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Another weapon to fight climate change? Put carbon back where we found it

Scientists and entrepreneurs are embarking on ambitious—and sometimes controversial—projects to remove carbon dioxide from ambient air and lock it away. 

What these efforts have in common is that they are geared in the long run to drag downward a number that climate experts agree holds the key to the health of the planet. That number is the atmospheric concentration of carbon dioxide, which for thousands of years had held stable at or a bit below 280 parts per million, until the industrial revolution kicked off in the middle of the 19th century. Today this critical number stands at some 420 parts per million—in other words, the percentage of CO2 in the atmosphere has risen roughly 50 percent since 1850. As it rises, the added carbon traps heat, causing the Earth to warm to increasingly dangerous levels. Carbon-capture proponents say that their work—to capture the main driver of climate change, radically scaled up in coming decades—will help bring this number down.

Read the original article in National Geographic.