Remember the sweltering days, the anxious farmers, the short tempers, the parched lawns and shriveled corn, and the long hot nights of the summer of 1988? Temperatures soared above 90 degrees on 52 days in Chicago, and record high utility bills faced everyone from Cairo to Rockford. More than 500 Illinoisans died of heat stress. News stories of impending agricultural disaster appeared daily and were finally realized at season's end with crop yields 40 percent below average. Dry lake beds appeared at 30 Illinois water supply reservoirs, and barges stalled on sandbars along the Illinois, Mississippi and Ohio rivers. Homeowners watched as lawns and evergreens burned, browned and died.

The hot and dry summer of 1988, rated as a highly unusual climatic event on the basis of today's Illinois climate, could become a frequent occurrence in the future if projected global warming develops. A major new environmental issue, the possibility of a world climate change caused by the "greenhouse effect" has gained increasing national and international attention over the last two years.

The phenomenon arises when harmful trace gases such as carbon dioxide, nitrous oxides, chlorofluorocarbons (CFCs) and methane accumulate in the atmosphere. The earth's normal outgoing radiation is captured by these gases and may result in a global warming over the next several decades.

Atmospheric models of possible global effects currently indicate that the earth's temperature could rise between 5 and 9 degrees Fahrenheit — as warm, or warmer, than it has been at any time during the last 200,000 years. As the atmosphere warms, its ability to hold water vapor is enhanced, meaning that global precipitation may increase by 7 to 15 percent. Increased temperatures and precipitation, however, will not be globally uniform. Some regions may get more rain; others will witness a drop in precipitation.

What if Illinois' climate warms over the next 30 to 50 years and its rainfall patterns are altered? It will surely mean a change in overall weather patterns. Winters will be warmer but so too will the summers which will have more 90-degree-plus days. Annual precipitation will show some seasonal variation and will likely be less than it has been in the 20th century. In addition, scientists now believe that even small global weather shifts could translate into more frequent and extreme weather conditions. This means Illinois will experience more severe storms, and windy conditions will become more common.

These sorts of climatic changes will affect Illinois' hydro-logic cycle, altering runoff, groundwater recharge and river flow throughout the state. A two degree increase in the state's annual temperature coupled with a 10 percent decrease in its precipitation would reduce the average annual runoff flowing into river basins by 25 percent in some areas of the state. In other areas, the warmer weather could alter spring runoff patterns by causing an earlier snowmelt. This could drastically intensify flood conditions in these areas.

Such variability in weather patterns and the hydrologic cycle will have enormous implications for Illinois and will affect nearly every sector of human activity in the state. The state's population could decrease as people move north to escape Illinois' warmer and drier climate. Agriculture, water demand patterns. the state's natural ecosystems, energy consumption patterns, and industrial development and commerce all would fall prey to an Illinois climate that would increasingly resemble that of today's Oklahoma.

In agriculture, higher temperatures, lower soil moisture, longer growing, seasons, modified summer rainfall patterns and increased carbon dioxide concentrations would mean an increased need for irrigation and a shift in production. As carbon dioxide concentrations increase, photosynthesis and plant growth are enhanced but plant transpiration is reduced. The changes would modify vegetation patterns which, in turn, would alter the soil's ability to hold moisture, further changing runoff and water distribution.

Competition for irrigation rights will certainly become a major state issue. An expansion of irrigation across those parts of Illinois where water can be obtained will mean an escalation of conflict over water and should lead to major changes in state water laws.

At a minimum, Illinois agriculture's reliance on corn and soybean production would require hardier species. But even hardier species would be unlikely to match the yields of today's corn and soybeans. It may be that cultivation of these crops will move to the more northern latitudes of the U.S. — or even into southern

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Canada — as recent studies by the U.S. Environmental Protection Agency suggest. Agriculture in Illinois would most likely shift to more drought-resistant crops, like wheat. Such changes will certainly have an impact on the state's current standing as a global exporter of agricultural products. And the changes in Illinois agriculture may well reflect similar changes elsewhere in the Midwest and in the world's other primary grain belts, raising the question of adequate global food supply.

