Why Did Global Warming Slow Down in the Nineties?
A global ban on ozone-destroying substances has kept the globe a little cooler. quattrostagioni/flickr Good news on the climate front, sort of: When we cut emissions of heat-trapping gases worldwide, global warming slows down. In a new analysis of temperatures and atmospheric greenhouse gas concentrations, researchers have found that the measurable reduction in emissions of ozone-depleting substances in the past 25 years has been matched by a break in the speed at which surface temperatures increased, compared to prior years. Since 1989, the year the international Montreal Protocol came into effect to protect the ozone layer, atmospheric chloroflurocarbon emissions (CFCs) have decreased by about 90 percent. Without this cut in CFCs, say the researchers, temperatures might currently be almost 0.1 degrees Centigrade (0.18 degrees Fahrenheit) hotter than they are—a small but significant difference in terms of climate conditions. Temperatures have risen about 0.85 degrees C (1.53 degrees...