https://www.eurekalert.org/pub_releases/2020-12/nsfc-wli121820.php
News Release 18-Dec-2020
NASA/Goddard Space Flight Center
More plants and longer growing seasons in the northern latitudes have converted parts of Alaska, Canada and Siberia to deeper shades of green. Some studies translate this Arctic greening to a greater global carbon uptake. But new research shows that as Earth's climate is changing, increased carbon absorption by plants in the Arctic is being offset by a corresponding decline in the tropics.
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Plant productivity in the frigid Arctic landscape is limited by the lengthy periods of cold. As temperatures warm, the plants in these regions have been able to grow more densely and extend their growing season, leading to an overall increase in photosynthetic activity, and subsequently greater carbon absorption in the region over the 35-year time span.
However, buildup of atmospheric carbon concentrations has had several other rippling effects. Notably, as carbon has increased, global temperatures have risen, and the atmosphere in the tropics (where plant productivity is limited by the availability of water) has become drier. Recent increases in drought and tree mortality in the Amazon rainforest are one example of this, and productivity and carbon absorption over land near the equator have gone down over the same time period as Arctic greening has occurred, canceling out any net effect on global productivity.
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