By the middle of the twenty first century, there is evidence that the Earth will be warmer than it has been at any time in human history, and quite possibly since the end of the dinosaurs, some 65 billion years ago. If we stay at the rate we our now (fossil fuel consumption / growth in population) then within the next two century the Earth's air might not be fit to breath. Many people in the world do not think that this is a major concern and that it is normal for the Earth's temperature to increase. However, if this temperature increase is put into perspective of several hundred years, there will be many devastating effects. This is why most scientists view global warming as a very serious and severe threat. Global warming does not require a reduction of the standard of living of people. However it does demand a rapid shift in the patterns of consumption of fuels such as oil, coal, and natural gas, to an economy more reliant on solar energy, hydrogen gas, wind biomass, and other renewable energy sources.
The term greenhouse effect is used to describe the increased warming of the Earth's surface and lower atmosphere due to increased levels of carbon dioxide and other atmospheric gases that absorb radiated energy in the atmosphere and then reradiate it back to the surface. But if it were not for the greenhouse effect, temperatures at the Earth's surface today would be much colder then they are now, and life as we know it could not exist. Scientists are now concerned that the greenhouse gases are being increased by human actions to levels that could be very harmful to life on Earth. Almost all specialists agree that without