August 22, 1981

A team of Federal scientists says it has detected an overall warming trend in the earth's atmosphere extending back to the year 1880. They regard this as evidence of the validity of the ''greenhouse'' effect, in which increasing amounts of carbon dioxide cause steady temperature increases. The seven atmospheric scientists predict a global warming of ''almost unprecedented magnitude'' in the next century. It might even be sufficient to melt and dislodge the ice cover of West Antarctica, they say, eventually leading to a worldwide rise of 15 to 20 feet in the sea level. In that case, they say, it would ''flood 25 percent of Louisiana and Florida, 10 percent of New Jersey and many other lowlands throughout the world'' within a century or less.

Senator Harrison A. Williams Jr. said today that he had learned that the special counsel for the Senate Select Committee on Ethics had recommended his expulsion from the Senate for his activities during the Abscam undercover investigation. The New Jersey Democrat, now in his 23d year in the Senate, said in a telephone interview that he had obtained his information from reliable sources. He also said that he had considered resigning, but that ''at this point my conscience tells me to stick and fight.'' ''You know,'' he added, ''it's just not right. I made foolish, meaningless mistakes, but I did not violate my trust or the law.'' The three Republicans and three Democrats on the ethics committee are scheduled to hold a closed meeting Monday to consider the report of the special counsel, Robert S. Bennett of Washington, who conducted the committee's inquiry. Sources close to the inquiry confirmed Mr. Bennett's recommendations, but declined to predict whether the panel would support them. Under committee rules, four votes are needed for a disciplinary resolution to be sent to the Senate floor.

Gasoline prices in the United States are expected to remain generally stable and possibly dip slightly over the next few months because of the failure yesterday of the oil ministers of the Organization of Petroleum Exporting Countries to agree on a uniform pricing policy. The result is particularly good news in view of the widespread expectation before and during the ministers' meeting in Geneva that OPEC would agree to a range of prices between $34 and $37 a barrel, rather than the current $32 to $40. Had the new range been adopted, with its $34 minimum price, it would have increased gasoline prices in the United States, many of which are tied to the $32 price that Saudi Arabia charges for its basic crude. OPEC's indecisiveness thus, in effect, saved American drivers 3 cents or more a gallon, oil analysts calculate. 'Good News for the Consumer' ''Obviously this is good news for the consumer,'' said John H. Lichtblau, executive director of the Petroleum Industry Research Foundation.

A three-day meeting of OPEC oil ministers ended today in failure to reach agreement on a new, lower range of prices.But Saudi Arabia, which accounts for one-fifth of the West's oil production, said it would maintain its price of $32 a barrel through 1982. The OPEC meeting, which many participants considered the most divisive and difficult in the group's 21-year history, appears to have produced a decisive victory for the Saudi policy of applying pressure to reduce world oil prices. One result of the meeting is that prices of petroleum products in the United States probably will remain stable or perhaps dip slightly. The price of gasoline at American service stations could drop by 3 cents or more a gallon from current averages of $1.34 to $1.41 a gallon, industry analysts calculate.

Pentagon officials gave a detailed report today on Wednesday's dogfight over the Gulf of Sidra to support the United States contention that American pilots shot down two Libyan planes only after being fired at first. The account included exerpts that the officials said were from intercepted radio communications by the lead Libyan pilot. According to one of the excerpts, the pilot said, in Arabic, ''I am preparing to fire,'' and, a moment later, ''I have fired.'' The officials said these statements were translated after the incident and were not known to the American pilots at the time of the encounter.