With Rapid Warming in Northern Latitudes, Massive Shift is Underway in Growing Seasons and Vegetation

An international team of researchers has found that rapid warming in northern latitudes has resulted in a decline in temperature seasonality --  the difference between summer and winter temperatures -- which in turn has shifted growing seasons in the region.  "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," says NASA in a press release today (10 March 2013).  "This landscape resembles what was found 250 to 430 miles (400 to 700 kilometers) to the south in 1982,"  the agency explains.  "It's like Winnipeg, Manitoba, moving to Minneapolis-Saint Paul in only 30 years," said co-author Compton Tucker of NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The findings were presented by an international team of 21 authors from 17 institutions in seven countries in “Temperature and vegetation seasonality diminishment over northern lands,” published on Sunday (10 March 2013) in Nature Climate Change. A non-technical summary released along with the article explains:

A greenhouse effect initiated by increased atmospheric concentration of heat-trapping gasses, such as water vapor, carbon dioxide, methane, etc., causes the Earth’s surface and nearby air to warm. The warming reduces the extent of polar sea ice and snow cover on the large land mass girdling the Arctic ocean, which increases the amount of solar energy absorbed by the now somewhat less-white surface. This sets in motion a cycle of positive reinforcement between warming and loss of sea ice and snow cover – the amplified greenhouse effect.

This amplified warming in the North, roughly above the border between Canada and the USA for example, is reducing temperature seasonality over time because the colder seasons are warming more rapidly than the summer.

Consequently, the total amount of heat available for plant growth in these cold climes is increasing from enhanced level of warming overall and a lengthening thaw season. The result is numerous large patches of vigorously productive vegetation, totaling more than a third of the Northern landscape, in resemblance of their lusher and less-seasonal Southern counterparts.

Boston University's Climate and Vegetation Research Group provides photographic evidence of the changes.  The future implications, the summary says, are "disturbing," with 17 state-of-the-art climate model simulations suggesting a shift in temperature seasonality of more than 20 degrees of latitude.

"Since we don't know the actual trajectory of atmospheric concentration of various agents capable of forcing a change in climate, long-term projections should be interpreted cautiously," says co-author Bruce Anderson, Professor of Earth and Environment at Boston University, in a press release (Amplified greenhouse effect shaping North into South) from Boston University.  "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," adds co-author Philippe Ciais, Associate Director, Laboratory of Climate and Environmental Science, Paris, France.

"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."

Above: "Of the 10 million square miles (26 million square kilometers) 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."  Credit: NASA's Goddard Space Flight Center Scientific Visualization Studio.

"The global implications of these large shifts in a region covering a fifth of our planet cannot be understated," says Martin Sommerkorn, Head of Conservation for WWF's Global Arctic Programme. Yet, he adds, "planning and management that governs these arctic spaces and ecosystems is proceeding with business as usual, whereas really it should be completely reframed to address the on-going and upcoming changes. The tools to implement such arctic stewardship...are readily available, yet unless they are swiftly adopted by the arctic states there will be not much ‘Arctic’ left to manage.”

Online Resources:

L. Xu, R. B. Myneni, F. S. Chapin III, T. V. Callaghan, J. E. Pinzon, C. J. Tucker, Z. Zhu, J. Bi, P. Ciais, H. Tømmervik, E. S. Euskirchen, B. C. Forbes, S. L. Piao, B. T. Anderson, S. Ganguly, R. R. Nemani, S. J. Goetz, P. S. A. Beck, A. G. Bunn, C. Cao and J. C. Stroeve, “Temperature and vegetation seasonality diminishment over northern lands,” Nature Climate Change, PUBLISHED ONLINE: 10 MARCH 2013.

Amplified greenhouse effect shaping North into South.  Press release (10 March 2013) from Boston University.  Additional material posted by Boston University:

• Simply Stated
  • Simple Summary (pdf file)
  • Main findings
  • Significance
  • Photographic Evidence
  • Slightly Technical Summary
• The Science
  • The Article
  • Supplementary Information
• About Seasonality
  • Why are there seasons on Earth? - YouTube Video
  • Is the timing of seasons constant? - Wikipedia Site
  • Importance of Seasonality

Amplified Greenhouse Effect Shifts North's Growing Seasons.  Press release (10 March 2013) from NASA.

Significant reduction in temperature and vegetation seasonality over northern latitudes.  Press release (10 March 2013) from Woods Hole Research Center.