That value is 2.74ppm higher than January 2010. It is 1.5ppm higher than December 2010.
2011 will be the first year that global CO2 concentrations will be higher than 390ppm for the first time in hundreds of thousands of years. And concentrations aren’t going down any time soon either. Despite the worst economic conditions since the Great Depression, global emissions in 2010 didn’t increase, but were “merely” flat. Until global emissions decrease by significant amounts year after year after year, concentrations will continue to rise to dangerous levels, precipitating changes in the globe’s climate system that will be irreversible for tens of thousands of years, at best.
How close are we to “dangerous levels”? The last collapse of the Greenland ice-sheet was found to occur between 400 and 560ppm. We’re only 10ppm away from the minimum of that range. We’ll blow past 400ppm within 5 years, which means dangers are just around the corner. As we’ve discovered in the past 10 years, global warming effects are not well predicted. Those effects have been larger, more complex and occurred sooner than anybody thought possible. There is no reason to assume situations will be different moving forward.