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TED-Ed 075・・Climate change ： Earth's giant game of Tetris
　　　　　　　　　（気候変動 ： 地球の巨大ゲーム『テトリス』）


易・・03分・・175wpm　　2014/05/28 新出　　英語字幕なし。日本語字幕あり。
　
★下記英文はｸﾞｰｸﾞﾙのマウスオーバー辞書が使えます｡　　　　　　（YouTubeが見易い))

To understand climate change, think of the game "Tetris."
For eons（長い間）, Earth has played a version of this game with blocks of carbon.

They enter the atmosphere as carbon dioxide gas from volcanoes, decaying plant matter, breathing creatures and the surface of the sea. And they leave the atmosphere when they're used by plants during photosynthesis（光合成), absorbed back into the ocean, or stored in soil and sediment.

This game of Tetris is called the carbon cycle, and it's the engine of life on Earth.

What's the connection to climate? Well, when that carbon dioxide is in the air, waiting to be reabsorbed, it traps a portion of the sun's heat, which would otherwise escape to space. That's why carbon dioxide is called a greenhouse gas.

It creates a blanket of warmth, known as the greenhouse effect, that keeps our Earth from freezing like Mars. The more carbon dioxide blocks hang out in the atmosphere waiting to be cleared, the warmer Earth becomes.

Though the amount of carbon in the atmosphere has varied through ice ages and astroid impacts, over the past 8,000 years the stable climate we know took shape, allowing human civilization to thrive.

But about 200 years ago, we began digging up that old carbon that had been stored in the soil. These fossil fuels, coal, oil and natural gas are made from the buried remains of plants and animals that died long before humans evolved. The energy stored inside them was able to power our factories, cars and power plants.

But burning these fuels also injected new carbon blocks into Earth's Tetris game. At the same time, we cleared forests for agriculture, reducing the Earth's ability to remove the blocks. And since 1750, the amount of carbon in the atmosphere has increased by 40%, and shows no sign of slowing.

Just like in Tetris, the more blocks pile up, the harder it becomes to restore stability. The extra carbon dioxide in the atmosphere accelerates the greenhouse effect by trapping more heat near the surface and causing polar ice caps to melt.

And the more they melt, the less sunlight they're able to reflect, making the oceans warm even faster. Sea levels rise, coastal populations are threatened with flooding, natural ecosystems are disrupted, and the weather becomes more extreme over time.

Climate change may effect different people and places in different ways. But, ultimately, it's a game that we're all stuck playing. And unlike in Tetris, we won't get a chance to start over and try again.
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