The Greenhouse Effect

Human activity alters local climate in a number of ways. We produce smoke that creates smogs and we churn up dust that shades us from the sun. We chop down the rainforests that recycle rainfall and make areas downwind drier.  But the number one impact of human activity on climate is to increase the “greenhouse effect”. It threatens to be global, long lasting and hard to reverse. The gases that contribute to the effect are being emitted from our power stations and vehicle exhaust pipes, our farms and our forests and they can stick around in the air for decades or centuries.  The greenhouse effect works like this. As the sun’s radiation hits the Earth’s surface, some of it is reflected right back into space, but much of it is absorbed by the land and oceans as infrared radiation—or heat. Some of the heat escapes into space, but a lot is trapped by greenhouse gases close to the Earth’s surface, causing the atmosphere to heat up.  The three most significant greenhouse gases are water vapour, carbon dioxide and methane. These greenhouse gases are naturally present in the air. Without them we would freeze. But the more concentrated they are, the more we heat up the planet.  Pumping greenhouse gases into the atmosphere is like putting an extra blanket over the Earth. We are starting to warm up. And there are other changes. Higher temperatures increase evaporation from the oceans and increase the atmosphere’s capacity to hold water. So, the air is getting wetter in many areas. And a hotter atmosphere is more energetic, so that it is able to generate stronger storms and other extreme weather events.