They have been using the minimum estimate for CO2 impact on heating since the 1970s. The level of pollution in the air has been hiding the true impact and as the various causes of pollution are removed the earth energy balance is changing such that it turns out that the highest end of the CO2 impact is actually correct, which doubles the heating effect. There has been about a third of climate scientists who have been warning about this but they have consistently been called the extremists or the doomers and they have been right all along. They were always right, the evidence was based on actual experiments of the impact of CO2 and not by measuring the planet.