Lochluichart wind farm - Greenhouse Gasses


	Climate change

	The science of climate change \| How much polution can we allow
	Greenhouse gases and their sources
	Carbon dioxide seems to act like a thermostat for the planet. The amount of carbon dioxide in the atmosphere has shadowed global temperatures for hundreds of millions of years.
	When levels are low we have ice ages; when they rise, the planet heats up. And humans are now adding carbon dioxide to the atmosphere at a rate that may be unprecedented.
	We are releasing carbon dioxide by destroying the planet's forests—carbon stored in trees returns to the air as they burn or rot. Similarly, and more importantly, we are releasing large amounts of carbon dioxide as we burn fossil fuels made of carbon, like coal and oil. Since 1800, the atmospheric concentration of carbon dioxide has risen from 270 to 370 parts per million—higher than at any time for 20 million years. Every tonne of carbon dioxide we add to the atmosphere increases the concentration, as the gas typically remains there for a century or more before disappearing. Scientists reckon a 60 percent cut in emissions below 1990 levels will be necessary to halt the rise. Anything less will only slow the rate of accumulation.
	The second most important man-made greenhouse gas is methane, which is produced by certain bacteria that thrive in human generated environments. These bacteria are found in landfills, rice paddies and the guts of our herds of ruminant animals, like cows and sheep.
	Methane is also present naturally underground. And we are releasing this methane from coal mines and from natural gas pipelines. Even the rotting vegetation in tens of thousands of giant water reservoirs could be adding to the build-up of methane in the atmosphere. Methane levels are now more than twice pre-industrial levels—and probably higher than for half a million years.
	There are other human sources of greenhouse gases. Putting nitrogen fertiliser onto soils increases the amount of nitrous oxide emitted into the air. And some ozone-destroying gases like CFCs—as well as some of their ozone-friendly replacements—are also powerful greenhouse gases. All of these will need to be controlled if climate change is to be slowed.