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What is Global Warming aka Climate Change?
Global warming is the increase of the average temperature in the
atmosphere and oceans over time due primarily to human influences. Since
the late 19th century, scientists have monitored the fluctuations in
temperature and studied global warming theories and trends to determine
the causes and to assess the extent to which they are due to human
activity. The greenhouse effect is largely caused by human-generated
carbon dioxide (CO2) and, to some extent, by increases in
solar activity. The term "global warming" is used to imply a human
influence while "climate change" is most often used in association with
changes in climate with no easily identifiable cause, such as the
processes that produced the Ice Ages .Current climate models
(simulations) based on estimates of increasing CO2
and, to a lesser extent, by decreasing sulfate aerosols, predict that
temperatures will increase by 1.4-5.8°C (2.5-10.4°F) between 1990-2100.
This is a somewhat wide range; however, it is difficult to predict CO2 emissions because of the number of variables involved. Some climate studies have shown that, even in the absence of the CO2
emission variable, global climate will increase by 0.5°C (0.9°F) over
the next one hundred years due to warming caused just by the ocean. In
addition, models predict that sea levels will rise by about 10 cm over the next century.Evidence of global warming includes decreased snowfall, rising sea levels and changes to weather trends. Precipitation levels, precipitation patterns, cloud cover, severe weather, and other elements will be impacted by the increase in greenhouse gas concentrations in the atmosphere. "Greenhouse gases" are so named because they trap radiant energy from the sun that would otherwise be radiated back into space.
The Kyoto Protocol
was developed by the United Nations Framework Convention on Climate Change (UNFCCC)
as an international agreement to reduce greenhouse gas emissions
worldwide. The Protocol was entered into force in February 2005, and
signed by countries committed to reducing CO2 emissions and 5
other greenhouse gases. They may also engage in emissions trading, or
the purchase of credits from other countries that remain under the
limits of greenhouse gas emissions. In this way, countries that may
exceed the limits can still comply with the protocol. To date, 141
countries have ratified the agreement. Unfortunately, neither the United
States nor Australia have been participating, which has generated
speculation as to whether the Kyoto Protocol will successfully reduce
greenhouse gases, even if completely implemented by all signed
countries.
Global
climate change has been studied on a large scale based on analyses of
global temperature fluctuations over thousands of years; for example,
since the last Ice Age, which occurred approximately 12,000 years ago,
global temperatures have been relatively stable. Studies on a smaller
scale, however, show that temperatures in the lower troposphere have
increased between 0.08 and 0.22°C per decade since 1979. Still, these
modern day changes are not always linear, which has created a source of
debate within the scientific community and the news media.The study of paleoclimatology
(ancient climates) is increasingly linked to modern day climate study.
For example, the Earth was in an ice age for the last 160,000 years
prior to the end of the last Ice Age. Earlier studies of this time
period showed little variability in temperatures; however, more recent
studies showed the variability to be about twice as great as previously
published, indicating that temperature fluctuations are more frequent
throughout time than first thought. However, this does not negate the
impact of human activity on the current rate of global warming.Climate change is caused by both natural and external forces, the latter including both human—greenhouse gases—and non-human causes such as changes in the Earth's orbit around the Sun, solar activity, and volcanic emissions. Science is increasingly pointing to human activities as the reason that global warming is accelerating.
The greenhouse gas theory
started in the 19th century when the Swedish chemist and 1903 Nobel
Laureate, Svante Arrhenius, determined that increases in greenhouse gas
concentration would lead to higher global mean temperatures, while
decreases would lead to colder global mean temperatures. His finding was
a result of his research on ice ages, and was largely rejected by his
peers at the time. A colleague of Arrhenius, Arvid Högbom, was one of
the first scientists to study the carbon cycle . Arrhenius used his data to base his assessment that in 1890, emission and absorption of CO2
in the atmosphere were roughly in balance, and that burning fossil
fuels would not cause problems. However, this was based solely on the
use of coal, not on the use of fossil fuels in the automobile and other
industries.Opponents to the global warming theory postulate that water vapor and clouds will cancel out warming effect of CO2 emissions. However, the warming trends over the past few decades are increasingly negating the cancellation hypothesis. Furthermore, sophisticated computer models of the climate, validated by the scientific community in demonstrating accurate simulations of known climate variations such as El Niño events
, have predicted that adding CO2
to the atmosphere will create a warmer climate in the future. The
degree to which this warming will occur varies by model, however, and
opponents of the global warming theory point out variables that models
are not equipped to factor, such as changes in vegetation and cloud
cover.» The Biggest Control Knob: Carbon Dioxide in Earth's Climate History, Richard B. Alley, Ph.D., Penn State, American Geophysical Union (AGU) lecture, December, 2009.
In spite of the dying debate, it is known that coal-burning power plants, automobile exhausts, factory smokestacks, and other waste vents contribute about 22 billion tons of CO2 (6 billion tons of pure carbon) and other greenhouse gases into the earth's atmosphere each year. CO2 levels have increased by about 31% since 1750, about 75% of which can be attributed to fossil fuel burning. The remaining 25% is largely due to land-use change, particularly deforestation.
In their 2006 report, the IPCC
stated that the atmospheric concentration of CO2
has exceeded levels over the natural range for the last 650,000 years.
The consensus is that human activity is, in almost all aspects of global
warming, the most likely cause. This is a change from the previous report that stated human activity was merely a likely cause.
