[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:06.60,0:00:08.12,Default,,0000,0000,0000,,To understand climate change,
Dialogue: 0,0:00:08.12,0:00:09.84,Default,,0000,0000,0000,,think of the game "Tetris."
Dialogue: 0,0:00:09.84,0:00:14.26,Default,,0000,0000,0000,,For eons, Earth has played a version of this game with blocks of carbon.
Dialogue: 0,0:00:14.26,0:00:17.80,Default,,0000,0000,0000,,They enter the atmosphere as carbon dioxide gas from volcanoes,
Dialogue: 0,0:00:17.80,0:00:19.34,Default,,0000,0000,0000,,decaying plant matter,
Dialogue: 0,0:00:19.34,0:00:20.51,Default,,0000,0000,0000,,breathing creatures
Dialogue: 0,0:00:20.51,0:00:21.97,Default,,0000,0000,0000,,and the surface of the sea.
Dialogue: 0,0:00:21.97,0:00:25.89,Default,,0000,0000,0000,,And they leave the atmosphere when they're used by plants during photosynthesis,
Dialogue: 0,0:00:25.89,0:00:27.51,Default,,0000,0000,0000,,absorbed back into the ocean,
Dialogue: 0,0:00:27.51,0:00:29.68,Default,,0000,0000,0000,,or stored in soil and sediment.
Dialogue: 0,0:00:29.68,0:00:32.18,Default,,0000,0000,0000,,This game of Tetris is called the carbon cycle,
Dialogue: 0,0:00:32.18,0:00:34.68,Default,,0000,0000,0000,,and it's the engine of life on Earth.
Dialogue: 0,0:00:34.68,0:00:36.76,Default,,0000,0000,0000,,What's the connection to climate?
Dialogue: 0,0:00:36.76,0:00:39.18,Default,,0000,0000,0000,,Well, when that carbon dioxide is in the air,
Dialogue: 0,0:00:39.18,0:00:40.82,Default,,0000,0000,0000,,waiting to be reabsorbed,
Dialogue: 0,0:00:40.82,0:00:42.70,Default,,0000,0000,0000,,it traps a portion of the sun's heat,
Dialogue: 0,0:00:42.70,0:00:44.84,Default,,0000,0000,0000,,which would otherwise escape to space.
Dialogue: 0,0:00:44.84,0:00:47.79,Default,,0000,0000,0000,,That's why carbon dioxide is called a greenhouse gas.
Dialogue: 0,0:00:47.79,0:00:49.58,Default,,0000,0000,0000,,It creates a blanket of warmth,
Dialogue: 0,0:00:49.58,0:00:51.26,Default,,0000,0000,0000,,known as the greenhouse effect,
Dialogue: 0,0:00:51.26,0:00:53.93,Default,,0000,0000,0000,,that keeps our Earth from freezing like Mars.
Dialogue: 0,0:00:53.93,0:00:57.79,Default,,0000,0000,0000,,The more carbon dioxide blocks hang out in the atmosphere waiting to be cleared,
Dialogue: 0,0:00:57.79,0:00:59.80,Default,,0000,0000,0000,,the warmer Earth becomes.
Dialogue: 0,0:00:59.80,0:01:01.88,Default,,0000,0000,0000,,Though the amount of carbon in the atmosphere
Dialogue: 0,0:01:01.88,0:01:05.01,Default,,0000,0000,0000,,has varied through ice ages and astroid impacts,
Dialogue: 0,0:01:05.01,0:01:09.26,Default,,0000,0000,0000,,over the past 8,000 years the stable climate we know took shape,
Dialogue: 0,0:01:09.26,0:01:12.14,Default,,0000,0000,0000,,allowing human civilization to thrive.
Dialogue: 0,0:01:12.14,0:01:14.14,Default,,0000,0000,0000,,But about 200 years ago,
Dialogue: 0,0:01:14.14,0:01:17.51,Default,,0000,0000,0000,,we began digging up that old carbon that had been stored in the soil.
Dialogue: 0,0:01:17.51,0:01:20.84,Default,,0000,0000,0000,,These fossil fuels, coal, oil and natural gas
Dialogue: 0,0:01:20.84,0:01:23.70,Default,,0000,0000,0000,,are made from the buried remains of plants and animals
Dialogue: 0,0:01:23.70,0:01:26.78,Default,,0000,0000,0000,,that died long before humans evolved.
Dialogue: 0,0:01:26.78,0:01:29.18,Default,,0000,0000,0000,,The energy stored inside them was able to power
Dialogue: 0,0:01:29.18,0:01:31.87,Default,,0000,0000,0000,,our factories, cars and power plants.
Dialogue: 0,0:01:31.87,0:01:37.04,Default,,0000,0000,0000,,But burning these fuels also injected new carbon blocks into Earth's Tetris game.
Dialogue: 0,0:01:37.04,0:01:39.84,Default,,0000,0000,0000,,At the same time, we cleared forests for agriculture,
Dialogue: 0,0:01:39.84,0:01:43.47,Default,,0000,0000,0000,,reducing the Earth's ability to remove the blocks.
Dialogue: 0,0:01:43.47,0:01:46.73,Default,,0000,0000,0000,,And since 1750, the amount of carbon in the atmosophere
Dialogue: 0,0:01:46.73,0:01:48.76,Default,,0000,0000,0000,,has increased by 40%,
Dialogue: 0,0:01:48.76,0:01:50.93,Default,,0000,0000,0000,,and shows no sign of slowing.
Dialogue: 0,0:01:50.93,0:01:53.76,Default,,0000,0000,0000,,Just like in Tetris, the more blocks pile up,
Dialogue: 0,0:01:53.76,0:01:56.74,Default,,0000,0000,0000,,the harder it becomes to restore stability.
Dialogue: 0,0:01:56.74,0:01:58.93,Default,,0000,0000,0000,,The extra carbon dioxide in the atmosphere
Dialogue: 0,0:01:58.93,0:02:00.92,Default,,0000,0000,0000,,accelerates the greenhouse effect
Dialogue: 0,0:02:00.92,0:02:03.11,Default,,0000,0000,0000,,by trapping more heat near the surface
Dialogue: 0,0:02:03.11,0:02:05.82,Default,,0000,0000,0000,,and causing polar ice caps to melt.
Dialogue: 0,0:02:05.82,0:02:09.03,Default,,0000,0000,0000,,And the more they melt, the less sunlight they're able to reflect,
Dialogue: 0,0:02:09.03,0:02:12.01,Default,,0000,0000,0000,,making the oceans warm even faster.
Dialogue: 0,0:02:12.01,0:02:15.54,Default,,0000,0000,0000,,Sea levels rise, coastal populations are threatened with flooding,
Dialogue: 0,0:02:15.54,0:02:17.84,Default,,0000,0000,0000,,natural ecosystems are disrupted,
Dialogue: 0,0:02:17.84,0:02:21.42,Default,,0000,0000,0000,,and the weather becomes more extreme over time.
Dialogue: 0,0:02:21.42,0:02:25.00,Default,,0000,0000,0000,,Climate change may effect different people and places in different ways.
Dialogue: 0,0:02:25.00,0:02:28.55,Default,,0000,0000,0000,,But, ultimately, it's a game that we're all stuck playing.
Dialogue: 0,0:02:28.55,0:02:30.05,Default,,0000,0000,0000,,And unlike in Tetris,
Dialogue: 0,0:02:30.05,0:02:32.98,Default,,0000,0000,0000,,we won't get a chance to start over and try again.