Global Warming Has Been on Natural 'Pause' Since 1998

Global temperatures between 1998 and 2013 indicate a "pause" in global warming, but scientists have revealed that this slowdown was actually due to natural cooling fluctuation, and not a decrease in greenhouse gas emissions like some believed.

The deceleration during this 15-year period is sometimes referred to as a "pause" or "hiatus" in global warming, and has raised questions about why the rate of surface warming on Earth has been markedly slower compared to previous decades. What's even more curious is that greenhouse gas levels have continued to rise throughout this period - proof for some that man-made emissions from the burning of fossil fuels is not to blame for global warming.

University of McGill researchers in this current study used statistical methodology developed in a previous paper, which had ruled out natural fluctuation with 99 percent certainty as the root cause for global warming in the industrial era.

But this time around, lead researcher Shaun Lovejoy applied the same technique to the 15-year period after 1998, during which time globally averaged temperatures remained high by historical standards, but were somewhat below most scientific predictions that estimated the effects of greenhouse gas emissions.

According to the new study, there has been a natural cooling fluctuation of about 0.28 to 0.37 degrees Celsius since 1998. This pattern is in line with variations that occur historically every 20 to 50 years, as evidenced by tree rings, ice cores and lake sediment.

The researchers also discovered that the cooling effect observed between 1998 and 2013 follows a larger pre-pause warming event from 1992 to 1998. This means that the natural cooling during the "pause" is no more than a return to the longer term natural variability, Lovejoy concluded.

"The pause thus has a convincing statistical explanation," he added in a statement.

So for those who had hoped that global warming had decided to slow down, think again, because it's just nature running its course.

The research was published in the journal Geophysical Research Letters.