Global Climate Change Page: 5 of 18

                                
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Climate Change, if it were to become a treaty in force, would also regulate three other trace
gases: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6),
whose limited concentrations in the atmosphere are anticipated to grow over the long-term.
Sulfate aerosols, a byproduct of air pollution, and other natural phenomena, are also viewed
as important for their transient and regional "climate cooling" effects in Earth's atmosphere.
The amount of carbon cycling fromnaturally occurring processes each year through the
biosphere as CO2 is enormous  some 800 billion tons. Ice cores and other proxy climate
data, which also indicate CO2 concentrations in the atmosphere, have shown, in general, a
relatively stabile global climate, at least over the past 10,000 years. As such, many scientists
suggest that the amount of CO2 generated by natural processes is about equal to the amounts
absorbed and sequestered by natural processes. However, human activity since the Industrial
Revolution (c.a. 1850), and primarily in the form of burning fossil fuels, is now generating
some additional24 billion tons of CO2 per year. Available evidence shows that about half this
amount is absorbed by natural processes on land and in the ocean, and that atmospheric
concentrations of CO2 are now about 32% higher than they were some 150 years ago. Some
scientists suggest that a large amount of CO2 may be stored in northern latitude soils and in
temperate and tropical forests, suggesting a greater importance of the role of natural
resources management and land-use practices in these regions, including burning of biomass
and deforestation. Scientists estimate that anthropogenic emissions of CO2 alone may
account for as much as a 60% increase in global mean temperatures of 0.90F, since 1850. For
more information on the science of global climate change, visit the CRS Electronic Briefing
Book: Global Climate Change web site. [http://www.congress.gov/brbk/html/ebgcc1.html].
State-of-the-art computer models of the Earth's climate (GCMs) have projected a
globally averaged warming of 3 to 8 degrees F over the next 100 years, if greenhouse gases
continue to accumulate in the atmosphere at the current rate. Prominent climate scientists
believe that such a warming could shift temperature zones, rainfall patterns, and agricultural
belts and, under certain scenarios, and cause sea level to rise. They further predict that global
warming could have far-reaching effects  some positive, some negative depending how it
may be experienced in a given region  on natural resources; ecosystems; food and fiber
production; energy supply, use, and distribution; transportation; land use; water supply and
control; and human health.
So-called "skeptics" of the global warming theory have called into question the reliability
of the computer climate models and their output used to make projections of future warming
that supported Kyoto Protocol negotiations. They also challenge some scientists' assertions

that, although recent episodic weather events may seem more extreme in nature, this is
indicative of long-term climate change. The Clinton Administration received criticism about
attributing seemingly more frequent weather anomalies to a warming of the climate. And so
the scientific questions remains: Can scientists now confirm that humans are indeed, at least
in part, the cause of recent climate changes? Also, as a result of this, is the Earth committed
to some degree of future global warming? If so, then what might be the consequences, and
what if any of those might be prevented?
Evidence of natural variability of climate is large enough that even the record-setting
warmth at the end of the 20th century does not allow a vast majority of knowledgeable
scientists to state beyond a reasonable doubt that weather extremes experienced over the past
two decades are attributable to "global warming," at least at the present time. However, the

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01-12-01