The first day of a three-day, Bush administration-sponsored conference on global climate change convened yesterday, attracting more than 1,200 scientists and environmentalists but yielding very few surprises. Senior administration officials attending the conference said both the causes and effects of global warming remain uncertain and the country should therefore be cautious about committing to solutions. Although Commerce Secretary Donald Evans said the conference was designed to “jump-start” a review of proposals to combat global warming, some environmentalists felt it was doing just the opposite — delaying any real policy decisions until the indefinite future. Jennifer Morgan, a climate change expert with the World Wildlife Fund, said of the conference that it “would have been a good program if it were still 1990. … The U.S. is working in a time warp.”