A study in the Jan. 2 edition of the British science journal Nature synthesized data from 143 scientific papers to examine whether a signal, or "fingerprint," of climate change can be found in how animals and plants have reacted to increasing temperatures.
Among their findings: In the temperate zone, the researchers estimate that, for species that have shown a change in timing, spring events are shifting about five days earlier every ten years.
One team member, fisheries and wildlife postdoctoral researcher Kimberly Hall at Michigan State University, helped wrangle data that comes not only from scientific outposts, but from the backyard recordings and personal journals of people across the world. The impact of global warming often appears as an early arrival of spring and is seen at bird feeders, heard in the earlier croaking of frogs and sniffed in the first waft of lilacs.
"Local weather is extremely variable from year to year, and animals and plants respond to many other factors besides temperature," Hall said. "To be able to detect impacts of climate warming, we have to have data sets that cover long periods, so trends can emerge from all of the noise."
The challenge: The average lifespan of a research grant is about three years. Few researchers focused on climate change 10 or 20 years ago, so many of the most convincing papers documenting long-term responses of wild plants and animals come from nonprofessional observers that were recording data as a hobby.
"The studies we reviewed often obtained data from persistent individuals, people who were curious about the wildlife around them and wrote down what they saw," she said. "Often the analyses that you can do with these types of data are pretty crude, but when they are combined with information from many other locations around the world, they paint a very telling picture."
Hall worked with Terry Root and Stephen Schneider at Stanford University, as well as Jeff Price at the American Bird Conservancy, Cynthia Rosenzweig with NASA and Alan Pounds in Costa Rica. Her job included searching literature from around the globe to find research papers to include in the study.
The project began as an effort to compile information for a recent international study, the Intergovernmental Panel on Climate Change Third Assessment report. The group reviewed more than 2,000 papers, then focused on a small subset that met the criteria for this additional study.
"The papers using individual's observations were inspiring," Hall said. "They show how much can be gained from being a patient observer, and that great data sets are probably all around us, hidden in desk drawers and just waiting for someone to look at them through the lens of climate change."
The regular recordings of the ecologically curious, when joined with data from researchers around the world and analyzed, show that animals of all kinds, as well as plants, appear to be shifting behaviors, seasonal timing and locations in response to a 0.6°C increase in the average global temperature in the last 100 years.
The most dramatic impacts, the study notes, are seen in the higher latitudes, which have warmed more than the lower latitudes in the past half-century.
"The majority of these changes bear the fingerprint of one factor - increasing temperature," Hall said. "When you put all these observations, all these notes from individuals, together, they suggest a strong unified signal of climate change from across the globe."
Hall said the study's significance lies in its foreboding. Global warming is projected to increase dramatically in coming years. While spring arriving early seems in itself innocuous, Hall said no one knows right now how these changes will affect the complex orchestration of the environment.
"If temperatures are changing and wildlife are reacting to it, but other resources, such as food supplies, or the types of habitats that are protected, are not changing at the same rate, it could be trouble for many species," Hall said.
Hall's current position at MSU is funded by The Nature Conservancy through its Smith Fellowship program.