Such is the profound nature of human - caused global warming, that it has overcome these many short - term natural cooling influences. (steynonline.com)
Volcanic eruptions (indicated in red by the stratospheric optical depth) impose a short term cooling influence of several years. (skepticalscience.com)
For instance, he says, «if you remove all the forest in the U.S., it would probably heat up the world, but have a slight cooling influence on the U.S., itself.» (scientificamerican.com)