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Climate change


Global climate change: Key impacts on the environment

Current observations prove that climate change and global warming is occurring (a summary of current observations, based on the Intergovernmental Panel on Climate Change’s (IPCC) most recent report, can be viewed here). The consequences of higher global average temperatures and predicted sea level rise are often highlighted in climate change discussions, but what about other effects on the earth’s natural systems and the environment, such as ecosystems? How might the “human environment,” such as human health and agriculture, be affected?  Are the Earth’s natural systems being affected by climate change at this time?


Current Impacts

According to the IPCC, there is sufficient evidence to conclude with high confidence that “anthropogenic warming over the last three decades has had a discernible influence on many physical and biological systems.” Moreover, “Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases” (IPCC, 2007).


Because of warming, changes in snowfall and ice have resulted in an increased number and size of glacial lakes; reduced permafrost has led to ground instability and rock avalanches in mountain regions. Changes also have occurred in some Arctic and Antarctic ecosystems, sometimes involving predators high in the food chain. Warmer temperatures are affecting hydrological systems by causing increased runoff and earlier spring peak discharge in many glacier and snow-fed rivers, and warmer waters can affect the structure and water quality of these lakes and rivers. Evidence from many different species indicates that terrestrial systems are being affected—warming has led to earlier timing of spring events, such as leaf-unfolding, bird migration, and egg-laying. Satellite imagery confirms there has been a trend toward earlier “greening” and springtime events, as well as longer thermal growing seasons for plant species. Evidence also shows the ranges of plant and animal species are being extended poleward.

Climate change is occurring. Because of a rapid warming trend over the past 30 years, the Earth is now reaching the warmest levels seen in the last 12,000 years. This map shows the global surface temperature anomaly from 1880 to 2006. Source: NASA Goddard Flight Center

The oceans are not immune—observed changes in marine and freshwater biological systems are associated with rising water temperatures and changes in ice cover, salinity and oxygen levels, and ocean circulation. Some of these observations include earlier migrations of fish in rivers, and altered ranges and abundances of fish, algae, and plankton species in higher latitudes. The picture to the left, for example, shows a lobster boat hauling in lobster traps from Long Island Sound. According to the Northeast Climate Impacts Assessment, ocean warming is predicted to eliminate suitable lobster habitat and lobster fisheries south of Cape Cod by mid-century, including Long Island Sound.

The figure below, from the “Climate 2007” report by the Intergovernmental Panel on Climate Change (IPCC), shows potential impacts on select components of the natural system and the human environment due to increases in the global annual mean temperature. Impacts will vary by region depending on the rate of temperature change, the level of adaptation, and differences in socio-economics. The black lines link different impacts and the dotted lines with arrows indicate continuing impacts with increasing temperature.



Source: IPCC, 2007: Summary for Policymakers. In: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds.)]. Cambridge University Press.


To explore more fully how climate change will affect natural systems and the human environment in the years to come, click on the links below, which provide a short summary on a number of topics covered by IPCC’s Working Group II “Summary for Policymakers” report. The full working Group II report can be accessed here.


Summary of the IPCC’s Working Group II findings:

Future Impacts—Freshwater Resources, Ecosystems, Food and Agriculture

Future Impacts—Coastal Areas

Future Impacts—Human Health, Economics


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