How People Tip the Carbon Balance

0:00Carbon dioxide in the air is rising. Is that natural, or caused by people?

0:06Carbon is held in stores: the air, forests, the ocean, and coal, oil and gas.

0:14Plants take in carbon dioxide by photosynthesis, and respiration returns it to the air.

0:21The ocean swaps carbon dioxide with the air too. Before industry, these flows roughly balanced.

0:28Coal, oil and gas are fossil fuels, a long-term store of carbon from ancient living things.

0:35Burning them moves this carbon into the air far faster than nature locks it away.

0:41Growing forests are a carbon sink: they take in more carbon than they release.

0:47Clearing forests removes a sink, and burning or rotting wood releases more carbon dioxide.

0:54The ocean takes up about a quarter of the carbon dioxide people release.

0:59It forms a weak acid in seawater, so the ocean becomes more acidic.

1:05Much of the rest builds up in the air.

1:08The graph shows parts per million, or ppm: carbon dioxide molecules in every million molecules of air.

1:16It was about 280 ppm before industry. Measurements since 1958 show it rising to over 420 in the 2020s.

1:27The yearly wiggle is northern plants taking in carbon dioxide in summer and returning it in winter.

1:34Some people think this rise is natural. The evidence says no.

1:40Each year, people release about twice as much carbon dioxide as the air gains.

1:46And the ocean is taking carbon in, not giving it out.

1:51People add carbon faster than nature removes it, by burning fossil fuels and clearing forests.