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NASA: Higher CO2 levels reponsible for 'greening' Earth

By
Brooks Hays
A map of the world visualizes the change in leaf area, or greening, over the past 30 years. Photo by Boston University/R. Myneni
A map of the world visualizes the change in leaf area, or greening, over the past 30 years. Photo by Boston University/R. Myneni

WASHINGTON, April 26 (UPI) -- New research confirms rising CO2 levels are driving the "greening" Earth effect observed by satellites.

Greening is evidence of accelerated plant growth and heightened rates of photosynthesis. Carbon dioxide is a main source of fuel for plants -- and thus, all life on Earth -- and previous studies show a rise in CO2 results in plant growth.

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But other sources of nutrients and external factors can accelerate photosynthesis and greening, including changes in nitrogen levels, land usage, temperature and weather.

An international team of researchers isolated each of these factors and ran them through a series of computer models. The results suggest rising CO2 levels best explain the increase in leaf cover, or greening, measured by NASA and NOAA satellites.

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Specifically, the analysis credited the atmosphere's CO2 spike with driving 70 percent of greening.

"The second most important driver is nitrogen, at 9 percent," study co-author Ranga Myneni, a professor of Earth and environmental sciences at Boston University, said in a news release. "So we see what an outsized role CO2 plays in this process."

The researchers shared their results in a paper published this week in the journal Nature Climate Change.

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The findings are consistent with studies that suggest accelerated plant growth has enabled plants to serve as a temporary but expanding reserve for excess CO2.

Researchers say the influence of CO2 on plants and any subsequent effects on vegetation's carbon sequestration abilities is likely to be short-lived.

"Studies have shown that plants acclimatize, or adjust, to rising carbon dioxide concentration and the fertilization effect diminishes over time," explained study co-author Philippe Ciais, associate director of the Laboratory of Climate and Environmental Sciences in France.

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