text: "Not only does the RSS satellite dataset show no global warming from December 1996 to April 2015, which is more than half of the entire satellite record," Monckton writes , "But the warming trend since 1900 is roughly 0.8C per century, well within natural variability." NOAA also expects that the higher CO2 levels will remain that way through May, but drop to lower levels as plants in the Northern Hemisphere begin to bloom, utilizing the CO2 for photosynthesis in the spring and summer.