Climatic Data, Nature of the Data

CLIMATE MODELING IS the process of trying to create mathematical models that represent to the highest possible level of accuracy the circulation of wind in the atmosphere and the exchange of heat into and out of it. Since efforts at modeling began in the 19th century, those efforts have become increasingly complex and sophisticated, particularly in recent decades. Two factors have contributed to that increasing sophistication: first, the dramatic improvement in computational power; second, the huge increases in the range and coverage of data that may be used in data sets for analysis in models. As new data become available, they enable researchers to propose modifications to existing models, while proposals to extend models prompt efforts to find ways to obtain the data necessary to determine the success of the proposal.

Climate models have now reached a third generation or series of iterations, which represents a high level of sophistication compared to the past. Land components of models take account of such variables as vegetation cover, elevation, albedo and salt circulation between land, sea and sea-ice. The same degree of sophistication is evident with respect to the ice and atmospheric components of models. The Goddard Institute of Space Studies (GISS) in New York manages a series of climate models in conjunction with the National Aeronautics and Space Administration (NASA). GISS models employ data collected since the 1850s, which are available on a grid basis for either annual or monthly average readings.

Accurate data only became available for most parts of the earth in recent decades, owing to the amount of [Page 240]resources required to make observations and because the perceived need for global observations has only comparatively recently emerged.

World War II provided the equipment and capability for collecting data, while it was the failure to complete satisfactory models on a regional or geographically-limited basis that did not properly integrate global effects that stimulated the increase in the scope of data collection. Nevertheless, GISS models provide datasets in the following categories: temperature; radiation; vertical heat fluxes; salt; water; pressure; height; velocity and horizontal mass fluxes.

Temperature is measured at data points in vertical and horizontal dimensions. Sophisticated climate models employ many layers within the atmosphere and data must be collected from each of these levels for models to be correctly computed. Meteorological equipment, such as weather balloons, which have become an advanced technology in their own right, is employed to collect temperature and other readings in the atmosphere.

In addition to raw temperature recordings, models are also able to use daily minimum and maximum temperatures and the variance between them (other periods may also be computed as required), as well as a composite ground temperature and the temperature of the ocean.

Radiation is a crucial data element because the heat exchange of the atmosphere determines global warming and, hence, climate change to a large extent. Data are collected on the amount of solar energy reflected nd absorbed by the surface of the Earth. The nature and extent of cloud cover is monitored, as is the extent of energy rebounding off that cloud cover. Aggregate and grid-specific releases of energy data are collected; one measure of atmospheric clarity that is employed is Boucher s Sulfate Burden, measured in milligrams per square meter.

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