Warming Climate is Changing Life on Global Scale
A vast array of physical and biological systems across the Earth are being affected by warming temperatures caused by human activity. These impacts include earlier leafing of trees and plants over many regions; movements of species to higher latitudes and altitudes in the Northern Hemisphere; changes in bird migrations in Europe, North America and Australia; and shifting of the oceans' plankton and fish from cold- to warm-adapted communities. Based on an analysis of aggregated data, we recently published a study which is the first to link observed global changes in diverse systems to human-caused, or anthropogenic, climate change.
The study found that humans are influencing climate through increasing greenhouse gas emissions, and that the warming world is causing impacts on physical and biological systems attributable at the global scale.
Researchers from NASA GISS and from 10 other institutions across the world analyzed data from published papers on 829 physical systems and some 28,800 plant and animal systems, stretching back to 1970. The analysis shows a picture of changes on continental scales; previous studies had looked mainly at single phenomena, or smaller areas. In physical systems, 95 percent of observed changes are consistent with warming trends. These include wastage of glaciers on all continents; melting permafrost; earlier spring river runoff; and warming of water bodies. The study also found that 90 percent of documented changes among living creatures are consistent with warming.
It is unlikely that any force other than human-influenced global warming could be driving these changes; factors such as deforestation or natural climate variations could not explain it. The work builds upon the consensus of the Intergovernmental Panel on Climate Change, which in 2007 declared human-made climate warming "likely" to have discernible effects on biological and physical systems.
Separating the influence of human-caused temperature increases from natural climate variations or other confounding factors, such as land-use changes or pollution is a real challenge. This was possible only through the combined efforts of the multi-disciplinary team, which examined observed changes in many different systems around the globe, as well as global climate model simulations of temperature changes.
Our findings show that patterns of change are strongest in North America, Asia and Europe, mainly because far more studies have been done there. On the other continents, including South America, Australia and Africa, documentation of changes in physical and biological systems is sparse, even though there is good evidence of human-influenced warming itself. There is an urgent need to study these and other environmental systems, especially in tropical and subtropical areas.
Examples of key impacts observed for the continents include:
North America: 1) Earlier plant flowering in spring of 89 species (examples, American holly, sassafras, box elder maple) as a response to global warming in Washington, DC area; earlier flowering in Boston, Massachusetts; 2) Intraspecific predation, cannibalism, and declining population among polar bears in southern Beaufort Sea; 3) Rapid melting of Alaska glaciers; 4) Earlier breeding and earlier arrival dates of birds (e.g., American robins are arriving 14 days earlier in Colorado; Canada geese in Manitoba); 5) Shoreline retreat in southern Gulf of St. Lawrence; 6) Advancing spring flight of butterflies in lowland California; Mollusks in Monterey, California; 7) Earlier high river flows in New England; 8) Earlier peak migration of Atlantic salmon in New England; 9) Earlier breakup and later freezing dates in lake and river ice cover; 10) Declining mountain snowpack in western North America; 11) Changes in diatoms in northern Canadian lakes; 12) Earlier streamflow timing across western North America; 13) Genetic shift in pitcher plant mosquito to more warm-adapted type in Eastern U.S.; 14) Marmots are emerging 38 days earlier in the Rockies; and 15) Frogs are calling earlier in Ithaca, New York.
Europe: 1) Changes in leaf-unfolding and flowering and animal growing phases in 19 European countries (e.g., hazel, lilac, apple, linden, and birch); 2) Earlier egg-laying of birds; earlier migration of birds (e.g., flycatchers); 3) Long-term changes within fish communities in Upper Rhone River; 4) Glacier melting in the Alps; 5) Rapid advance of spring arrival of long-distance migratory birds in Europe; 6) Mountain birch tree-limit rise in Sweden; 7) Changes in lake diatoms to warmer-adapted species in Finnish Lapland; 8) Earlier pollen release in the Netherlands; and 9) Apple trees are leafing 35 days earlier in Spain.
Asia: 1) Greater growth of Siberian pines in Mongolia; 2) Earlier break-up and thinning of river and lake ice in Mongolia; 3) Change in freeze depth of permafrost in Russia; and 4) Earlier flowering of ginkgo in Japan.
South America: 1) Glacier wastage in Peru; and 2) Melting Patagonia icefields are contributing to sea-level rise.
Africa: 1) Decreasing aquatic ecosystem productivity of Lake Tanganyika.
Australia: 1) Early arrival of Australian migratory birds (e.g., flycatcher, fantail); and 2) Declining water levels in Western Victoria.
Antarctica: 1) Population of emperor penguins had declined by 50% on Antarctic Peninsula; and 2) Retreating glacier fronts.
Ocean: 1) Long-term decline in krill stock in Southern Ocean; 2) Increasing abundance of tropical/subtropical species and decreasing abundances of temperate/subpolar species in California current; and 3) Increasing plankton abundance in cooler regions and decreasing plankton in warmer regions in Northeast Atlantic.
Rosenzweig, C., D. Karoly, M. Vicarelli, P. Neofotis, Q. Wu, G. Casassa, A. Menzel, T.L. Root, N. Estrella, B. Seguin, P. Tryjanowski, C. Liu, S. Rawlins, and A. Imeson, 2008: Attributing physical and biological impacts to anthropogenic climate change. Nature, 453, 353-357, doi:10.1038/nature06937.
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Please address all inquiries about this research to Dr. Cynthia Rosenzweig.