Climate Modeling

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Climate Modeling

Introduction

Climate modeling refers to the use of mathematical or software-based methods that seek to simulate the many interactions that occur in the environment between air, water, and land. Altering one or more of the variables in the model will produce a change. If the model accurately represents the natural condition, then the change may provide useful information on local, national, or even global conditions over the selected time frame.

Meteorologists utilize models to predict the weather over local or wider regions. In another example, the path of a hurricane is modeled and the outcome used to issue warnings to those predicted to be in the path of the storm. The data from some climate models has indicated that the frequency and ferocity of hurricanes will increase as the sea temperature warms as a result of the continuing warming of Earth’s atmosphere.

On a global scale, models have and continue to be developed to try and predict the global climate. Although actual measurements exist for some aspects of the atmosphere and the oceans, climate models are necessary for a better understanding of the short-term climate behavior and variations. Furthermore, models are the only way that future global climate change on Earth can be estimated.

Historical Background and Scientific Foundations

In the nineteenth century, scientists attempted to generate patterns of atmospheric movement by using physical laws to model gas movement above a heated and rotating sphere. These efforts failed.

Instead, scientists moved from the global to the local, seeking to understand local weather patterns at thousands of sites worldwide. By integrating this information together, it was hoped that an approximation of global climate would result.

But, until the development of computers, such efforts were primitive. The ability to perform many calculations (at least relative to the calculations that previously were literally made by hand) made early computers an attractive tool to try and simulate air motion in the atmosphere. In the late 1940s, scientists utilized one of the earliest computers, a room-sized machine dubbed ENIAC (Electronic Numerical Integrator and Computer), to two-dimensionally simulate climate. The result required 24 hours, meaning that the model could only just keep up with the actual weather. The inability of the computer program (with its few kilobytes of memory) to cope with the myriad of interactions that actually operated in real life hobbled predictions of future climate developments.

Climate modeling took a step forward in 1955, when a group of scientists at Princeton University modeled the movement of air in two dimensions over a large mountain range. The model, which incorporated the tendency of air to circulate as eddies—similar to the little whirlpools of water seen in a flowing stream—more accurately modeled air flow, and is considered to be the first General Circulation Model (GCM).

By 1965, a three-dimensional model had been developed for the atmosphere. The model was crude by today’s standards; nonetheless, some aspects of the atmosphere such as the global movement of water vapor, agreed with measurements taken at the surface and from weather balloons.

At about the same time, a two-dimensional GCM for the entire globe was developed

In the 1970s, climate-modeling efforts accelerated as more scientists became involved, as computer memory and calculation speed increased, and as many more actual measurements were acquired. By this time, atmospheric measurements were being made from rockets and orbit-

WORDS TO KNOW

ATMOSPHERE: The air surrounding Earth, described as a series of layers of different characteristics. The atmosphere, composed mainly of nitrogen and oxygen with traces of carbon dioxide, water vapor, and other gases, acts as a buffer between Earth and the sun.

GAIA HYPOTHESIS: The hypothesis that Earth’s atmosphere, biosphere, and its living organisms behave as a single system striving to maintain a stability that is conductive to the existence of life.

GLOBAL WARMING: Warming of Earth’s atmosphere that results from an increase in the concentration of gases that store heat, such as carbon dioxide (CO₂).

ing satellites, producing a wealth of knowledge about the entire atmosphere, and enabling the simultaneous examination of huge geographic areas.

Increasing model complexity driven in part by increasing computational power allowed the development of models that addressed specific areas of climate such as weather prediction over small geographic ranges (i.e., a city) within a short time (i.e., less than one hour).

As well, as evidence concerning the accumulation of carbon dioxide (CO₂) in the atmosphere became unde-

niable, some climate models began to consider global climate change as a long-term problem that warranted modeling, to better understand the effect of CO₂ on global climate accumulation and devise approaches to lessen undesirable atmospheric changes.

In 2008, climate modeling is a sophisticated undertaking. Models can now accurately account for factors including the influences of clouds and ocean circulation on climate. Modeling studies have indicated, for example, that changing ocean temperatures are affecting the wind pattern in monsoons to produce more intense monsoon rainfall. Computer simulation programs and climate models are being used at agencies such as U.S. National Hurricane Centers in Miami and Honolulu, and the Canadian Hurricane Center in Dartmouth, Nova Scotia, Canada, to gauge when conditions are favorable for the development of storms and to predict the track of storms.

Impacts and Issues

Climate modeling innovations continue, as the need to understand the changing atmosphere becomes more urgent. In 2004, for example, the National Center for Atmospheric Research in Boulder, Colorado, implemented a supercomputer-based model (the Community Climate System Model, version 3; CCSM3) that provided data to the Intergovernmental Panel on Climate Change (IPCC). The data contributed to the IPCC

report released in 2007, which stated the “unequivocal” reality of human-driven global warming.

The model predicts that the continued emission of large quantities of CO₂ could lead to a global temperature increase that is greater than previously thought. Even if the extent of temperature change is not as marked as CCSM3 predicts, it and other models have established the reality of global warming.

Another climate model implemented in 2007 by the National Aeronautics and Space Administration (NASA) has predicted that intensity of severe thunderstorms will increase in certain regions of the United States as the atmosphere continues to warm. The result could be increased wildfires due to lightning strikes. By further refining the model, NASA researchers hope that predictive capacity similar to that available for hurricanes may be available for storm prone regions of the country. The result could be less devastation, less loss of property, and fewer deaths.

BIBLIOGRAPHY

Books

Hillman, Mayer, Tina Fawcett, and Sudhir ChellaRajan. The Suicidal Planet: How to Prevent Global Climate Catastrophe. New York: Thomas Dunne Books, 2007.

Lovelock, James. The Revenge of Gaia: Earth’s Climate Crisis and the Fate of Humanity. New York: Perseus Books, 2007.

Svensmark, Henrik, and Nigel Calder. The Chilling Stars: The New Theory of Climate Change. London: Totem Books, 2007.

Periodicals

Flemming, James R. “The Climate Engineers.” Wilson Quarterly (Spring 2007).

Brian D. Hoyle

Environmental Science: In Context