Scientists Reveal What Has Caused the Global Warming 'Pause' Since 1998

First Posted: Jul 22, 2014 08:21 AM EDT

There's been a lot of debate over the global warming "pause" that has occurred between 1998 and 2013. Now, though, researchers may have found out why this pause has occurred. It turns out that it may be due to natural fluctuations in our own climate.

The deceleration in rising temperatures after 1998 is often referred to as a pause, or a hiatus, in global warming. It's raised questions about why the rate of surface warming on Earth has been markedly slower than in previous decades. What's more curious is that levels of greenhouse gases have continued to rise throughout the period.

In order to better understand why global warming seemed to be on hold, the researchers applied a statistical methodology developed in a previous paper. This earlier study used pre-industrial temperature proxies to analyze historical climate patterns and ruled out the possibility that global warming in the industrial area is just a natural fluctuation in Earth's climate. The researchers applied the same approach to the 15-year period after 1998.

So what did they find? It turns out that there has been a natural cooling fluctuation of about .28 to .37 degrees Celsius since 1998. This pattern is in line with variations that occur historically every 20 to 50 years.

That's not all the researchers found, either. The cooling effect follows a slightly larger pre-pause warming event that occurred from 1992 to 1998. This means that the natural cooling during the "pause" is actually a return to the longer term natural variability. This means that warming is an issue, and that the warming hiatus can be chalked up to natural patterns rather than being an actual pause when it comes to global warming.

The findings are published in the journal Geophysical Research Letters.

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