English /German . . . . . CAN Europe homepage . . . . . .Back to intro "What YOU can do" page
Climate Change is likely to have a significant impact on the global environment. In general, the faster the climate changes, the greater will be the risk of damage. Mean sea level is expected to rise 15-95 cm by the year 2100, causing flooding of low-lying areas and other damage. Climatic zones could shift towards the poles by 150-550 km in the mid-latitude regions. Forests, deserts, rangelands and other unmanaged ecosystems would face new climatic stresses. As a result, many will decline or fragment, and individual species will become extinct.
Human society will face
new risk and pressures. Food security is unlikely to be threatened at the global
level, but
some regions are likely to experience food shortages and hunger. Water resources
will be affected as precipitation
and evaporation patterns change around the world. Physical infrastructure will
be damaged, particularly by sea-level
rise and by extreme weather events. Economic activties, human settlements, and
human health will experience many
direct and indirect effects. The poor and disadvantaged are the most vulnerable
to the negative consequences of
climate change.
The earth's climate is driven by a continuous flow of energy from the sun. This
energy arrives mainly in the form of visible light. About 30% is immediately
scattered back into space, but most of the 70% that is absorbed passes down
through the atmosphere to warm the earth's surface. (Without this natural greenhouse
effect the earth would be about 30 degrees Celsius cooler and would be unfit
for us to live on!). The earth must send this energy back into space in the
form of infrared radiation. Being much cooler than the sun, the earth does not
emit energy as visible light. Instead, it emits infrared, or thermal radiation.
"Greenhouse gases" in the atmosphere block infrared radiation from escaping directly from the suface to space. Infrared radiation cannot pass straight through the air like visible light. Instead, most departing energy is carried away from the surface by air currents and clouds, eventually escaping to space from altitudes above the thickest layers of the greenhouse gas blanket.
The main greenhouse gases are water vapour, carbon dioxide, ozone, methane, nitrous oxide, and the chlorfluorcarbons (CFCs). Levels of all key greenhouse gases (with the possibel exception of water vapour) are rising as a direct result of human activity. Emissions of carbon dioxide (mainly from burning coal, oil, and natural gas), methane and nitrous oxide (due to agriculture and changes in land use), ozone (generated by chemical reactions to the fumes in car exhausts) and CFCs (manufactured by industry) are changing how the atmosphere absorbs energy. This is all happening at an unprecedented speed.The result is known as the "enhanced greenhouse effect".
The climate system must adjust to rising greenhouse gas levels to keep the global "energy budget" in balance. In the long term, the earth must get rid of energy at the same rate at which it receives energy from the sun. Since a thicker blanket of greenhouse gases helps to reduce energy loss to space, the climate must change somehow to restore the balance between incoming and outgoing energy. This adjustment will include a "global warming" of the earth's surface and lower atmosphere. But this is only part of the story. Warming up is the simplest way for the climate to get rid of the extra energy. But even small rise in temperature will be accompanied by many other changes: in cloud cover and wind patterns, for example. Some of these changes may act to enhance the warming, others to counteract it.
