IF the sea level rises because of an increase in the earth's temperature, the island nations of the South Pacific will be among the biggest losers; some are barely above water now.So it is not surprising that global warming, the so-called greenhouse effect, will be one of the major issues when the 15 members of the South Pacific Forum meet here today and tomorrow. "We in the Pacific area feel we do not contribute much to global warming," says the Hon. Bailey Olter, the new president of the Federated States of Micronesia. "We will be asking the industrialized countries to take it easy and think about us." With the exception of member Australia, industrial output on these recently independent island nations is minimal. Sen. Gareth Evans, Australia's minister for foreign affairs and trade says the global warming issue "is very lively" among developing countries in general. And most countries, he says, are preparing for the United Nations conference on the environment and development to be held in 1992 in Rio de Janeiro. After the regional meeting ends on July 30, the forum leaders will get an opportunity to express their concerns to the major producers of carbon dioxide, the source of global warming. Representatives of the United States, Britain, China, France, Japan, and the European Community have been invited to meet the forum members on Aug. 1-2. The forum leaders will also discuss setting up an information-sharing network on organized crime groups, which in the past have preyed on smaller, developing countries. Some of the issues the leaders will discuss have been on the agenda before. For example, most of the leaders are opposed to French nuclear testing. So far this year, the French have conducted six tests at Moruroa Atoll in French Polynesia. This month, Senator Evans called in the French ambassador to protest the latest test on July 16. France, for its part, says it will not cease testing and considers criticism an intrusion on its national sovereignty. "To the extent that [France] is still demonstrating a willingness to take absolutely no notice to a consistent, systematic, and repeated regional position, then it does demonstrate a degree of insensitivity with which forum countries, including Australia, can be very unhappy," says Mr. Evans. The leaders will also discuss the US destruction of chemical weapons at Johnston Atoll, a US-administered island 825 miles southwest of Honolulu. The chemical weapons facility was the most controversial issue at last year's forum. Since the last forum, President Bush met with forum leaders in Hawaii, assuring them the facility will not be expanded. The US says it will use Johnston Atoll to destroy chemical weapons previously transferred from Okinawa, weapons removed from Germany last year, and World War II-era bombs found on the Solomon Islands. The US has said it will not use the Johnston facility to destroy Iraqi chemical weapons.