Glaciers are melting, sea levels are rising, cloud forests are drying, and wildlife is scrambling to keep pace. It's becoming clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than in the last 650,000 years.
We call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. As the Earth spins each day, the new heat swirls with it, picking up moisture over the oceans, rising here, settling there. It's changing the rhythms of climate that all living things have come to rely upon.
What will we do to slow this warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the face of the Earth as we know it—coasts, forests, farms and snow-capped mountains—hangs in the balance.
Snow-mantled crags frame the severe beauty of Queen Maud Land in central Antarctica. Discovered in 1820, the region is known for its jagged peaks with forbidding names like the Jaw of Fenris and The Razor.
In recent years, global warming has been the subject of a great deal of political controversy. As scientific knowledge has grown, this debate is moving away from whether humans are causing warming and toward questions of how best to respond.
Signs that the earth is warming are recorded all over the globe. The easiest way to see increasing temperatures is through the thermometer records kept over the past century and a half. Around the world, the earth's average temperature has risen more than 1 degree Fahrenheit (0.8 degrees Celsius) over the last century, and about twice that in parts of the Arctic.
This doesn’t mean that temperatures haven't fluctuated among regions of the globe or between seasons and times of day. But if you average out the temperature all over the world over the course of a year, you see that temperatures have been creeping upward.
Although we can't look at thermometers going back thousands of years, we do have some records that help us figure out what temperatures and concentrations were like in the distant past. For example, trees store information about the climate in the place where they live. Each year, trees grow thicker and form new rings. In warmer and wetter years, the rings are thicker. Old trees and wood can tell us about conditions hundreds or even several thousands of years ago.
Keys to the past are also buried under lakes and oceans. Pollen, creatures and particles fall to the bottom of oceans and lakes each year, forming sediments. Sediments preserve all these bits and pieces, which contain a wealth of information about what was in the air and water when they fell. Scientists reveal this record by inserting hollow tubes into the mud to collect sediment layers going back millions of years.
For a direct look at the atmosphere of the past, scientists drill cores through the earth's polar ice sheets. Tiny bubbles trapped in the gas are actually pieces of the earth's past atmosphere, frozen in time. That's how we know that the concentrations of greenhouse gases since the industrial revolution are higher than they've been for hundreds of thousands of years.
Computer models help scientists to understand the Earth's climate, or long-term weather patterns. Models also allow scientists to make predictions about the future climate. Basically, models simulate how the atmosphere and oceans absorb energy from the sun and transport it around the globe. Factors that affect the amount of the sun's energy reaching Earth's surface are what drive the climate in these models, as in real life. These include things like greenhouse gases, particles in the atmosphere (such as from volcanoes), and changes in energy coming from the sun itself.
articles from National Gerographic & Natural Resources Defense Council
Have you seen 2012 movie?there are some scene really amaze me..it show that the scientist are giving explanation of how the world fall..the water level of the ocean increase, the artic and antartica ice started melting, volcano began active, pollutions increase etc.. so, as a human what would you do? Even small little things is enough for our enviroment..simple air pollution: BURN RUBBISH everyday..everyday i went out from home to office,oh my God!my cloth! the smoke of the burn rubbish..actually my nose are sensitive, it cause a running nose..i am allergy of smoke & dust..don't you know, because of it i almost suffered asthma. But my doctor said, you are lucky!when i get back home..smoke again..huhu..the clothes hanging there to dry, got the smell of the smoke..oh neighbourhood..stop burning..even the smoke didn't get to your house, but it come to my house & nose..hard to feel the fresh air..well because of that..hard for me to take a walk with my nephew.i don't want her to suffer asthma..kids are sensitive you know..