An anonymous reader writes: A new study from the UN's Intergovernmental Panel on Climate Change (IPCC) shows that carbon dioxide (CO2) concentrations in the atmosphere are likely to remain above 400 parts per million (ppm) for many years. Specifically, scientists forecasted that levels would not dip below 400pm in "our lifetimes." The CO2 concentrations of "about 450ppm or lower are likely to maintain warming below 2 degrees Celsius over the 21st century relative to pre-industrial levels." However, lead author on the paper Richard Betts said we could pass that number in 20 years or less. In an article on The Guardian, he said even if we reduce emissions immediately, we might be able to delay reaching 450ppm but "it is still looking like a challenge to stay below 450ppm." El Nino has played a significant role in climbing carbon dioxide levels, but it's likely we'll see higher CO2 levels than the last large El Nino storm during 1997 and 1998 because "manmade emissions" have risen by 25 percent since that storm, according to The Guardian. Met Office experts predicted in November 2015 that in May 2016 "mean concentrations of atmospheric CO2" would hit 407.57ppm -- the actual figure was 407.7ppm. The NOAA reported during 2015 that the "annual growth rate" of CO2 in the atmosphere rose by 3.05ppm. NOAA lead scientist Pieter Tans said, "Carbon dioxide levels are increasing faster than they have in hundreds of thousands of years. It's explosive compared to the natural processes."