Growing seasons in Earth's northern latitudes are shifting and vegetation increasingly resembles lusher latitudes to the south, scientists say. With climate change, temperatures and vegetation in northern latitudes resemble those found 4 degrees to 6 degrees of latitude farther south as recently as 1982, they said. NASA scientists along with U.S. and international researchers analyzed the relationship between changes in surface temperature and vegetation growth from 45 degrees north latitude to the Arctic Ocean. "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," Ranga Myneni of Boston University's Department of Earth and Environment said in a NASA release Monday. "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 researchers analyzed satellite data to quantify vegetation changes at different latitudes from 1982 to 2011. Increased temperatures and a longer growing season have created large patches of vigorously productive vegetation spanning a third of the northern landscape, or more than 3.5 million square miles, an area about equal to the contiguous United States. This landscape resembles what was found 250-430 miles to the south in 1982, researchers said. "It's like Winnipeg, Manitoba, moving to Minneapolis-St. Paul in only 30 years," Compton Tucker of NASA's Goddard Space Flight Center in Greenbelt, Md., said. Increased concentrations of heat-trapping greenhouse gasses cause Earth's surface, ocean and lower atmosphere to warm, driving the changes, Myneni said. "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." Climate models suggest increased temperatures in arctic and boreal regions would be the equivalent of a 20-degree latitude shift by the end of the 21st century, the researchers said.