Vice Pres. Al Gore yesterday warned a group of fifth graders that more heat waves are likely in the future because of global warming and told the kids that Republicans in Congress were blocking funds that could help save the environment. Gore and Bill Nye, who hosts a TV science program for kids, unveiled new data indicating that the Arctic ice sheet has melted by roughly 5 percent since the 1970s. In the meantime, the warming waters of the Mediterranean Sea have been attracting growing numbers of tropical fish that compete with indigenous species, according to a new study by Icram, Italy’s leading marine research center. The problem is attributed to warming winters in the region.