The climate trends are overwhelming. Earth had its fourth-warmest year on record in 2013, and all of the 10 warmest years on record have occurred since 1998, the National Oceanic and Atmospheric Administration reported last week. It is true, as the skeptics like to point out, that long-term climate modeling remains an inexact science. Some environmentalists hurt their cause by leaping to blame every extreme weather event on global warming. And a changing climate produces winners as well as losers. But climate scientists are 95% to 100% sure that human activity — emission of greenhouse gases — is the dominant cause of dramatic warming. That warming is already raising sea levels, acidifying oceans, melting glaciers and intensifying heat waves, downpours, droughts and wildfires. January's cold snap has caused plenty of misery. The damage will only be compounded if it becomes an excuse for yet another year of denial and delay in addressing climate dangers.