Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
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1.1. Background
Other reports in this collection
Aviation is an integral part of the infrastructure of today's society. It plays an important role in the global economy; it supports both commerce (through business travel
and air freight) and private travel. Aviation also plays an important role in military activity. As such, aviation affects the lives of citizens in every country in the world,
regardless of whether they fly. The activities of the civil air transport industry have long been circumscribed by matters of public interest in addition to economic factors.
Of most importance historically are matters related to safety and environmental issues associated with local noise and air pollution. Two global environmental issues
have emerged for which aviation may have potentially important consequences: Climate change, including changes to weather patterns (i.e., rainfall, temperature,
etc.), and, for supersonic aircraft, stratospheric ozone depletion and the resultant increase in UV-B radiation at the Earth's surface. Boxes 1-1 and 1-2 contain general
descriptions of the basic science and the political process related to these two issues (without addressing aviation in particular), respectively.
Box 1-1. Climate Change and the Framework Convention
Human activities release greenhouse gases into the atmosphere. The atmospheric concentrations of carbon dioxide, methane, nitrous oxide,
chlorofluorocarbons, and tropospheric ozone have all increased over the past century. These rising levels of greenhouse gases are expected to cause
climate change. By absorbing infrared radiation, these gases change the natural flow of energy through the climate system. The climate must somehow
adjust to this "thickening blanket" of greenhouse gases to maintain the balance between energy arriving from the sun and energy escaping back into space.
This relatively simple picture is complicated by increased amounts of sulfate aerosol from human activities that modulate incoming solar radiation and tend to
cause a cooling effect on climate, at least on regional and hemispheric scales.
Global mean surface air temperatures have increased by 0.3-0.6°C since the late 19th century, and recent years have been among the warmest on record.
Any human-induced effect on climate, however, is superimposed on natural climate variability resulting from climate fluctuations (e.g., El Niño) and external
causes such as solar variability and volcanic eruptions. More sophisticated approaches are now being applied to the detection and attribution of the causes
of change in climate by looking, for example, for spatial patterns expected from climate-forcing change by greenhouse gases and aerosols. To date, the
balance of the evidence suggests that there is a discernible human influence on the global climate.
Model projections of future climate, based on the present understanding of climate processes and using emission scenarios (IS92) based on a range of
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