May 14, 2008
A new NASA-led study shows that human-caused climate change has
impacted a wide range of Earth's natural systems, from permafrost
thawing to plants blooming earlier across Europe to lakes declining in
productivity in Africa.
Cynthia Rosenzweig of NASA's Goddard Institute for Space Science in
New York and scientists at 10 other institutions have linked physical
and biological impacts since 1970 with rises in temperatures during
that period. The study, published May 15 in the journal Nature,
concludes that human-caused warming is resulting in a broad range of
impacts across the globe.
"This is the first study to link global temperature data sets, climate
model results, and observed changes in a broad range of physical and
biological systems to show the link between humans, climate, and
impacts," said Rosenzweig, lead author of the study.
Rosenzweig and colleagues also found that the link between
human-caused climate change and observed impacts on Earth holds true
at the scale of individual continents, particularly in North America,
Europe, and Asia.
To arrive at the link, the authors built and analyzed a database of
more than 29,000 data series pertaining to observed impacts on Earth's
natural systems, collected from about 80 studies each with at least 20
years of records between 1970 and 2004. Observed impacts included
changes to physical systems, such as glaciers shrinking, permafrost
melting, and lakes and rivers warming. Impacts also included changes
to biological systems, such as leaves unfolding and flowers blooming
earlier in the spring, birds arriving earlier during migration
periods, and ranges of plant and animal species moving toward the
poles and higher in elevation. In aquatic environments such as oceans,
lakes, and rivers, plankton and fish are shifting from cold-adapted to
The team conducted a "joint attribution" study in which they showed,
first, that at the global scale, about 90 percent of observed changes
in diverse physical and biological systems are consistent with
warming. Other driving forces, such as land use change from forest to
agriculture, were ruled out as having significant influence on the
Next, the scientists conducted statistical tests and found that the
spatial patterns of observed impacts closely match temperature trends
across the globe, to a degree beyond what can be attributed to natural
variability. So, the team concluded that observed global-scale impacts
are very likely due to human-caused warming.
"Humans are influencing climate through increasing greenhouse gas
emissions and the warming is causing impacts on physical and
biological systems that are now attributable at the global scale and
in North America, Europe, and Asia," said Rosenzweig.
On other continents, including Africa, South America, and Australia,
documentation of observed changes in physical and biological systems
is still sparse despite warming trends attributable to human causes.
The authors concluded that environmental systems on these continents
need additional research, especially in tropical and subtropical areas
where there is a lack of impact data and published studies.
Goddard Institute for Space Studies, N.Y.
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