Global warming is the slow increase in the average temperature of the earth’s atmosphere because an increased amount of the energy (heat) striking
the earth from the sun is being trapped in the atmosphere and not radiated out into space.
The earth’s atmosphere has always acted like a greenhouse to capture the sun’s heat,
ensuring that the earth has enjoyed temperatures that permitted the emergence of life forms as we know them, including humans.
Without our atmospheric greenhouse the earth would be very cold. Global warming, however,
is the equivalent of a greenhouse with high efficiency reflective glass installed the wrong way around.
So much heat is being kept inside greenhouse earth that the temperature of the earth is going up faster than at any previous time in history.
NASA provides an excellent course module on the science of global warming
Climate is changing! Why should we be worry about it?
Because it will affect people around the world. Rising global temperatures are expected to raise sea levels,
and change precipitation and other local climate conditions.
Changing regional climate could alter forests, crop yields, and water supplies.
It could also affect human health, animals, and many types of ecosystems.
Deserts may expand into existing rangelands, and features of some of our National Parks and National Forests may be permanently altered.