WEBVTT 99:59:59.999 --> 99:59:59.999 think of the game Tetris. 99:59:59.999 --> 99:59:59.999 For eons Earth has played a version of this game with blocks of carbon. 99:59:59.999 --> 99:59:59.999 They enter the atmosphere as carbon dioxide gas from volcanoes, 99:59:59.999 --> 99:59:59.999 decaying plant matter, 99:59:59.999 --> 99:59:59.999 breathing creatures 99:59:59.999 --> 99:59:59.999 and the surface of the sea. 99:59:59.999 --> 99:59:59.999 And they leave the atmosphere when they're used by plants during photosynthesis, 99:59:59.999 --> 99:59:59.999 absorbed back into the ocean 99:59:59.999 --> 99:59:59.999 or stored in soil and sediment. 99:59:59.999 --> 99:59:59.999 This game of Tetris is called the carbon cycle, 99:59:59.999 --> 99:59:59.999 and it's the engine of life on Earth. 99:59:59.999 --> 99:59:59.999 What's the connection to climate? 99:59:59.999 --> 99:59:59.999 Well, when that carbon dioxide is in the air, 99:59:59.999 --> 99:59:59.999 waiting to be reabsorbed, 99:59:59.999 --> 99:59:59.999 it traps a portion of the sun's heat, 99:59:59.999 --> 99:59:59.999 which would otherwise escape to space. 99:59:59.999 --> 99:59:59.999 That's why carbon dioxide is called a Greenhouse Gas. 99:59:59.999 --> 99:59:59.999 It creates a blanket of warmth, 99:59:59.999 --> 99:59:59.999 known as the Greenhouse Effect, 99:59:59.999 --> 99:59:59.999 that keeps our Earth from freezing like Mars. 99:59:59.999 --> 99:59:59.999 The more carbon dioxide blocks hang out in the atmosphere waiting to be cleared, 99:59:59.999 --> 99:59:59.999 the warmer Earth becomes. 99:59:59.999 --> 99:59:59.999 Though the amount of carbon in the atmosphere 99:59:59.999 --> 99:59:59.999 has varied through ice ages and astroid impacts, 99:59:59.999 --> 99:59:59.999 over the past 8,000 years the stable climate we know took shape, 99:59:59.999 --> 99:59:59.999 allowing human civilization to thrive. 99:59:59.999 --> 99:59:59.999 But about 200 years ago, 99:59:59.999 --> 99:59:59.999 we began digging up that old carbon that had been stored in the soil. 99:59:59.999 --> 99:59:59.999 These fossil fuels, coal, oil and natural gas 99:59:59.999 --> 99:59:59.999 are made from the buried remains of plants and animals 99:59:59.999 --> 99:59:59.999 that died long before humans evolved. 99:59:59.999 --> 99:59:59.999 The energy stored inside them was able to power 99:59:59.999 --> 99:59:59.999 our factories, cars and power plants. 99:59:59.999 --> 99:59:59.999 But burning these fuels also injected new carbon blocks into Earth's Tetris game. 99:59:59.999 --> 99:59:59.999 At the same time, we cleared forests for agriculture, 99:59:59.999 --> 99:59:59.999 reducing the earth's ability to remove the blocks. 99:59:59.999 --> 99:59:59.999 And since 1750, the amount of carbon in the atmosophere 99:59:59.999 --> 99:59:59.999 has increased by 40%, 99:59:59.999 --> 99:59:59.999 and shows no sign of slowing. 99:59:59.999 --> 99:59:59.999 Just like in Tetris, the more blocks pile up, 99:59:59.999 --> 99:59:59.999 the harder it becomes to restore stability. 99:59:59.999 --> 99:59:59.999 The extra carbon dioxide in the atmosphere 99:59:59.999 --> 99:59:59.999 accelerates the Greenhouse Effect 99:59:59.999 --> 99:59:59.999 by trapping more heat near the surface 99:59:59.999 --> 99:59:59.999 and causing polar ice caps to melt. 99:59:59.999 --> 99:59:59.999 And the more they melt, the less sunlight they're able to reflect, 99:59:59.999 --> 99:59:59.999 making the oceans warm even faster. 99:59:59.999 --> 99:59:59.999 Sea levels rise, coastal populations are threatened with flooding, 99:59:59.999 --> 99:59:59.999 natural ecosystems are disrupted, 99:59:59.999 --> 99:59:59.999 and the weather becomes more extreme over time. 99:59:59.999 --> 99:59:59.999 Climate change may effect different people and places in different ways. 99:59:59.999 --> 99:59:59.999 But, ultimately, it's a game that we're all stuck playing. 99:59:59.999 --> 99:59:59.999 And unlike in Tetris, 99:59:59.999 --> 99:59:59.999 we won't get a chance to start over and try again.