Global Warming

Nowadays, to prevent global warming is becoming more and more important. For years, the level of human’s life is increase. And of course, this cause lots of other things and all of this result in global warming.

As we all know, global warming means not only the temperature of all parts of the world to increase, but harm human’s life as well. In spite of this, many people still spoil our life and pollute the environment for their own benefit. Because of this, I want to say: Present, the earth is human’s only home, it is like a mother protects us as her baby. If we don’t love our mother, what could we do else?

You know, Egypt is a very big country in North Africa and ninety percent of the land area is desert which is hot and seldom rains in all the year. That’s because human’s improper development of nature. The country is suffering from the effects of the global warming and I believe that many countries near the Equator have this pain as well.

Now, let’s talk about the dangers of global warming in the polar region. There are polar bears in arctic and penguins at the south polar. They are the peculiar animals at the polar region. Global warming causes the icebergs to melt and these animals will disappear in the world. For the cute animals, we also need to prevent global warming.

In my opinion, though global warming causes many dangerous things, it can avoid if people pay attention to this. And after this, we will have a better life and live in a more beautiful world.

I had finished my speaking. Hope you will have a new, extensive understanding of global warming. Thank you!

 

第二篇：global warming 原文

SAN FRANCISCO - Rising seas, melting polar ice caps (两极的冰盖

)and strange weather tend to grab headlines as Earth's climate grows warmer. But there are other dramatic outcomes that scientists are only beginning to grasp and which could damage structures in northern areas, reconfigure重新装配towering mountains and alter biology.

As winters get milder温暖的, changes occur underfoot and go largely unnoticed until critical thresholds are reached. Railroad tracks are deformed变形的. Rocky peaks crack apart and spill into ravines峡谷 . Whole mountainsides山腰lose footing, creating flows of ice and mud that move as fast as a BMW on the Autobahn.

Thawing out

Seasonally frozen areas in the Northern Hemisphere decreased by 15 to 20 percent during the 20th Century, In the last 20 years, the decrease is more dramatic," he said.

In locations across the former Soviet Union, where long-running observations are starting to generate导致 meaningful results, the warm-up has been documented as a 1-degree increase in the average temperature of soil 16 inches (40 centimeters) below the surface. "The change is real," Zhang said. "It is happening."

The effect is not just in the far north. Some 80 percent of U.S. soil freezes every winter. Change to the cycle will affect crops, native plants and even how much carbon is exchanged between Earth's surface and atmosphere, Zhang and others say.

There is "widespread evidence" that global warming is responsible for the observed changes in seasonally frozen soil and permafrost永久冻土层, said Frederick Nelson, a geographer at the University of Delaware. Deep-seated change

Nelson examines what happens below the surface.

Permafrost exists at depth, and the surface layer above it freezes seasonally. When the seasonal freezing is of shorter duration, 持续期间 owing to climate warming, the seasonal thaw runs deeper and extends into the former permafrost, Nelson told Live Science. The active layer -- freezing and thawing each year -- grows deeper.

Because water in the soil expands when frozen and loses volume体积upon melting, it causes uneven不均匀的movements in the ground surface. Under

sustained climatic warming, the consequences of disappearing permafrost could be "very severe" for structures, Nelson said.

The problem could be particularly acute严重的for urban and suburban places in the far North, such as Barrow and Fairbanks, Alaska. Nelson notes, however, the problem can be mitigated减轻if engineers look ahead.

Zhang is helping the builders of an ambitious Tibetan railroad do just that.

The Qinghai-Xizang railroad will be 695 miles (1,118 kilometers) long when completed in 2007. Most of it is above 13,000 feet (4 kilometers), and about half of it is being built on permafrost, much of which is likely to melt in coming years, Zhang said.

So Zhang has helped the engineers devise想出 an insulation隔离system -- a thick layer of crushed rock over the permafrost.

All of Nature can't be insulated, however.

Mountain makeovers

Antoni Lewkowicz of the University of Ottawa has studied several northern landslides and rockslides that he says can be at least partially attributed to thinning and weakening of ice or permafrost caused by climate warming. In one case, an earthquake broke off a weakening glacier in the Yukon. About 500,000 tons of ice raced down a mountain.

"By the time it reached the bottom it would have been going about 140 mph," Lewkowicz said.

At other remote catastrophe sites, Lewkowicz has documented a bizarre奇形怪状的situation in which thin permafrost sits atop unfrozen sand containing groundwater under pressure. The system is stable until the icy overlay gets slushy融雪的. The whole mess then gives way.

Some of these events expose a layer of earth -- perhaps a very salty layer -- on which nothing can grow for years, resulting in "profound ecological .生态的effects," Lewkowicz said.

And landslides山崩like this could become common if the climate grows warmer, as many scientists expect it will.

Charles Harris of Cardiff University in the United Kingdom documented rockslides high in the Swiss Alps that, again, were related to thawing permafrost. During 2003, the warmest summer on record in the Alps, the

slushy active layer of the permafrost moved down from its long-term average depth of 15 feet (4.5 meters) to 29 feet (9 meters).

"There is likely to be an increase in rockfalls and landslides" at high-altitude sites, Harris said.

More research is needed, the scientists agree, to understand exactly what is happening globally, what the future holds, and what might be done to mitigate certain problems.

Many parts of the planet haven't been closely examined. And there are several causes and effects that haven't been explored. Heavy rainfall, for example, could be a contributing factor to some of the landslides and rockslides, and other studies predict heavier rainfall is one possible result of climate warming.

Nelson, the University of Delaware geographer, says thawing permafrost will "profoundly affect" biological activity in ways that are not fully known.

, climatic warming might be expected to degrade使降解permafrost, but the relationship may not be quite so straightforward," Nelson said. "A warming climate may also increase the number and density密度of shrubby灌木的plants that shade the surface, which could ultimately help to protect the permafrost. The jury is still out on a lot of this."