Air

Greenhouse gases

Greenhouse gases such as water vapor (the predominant one), carbon dioxide, methane, and nitrous oxide contribute to the greenhouse effect, a natural phenomenon that traps heat in the atmosphere. The gases result from natural processes (such as volcanoes, cloud cover, ocean currents and plant respiration) and human activities (such as the burning of fossil fuels and emissions from landfills and agricultural processes).

Since industrialization, human activities such as the burning of fossil fuels have increased the amount of greenhouse gases emitted into the atmosphere. There is active debate in scientific, environmental and policy sectors over the potential of greenhouse gases to enhance the greenhouse effect, forcing the atmosphere to warm and the climate to change. The increase of greenhouse gases in the atmosphere is one of several factors suspected of playing a role in heating and cooling the atmosphere (changes in the amount of solar energy reaching the Earth may be another).

Some environmentalists and scientists predict that rapid and continued warming of the Earth’s temperature could trigger serious consequences:

• increased temperatures of air and water around the world
• melting glaciers and increased sea levels
• impacts on water resources and availability
• extreme weather events (such as floods and droughts)
• health impacts (such as heat stress and the spread of infectious diseases)
• longer growing seasons in northern climates
• increased vegetation growth

At the same time, there are scientists who theorize that the expected warming is likely to follow a more gradual trend, as it has over the past several thousand years. They point to research showing changing levels of incoming solar radiation and the moderating effects of clouds, particulate matter and water vapor in the atmosphere.

Scientists agree that a great deal more research needs to be done into the enhanced greenhouse gas effect and the Earth’s carbon cycle, including the importance of clouds, the role of oceans in absorbing carbon dioxide and the impacts of natural climate events.

Meanwhile, there is increasing international pressure to slow the rate of man-made greenhouse gases and ultimately to reduce these emissions. In 1997, an international meeting of government representatives adopted the Kyoto Protocol to reduce/limit greenhouse gas emissions in developed countries and countries of the former Soviet Union. The Protocol proposes an overall reduction of 5.2 per cent below 1990 levels for greenhouse gases and provides for a complex array of different approaches to be adopted by individual countries to meet their emission reduction targets.