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Thursday, March 10, 2011


There is a hypothesis which states that the variation of the Sun, with a possibility reinforced by feedback from clouds, can contribute to current warming. The difference between this mechanism with the warming due to greenhouse effect is the increased activity of the Sun would heat the stratosphere reverse the greenhouse effect will cool the stratosphere. Cooling the lower stratosphere has been observed at least since 1960, which will not occur when the solar activity becomes the major contributor to the current warming. (Depletion of the ozone layer can also provide the cooling effect but the depletion occurred from the late 1970s.) Phenomenon Solar variation combined with volcanoes probably had given the warming effect from pre-industrial times until 1950, and the cooling effect since 1950 .

There are some research results stating that the contribution of the Sun may have been overlooked in global warming. Two scientists from Duke University estimated that the Sun may have contributed to the 45-50% increase in average global temperature over the period 1900-2000, and about 25-35% between 1980 and 2000. Stott and his colleagues argue that climate models are used as guidelines when making estimates exaggerated the effects of greenhouse gases compared to the influence of the Sun, they also suggest that the cooling effects of volcanic dust and sulfate aerosols have also been underestimated. Nevertheless, they conclude that even by increasing the sensitivity of climate to influence of the Sun though, most of the warming that occurred in recent decades is caused by greenhouse gases.

In 2006, a team of scientists from the United States, Germany and Switzerland stated that they did not find an increase in the level of "explanation" of the Sun in a thousand years. Solar cycle to a small increase of 0.07% in brightness over the last 30 years. This effect is too small to contribute to global warming. A study by Lockwood and Fröhlich found no relation between global warming and variations of the Sun since 1985, either through the variation of solar output or variations in cosmic rays.

In early 1896, scientists thought that the burning of fossil fuels will change the composition of the atmosphere and to increase global average temperatures. This hypothesis was confirmed in 1957 when researchers working on global research program of the International Geophysical Year, took samples of the atmosphere from the top of Mauna Loa mountain in Hawaii.

The measurement results show an increase in the concentration of carbon dioxide in the atmosphere. After that, the composition of the atmosphere continues to be measured carefully. The data collected indicate that indeed an increase in the concentration of greenhouse gases in the atmosphere.

The scientists also have long suspected that the global climate warms up, but they are not able to provide appropriate evidence. Temperatures continue to vary from time to time and from one location to another location. Need many years of climate observations to obtain data that showed a tendency (trend) is clear. Note in the late 1980s showed a little of this warming trend, but statistics are few and can not be trusted.

Weather station at the beginning, is located close to urban areas so that the temperature measurement will be influenced by the heat emitted by buildings and vehicles and also heat stored by the building and road materials. Since 1957, the data obtained from a reliable weather station (located far from urban areas), and from satellites. These data provide a more accurate measurement, especially at 70 percent of the planet's surface covered with oceans. Data that more accurately shows that the surface of the Earth's warming trend actually occurs. When seen at the end of the 20th century, noted that the ten warmest years over the last hundred years occurred after 1980, and the three hottest years occurred after 1990, with 1998 being the hottest.

In a report issued in 2001, the Intergovernmental Panel on Climate Change (IPCC) concluded that global air temperatures have risen 0.6 degrees Celsius (1 degree Fahrenheit) since 1861. The panel agreed that the warming is mainly caused by human activities that add greenhouse gases to the atmosphere. The IPCC predicts an increase in global average temperatures will rise 1.1 to 6.4 ° C (2.0 to 11.5 ° F) between 1990 and 2100.

The IPCC panel also warned that although the concentration of gases in the atmosphere has not increased since 2100, still continues to warm climate during certain periods due to emissions that have been released previously. carbon dioxide will remain in the atmosphere for a hundred years or more before nature can absorb it again.

If greenhouse gas emissions continue to increase, experts predict, karbondioksioda concentration in the atmosphere can be increased up to threefold in the early-22 th century when compared to the pre-industrial era. As a result, there will be dramatic climate change. Although the actual events of this climate change has occurred several times throughout the history of Earth, humans will face this problem with the risk of a very large population.

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