Global Warming
Global Warming or Global Warming is a process of increasing the average temperature of the atmosphere, ocean, and land surface.Global
average temperature at the Earth's surface has increased by 0.74 ° C ±
0:18 (1:33 ± 0:32 ° F) during the last hundred years. Intergovernmental
Panel on Climate Change (IPCC) concluded that, "most of the increase in
global average temperatures since the mid-20th century, most likely
caused by increased concentrations of greenhouse gases resulting from
human activity" via the greenhouse effect. These
basic conclusions have been endorsed by at least 30 scientific
societies and academies, including the national science academies of all
G8 countries. However, there are still some scientists who do not agree with some of the conclusions that the IPCC stated.Climate
models referenced by the IPCC project shows global surface temperature
will increase by 1.1 to 6.4 ° C (2.0 to 11.5 ° F) between 1990 and 2100.
Guesstimate
the difference was caused by the use of different scenarios on
emissions of greenhouse gases in the future, as well as models with
differing climate sensitivity. While
most research focuses on the period up to 2100, warming and sea level
rise is expected to continue for more than a thousand years even if
greenhouse gas emission levels have stabilized. This reflects the large heat capacity of the oceans.Increasing
global temperature will cause other changes such as rising sea levels,
increased intensity of extreme weather phenomena, [2] as well as changes
in the amount and pattern of precipitation. The
effects of global warming include its impact on agricultural output,
loss of glaciers, and the extinction of various animal species.Some
of the things that scientists are still doubtful about the amount of
warming expected in the future, and how warming and the changes that
occur will vary from one region to another. Until
now there is still political and public debate in the world about what,
if any, action should be taken to reduce or reverse further warming or
to adapt to the consequences that exist. Most
of the governments in the world have signed and ratified the Kyoto
Protocol, aimed at reducing emissions of greenhouse gases.Causes of Global Warming,The greenhouse effectAll energy sources that exist on Earth comes from the Sun. Most of the energy in the form of short-wave radiation, including visible light. When this energy arrives Earth's surface, he turned from the light into heat that warms the Earth. The surface of the Earth, will absorb some of the heat and reflect the rest. Some of this heat tangible long-wave infrared radiation into space. However,
some of the heat remains trapped in the Earth's atmosphere due to
accumulated amount of greenhouse gases include water vapor, carbon
dioxide, sulfur dioxide and methane into the trap this radiation. These gases absorb and reflect radiation emitted heat the Earth, and consequently will be stored on the surface of the Earth. This situation occurs continuously, resulting in an annual average temperature of the earth continues to rise.These gases working in greenhouse gases. With the increasing concentration of these gases in the atmosphere, the more heat is trapped underneath.The greenhouse effect is very much needed by all living things on earth, because without it, the planet would be very cool. With
an average temperature of 15 ° C (59 ° F), the earth actually has more
hot 33 ° C (59 ° F) from the original temperature, if there is no
greenhouse effect earth's temperature is only -18 ° C so that the ice
will cover the entire Earth's surface. But on the contrary, if these gases in the atmosphere has been excessive, will cause global warming.Feedback effectsElements of the cause of global warming is also influenced by a variety of feedback processes that result. An example is the evaporation of water. In
the case of warming due to increasing greenhouse gases such as CO2,
warming will initially lead to more water to evaporate into the
atmosphere. Because
water vapor is itself a greenhouse gas, warming will continue and
increase the amount of water vapor in the air until it reaches
equilibrium with the water vapor concentration. The resulting greenhouse effect greater than the effect of CO2 alone. (Although
this feedback increases the absolute water content in the air, the
relative humidity of the air is almost constant or even decreases
slightly because the air becomes warmer). [3] This feedback affects only
slowly as CO2 has a long time in the atmosphere.Feedback effects due to the influence of clouds is the subject of current research. When viewed from below, clouds will reflect infrared radiation to the surface, thereby increasing the warming effect. In
contrast when viewed from above, the clouds will reflect sunlight and
infrared radiation to space, thereby enhancing the cooling effect. Whether
the net effect produces heating or cooling depending on some specific
details such as the type and altitude of the cloud. These
details are difficult to represent in climate models, partly because
the cloud is very small compared to the distance between the boundaries
of computational climate models (about 125 to 500 km for the models used
in the IPCC Fourth Report of view). Nevertheless,
cloud feedback is ranked two when compared with the water vapor
feedback and is considered positive (adding heating) in all the models
used in the IPCC Fourth Report of view.Another important feedback is the loss of reflectance (albedo) of ice. As global temperatures increase, ice near the poles melts at an increasing rate. Along with melting ice, land or water below will open. Both
land and water has the ability to reflect light much less when compared
to ice, and consequently will absorb more solar radiation. This will add to the heating and causing more ice to melt, causing a continuous cycle.Positive
feedback due to release of CO2 and CH4 from the softening of frozen
ground (permafrost) are other mechanisms that contribute to warming. In addition, the melting ice will also release CH4 are also positive feedback.The
ability of the oceans to absorb carbon will also be reduced when it
warms up, this is caused by the decreased levels of nutrients in the
mesopelagic zone limiting phytoplankton pertumbuhandiatom than a carbon
sink that low.Variations in the SunThere
is a hypothesis that states that the variation of the Sun, with a
possibility reinforced by feedback from clouds, can contribute in the
current warming. The
difference between this mechanism with the warming due to the
greenhouse effect is the increased activity of the Sun would heat the
stratosphere reverse the greenhouse effect should cool the stratosphere.
Cooling
of the lower stratosphere has been observed at least since 1960 that
will not happen when solar activity being the main contributor to recent
warming. (Depletion
of the ozone layer can also provide the cooling effect but the
depletion occurred from late 1970's.) Phenomenon solar variability
combined with volcanic activity may have given the warming effect from
pre-industrial to 1950, as well as a cooling effect since 1950 .There is some research that states that the contribution of the Sun may have been overlooked in global warming. Two
dariDuke University scientists estimate that the Sun may have
contributed to the 45-50% increase in global average temperature over
the period 1900-2000, and about 25-35% between 1980 and 2000. Stott
and his colleagues argued that the climate models are used as
guidelines now make exaggerated estimates of the effect of greenhouse
gases compared to the influence of the Sun, they also argued that the
cooling effects of volcanic dust and sulfate aerosols have also been
underestimated. [11] Despite this, they
concluded that even with the increased sensitivity to the effects of
climate sun though, most of the warming that has occurred in recent
decades is due to greenhouse gases.In
2006, a team of scientists from the United States, Germany and
Switzerland declared that they did not find an increase in the level of
"testimony" from the Sun in the last thousand years. Solar cycle is only a small increase of 0.07% in the rate of "statement" during 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 solar variability since 1985, whether through variations of solar
output or variations in cosmic raysTerimakasih Anda telah membaca tentang Global Warming
Judul: Global Warming
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