A group of international researchers assessed 17 state-of-the-art climate model simulations and based on these have found that temperature seasonality shifts and green plants could move further north by as much as a whooping 20 degrees latitude by the turn of the century. So far, in the past 30 years alone, southern vegetation has moved up north by seven degrees, turning once pale regions into lush green patches in a very short amount of time.
The researchers note that as a result of increased atmospheric greenhouse gases, surface temperatures have risen and the air has become warmer. A whole cycle of events unfolds from here on as snow and ice retreat from surfaces around the Arctic Ocean, causing even more solar energy to be absorbed, which in term further destabilizes the ecosystem.
"The amplified warming in the circumpolar area roughly above the Canada-USA border is reducing temperature seasonality over time because the colder seasons are warming more rapidly than the summer," says Liang Xu, a Boston University doctoral student and lead co-author of the study.
Since more solar energy in the form of heat is available, plants can grow more rapidly and over more extended landmasses. During the past 30 years large patches of vigorously productive vegetation have been created, totaling more than a third of the northern landscape—over 9 million km2, which is roughly about the area of the USA— resembling the vegetation that occurs further to the south, says Dr. Compton Tucker, Senior Scientist, NASA's Goddard Space Flight Center, Greenbelt, Maryland.
For their study, the scientists first chose a reference point and period. Then the team examined 17 climate models that revealed increased temperatures in the northern latitudes would be the equivalent of a 20-degree latitude shift by the end of this century relative to a period of comparison from 1951-1980.
While more, greener plants might sound like an enchanting prospect, make no mistake - it's not! This translates in a tremendous destabilization of the ecosystem, that puts the region at high risk of permafrost thawing, frequent forest fires, outbreak of pest infestations, and summertime droughts. Yes, forest fires in the north.
Moreover, plant growth and shift in temperature seasonality might not remain on its current projected trajectory. An amplified greenhouse gas effect is likely to cause a chain of events that can not be accurately predicted, like the release of even more carbon into the atmosphere from patches trapped in currently frozen ground.
"The way of life of many organisms on Earth is tightly linked to seasonal changes in temperature and availability of food, and all food on land comes first from plants," says Dr. Scott Goetz, Deputy Director and Senior Scientist, Woods Hole Research Center, Falmouth, USA. "Think of migration of birds to the Arctic in the summer and hibernation of bears in the winter: Any significant alterations to temperature and vegetation seasonality are likely to impact life not only in the north but elsewhere in ways that we do not yet know."
The findings were reported in the journal Nature Climate Change.