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Climate Variability and Change

Climate change can have tremendous consequences for the lives and livelihoods of individuals as well as for entire civilizations. While favorable climate is believed to have facilitated the "cradle of civilization" that sprang from the fertile lands of Mesopotamia, past climate change has displaced or even eliminated cultures and societies. One of the most notable displaced the Vikings, who in the late twelfth century abandoned villages and towns in Greenland and Iceland after temperatures cooled by only a few degrees centigrade.

Changes in climate can benefit or impact societies, and our ability to mitigate, adapt to, or capitalize on climatic change depends critically on understanding the processes at work and our ability to predict their future behavior. NASA's role in characterizing, understanding, and predicting climate variability and change focuses on global observations of the more slowly responding components of the system (primarily oceans and ice), naturally occurring processes and human activities that affect climate, and their interactions within the Earth system. The Climate Variability and Change Focus Area organizes NASA research to address the following major questions:

  • How is the global ocean circulation varying on interannual, decadal, and longer time scales?
  • What changes are occurring in the mass of the Earth's ice cover?
  • How can climate variations induce changes in the global ocean circulation?
  • How is global sea level affected by natural variability and human-induced change in the Earth system?
  • How can predictions of climate variability and change be improved?

Climate Varibility and Change Roadmap
Chart: As depicted in the above diagram, climate variability and change research incorporates comprehensive observations into models that can accurately predict climatic change over seasonal, interannual, decadal, and longer time periods. [+ larger image]

The oceans are a major part of the climate system, and a unique NASA contribution to climate science is the near-global coverage of observations from space of selected ocean properties every 2 to 10 days. Additionally, NASA provides observations of the vast expanses of polar ice on the temporal and spatial scales necessary to detect change and sampling of the other critical elements of the climate system that link climate to other focus areas such as cloud distribution, snow cover, surface temperatures, and humidity characteristics.

The Nation benefits from NASA's substantial investments to characterize and understand the nature and variability of the climate system. Current capabilities include global measurements of sea surface topography, ocean vector winds, ice topography and motion, and mass movements of the Earth’s fluid envelope and cryosphere. Critically-needed new measurements include sea-ice thickness, sea-ice snow cover, decadal change in ice mass over land, and sea-surface salinity.

Sea ice modulates the exchange of energy, moisture, and momentum between the ocean and atmosphere and affects ocean circulation through brine rejection when formed. As such, its thickness and spatial characteristics need to be well understood. NASA investments have enabled monitoring of the spatial characteristics of sea ice, but the critical thickness dimension needs to be observed in order to sufficiently quantify the role of sea ice in the climate system and how changes in ice cover affect ocean circulation.

Characterizing snow depth on sea ice is also crucial to understanding the extent to which the sea-ice cover influences the broader climate. Snow is a much more effective insulator than ice, so from an energy exchange perspective, it is as important, if not more so, than sea ice. We currently have crude means of estimating snow depth on sea ice, but substantial research is needed to develop robust measurements of this parameter. Current measurements of ice mass over land must be followed by future missions to determine longer-term change in ice mass and its contribution to sea level. Ancillary measurements (e.g., ice thickness and velocity) are required to understand the mechanisms that drive these changes. Companion focus areas address complementary measurements: soil moisture, atmospheric aerosols, aerosol-cloud-radiation feedbacks, and atmospheric CO2.

Understanding interactions within the climate system also requires strong modeling and analysis efforts. The climate system is dynamic and complex, and modeling is the only way we can effectively integrate the observations and current knowledge of individual components to fully characterize current conditions and underlying mechanisms as well as to project the future states of the climate system. This requires a concerted effort both to improve the representation of physical, chemical and biological processes in models, and to incorporate observations into climate models through data assimilation and other techniques. The ultimate objective is to enable a predictive capability of climate change on time scales ranging from seasonal to multi-decadal.