Bloomberg: Smoke spreading across the sky from intense wildfires in North America could act temporarily to blunt the effect of global warming in the Arctic, climate researchers said. The Arctic may cool for weeks or months at a time as smoke from northern wildfires drifts into the region, said researchers at the University of Colorado and the U.S. National Oceanic and Atmospheric Administration. The cooling effect was observed above the snow-free tundra, and to a greater extent over the darker, …