Their testimony came in the third in a series of hearings Senator Barbara Boxer, chair of the Senate Environment and Public Works Committee, is holding prior to drafting national legislation. On March 21, former Vice President Al Gore, whose movie on global warming recently won an Oscar for documentary films, will appear before her committee.

Boxer had hoped California’s forecast of a huge financial dividend from controlling emissions would help soothe the discontent of some committee Republicans skeptical about global warming and fearful of the impact curbs will have on the economy.