Global Warming

Introduction

Global warming refers to a long-term increase in the Earth's average surface temperature that results in large-scale changes in global climate, including redistribution of climatic zones defined by temperature, precipitation, and associated ecosystems. Global climate changes and episodes of global warming, have occurred throughout geologic history as a result of natural variations in incoming solar radiation, atmospheric chemistry, and oceanic and atmospheric circulation.

Anthropogenic, or human-caused, global warming and climate change are an ongoing outcome of human activities during the last 150 years, that is, since the Industrial Revolution, when human burning of fossil fuels multiplied many times. Scientific data show that atmospheric concentrations of carbon dioxide, methane, nitrous oxide, and human-made chemicals called halocarbons are increasing as a result of emissions associated with human activities, and models predict that this environmental change may lead to global warming. Studies of Antarctic ice cores published in 2005 showed that atmospheric carbon dioxide is now 27% higher than any other point in the last 650,000 years.

Predictions and Evidence of Global Warming

Most atmospheric scientists today, with few exceptions, are convinced that the well-documented increase in greenhouse gases is resulting in an intensification of Earth's naturally occurring greenhouse effect, with resulting climate change. The exact climatic response to increased concentrations of radia-tively active gases, and its potential effects on humans are, however, difficult to predict. If global climate change proceeds as most recent scientific studies forecast, it will have substantial and disastrous climatic, ecological, and sociopolitical consequences.

The Earth's surface is surface temperature is variable from place to place and over time. Furthermore, the systems that interact to maintain the planet's temperature and climate are extremely complex; cause-and-effect relationships between changes in one system, the atmosphere in this case, and results in another, global climate, are very difficult to predict, observe, and “prove.” In spite of these scientific challenges, there is significant evidence that the Earth has warmed significantly during the past 150 years or so, and that global climate has responded to the temperature increase. Climate records show a 1°F increase in the average temperature of the Earth's oceans, atmosphere, and solid surface since the late 1900s. Geologic and historical studies document dramatic thinning and shrinkage of the polar ice caps, and retreat of Earth's alpine glaciers. Less conclusive, but still suggestive, data supporting anthropogenic global warming include a several centimeter increase in global sea-level since 1900, and alterations in large-scale weather phenomena like the southeast Indian monsoon, Atlantic hurricane season, El Niño Southern Oscillation, and North African drought cycle.

Other predicted consequences of warming include large-scale shifts in atmospheric and oceanographic circulation patterns, melting of the polar ice caps, global sea-level rise, reorganization of the Earth's climatic zones, and establishment of new large-scale weather patterns. Such changes in the distribution of heat, precipitation, and weather phenomena like storms and floods would affect the productivity and distribution of natural and managed vegetation. Animals and microorganisms would experience dramatic changes in their habitats, and perhaps face much higher rates of species extinction. Most ecologists consider ...