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Written By:
Meghna Tare
Global warming refers to the effect
on the climate of anthropogenic activities, in particular the burning of
fossil fuels (coal, oil and gas) and large-scale deforestation
activities, which cause large amounts of ‘greenhouse gases’ to be
released into the atmosphere, of which the most important is carbon
dioxide. The other greenhouse gases are nitrous oxide,
chlorofluorocarbons (CFC’s), methane, and sulfur hexafluoride.
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Greenhouse gases allow short
wavelength light, such as ultraviolet light, to pass but not long
wavelength light (e.g. infrared radiation). Accordingly, the infrared
(heat) is trapped near the Earth’s surface keeping it warmer than it
would otherwise be (See:
All good things in life come
to an end! But what if life comes to an end?). Associated with this warming are changes in
the climate, both global and regional (Houghton, 2005).
The scientific opinion on climate change, as expressed by the United
Nations Intergovernmental Panel on Climate Change (IPCC, 2001) and
explicitly endorsed by the national science academies of the G8 nations,
is that the average global temperature has risen 0.6 ± 0.2 °C since the
late 19th century, and that it is likely that most of the warming
observed over the last 50 years is attributable to human activities.
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Atmospheric carbon
dioxide has increased from around 280 parts per million (by volume) in
1800 to around 315 in 1958 and 380 in 2005, a 31% increase over 200
years (IPCC, 2001). Other greenhouse gas emissions have also increased.
Future carbon dioxide levels are expected to rise due to ongoing
economic development dependent on fossil fuel usage, though the actual
trend for the future will depend on economic, sociological,
technological, and natural developments. The Intergovernmental
Panel on Climate Change has concluded that there will be both global and
regional climatic change, altered precipitation patterns, occurrence of
extreme events such as droughts and hurricanes and an increase in
climate variability (Houghton et al., 2001) during the next 100 years (IPCC,
1995, 2001). According to ice core climate record, today’s rising
atmospheric carbon dioxide concentration, at 380 parts per million by
volume, is 27 % higher than its highest recorded level during the last
650,000 years (Brook, 2005).
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Potential Impacts
of Climate Change
The thermohaline circulation is a
global ocean circulation. It is driven by differences in the density of
the sea water which is controlled by temperature and salinity (Broecker,
1995). The thermohaline circulation is sometimes called
the “ocean conveyor belt” and plays an important role in supplying heat
to the polar regions. There are projections that global warming could
shut down or slow down this thermohaline circulation and trigger cooling
in the North Atlantic, or lessen warming in regions such as Europe which
are dependent on the Gulf Stream to keep them warm. (See:
Global warming and changing oceans).
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The oceans have a tremendous
capacity to absorb carbon dioxide from the atmosphere, making the water
more acidic. “Ocean acidification” is the name given to
the ongoing decrease in the pH of the oceans, caused by their uptake of
anthropogenic carbon dioxide from the atmosphere. Between 1751 and 2004
surface ocean pH is estimated to have dropped from approximately 8.25 to
8.14 (Jacobson, 2005). This changing ocean chemistry may lead to sharp
decline in marine biodiversity. Many species of marine organisms
that form calcite shells may become extinct as a direct result of ocean
acidification (See:
Ocean
Acidification Bad for Shells and Reefs and
CO2
and Ocean Acidification). Observed species
composition changes may be driven by the changes in ocean acidification
and beginning with changes to species at the bottom of the food web and
affecting species throughout the food web all the way to top predators
in a cascade of effects. We are already seeing dramatic changes of
indicators species in all of the world's oceans.
Glaciers have been retreating
worldwide since the end of the Little Ice Age (around 1850), but in
recent decades glaciers have begun melting at rates that cannot be
explained by historical trends. Projected climate change over the next
century will further affect the rate at which glaciers melt. Average
global temperatures are expected to raise another 1.4-5.8ºC by the end
of the 21st century (IPCC, 2001).
Glaciers from the Andes to the Himalayas are melting
bringing long-term threats of higher sea levels that could swamp island
states and low-lying coastal areas. Like a canary in a coal mine, the
dwindling of the glaciers is visible evidence, an indicator that the
earth really is getting hotter (See:
Himalayan Glaciers
and
Global Warming Melts Alaska’s Glaciers).
Read about how melting glaciers
are predicted to cause significant rises in sea level
over the course of the twenty-first century increasing the risk of
coastal flooding for countries like Maldives and India (
See:
Is Global warming flooding
India? and
Rising Sea-Levels Submerging
the Maldives).
