Can Global Climate Models be Used for Water Resource ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Can Global Climate Models be Used for Water Resource Planning?
Author:David Ahlfeld <> (Univ. of Massachusetts)
Presenter:David Ahlfeld <> (Univ. of Massachusetts)
Date: 2006-06-18     Track: Special Sessions     Session: Global Climate Change and Hydrologic Processes

Water resources planning is needed to adapt to a changing climate. As precipitation, wind and temperature patterns shift, water availability and demand by humans and other ecosystems will change. These shifts have the potential to impact water supply, agriculture, forestry and all non-human natural systems. Many large scale water resource projects, such as reservoirs, distribution systems, groundwater recharge facilities and desalinization systems can take many years to plan and construct. Shifting the location of agricultural activities may also require large lead times. Models are needed to predict climate one or more decades into the future to assist in rational planning of water resource systems as water needs change. It is important that these models predict trends at the decadal time scale, but also provide an indication of the permanence of these changes to distinguish changes which are permanent rather temporary excursions from the climate under which industrial civilization has evolved. Global Climate Models (GCM) and Regional Climate Models (RCM) have the potential to be useful tools for water resource planning under a changing climate. GCMs have been under development for many years with a primary goal of quantifying the long-term impact, on climate, of emissions of greenhouse gases. The focus has been on global average conditions. RCMs are a more recent development that seek to model climate at finer grid scales and shorter time frames. Several major RCM projects are under development including those that focus on North America and Europe. In the present study, an intercomparison study is conducted of the ability of GCMs to replicate observed 20th century climate. In addition, the GCMs are examined for their ability to provide meaningful results at different spatial scales. Comparisons are made with the CMAP observed precipitation data set which covers the period 1979-2000. GCM results are acquired from the IPCC database maintained by the Program for Climate Model Diagnosis and Intercomparison at LLNL. A comparison is made in three regions of North America. An additional comparison is conducted over a series of successively smaller averaging regions in portions of eastern North America. Precipitation and temperature averaged over monthly, seasonal and annual time periods is considered. Most models compare well with observed precipitation for the central and eastern regions at all time scales. For the western region, all models over-predict precipitation at most time scales both for the entire averaging region and for subdivisions of the region.