1 00:00:06,367 --> 00:00:07,998 To understand climate change, 2 00:00:07,998 --> 00:00:09,747 think of the game Tetris. 3 00:00:09,747 --> 00:00:13,783 For eons Earth has played a version of this game with blocks of carbon. 4 00:00:13,783 --> 00:00:17,670 They enter the atmosphere as carbon dioxide gas from volcanoes, 5 00:00:17,670 --> 00:00:19,340 decaying plant matter, 6 00:00:19,340 --> 00:00:20,508 breathing creatures 7 00:00:20,508 --> 00:00:22,010 and the surface of the sea. 8 00:00:22,010 --> 00:00:25,930 And they leave the atmosphere when they're used by plants during photosynthesis, 9 00:00:25,930 --> 00:00:27,617 absorbed back into the ocean 10 00:00:27,617 --> 00:00:29,808 or stored in soil and sediment. 11 00:00:29,808 --> 00:00:32,185 This game of Tetris is called the carbon cycle, 12 00:00:32,185 --> 00:00:34,312 and it's the engine of life on Earth. 13 00:00:34,312 --> 00:00:36,700 What's the connection to climate? 14 00:00:36,700 --> 00:00:39,151 Well, when that carbon dioxide is in the air, 15 00:00:39,151 --> 00:00:40,904 waiting to be reabsorbed, 16 00:00:40,904 --> 00:00:42,783 it traps a portion of the sun's heat, 17 00:00:42,783 --> 00:00:44,782 which would otherwise escape to space. 18 00:00:44,782 --> 00:00:47,839 That's why carbon dioxide is called a greenhouse gas. 19 00:00:47,839 --> 00:00:49,537 It creates a blanket of warmth, 20 00:00:49,537 --> 00:00:51,219 known as the greenhouse effect, 21 00:00:51,219 --> 00:00:53,500 that keeps our Earth from freezing like Mars. 22 00:00:53,500 --> 00:00:57,885 The more carbon dioxide blocks hang out in the atmosphere waiting to be cleared, 23 00:00:57,885 --> 00:00:59,920 the warmer Earth becomes. 24 00:00:59,920 --> 00:01:01,883 Though the amount of carbon in the atmosphere 25 00:01:01,883 --> 00:01:05,010 has varied through ice ages and astroid impacts, 26 00:01:05,010 --> 00:01:09,385 over the past 8,000 years the stable climate we know took shape, 27 00:01:09,385 --> 00:01:12,218 allowing human civilization to thrive. 28 00:01:12,218 --> 00:01:13,967 But about 200 years ago, 29 00:01:13,967 --> 00:01:17,468 we began digging up that old carbon that had been stored in the soil. 30 00:01:17,468 --> 00:01:20,941 These fossil fuels, coal, oil and natural gas 31 00:01:20,941 --> 00:01:23,613 are made from the buried remains of plants and animals 32 00:01:23,613 --> 00:01:26,908 that died long before humans evolved. 33 00:01:26,908 --> 00:01:29,136 The energy stored inside them was able to power 34 00:01:29,136 --> 00:01:32,038 our factories, cars and power plants. 35 00:01:32,038 --> 00:01:37,083 But burning these fuels also injected new carbon blocks into Earth's Tetris game. 36 00:01:37,083 --> 00:01:40,087 At the same time, we cleared forests for agriculture, 37 00:01:40,087 --> 00:01:43,385 reducing the earth's ability to remove the blocks. 38 00:01:43,385 --> 00:01:46,719 And since 1750, the amount of carbon in the atmosophere 39 00:01:46,719 --> 00:01:48,718 has increased by 40%, 40 00:01:48,718 --> 00:01:51,385 and shows no sign of slowing. 41 00:01:51,385 --> 00:01:53,885 Just like in Tetris, the more blocks pile up, 42 00:01:53,885 --> 00:01:56,771 the harder it becomes to restore stability. 43 00:01:56,771 --> 00:01:58,939 The extra carbon dioxide in the atmosphere 44 00:01:58,939 --> 99:59:59,999 accelerates the Greenhouse Effect 45 99:59:59,999 --> 99:59:59,999 by trapping more heat near the surface 46 99:59:59,999 --> 99:59:59,999 and causing polar ice caps to melt. 47 99:59:59,999 --> 99:59:59,999 And the more they melt, the less sunlight they're able to reflect, 48 99:59:59,999 --> 99:59:59,999 making the oceans warm even faster. 49 99:59:59,999 --> 99:59:59,999 Sea levels rise, coastal populations are threatened with flooding, 50 99:59:59,999 --> 99:59:59,999 natural ecosystems are disrupted, 51 99:59:59,999 --> 99:59:59,999 and the weather becomes more extreme over time. 52 99:59:59,999 --> 99:59:59,999 Climate change may effect different people and places in different ways. 53 99:59:59,999 --> 99:59:59,999 But, ultimately, it's a game that we're all stuck playing. 54 99:59:59,999 --> 99:59:59,999 And unlike in Tetris, 55 99:59:59,999 --> 99:59:59,999 we won't get a chance to start over and try again.