The geographic ranges of most plant
and animal species are limited by climatic factors, including
temperature, precipitation, soil moisture, humidity, and wind. Any shift
in the magnitude or variability of these factors in a given location
will impact the organisms living there. Species sensitive to temperature
may respond to a warmer climate by moving to cooler locations at higher
latitudes or elevations (McMichael et al, 1996) (See:
Climate Change Threatens
Monarch Butterflies).
Species that already live at higher elevation are likely to lose their
habitat altogether and go extinct.
The Arctic's sea ice is home to a
wide variety of wildlife including polar bears, arctic foxes, seals and
walruses. The sea ice is also used as a transportation route by caribou
and is a traditional hunting ground for the Inuit. Long term temperature
records from the surrounding land masses in the Arctic, including ice
cores, tree rings, and lake bed pollen samples, suggest that the Arctic
land area is now warmer than it has been in at least 400 years. This
warming trend is creating significant impact on the Inuit community and
depriving them of their daily livelihood. (See:
On Thin Ice:
Study of Climate Change Impact on Polar Inuit of NW Greenland)
Coral reefs, atolls, mangroves,
boreal and tropical forests, can be especially vulnerable to climate
change. Climate change may increase existing risks of extinction of
already threatened or vulnerable species. Biodiversity loss is the
likely outcome of climate change and may exceed that seen on earth over
the last 50 million years. In 1998 coral reefs around the world
experienced the most extensive and severe bleaching in recorded history.
If the overall warming is accompanied by more frequent periods of
sustained high temperatures, mass bleaching events will become more
frequent and widespread (Wilkinson et al., 1999)(See:
Disappearing Plankton: Loss of a Carbon Sink Global Warming to Contribute to Loss of Mangrove Forests,
Global Warming Bleaching
Corals).
Warmer temperatures increase the
probability of drought. Greater evaporation, particularly during summer
and fall, could exacerbate drought conditions and increase the risk of
wildfires (See:
Climate Trend and Forest
Fires). Extremes events like
heat waves, river and coastal flooding, droughts, landslides, storms,
hurricanes and tornadoes may become more intense and occur more
frequently. These severe weather and geological events will have
negative effects on society by damaging homes and villages and resulting
in loss of life (See:
Global Warming and Hurricanes).
The Conservation Science Institute
has launched a global warming and climate changes initiative and will
continue to synthesize and distribute information about this topic
through this CSI climate change web site, the CSI Report and by
promoting CSI Fellows who work on this topic. CSI has assigned Fellow
Meghna Tare to coordinate the CSI global warming and climate change
program and ask that you direct questions and inquiring to her about
this program. You can also support the CSI global warming and climate
change program through donations to CSI and becoming a member or you may
want to consider applying for a CSI fellowship. |
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References
Broecker, W. 1995.
Chaotic Climate, Scientific
American, November, 62-68
Brook, E., 2005.
Tiny bubbles tell
all. Science 310, 1285-12
Jacobson, M. Z. 2005. Studying
ocean acidification with conservative, stable numerical schemes for
nonequilibrium air-ocean exchange and ocean equilibrium chemistry. J.
Geophys. Res. Atm. 110, D07302
Houghton, J. 2005.
Global warming. Rep. Prog. Phys. 68:1343–140
Houghton, J. T., Y.
Ding, D. J. Griggs, M. Noguer, P. J. van der Linden and D. Xiaosu, eds.
2001. Climate Change 2001: The Scientific Basis (Cambridge Univ.
Press, Cambridge, U.K.)
McMichael, A.J., A.
Haines, and R. Slooff. 1996. Climate Change and Human Health. World
Health Organization, World Meteorological Organization, United Nations
Environmental Program, Geneva: 305.
Pittock, B., D. Wratt,
R. Basher, B. Bates, M. Finlayson, H. Gitay, A. Woodward, A. Arthington,
P. Beets, B. Biggs. 2001. in Climate Change 2001: Impacts,
Adaptation, and Vulnerability (Cambridge Univ. Press, Cambridge,
U.K.).
Raven,
J. A. 2005. Ocean acidification due to increasing atmospheric carbon
dioxide. The Royal Society, London, UK. This report can be found
at www.royalsoc.ac.uk
Wilkinson, C.O., H. C.
Linden, G. Hodgson, J. Rubens, and A. E. Strong. 1999. Ecological and
socioeconomic impacts of 1998 coral mortality in the Indian Ocean: An
ENSO impact and a warning of future change? Ambio 28: 188-196 |
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