It would be hard to think of a more difficult assignment and a more demanding need than President Carter has given the new Commission on World Hunger. He has allowed the commission two years in which to come up with a final report that will give the dimensions of the great abyss of the hungry and propose ways to implement answers to the worldwide need.

Creating the commission, the president named Sol Linowitz, former ambassador to the Organization of American States and one of the prime movers in ratification of the Panama Canal treaties, to be chairman. Linowitz has enlisted some of the nation's leading nutritionists and pollution authorities, along with two senators and two members of the House who have been interested in the need.

Linowitz is taking a practical approach. It is not, he says, an effort by the United States to feed the world on a do-good basis. How the world can feed itself is the objective.

Inevitably, this takes in the population explosion. Linowitz puts the number of the severely malnourished, those who live on the borderline of starvation, at 500 million. The estimate is that 10 million die annually of diseases related to malnutrition and perhaps half of that number are children.

Two weeks ago in this space I wrote about the grim reality of world hunger. In that column I attributed to the Enivornmental Fund the statement that the rate of population increase remained at roughly 2 percent worldwide, contrary to the figures used by other population groups showing the rate had declined to 1.8 or perhaps even 1.7.

That drew an indignant letter from the Population Crisis Committee insisting that their figure of 1.7 to 1.8 annually was correct.

But whatever the precise figure for population growth, there can be no question as to widespread - and growing - hunger. The basic figure I relied on came from Chairman Robert McNamara of the World Bank, who is hardly a naive optimist in these matters. In his annual report he gave figures from a report by specialists in the bank showing that even if all the aid and the other sources of help are lived up to the number living in absolute poverty by the year 2000 would be 600 million.

That is a daunting statistic requiring a rugged imagination to translate into actual human terms. It may be, as I suggested before, considerably more than that, perhaps one-fourth of the world's population.

As Linowitz is well aware, the impoverished are not a passive body waiting to starve and die. As much as the peril of the arms race, they are a threat to stability and a potential of great danger. Breakdown, rioting, disruption can occur where it can work the greatest harm to the industrialized world as in the channels of the oil flow from East to West.

"We cannot have a peaceful and prosperous world," Carter said in announcing the formation of the commission, "if a large part of the world's people are at or near the edge of hunger. So long as food shortages exist in developing countries, the possibility remains of another world food crisis like that of 1973-74. Such a crisis could trigger another ruinous cycle in food prices and thus contribute powerfully to inflation."

Congress has cut back proposed programs for aid for family planning in countries where it is most needed. That reflects the nervousness from which this whole question of trying to limit the growth of population suffers. As a result the amounts provided in U.S. aid are minuscule and then given off the record.

While the president made a passing reference to reducing "population growth," the commission must confront the root cause of pooverty. That will be far from easy since the inhibitions that work against family planning are so formidable both here at home and in the developing world.

One of the first tasks is to set the U.S. administrative house in order. Presently 26 different agencies are dealing with world hunger. That cluttering underbrush must be cut back before the commission will have a clear path to work on the basic problem.

The record of presidential commissions has not been altogether happy. Their reports have too often tended to fall into the dusty file-and-forget category. It will take a strong and assertive public opinion to ensure that this is not the fate of the two reports the president has called for, one would be a status report due next July, a final report by May 31, 1980.

The specialists recruited to work with the commission are an impressive roster of men and women of great knowledge in the field. But they will be working part-time, as will the commission itself, and part-time may not be enough.