Ecosystems / Air
Take a deep breath, and you play your part in the constant recreation of the atmosphere of the earth. The mixture of gases that wraps itself like a gossamer mantle around our planet not only makes life possible; life in turn has its effect on the planetary atmosphere.
It was not ever thus. Primordial earth’s atmosphere contained no oxygen. Then life appeared in the oceans; eventually micro-organisms evolved that used sunlight to produce energy. The byproduct of this photosynthesis was oxygen, which was released into the atmosphere. Carbon was trapped in the fossilized bodies of these micro-organisms and fell to the ocean floors, and over aeons became fossil fuels. Slowly the earth became a planet with a cooler, oxygen-rich atmosphere, and the blossoming of life began in earnest. The earth’s atmosphere, made up of a delicately balanced blanket of gases, traps enough heat to sustain life. These fundamental gases shape the environmental conditions on the planet, such as rainfall and evaporation levels.
But as humans have cleared critical photosynthesizing plants and organisms, and burned more and more fossil fuels, the balance that made most life on earth possible has been upset. Levels of atmospheric carbon dioxide and other polluting gases have been rising steadily since the Industrial Revolution, and with disastrous results.
These gases create a ‘greenhouse effect’, thickening the natural canopy of gases in the atmosphere and causing more heat to become trapped. As a result, the global temperature is increasing, throwing the world’s climate out of its natural balance and into chaos.
The global temperature is set to rise by between 1.5 and 5.8°C and sea level by between 10 and 90 cm, as a result of global warming. The impacts, particularly of changes in rainfall, are likely to be severe, especially in many developing countries. Any action taken now – to reduce carbon emissions, for example – will have a delayed reaction as global temperatures continue to rise. But to take no action at all – effectively the preferred policy worldwide – is simply to invite disaster.
AIR – THE FACTS
The global warming caused by this greater concentration of carbon in the air is producing an anticipated speed of climate change greater than anything seen for at least 10,000 years.
Among the anticipated consequences of increased global temperatures are:
• flooding as polar ice caps melt, raising sea levels;
• extreme weather events due to shifting ocean currents;
• deserts to spread across Europe as land dries up.
Historic and Projected Variations of the Earth’s Surface Temperature
Source: Millennium Ecosystem Assessment
© Copyright 2005 New Internationalist
Publications Ltd. All rights reserved.