Global Greenhouse

The greenhouse effect results from "the dirty of the atmospheric infrared window" by some atmospheric trace gases, permitting incoming solar radiation to reach the surface of the Earth unhindered but restricting the outward flow of infrared radiation. These atmospheric trace gases are referred as greenhouse gases. They absorb and reradiate this outgoing radiation, effectively storing some of the heat in the atmosphere, thus producing a net warming of the surface. The process is called the greenhouse effect. The various independent historical observational measurements conclude that the global average near-surface temperature has increased by about 0.5 degree centigrade over the past 100 years. This observed warming trend is continuing despite the influence of the Mt. Pinatubo volcanic eruption, which caused volcanic emissions to reduce incoming solar radiation for nearly two years. The likelihood that this global warming is due to primarily to natural variability is low. Scientists believe that this global warming trend is resulted from the enhanced greenhouse effect. The notion of an "enhanced" greenhouse effect refers primarily to the incremental global warming caused by the exponentially increasing concentrations of anthropogenically introduced greenhouse gases over and above the greenhouse effect caused by naturally occurring

greenhouse gases. Although there exist large uncertainties, scientists suggest that the emissions of greenhouse gases and sulfate aerosols could, by the end of the next century, lead to an increase in global mean temperatures of about 1-4 degree centigrate. According to a climate model from the Hadley Center for Climate Prediction and Research, in the United Kingdom, there is strong evidence that man-made greenhouse gas emissions are responsible for global warming over the past few decades, however, the sun and volcanoes played a significant part in effecting temperatures during the first half of the twentieth century. The main anthropogenic (man made pollution) driver is burning fossil fuel to produce energy, a process that emits the most significant greenhouse gas, carbon dioxide. This global warming trend can cause a significant global climate changes. Human society is highly dependent on the Earth's climate. Climate patterns and human adaptations determine the availability of food, fresh water, and other resources for sustaining life. Largely adapting to the seasonal and year-to-year patterns of temperature and rainfall has also shaped the social and economic characteristics of society. Some potential effects associated with climate change are listed in the following. (From U.S. Climate Action Report)

* Water Resources

The quality and quantity of drinking water, water availability for irrigation, industrial use, and electricity generation, and the health of fisheries may be significantly affected by changes in precipitation and increased evaporation. Increased rainfall may cause more frequent flooding. Climate change would likely add stress to major river basins worldwide.

* Coastal Resources

An estimated 50 cm rise in sea level by the year 2100, could inundate more than 5,000 square miles of dry land and an additional 4000 square miles of wetlands in the U.S.

* Health

Heat-stress mortality could increase due to higher temperatures over longer periods. Changing patterns of precipitation and temperature may produce new breeding sites for pests, shifting the range of infectious diseases.

* Agriculture

Impacts of Climate change in developing countries could be significant.

* Forests

Higher temperatures and precipitation changes could increase forest susceptibility to fire, disease, and insect damage.

* Energy and Transportation

Warmer temperatures increase cooling demand but decrease heating requirements. Fewer disruptions of winter transportation may occur, but increased flooding or lowered river levels may affect water transport. Carbon Dioxide (CO2)

The global Carbon Dioxide budget is complex and involves transfer of CO2 between the atmosphere, the oceans, and the biosphere. Through the photosynthetic process, the land removes about 100 pentagrams of carbon in the form of CO2 per year. However, about the same quantity of carbon in the form of CO2 is added to the atmosphere each year by vegetation and soil respiration and decay. The world's oceans release about 100 Pg C in the form of CO2 into the atmosphere per year and in turn absorb about 104 Pg C each year. Most of the oceanic carbon is in the form of sedimentary carbonates. Burning of fossil fuels adds about 5 Pg C and biomass burring and deforestation add about another 2 Pg C to the atmosphere in the form of CO2 annually. By summing all of the fluxes of CO2 into and out of the atmosphere, we can find that about 3 Pg C in