Earth and Sky科普英语：Forests and CO2 森林和二氧化碳
The amount of fossil fuel emissions released into the atmosphere has steadily risen since the Industrial Revolution. But recently, part of those emissions have been disappearing. Learn more about forests and CO2 -- on today's Earth and Sky.
DB: This is Earth and Sky. When we burn fossil fuels, we send carbon dioxide -- or CO2 -- into the air. Most scientists think this CO2 contributes to global warming. In the past 20 years, levels of CO2 in the atmosphere haven't risen as much as expected from the rate of our CO2 emissions. Researchers think forests are absorbing some of this extra CO2.
Steven Wofsy: They're doing us a very big favor. They're taking 25% of the fossil fuel CO2 and making it disappear from the atmosphere...
DB: Steven Wofsy researches atmospheric and environmental chemistry at Harvard University.
Steven Wofsy: So we'd very much like to understand why plants are doing this now -- they weren't doing it 20 years ago and what holds the future ... Perhaps plants will continue to take up CO2, perhaps they won't, perhaps what's been stored will actually come back into the atmosphere.
DB: Global warming has extended the growing season and the amount of CO2 that plants can absorb in a year. But Wofsy said that global warming could eventually damage forests by favoring pests. He's helping to design new satellite instruments to better measure how much CO2 is exchanged between forests, oceans and the air. For more, come to today's show at earthsky.org. Special thanks to the National Science Foundation -- where discoveries begin. I'm Deborah Byrd for Earth and Sky.
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