NEPA Procedures - Global Climate Change
Climate represents a long term average of various weather features such as temperature
and precipitation. A 30-year average is normally used to define climate at any
particular location. Climate determines how resources such as water and vegetation
are distributed and, until the onset of technology, climate also determined where people
lived and worked. Many factors, such as topography, proximity to large bodies of
water, and latitude affect a particular location's long-term climate.
Climate is subject to variations over various time scales ranging from decades to
hundreds of thousands of years. In recent years there has been a great deal of
concern about possible anthropogenic effects on global climate caused by emissions of the
so-called “greenhouse” gases. The most important greenhouse gases emitted
by human activities are carbon dioxide, methane, nitrous oxides, and chlorofluorocarbons.
These gases have the capability of affecting the heat balance of the atmosphere by
absorbing heat radiated from the earth’s surface and re-radiating it back down to the
surface, thereby causing surface temperatures to rise.
It must be remembered that there are natural greenhouse gases in the atmosphere, most
notably carbon dioxide and water vapor. These, along with other gases form a natural
blanket that traps heat in our atmosphere, without which the earth would be a frigid place
with very little life. This process is often called the "greenhouse
effect," but it doesn't work quite like a greenhouse. A greenhouse stays warm
because the glass roof allows solar energy in, but prevents heat loss through mixing with
the cooler air outside. The concern is that the large increase in the greenhouse
gases as a result of industrialization is resulting in warming on a global scale.
Temperature records over the last 100 years have shown a steady warming of
the atmosphere. Temperature trends are not the same over all areas of the
globe; there are large regional variations caused by the different ways the atmosphere
responds in various areas. The Intergovernmental Panel on Climate Change (IPCC) has
conducted a comprehensive assessment of all aspects of global climate change.
