GLERL Fiscal Year 1999 Quarter 3 Milestone Report: F. Quinn, B. Lofgren, and T. Croley

PM: Improvement of Forecasts for Application to Climate-sensitive Sectors through Collaboration with Decision Makers and Other Climate Forecast Users.

MILESTONE: Develop climate/hydrologic scenarios for the Great Lakes-St. Lawrence River basin using monthly data from the Canadian Climate center GCM transient runs with aerosols

The U.S. National Assessment of the Potential Consequences of Climate Variability and Change for the Nation, conducted as part of the U.S. Global Change Research Program, is providing a detailed understanding of the consequences of climate change for the nation and will examine the possible coping mechanisms that exist to adapt to climate change. This assessment includes regional activities, sectoral activities, and a broad synthesis. It is being conducted as a public-private partnership and emphasizes a process driven by the needs of the stakeholders throughout the country who are best positioned to identify the priority information needs, and the most rewarding ways of responding. Twenty regional assessments are focusing on the issues of most importance at the regional level across the United States. The Great Lakes assessment region is geographically and climatologically unique. Because the Great Lakes themselves constitute 95% of the nation's fresh surface water, many of the concerns regarding the effects of climate change and variability are water-related. For example, groups from industries such as agriculture, commercial fishing and shipping, and leisure activities such as boating and swimming are concerned about water quality and quantity in the region. The assessment of climate change impacts on the water resources sector in the Great Lakes Basin is being led by the Great Lakes Environmental Research Laboratory (GLERL). The focus of this milestone is the development of the climate/hydrologic scenarios to be used to be used in the assessment process. This study contributes to the Strategic Plan Objective "Implement Seasonal to Interannual Climate Forecasts" and the performance measure "Deliver Climate Services and Assess Socioeconomic Impacts" by beginning to assess the regional impacts of climate on key economic sectors and water resource management decisions in the Great Lakes basin.

The climate/hydrologic scenarios were developed using outputs from the Canadian Climate Center's Coupled General Circulation Model version 1 (CGCM1), run with a transient level of atmospheric CO2 concentration and also accounting for the direct effects of a transient concentration of tropospheric sulfate aerosols. Data on precipitation, air temperature, wind speed, cloud cover, and humidity were taken from the General Circulation Model (GCM) grid points, to be interpolated to the Great Lakes' tributary basins. The application procedure applies monthly ratios of GCM future to GCM base climate data and applies them to observed historical climate data sets. This allows the assessment of mean changes in the hydrologic and climatic variables, but not changes in variability. The resulting data sets were applied to GLERL's Great Lakes Advanced Hydrologic Prediction suite of models and ice cover models to assess impacts to Great Lakes water supplies, lake levels, ice cover, and tributary river flows for the 121 Great Lakes major tributary basins.

There are a broad range of customers for this data. The results have been disseminated by providing the basic and modeled data and through symposia and panel discussions at professional meetings, interest group meetings, Congressional Briefings, and the media. In addition to their use in the National Assessment, the scenarios are currently being used by the International Joint Commission on their Bilateral Reference on Great Lakes Withdrawals and Consumptive Uses of Water. The data are being used by GLERL and the Corps of Engineers to assess the effectiveness and robustness of the current Lake Superior and Lake Ontario regulation plans under the reduced water supply conditions represented by the scenarios. Other customers include the Lake Carriers Association and other navigation interests, the eight Great Lakes States and the provinces of Ontario and Quebec, and other diverse groups including urban planners and land developers, insurance companies, and tourism groups. Finally, native groups and environmental and wilderness groups within the region have professional and recreational interests that depend significantly upon the water resources of the Great Lakes basin.

Figure 1, Lake Michigan-Huron water levels, base case (1954-1995) and 2030 simulation.

The scenarios developed through this effort are significant as they are the first for Great Lakes studies using a transient GCM with the direct effect of aerosols. They are also the first using a GCM to look at impacts as soon as 2030 and also at 2050 and 2090. This project demonstrated that major impacts to Great Lakes water resources could be expected to occur as early as 30 years in the future (Figure 1) with lake levels lowered by a much as 1.1 meters (Table 1). The regulation plan for Lake Ontario was unable to meet the Orders of Approval and failed under the simulated low water supplies.

Lake	Difference from base conditions (meters) for period centered about
Lake	2030	2050
Superior	-0.4	-0.5
Michigan-Huron	-1.1	-1.3
Erie	-0.8	-1.0
Ontario	-0.4	-0.6

This project was successfully completed in June of this year and is currently being used as a climate/hydrological scenario in the ongoing Great Lakes regional water resource assessment of the U.S. National Climate Assessment. This project contributed to the NOAA SP objective and performance measure by providing scenarios to assess the regional impacts of climate change on key economic sectors and resource management decisions.

The data from this study will be used for water resource impact assessments and for the assessment of alternative lake regulation plans for the Great Lakes basin as part of the National Assessment.

GLERL 1999 Milestone Reports