El Niño/La Niña Global Surface Temperature Influence - 1967-2012
Snce El Nino and La Nina have such an impact on global atmospheric temperatures, the best way to look at the atmospheric temperature change is to categorize the global temperature by “type of year”, which indicates that the atmospheric temperatures have been increasing at the same steady rate (about .16°C /decade) since 1970
Source: wunderground.com
URL:     http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2374