Teams of researchers have analyzed that a 12-year hiatus in global warming is actually attributable to volcanic eruptions and trade winds. After two decades of rapid increase in surface temperatures, scientists noticed a pause in global warming in the past 12 years. It was surprising that the pause existed despite a rapid increase in atmospheric concentrations of heat-trapping carbon dioxide since the 1960s.

Researchers used observations of volcanic activity between 1988 and 2012 to see the impact on global warming. It was found that volcanic eruptions send sulfuric acid droplets and tiny sulfate particle so high in the air that they reach stratosphere and reduce the temperature of the troposphere for one or two years before the particles come on the ground again.

The gas forms 'volcanic aerosols' or tiny droplets of sulfuric acid above the troposphere that act as a reflector to incoming sunlight to send back into space. As a result, the earth's atmosphere experiences a cooling effect.

The amount of volcanic aerosols has increased in the stratosphere in the last decade, said Lawrence Livermore climate scientist Benjamin Santer, who serves as lead author of the study. "This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence", he added.

Also, it was found by researchers that the second factor that has cooled the earth's atmosphere is the westward-blowing trade winds that have intensified to unprecedented levels over the past 20 years.

Warm surface waters have been carried by the winds to west where they converge and gather at ever-deeper depths. Cold water has replaced the warm surface waters in the eastern Pacific after welling up from deep ocean and spreading west into the central Pacific as well as along the coasts of South and North America.

Scientists have said that if the trade winds follow this pattern till 2020, it is highly unlikely that global average surface temperatures will rise much above the 2001-2010 average.