This page best viewed at 600 x 800 pixels using Microsoft Internet Explorer 4 or higher or Netscape Navigator 4 or higher . But now, science is discovering that many of our everyday activities are slowly changing the climate, in Montana and around the world. And while the effects may seem barely perceptible at first, they will grow over time and result in major changes that will alter our children's future. But these gases called greenhouse gases because they allow sunlight to pass through, but they trap heat close to Earth, just like a greenhouse have increased dramatically over the last 100 years . There is little dispute among scientists that these increases are due to human activities largely deforestation and the burning of fossil fuels.
Skeptics correctly state that most of the gases that are emitted are from natural sources.
For instance, plants give off molecules of carbon dioxide at night and swamps release methane. But our natural systems have evolved over millions of years resulting in a delicate balance between what is emitted through natural processes and what can be absorbed through other natural processes. And because these gases stay in the atmosphere for a very long time 300 years for carbon dioxide even relatively small additions build up over time, thickening the blanket that encircles the Earth. Because of this, the carbon dioxide humans have already emitted will still be influencing climate for years to come regardless of when we begin reducing emissions in the future. These carbon reservoirs have important implications for any current and future policy decisions regarding regulation and reduction of greenhouse gas emissions.