Ocean cooling 'contributed to global warming hiatus during mid-20th century '

London, Sept 23 (ANI): A new study has indicated that the ocean cooling in North Atlantic around 1970 contributed to the hiatus of global warming in the Northern Hemisphere during the mid-20th century, and not tropospheric pollution.

David W. J. Thompson at Colorado State University, John M. Wallace at the University of Washington,John J. Kennedy at the Met Office and Phil D. Jones of the University of East Anglia discovered an unexpectedly abrupt cooling event that occurred between roughly 1968 and 1972 in Northern Hemisphere ocean temperatures.

"We knew that the Northern Hemisphere oceans cooled during the mid-20th century, but the sudden nature of that cooling surprised us," Nature quoted Thompson as saying.

"Accounting for the effects of some forms of natural variability - such as El Nino and volcanic eruptions - helped us to identify the suddenness of the event," Jones said.

Although previous studies have claimed that the large buildup of tropospheric aerosol pollution in the rapidly industrializing Northern Hemisphere was majorly responsible for global warming, the new study indicates otherwise.

"The suddenness of the drop in Northern Hemisphere ocean temperatures relative to the Southern Hemisphere is difficult to reconcile with the relatively slow buildup of tropospheric aerosols," Thompson said.

"We don't know why the Northern Hemisphere ocean areas cooled so rapidly around 1970. But the cooling appears to be largest in a climatically important region of the ocean," Wallace said.

The study appears in the journal Nature. (ANI)