Impacts from the phenomenon
known as global warming include environmental, social, and economic effects.
Environmental impacts include sea-level rise, melting of the polar ice caps,
and an average increase in temperature. These impacts are documented in the
reports of the Intergovernmental Panel for Climate Change (IPCC), which
commissions reports by scientists worldwide on the issue of climate change. The
IPCC Report of 2007 is the first one that reflects scientific consensus that
global warming is underway, and that it is primarily human induced. For example,
human activities, such as fossil fuel burning, land-use changes, agricultural activity,
and the production and use of halocarbons are among the factors causing climate
change. The economic report by Nicholas Stern in 2007 highlights that climate
change has potentially disastrous consequences for humanity.
Temperature
Variability
Perhaps best known, is
that temperature variability, specifically temperature increase, will be one of
the effects of climate change. While the range of projections relating to
temperature rise varies, the IPCC scenarios, using a range of climate models,
predict overall a rise in globally-averaged surface temperature of 2.5–10 degrees
F (1.4 to 5.8 degrees C) 1990– 2100. While at local and regional levels this
figure will vary, at a global level it is roughly 2–10 times larger than the
observed warming of the 20th century, and is unprecedented during at least the
last 10,000 years, based on paleoclimatic data.
Changes in temperature
and precipitation (rainfall) patterns have increased all around the world. In
the United States, average temperatures have increased by roughly 1 degree F (0.6
degrees C) during the past century, and precipitation has increased by five to
10 percent. Alaska has sustained an average temperature increase of 4–7 degrees
F (2–4 degrees C) in just the past 50 years. Temperature increase has also had
a number of related effects, such as the increased melting of the summer Arctic
sea ice. Since 1979, more than 20 percent of the polar ice cap has melted in
response to increased surface and ocean temperatures. The oceans are warming.
Global ocean temperature has risen by 0.18 degrees F (0.10 degrees C) from the
surface to a depth of (2,297 ft.) 700 m. 1961–2003.
Warming
of Water Masses
Key oceanic water
masses are changing. Southern Ocean mode waters and Upper Circumpolar Deep Waters
have warmed from the 1960s to about 2000. A similar, but weaker pattern of
warming in the Gulf Stream and Kuroshio mode waters in the North Atlantic and
North Pacific has been observed. Longterm cooling is observed in the North
Atlantic subpolar gyre and in the central North Pacific.
Sea
-Level Rise
Another predicted
effect of climate change is an increase in sea level. Sea-level rise is caused
by thermal expansion of the oceans, melting of glaciers and ice caps, melting
of the Greenland and Antarctic ice sheets, and changes in terrestrial storage.
Changes in sea level will be felt through increases in intensity and frequency
of storm surges and coastal flooding; increased salinity of rivers, bays, and
coastal aquifers resulting from saline intrusion; increased coastal erosion;
loss of important mangroves and other wetlands (the exact response will depend
on the balance between sedimentation and sea-level change); and impact on
marine ecosystems such as coral reefs.
Sea-level rise is
accelerating worldwide. Globally, 100 million people live within about 3.3 ft.
(1 m.) of present day sea level. Eight to 10 million people live within 3.3 ft.
(1 m.) of high tide in each of the unprotected river deltas of Bangladesh,
Egypt, and Vietnam. IPCC reports estimate that the global average sea level rose
at an average rate of .07 in. (1.8 mm.) per year 1961–2003, and within that
period, the rate of rise was faster 1993–2003, about 0.12 in. (3.1 mm.) per
year. Overall, the IPCC concludes there is high confidence that the rate of
observed sea level rise has risen from the 19th to the 20th century. The total
20th century rise is estimated to be 0.55 ft. (0.17 m.) In 2001, IPCC
projections were for a sea-level rise of between 3.5–34.6 in. (9–88 cm.)
1990–2100 and a global average surface temperature rise of between 2.5–10.4
degrees F (1.4 and 5.8 degrees C.). In 2007, IPCC projections based on
different scenarios predict seal level rise from 0.01 to up to 0.02 in.
(.18–.59 mm.) by 2099.
Toward the end of the 21st
century, projected sealevel rise will affect low-lying coastal areas with large
populations. The cost of adaptation could amount to at least five to 10 percent
of Gross Domestic Product. Mangroves and coral reefs are projected to degrade further,
with additional consequences for fisheries and tourism. Snowmelt runoff as a
result of seal level rise will have major consequences. For example, one change
will be a change from spring peak flows to late winter peaks in
snowmelt-dominated regions. Many species, both aquatic and riparian (riverine) have
evolved to take opportunity of the spring flows as a result of snowmelt. For
example, some fish time their reproduction strategies specifically to avoid the
stress of springtime flows. Changes in springtime flow regimes, or high winter
flows associated with rain or snow events, can scour streambeds and destroy
eggs. Trees that provide riparian habitat along rivers may find it harder to reproduce
as they depend on high spring flows. Many species, such as salmon, already under
pressure from other environmental impacts, will be further impacted by climate
change. For example, higher temperatures and a reduced stream flow in the
Columbia River Basin may be increasing the mortality of juvenile coho salmon;
in some cases increased temperatures may be creating thermal barriers for the
migration of adult salmon.
There are a number of
associated events that are a result of climate change and will also have
impacts on sea-level rise. For example, the Kangerdlugssuaq Glacier in
Greenland is moving much faster, melting at a rate of 8.7 mi. (14 km.) a year
in comparison to just 3.2 mi. (5 km.) a year in 1988. This loss will also have
serious implications for sea-level rise, with some scientists predicting that
within the next 100 years, ice cover in this region will completely disappear
over summer and that species living within it, such as polar bears, will be
threatened. The complete melting of the Greenland Ice Sheet and the West
Antarctic Ice Sheet would lead to a contribution to sea-level rise of up to 23
ft. (7 m.) and about 16 ft. (5 m.), respectively.
Incidence
and Severity of Storms
Increased incidence and
frequency of storms is another predicted effect of climate change. For example,
since 1996, the number of named tropical storms in the North Atlantic per year
has increased by 40 percent, a figure considered extreme in the 1950s. Some
research indicates that there is a link between higher sea-surface temperatures
and storm frequency. Researchers have found that 1970–2004, warmer sea-surface
temperature has been the major factor in the increase in category 4 and 5 hurricanes
globally. Scientists have also shown that there is a strong correlation between
sea temperature and annual hurricane power in three different hurricane basins
in the North Atlantic, and two in the Pacific. Hurricane Katrina and the
tsunami in Southeast Asia are both examples of the increased frequency and
intensity of natural events that result from climate change.
Atmospheric
Composition
Another effect of
climate change is changes in atmospheric composition. It is possible to measure
these changes, as the composition of air, prior to industrialization, is known
from testing air bubbles frozen in ice cores from Antarctica. Since
pre-industrial times, the concentration of CO2 within the atmosphere
has risen from about 270–280 parts per million by volume (ppm) to over 360 ppm
today. Moreover, CH4 has risen from about 700 parts per billion by
volume (ppb) to over 1700 ppb, and N2O has increased from about 270
ppb to over 310 ppb. Halocarbons, substances that are not naturally present in
the atmosphere, are now present in large amounts.
This
is important because changes within the atmosphere have disrupted the total
energy budget of the planet. The balance between incoming, solar shortwave radiation,
and the outgoing long-wave radiations has upset the normal radiative balance.
This change is called radiative forcing. The Earth’s response to this phenomenon
is to try to restore the balance by warming the lower atmosphere. In so doing,
the surface temperature of the planet increases.
Source: Encyclopedia of Global Warming and Climate Change (Click Here)
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