I know, I know. We don't need more bad news. But I'm in the business of reporting news, good and bad. So here's the latest, with a sprinkling of hope for good measure: The National Oceanic and Atmospheric Administration has released a studyshowing that even if carbon dioxide emissions were completely halted right now, the world will still feel the effects of global warming for a millenium. And there's no going back.We've known for a while that carbon dioxide lingers for many years in the atmosphere, the study's authors say, but new research shows how that lingering will influence climate for centuries to come.From NOAA: "The study examines the consequences of allowing CO2 to build up to several different peak levels beyond present-day concentrations of 385 parts per million and then completely halting the emissions after the peak. The authors found that the scientific evidence is strong enough to quantify some irreversible climate impacts, including rainfall changes in certain key regions, and global sea level rise. If CO2 is allowed to peak at 450-600 parts per million [it’s at about 285 ppm now], the results would include persistent decreases in dry-season rainfall that are comparable to the 1930s North American Dust Bowl in zones including southern Europe, northern Africa, southwestern North America, southern Africa and western Australia."The reason carbon dioxide and its impact on our climate is expected to linger has to do with the ocean. It helps regulate climate--including how much carbon dioxide is in the atmosphere.But, just because there's no turning back on how much carbon dioxide we've put into the atmosphere so far, there's no reason to give up trying to reduce what we pump out going forward. The impacts of climate change, the study's authors say, will be less severe the less carbon dioxide we continue to emit.