In his State of the Union address last night, Pres. Clinton called global warming “the greatest environmental challenge of the new century,” and said that “if we fail to reduce emissions of greenhouse gases, deadly heat waves and droughts will become more frequent, coastal areas will be flooded, economies disrupted.” He stressed that cutting emissions doesn’t mean slowing economic growth, and proposed tax incentives for clean energy and efficient cars, appliances, and homes. And he called on Congress to make U.S. clean-energy technologies available to the developing world. Clinton also proposed a permanent Lands Legacy conservation fund for protecting land and restoring wildlife. Twice he praised Vice Pres. Al Gore for his initiatives to create liberal — oops, he meant livable — communities by preserving open space and tackling sprawl.