Collectively, the 40 industrialized nations that agreed to reduce greenhouse-gas emissions under the Kyoto Protocol have met their goal of cutting emissions to an average of about 5 percent below 1990 levels, the United Nations reported this week. But some of the biggest reductions were due to economic declines in central and eastern European countries in the 1990s. Between 2000 and 2006, emissions of the 40 nations rose by 2.3 percent, a trend that threatens to wipe out past improvements.