Researchers reported Wednesday that global warming was interrupted in 1970 when a cold snap in northern oceans caused world temperatures to temporarily decrease. 

Between 1968 and 1972, temperature records show that sea surface temperatures in the Northern Hemisphere dropped 0.3 degrees Celsius (0.5 F) rapidly. This occurred mainly in the North Atlantic, and scientists used to think it was just a side effect of the slow build up of air pollution from cars and power plants, which blocked sunlight. 

But now, American and British scientists, who examined the above mentioned temperature records, are saying that the sudden temperature drop in 1970 occurred during the same time as a "sudden inflow of cold water from the Arctic." This flow of cold, fresh water into the North Atlantic is known as the "Great Salinity Anomaly," and the scientists believe a cold spell in these oceans led to a decrease in world temperatures, resulting in a momentary pause in the global warming trend. 

These scientists, led by David Thompson, lead author of the study at Colorado State University, found the temperature drop after eliminating other factors that can block sunlight, such as volcanic ash blocking sunlight and long-term shifts in ocean temperatures and currents. 

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

The findings of Thompson and his co-author of the study, Phil Jones, of Britain's University of East Anglia, sharply contrast all previous predictions surrounding this temperature decrease from 1968 to 1972 because this new study notes that this "pulse" of cooler temperatures seemed to occur due to natural variations rather than human activity. 

"No one is postulating that the 'Great Salinity Anomaly' has any relationship to warming or the greenhouse effect from humans," said Jones. 

In contrast, the U.N. panel of climate scientists mentioned that average world temperatures have increased by 0.7 degrees Celsius since the Industrial Revolution. Sea ice is made of fresh water, and with fossil fuels emitting carbon dioxide and supposedly warming world temperatures since the Industrial Revolution, sea ice in the Arctic could have melted and flowed into the North Atlantic due to man-made activity. 

Jones was involved with the hacked e-mails at the University of East Anglia in 2009, and was accused of exaggerating evidence that supports global warming. After a review, he was reinstated and all accusations were cleared. Now, when asked how he thinks climate skeptics will react when he releases this study "highlighting the cause of cooling rather than warming," Jones said, "Maybe it will get them thinking."

This study was published in Nature this month.