According
to Wikipedia, global warming is "the observed increase in the average
temperature of the Earth's near-surface air and oceans in recent decades
and its projected continuation."
Many observations
indicate that global warming has taken place during the 20th century.
This has resulted in an increase of the average surface temperature, a
decrease in the snow cover and ice extent, and a rise in the sea level.
The amount of precipitation, the amount of cloud cover, and the presence
of extreme temperatures, especially in places where it's unusual to
have extreme temperatures, are affected by global warming.
There
are natural reasons that will affect global warming, as carbon dioxide
is naturally in the air due to the fact that all living organisms that
breathe in oxygen, exhale carbon dioxide, which is then taken in by
trees and other plant life, which in return, give out oxygen for humans,
animals, and other organisms that utilize oxygen. However, human
activities over the last 50 years have significantly increased the
levels of carbon dioxide (CO2) and other household gases in our
atmosphere. This has led to the global warming that is occurring on
Earth today. CO2 and other greenhouse gases tend to warm the Earth's
surface, while anthropogenic aerosols tend to cool the Earth's surface.
Other current facts about global warming include
-
The average surface temperature has increased by about 0.6 C (1.0 F)
over the last 100 years. - Snow cover and ice extent have decreased. -
The sea level has risen by 4-8" (10-20 cm) over the past 100 years. -
About 75% of the annual increase in atmospheric carbon dioxide is due to
the burning of fossil fuels, while the other 25% is attributed to
anthropogenic changes in land use, like deforestation, overgrazing, and
over cultivation, that reduces the net uptake of carbon dioxide. - In
the 20th century, precipitation has likely increased in some land areas
and decreased in others. - There has been some increase in cloud cover. -
It's very likely that there has been less extreme low temperatures and
slightly more extreme high temperatures. - There have been more warm
episodes of the El Nino since the mid-1970s. - There's been an increase
of droughts in some regions (especially in parts of Asia and Africa)
over the last few decades, which is different from the pattern of small
global increases in severe drought or severe wetness over the 20th
century.
However, it seems that global warming has NOT changed some important aspects of climate:
-
Some areas of the globe, like parts of the Southern Hemisphere oceans
and parts of Antarctica, have not warmed in recent decades.
-
There are no significant trends in the Antarctic sea-ice extent since
1978, the first year that reliable satellite measurements were used.
-
There are no significant trends of global changes in tropical and
extra-tropical storm intensity and frequency evident over the 20th
century. Instead, there are variations within decades and across
different decades, but not enough evidence to conclude that there were
any significant changes across the 20th century itself.
- There
are no systematic changes in the frequency of tornadoes, thunder days,
and hail events in the limited areas that were analyzed.
It is
clear that there is much evidence present in today's world that global
warming is a real phenomenon, not something that is made up to scare
people. Knowing these facts should help you learn what global warming
exactly is and what you can do to help reduce or reverse global warming.
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