Global lower stratospheric temperatures in January to March 2012 were the coldest ever measured (by satellites) according to Remote Sensing Systems (RSS). A cooling lower stratosphere is strong evidence of a strengthening greenhouse effect caused by increasing levels of greenhouse gases in the lower atmosphere (the troposphere). Heat from the lower atmosphere is radiated upwards at lower temperatures as increasing levels of greenhouse gases trap more heat in the troposphere. The lower stratosphere, which lies just above the troposphere receives less heat from below. Lower stratospheric cooling was predicted by climate scientists before it was observed. The combination of a warming troposphere and cooling lower stratosphere cannot be explained by external factors such as a warming sun or more cosmic rays. A warming sun would warm both the troposphere and the lower stratosphere.
