Amplified Greenhouse Effect Making Attic Seasons Resemble South

New research shows that climate change has already altered seasons and vegetation in the Arctic, making them more like the southern regions.

The study, conducted by an international team of 21 authors from 17 institutions, was published in the journal Natural Climate Change on Sunday. Researchers looked at the latest data made available via ground and satellite streams and have found the climate change that's already happened, is equivalent to about five degrees of latitude.

"A greenhouse effect initiated by increased atmospheric concentration of heat-trapping gasses -- such as water vapor, carbon dioxide and methane -- causes the Earth's surface and nearby air to warm," said Prof. Ranga Myneni, Department of Earth and Environment, Boston University and lead co-author.

"The warming reduces the extent of polar sea ice and snow cover on the large land mass that surrounds the Arctic ocean, thereby increasing the amount of solar energy absorbed by the no longer energy-reflecting surface. This sets in motion a cycle of positive reinforcement between warming and loss of sea ice and snow cover, thus amplifying the base greenhouse effect."

The authors measured seasonality changes using latitude as a yardstick. They first defined reference latitudinal profiles for the quantities being observed and then quantified changes in them over time as shifts along these profiles.

The researchers found that most of the warming that's happening in the Arctic is taking place in winter, with somewhat less happening in spring and fall and the least occurring in the summer.

"If you start warming the winters more, and the transitional seasons a little bit more, you're basically flattening out the bell shape," Myneni said. "The bell in the North is looking less like a bell shape." This means that climate change is giving the Arctic the temperature profile of the south.

Myneni notes that that warmer temperature does not mean more hours of daylight. Nor will they improve thin Arctic soils or prevent melting permafrost from destabilizing the land.

"These changes will affect local residents through changes in provisioning ecosystem services such as timber and traditional foods," says Research Professor Bruce Forbes, University of Lapland, Rovaniemi, Finland. They will also impact the global community through changes in regulatory ecosystem services relating to emissions of greenhouse gases. "The soils in the northern land mass potentially can release significant amounts of greenhouse gases which are currently locked up in the permanently frozen ground. Any large-scale deep-thawing of these soils has the potential to further amplify the greenhouse effect," says co-author Philippe Ciais, Associate Director, Laboratory of Climate and Environmental Science, Paris, France.

The study was funded by NASA and included an international team of 21 authors from 17 institutions in seven countries.