Northern latitudes become greener with global warming


An international team of university and NASA scientists examined the relationship between changes in surface temperature and vegetation growth from 45 degrees north latitude to the Arctic Ocean. Shocking new images revealed by NASA show the Arctic is becoming lusher and greener as temperatures rise. These results show temperature and vegetation growth at northern latitudes now resemble those found 4 degrees to 6 degrees of latitude farther south as recently as 1982.

The images show how the extreme of the Northern Hemisphere is changing, with previously frozen areas now showing lush green grass and trees growing.

733097main1_Northern_ndvi_FINAL-673
Of the 26 million square kilometers (10 million square miles) of northern vegetated lands, 34 to 41 percent showed increases in plant growth (green and blue), 3 to 5 percent showed decreases in plant growth (orange and red), and 51 to 62 percent showed no changes (yellow) over the past 30 years. Satellite data in this visualization are from the AVHRR and MODIS instruments, which contribute to a vegetation index that allows researchers to track changes in plant growth over large areas.
Credit: NASA’s Goddard Space Flight Center Scientific Visualization Studio

“Higher northern latitudes are getting warmer, Arctic sea ice and the duration of snow cover are diminishing, the growing season is getting longer and plants are growing more,” said Ranga Myneni of Boston University’s Department of Earth and Environment. “In the north’s Arctic and boreal areas, the characteristics of the seasons are changing, leading to great disruptions for plants and related ecosystems.”

An amplified greenhouse effect is driving the changes, according to Myneni. Increased concentrations of heat-trapping gasses, such as water vapor, carbon dioxide and methane, cause Earth’s surface, ocean and lower atmosphere to warm. Warming reduces the extent of polar sea ice and snow cover, and, in turn, the darker ocean and land surfaces absorb more solar energy, thus further heating the air above them.

“This sets in motion a cycle of positive reinforcement between warming and loss of sea ice and snow cover, which we call the amplified greenhouse effect,” Myneni said. “The greenhouse effect could be further amplified in the future as soils in the north thaw, releasing potentially significant amounts of carbon dioxide and methane.”

However, researchers say plant growth in the north may not continue on its current trajectory. The ramifications of an amplified greenhouse effect, such as frequent forest fires, outbreak of pest infestations and summertime droughts, may slow plant growth.

Also, warmer temperatures alone in the boreal zone do not guarantee more plant growth, which also depends on the availability of water and sunlight.

“Satellite data identify areas in the boreal zone that are warmer and dryer and other areas that are warmer and wetter,” said co-author Ramakrishna Nemani of NASA’s Ames Research Center in Moffett Field, Calif. “Only the warmer and wetter areas support more growth.”

The study was published Sunday, March 10, in the journal Nature Climate Change.

 

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Via: NASA

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