Читать книгу Shaped by Snow. Defending the Future of Winter онлайн

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It doesn’t take much carbon dioxide to cause this. Carbon dioxide is measured in the atmosphere by parts per million (ppm). Pre-industrial-era carbon concentration was around 280 ppm. This means that for every one million molecules of other gases in the atmosphere, there were 280 molecules of carbon dioxide. This is the level that the current life-forms on our planet evolved to survive in. By the environmental group 350.org’s estimate, 350 ppm is a reasonable and healthy goal for our planet—hence the organization’s name. Currently, we’re over 400 ppm. It’s likely that we’ve passed 400 ppm for the last time in modern times, and we’re releasing approximately 2 ppm into the atmosphere each year. Once we pass 450 ppm, scientists believe, we will not be able to mitigate the earth’s warming.

Large swaths of materials on the earth sequester carbon dioxide, storing it for long periods of time and preventing it from entering the atmosphere. When they absorb more carbon than they release, we call them carbon sinks. Dense forests are a type of carbon sink; trees and plants take in carbon dioxide during photosynthesis and convert it into starch. Oceans are another. Dissolved carbon dioxide in the oceans gets used by organisms like phytoplankton for similar purposes. An important carbon sink is the permafrost, soil in places like the Arctic Circle that’s been frozen for at least two years, though much of it’s been frozen for tens or hundreds of thousands of years. Frozen organic matter in these soils contains large amounts of both carbon dioxide and methane.