For 20 years scientists have been talking about the weather changes that will come from the buildup of carbon dioxide in the atmosphere and now the Department of Energy is going to try to do something about it.

DOE is planning to coordinate a battery of government-sponsored investigations aimed at discovering exactly where the excess carbon dioxide, caused by the burning of fossil fuels, is going. It will then project what temperature and rainfall changes will result in the United States and around the world.

The DOE program is one element in a proposed five-year national climate plan to be unveiled March 24 before a newly formed National Climate Program Advisory Committee.

The plan, mandated by 1978 legislation, is still undergoing review by the 12 federal departments and agencies that have weather programs and the Office of Management and Budget, which supervises their budgets.

As of now, the plan attempts to coordinate about $120 million worth of climate research programs that are spread throughout the government.

It will focus on three particular areas:

Climate services. Through matching grants with states, the National Climate Program Office hopes to expand the tailoring of local weather forecasting services to the needs of specific users. For instance, "loggers need to know more about snowfall patterns for long-term planning," Chris Bernabo, a climate office consultant, said yesterday in describing the program.

Increased study of the effects of weather. The DOE study will fall into this category along with expansion of the Agriculture Department's investigations by satellite of worldwide crop changes caused by weather.The National Aeronautics and Space Administration is attempting to measure incoming solar radiation that affects weather. The National Science Foundation will expand its studies of the oceans, the sea's absorption of heat and warm water circulation patterns, both of which change over the years and bring about shifts in weather and climate over land.

Understanding and predictability of weather. The National Oceanic and Atmospheric Administration will direct renewed research in ways to make more accurate predictions of weather, focusing primarily on numerical modeling based on increased data collection.

Each of the involved agencies will make presentations of their own programs. The newly formed 13-member advisory panel will decide what changes, if any, it wants to make in the overall program.