Топик: Global warming
Топик: Global warming
"Global warming" has been introduced by the scientific
community and the media as the term that encompasses all potential changes in
climate that result from higher average global temperatures. Hundreds of
scientists from many different countries are working to understand global
warming and have come to a consensus on several important aspects. In general,
Global warming will produce far more profound climatic changes than simply a
rise in global temperature.
An analysis of temperature records shows that the Earth has warmed
an average of 0.5°C over the past 100 years. This is consistent with
predictions of global warming due to an enhanced greenhouse effect and
increased aerosols. Part of the current global warmth is associated with the
tropical El Nino, without which a record global temperature would probably not
have occurred.
The Earth's climate is the result of extremely complex interactions
among the atmosphere, the oceans, the land masses, and living organisms, which
are all warmed daily by the sun's energy. This heat would radiate back into space
if not for the atmosphere, which relies on a delicate balance of heat-trapping
gases - including water vapor, carbon dioxide, nitrous oxide, and methane - to
act as a natural "greenhouse," keeping in just the right amount of
the sun's energy to support life.
For the past 150 years, though, the atmospheric concentrations of
these gases, particularly carbon dioxide, have been rising. As a result, more
heat is being trapped than previously, which in turn is causing the global
temperature to rise. Climate scientists have linked the increased levels of
heat-trapping gases in the atmosphere to human activities, in particular the
burning of fossil fuels (coal, oil, and natural gas for heating and
electricity; gasoline for transportation), deforestation, cattle ranching, and
rice farming.
As the Earth's climate is the result of extremely complex
interactions, scientists still cannot predict the exact impact on the earth's
climate of these rising levels of heat-trapping gases over the next century.
The current best estimate is that if carbon dioxide concentrations double over
preindustrial levels, according to the scientific possible scenarios, an
atmospheric doubling of carbon dioxide could occur as early as 2050.
In 1995, scientists with the Intergovernmental Panel on Climate
Change - the authoritative international body charged with studying this
issue-reached a conclusion in the Second Assessment Report, which summarizes
the current state of scientific knowledge on global warming, also called
climate change.
For the first time ever, the Panel concluded that the observed
increase in global average temperature over the last century "is unlikely
to be entirely natural in origin" and that "the balance of evidence
suggests that there is a discernible human influence on global climate."
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