Analysis shows effects of climate change on almost 30,000 biological and physical phenomena.
A comprehensive analysis of trends in tens of thousands of biological and physical systems has provided more evidence to bolster the near-universal view that man-made climate change is altering the behaviour of plants, animals, rivers and more.
The study, by an international research team featuring many members of the Intergovernmental Panel on Climate Change (IPCC), is a statistical analysis of observations of natural systems over time. The data, which stretch back to 1970, capture the behaviour of 829 physical phenomena, such as the timing of river runoff, and around 28,800 biological species.
Researchers led by Cynthia Rosenzweig of NASA's Goddard Institute for Space Studies in New York created a map of the planet with a colour-coded grid showing how much different regions have warmed or cooled between 1970 and 2004.
They then placed each of the thousands of datasets on the map and determined whether they were “consistent with warming” or “not consistent with warming”. Trees, for example, might flower earlier in regions where the climate has warmed significantly.
In around 90% of cases where an overall trend was observed, it was consistent with the predicted effects of climate warming, the researchers report in this week's Nature1.
“Human-caused climate change is having a broad range of impacts on physical and biological systems, not only at a global scale, but at a continental scale,” says Cynthia Rosenzweig.
The bulk of the observations come from Europe, from a single meta-analysis of a collaborative database of observations of annual natural events2. Several hundred more came from studies elsewhere in the world, although Africa, Australia and Latin America are relatively poorly represented.
Rosenzweig's team does not claim, therefore, to have shown that human-caused global warming is causing changes to these southern continents on an individual basis.
Among the warming-linked changes seen in the study are the timing of plant flowering, bird nesting, ice melting, salmon migration and pollen release; declines in populations of polar bears, krill and penguins; and increased growth of Siberian pines and cool-water ocean plankton.
"This paper outlines an extremely robust case for linking a range of observed physical and biological changes to human-induced climate change, specifically warming," says Roger Jones of the Centre for Australian Weather and Climate Research. "Unfortunately, the coverage of such data is not global and many regions of the world, including Australia, are not very well covered. Many of the regions that lack coverage are also thought to be highly vulnerable to the impacts of climate change."
Cagan Sekercioglu of Stanford University in California studies bird ranges and, among other things, their response to climate change. He is convinced that climate change is affecting many natural systems, and is disappointed that many regions still lack adequate data.
“In Africa there are 14 studies altogether, including the Middle East,” he says. “The big oil-producing countries like Saudi Arabia and Venezuela don't have any studies, and it is kind of embarrassing that my own country, Turkey, has no studies.”
Sekercioglu is impressed by the scope of the study, but says that there was already a wealth of evidence that climate change is affecting the world. “We shouldn't even need to publish such papers at this point,” he says. “This paper is an argument that climate change is causing the observed changes. This should be a given. Thirty years later we are still trying to convince people of this.”
Rosenzweig sees those 30 years differently. It was about 30 years ago that the Goddard Institute for Space Studies began work on climate-change models. “Less than 30 years after the fist model was developed, we are working on the second global treaty [the successor to the Kyoto Treaty, which will expire in 2012]. I think that the global-warming issue is the [biggest] challenge facing our planet, but at the same time it is leading us to sustainability because of the rapidly growing action. It is finally shaking us up and getting us to realize what is going on with the planet."
Rosenzweig, C. et al. Nature 453, 353-357 (2008).
Menzel, A. et al. Glob. Change Biol. 12, 1969-1976 (2006).