Earth’s median surface temperature could rise 5.2 degrees C) by 2100, the scientists at the Massachusetts Institute of Technology found, compared to a 2003 study that projected a median temperature increase of 4.3 degrees F (2.4 degrees C). The new study, published in the American Meteorological Society’s Journal of Climate, said the difference in projection was due to improved economic modeling and newer economic data than in previous scenarios. The MIT team used computer simulations that took world economic activity as well as climate processes into account, they said in a statement. “Without action, said study co-author Ronald Prinn, “there is significantly more risk than we previously estimated. This increases the urgency for significant policy action.” The study coincided with the US government announcing a plan to set national emissions standards for cars and trucks to cut climate-warming pollution and as a bill to institute a cap-and-trade system to curb greenhouse gases was debated in the House Energy and Commerce Committee.