Energy users and producers are likely to face mixed consequences. A longer summer with many more 90-degree-plus days, as in 1988, will mean a greater demand for air conditioning. Conversely, milder and shorter winters will mean a falling demand for winter heating. Changes in energy demand such as these will require utilities to alter their production patterns. Utilities that depend on reservoir or lake water for cooling will also have to take into account that there will be less water and higher surface water temperatures.

Other sectors of our economy will also experience problems. As the drought of 1988 so succinctly illustrated, less water in the state's hydrologic system will mean more frequent low flows in major streams and rivers. The transport of bulk commodities such as grains, petroleum and coal on the Midwest's complex barge system may have to be greatly curtailed. A more limited barge system in Illinois and the Midwest could have a positive effect, though, on the region's railroads and on Great Lakes shipping.

The benefits of enhanced Great Lakes shipping may pass by Illinois, however. Illinois State Water Survey studies indicate that the level of Lake Michigan could fall somewhere between two feet and nine feet below the lake's current average. The effects of a two- to three-foot drop would be "manageable" but would require a $200 million investment over the next 50 years to install new water intakes, extend storm outflows, deepen harbors, build new docks, etc. A drop of nine feet, however, could effectively end Chicago's role as a Great Lakes port.

Such a drop would also require massive pumping of water from the lake — a move strongly opposed by other Great Lakes states during the drought of 1988 — to maintain the current flow levels through the Chicago and Illinois river systems.

In addition to water resources, all other natural resources in Illinois will be affected by a significant change in climate. Tree species such as birch that cannot survive in the new climate will disappear. Certain wetlands and the life that thrives in and around them would also disappear. Entire ecosystems will have to adapt or disappear.

People will also have to learn to adapt, particularly those who live in urban areas, or move to more northerly climes. More than 80 percent of Illinoisans live in communities of 100,000 population or more, including seven million in the Chicago metropolitan area. Over the last 100 years, these urban areas already have created their own climates — distinctly warmer and generally drier, humidity-wise, than the surrounding rural areas. A projected increase in summer temperatures by five to nine degrees, coupled with temperatures above 90 degrees on two-thirds of all summer days, will make living and working in our metropolitan areas much more difficult and costly, as well as generally less pleasant.

Illinois would definitely be a victim of global warming, but it is also a cause. As a manufacturing state, it is a major emitter of trace gases to the atmosphere, producing 4 percent of all global carbon dioxide released and 8 percent of all CFCs. Emissions from vehicles, from manufacturing, from animal waste (methane), and from mining, producing and burning coal all place Illinois among the nation's top contributors to trace gases in the environment.

As a major producer of trace gases, Illinois has justifiably deep concerns about how future controls and restrictions would affect all aspects of its industrial base. These controls would alter manufacturing processes by requiring expensive new technologies. Moreover, industries planning future structures and operations with lifetimes of 30-70 years, as well as water management concerns (e.g., dams, culvert, bridges and canals) and utilities must begin to deal with this issue now, regardless of the scientific uncertainties.

Conversely, these problems could also be opportunities for Illinois industry to develop and produce the new technologies needed to reduce trace gas emissions, to find substitutes for the most harmful of them, and to prepare Illinois' industrial and agricultural infrastructures for the new climate. This situation offers challenges to the strong scientific, technical and intellectual groups in Illinois.

The impacts that one can prophesy for Illinois from a significantly changed climate help explain the deep national and international concerns over the "greenhouse effect." In the last three years, more than 25 potential laws relating to global warming have been proposed in Congress. Gov. James R. Thompson sits on a National Governors' Association task force that was established to assess the global climate change issue and recommend policy for the states.

Illinois has a major stake in this policy development which will be extremely complex and distinct from any previous environmental issue. Conditions presently suggest that the strategy to deal with global warming will ultimately involve a mixture of adaptation and prevention. Since policy is developing around the global climate change issue nationwide, it is imperative that Illinois become involved in the debate.

Stanley A. Changnon is the principal scientist and chief emeritus of the Illinois State Water Survey, a division of the state's Department of Energy and Natural Resources. Peter J. Lamb is head of the survey's climate and meteorology section. Both are active nationally and internationally in research concerning climate change and its potential effects.

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