those processes interrelate with other systems.[2
The adjacent image depicts the various processes occurring in the atmosphere and how they relate to other Earth systems such as agriculture, land, sea and air transportation, other ecosystems, air pollutant emissions, the water cycle (evaporation and rainfall), forests and forest fires, deserts and desert dust, industry, etc.
To the extent that atmospheric science focuses primarily on the Earth's atmosphere, it can be regarded as a subfield of the "Earth sciences" discipline, each of which is a particular synthesis of the fundamentals of... More »
HalocarbonLast Updated on 2011-10-28 00:00:00
A halocarbon is an organic chemical molecule composed of at least one carbon atom bound covalently with one or more halogen atoms; the most common halogens in these molecules are fluorine, chlorine, bromine and iodine. Naturally occurring halocarbons are created by certain volcanic eruptions, forest fires, fungal decay, certain marine organism metabolism and are found in tissues of diverse organisms ranging from marine snails to various plants.
Many halocarbons become air pollutants, water pollutants in surface and groundwater resources and as soil contaminants. In the atmosphere, some of these chemicals produce significant impacts of upper atmosphere ozone depletion and also as radiative forcing gases implicated in climate change. In fact, many scientists have suggested that effective regulation of halocarbons may be a more cost effective approach to mitigating global warming... More »
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