Why Global Warming Took a Break and When It's Going to Start Again

The average temperature of Earth has barely risen over the past 16 years. So if global warming is still occurring, why does it seem like it's taking a break? Scientists may have the answer and have also announced that warming will continue again soon.

While global temperatures rose drastically into the late 1990s, the global average temperature has risen only slightly since 1998. This is particularly surprising consider that climate models predicted considerable warming due to rising greenhouse gases. Now there may be an explanation.

Two of the most important systems behind natural climate fluctuations are the weather phenomenon known as El Niño and La Niña. The year 1998 was a strong El Niño year, which is why it was so warm. In contrast, La Niña has made the past few years cooler than they normally would have been.

In fact, climate models had it so "wrong" mostly because it's impossible to predict the year in which these weather patterns will emerge. Although climate models can predict the long term, short term downturns due to La Niña are difficult to take into account.

It's not just these weather patterns that have caused the recent cooling, though. Solar irradiance has also been weaker than predicted in the past few years. This is mostly because the identified fluctuations in the intensity of solar irradiance are unusual at present. While the so-called sunspot cycles each lasted eleven years in the past, this latest period of weak solar irradiance lasted 13 years. In addition, floating particles in the atmosphere have increased, which also blocks out solar irradiance.

Despite this warming hiatus, though, scientists point out that there's no reason to doubt existing calculations for the climate activity of greenhouse gases or the latest climate models.

"Short-term climate fluctuations can be easily explained," said Reto Knutti, one of the researchers, in a news release. "They do not alter the fact that the climate will become considerably warmer in the long term as a result of greenhouse gas emissions."

The findings reveal exactly why our climate seems to have cooled over the past few years. Not only that, but it shows that once solar activity, aerosol concentrations in the atmosphere and weather phenomena such as El Niño return to values of previous decades, we'll start to see warming once more.

The findings are published in the journal Nature Geoscience.