Scientists working on a landmark U.N. climate change report are struggling over how to address a wrinkle in the meteorological data that has given ammunition to global-warming skeptics: The heating of Earth's surface appears to have slowed in the past 15 years even though greenhouse gas emissions keep rising.Some statisticians have dismissed the purported slowdown as a statistical mirage, arguing among other things that it reflects random climate fluctuations and an unusually hot year picked as the starting point for charting temperatures. They also say the data suggests the "missing" heat is simply settling — temporarily — in the ocean.
