Global Warming

Introduction:

According to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is a result of increased human activities in the technological and industrial development. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases – primarily carbon dioxide, methane, and nitrous oxide. All these gases possess heat trapping properties, scientists are yet not sure how the earth responds to them.

Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. Scientists expect that the average global surface temperature could rise in the next fifty years, with significant regional variation. Evaporation will increase as the climate warms, which will increase average global precipitation. Soil moisture is likely to decline in many regions, and intense rainstorms are likely to become more frequent. Sea level is likely to rise two feet along most of the U.S. coast. Scientists also predict the melting down of glaciers in the Poles, which will increase the sea level submerging low land areas.

The adverse impacts of global warming:

Rising global temperatures are expected to raise sea level, and change precipitation and other local climate conditions. Changing regional climate could alter forests, crop yields, and water supplies. It could also affect human health, animals, and many types of ecosystems. Deserts may expand into existing rangelands, and features of some of our National Parks may be permanently altered. Many of the potentially most important impacts depend upon whether rainfall increases or decreases, which can not be reliably projected for specific areas.

Greenhouse gases:

Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occuring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: What Are Emissions Inventories? An emission inventory is an accounting of the amount of air pollutants discharged into the atmosphere. It is generally characterized by the following factors: the chemical or physical identity of the pollutants included, the geographic area covered, the institutional entities covered, the time period over which emissions are estimated, and the types of activities that cause emissions. Emission inventories are developed for a variety of purposes. Inventories of natural and anthropogenic emissions are used by scientists as inputs to air quality models, by policy makers to develop strategies and policies or track progress of standards, and by facilities and regulatory agencies to establish compliance records with allowable emission rates. A well constructed inventory should include enough documentation and other data to allow readers to understand the underlying assumptions and to reconstruct the calculations for each of the estimates included.

Serious changes taking place in the Arctic