The amount of heat-trapping carbon dioxide in the atmosphere jumped dramatically in 2012, the National Oceanic and Atmospheric Administration reported on Wednesday. Scientists say the rise in CO2 reflects increased burning of fossil fuels.

Last year saw the second greatest jump in carbon emissions since record-keeping began in 1959. “As carbon concentrations continue to rise and we see more and more extreme weather and other effects of global warming, it is clear Congress has got to get its act together and pass strong legislation. That is why Sen. Boxer and I introduced the Climate Protection Act, bold legislation to cut emissions by a significant amount and invest in energy efficiency and sustainable energy,” Sanders said. “I fear very much that history will look back at this period and ask, ‘How could it be that the United States did not address this planetary crisis when it had the chance?’”