Global warming refers to the recent increase in the Earth's temperature. The effects of this climate change are already being felt around the world. Scientists predict that temperatures will rise up to 6°C further over the next century. This may cause rises in sea level, extreme weather events such as hurricanes and heat waves, and war and disease, particularly in developing countries.
It is generally agreed that global warming is caused by greenhouse gases emitted by humans into the Earth's atmosphere. The biggest contributor is carbon dioxide, which is generated by burning fossil fuels such as coal, oil or gas. Every car or plane journey contributes directly to the Earth's change in climate. Most of the world's electricity is also generated from these fuels, despite renewable alternatives such as wind and solar power.
The ideal solution would be an immediate and drastic drop in global carbon emissions. However this is not going to happen in our lifetimes. In fact, rapid economic development in countries such as China and India, as well as ongoing growth in the rest of the world, mean that carbon emissions are still increasing year on year. The Kyoto Protocol is a first international attempt to address the issue seriously, but it has met with limited success.
Carbon credits (or carbon offsets) offer an interim solution for companies and individuals. After calculating the quantity of carbon emitted by flying, driving and using electricity, the carbon emitter pays for a project that reduces carbon emissions by this same amount. Since greenhouse gases circulate freely in the atmosphere, this project can be located anywhere in the world.
Carbon Catalog lists many different types of carbon project. Those involving solar, wind andhydroelectric power generate energy from renewable sources instead of fossil fuels. Others reduce fuel use by increasing efficiency, switching fuels, or generating heat and electricity together.
Many projects lower energy requirements via better lighting, materials, buildings or public transport.
After carbon dioxide, the second most important greenhouse gas is methane.
While there is much less methane in the atmosphere, every tonne causes 20-70 times as much warming as a tonne of carbon dioxide. Many projects capture industrial or agricultural methane and burn it to generate energy.