Reason Behind Global Warming Lull: Stadium Waves Explain Climate Change

Global warming seems to be on hiatus. In fact, this particular issue was discussed extensively within the recent Intergovernmental Panel on Climate Change (IPPC) Fifth Assessment Report. Now, scientists may have discovered a reason for this seeming pause in climate change. It turns out that large-scale circulation in the world's atmosphere and ocean might have helped "pause" warming.

Our Earth plays host to large-scale circulation regimes. For example, El Niño is one of the most familiar of these. Although scientists believed that this climate variability was relatively unpredictable, though, it turns out that it may be far more predictable than we might once have thought. Researchers have no pointed to the so-called "stadium-wave" signal, which could propagate across the Northern Hemisphere through a network of ocean, ice and atmospheric circulation regimes that self-organize into a collective tempo.

There are two main ingredients for the propagation and maintenance of this stadium wave signal: the Atlantic Multidecadal Oscillation (AMO) and the sea ice extent in the Eurasian Arctic shelf seas. The AMO sets the signal's tempo while the sea ice bridges communication between ocean and atmosphere. Positive and negative feedbacks interact to support reversals of the circulation regimes. As a result, climate regimes evolve in a spatially and temporally ordered manner. This means that their repetition is regular and that the order of quasi-oscillatory events remains consistent.

In fact, the researchers found that this stadium wave periodically enhances or dampens the trend of long-term rising temperatures. This, in turn, could potentially explain the recent hiatus in rising global surface temperatures.

"The stadium wave signal predicts that the current pause in global warming could extend into the 2030s," said Marcia Wyatt, one of the researchers, in a news release.

The findings are important for future climate models. The new research flies in the face of other predictions, which project an imminent resumption of warming temperatures. If the stadium wave signal is correct, it's likely that this hiatus may last a little longer than expected. That's not to say that the researchers are done examining this particular phenomenon, though.

"How external forcing projects onto the stadium wave, and whether it influences signal tempo or affects timing or magnitude shits, is unknown are requires further investigation," said Wyatt in a news release. "While the results of this study appear to have implications regarding the hiatus in warming, the stadium wave signal does not support or refute anthropogenic global warming. The stadium wave hypothesis seeks to explain the natural multidecadal component of climate variability."

The findings are published in the journal Climate Dynamics.