Northern latitudes are greening up, says a NASA-funded study, increasingly resembling the lusher latitudes of the south.
Using a 30-year record of land surface and newly improved satellite data sets, an international team of scientists examined the relationship between changes in surface temperature and vegetation growth from 45 degrees north latitude to the Arctic Ocean.
The results show that temperature and vegetation growth at northern latitudes now resemble those found four to six degrees of latitude farther south as nas 1982.
"Higher northern latitudes are getting warmer, Arctic sea ice and the duration of snow cover are dniminishing, the growing season is getting longer and plants are growing more," says 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."
The team used satellite data to quantify vegetation changes at different latitudes from 1982 to 2011. The data came from NOAA's Advanced Very High Resolution Radiometers (AVHRR) onboard a series of polar-orbiting satellites and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites.
Thanks to global warming and a longer growing season, there are now large patches of vigorously productive vegetation spanning more than 3.5 million square miles - about equal to the contiguous United States - in a landscape resembling what was found 250 to 430 miles to the south in 1982.
"It's like Winnipeg, Manitoba, moving to Minneapolis-Saint Paul in only 30 years," says Compton Tucker of NASA's Goddard Space Flight Center.
To find out what's in store for the future, the team analyzed 17 climate models - and found that increased temperatures in Arctic and boreal regions would be the equivalent of a 20-degree latitude shift by the end of this century relative to the period between 1951and 1980.
However, the researchers say the trend may not continue. As the area warms, forest fires, outbreak of pest infestations and summertime droughts may slow plant growth.