I write about this stuff for a living and still forget which is which is as far as La Nina and El Nino are concerned. So, to recap: La Nina is where water surface temperatures in the eastern Pacific are lower than usual by a few degrees, El Nino is where those temperatures are a bit warmer. Both events cause weird weather, with 2011's La Nino kicking the pants off the Atlantic North American coast and the southern Pacific. Meanwhile, an El Nino event typically accentuates drought in the upper-Midwest of the United States while bringing rain and flooding to the Southwest and particularly southern California. While doing terrible things to many parts of the world, an El Nino means a decreased likelihood of hurricanes on the East Coast.
It's hard to say that either climate event "evens out" on a global scale, but there are some winners and losers. It might be theoretically possible to make the effects of El Nino and La Nina fluctuations even out at least a little bit better, however, with improved forecasting, particularly in how the cycles respond to global warming. Right now, it's hard. The effects of 2011's La Nina actually took us somewhat by surprise. That's bad. According to a paper out in this week's Nature Climate Change, courtesy of a team based at the International Pacific Research Center at the University of Hawaii, we might be getting close to being able to accurately predict future cycles as they relate to climate change.
La Nino and El Nino events, a.k.a. the El Niño – Southern Oscillation (ENSO), fall into an ugly sort of middle ground in terms of prediction. They are too long-term to forecast like we forecast day-to-day weather, but not long-term enough to look at in terms of millenia, like climate change. The big problem is that our instrument records don't go far enough back to get a good handle on the Southern Oscillation. But the University of Hawaii team has compiled 2,222 tree-ring chronologies covering the past seven centuries, revealing in fine resolution temperature and precipitation records of those years. The result is a highly accurate archive of global ENSO activity, and one that has implications for how we view climate change.
"In the year after a large tropical volcanic eruption, our record shows that the east-central tropical Pacific is unusually cool, followed by unusual warming one year later. Like greenhouse gases, volcanic aerosols perturb the Earth's radiation balance. This supports the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming," says lead author Jinbao Li in a press release.
"Many climate models do not reflect the strong ENSO response to global warming that we found," adds co-author Shang-Ping Xie. "This suggests that many models underestimate the sensitivity to radiative perturbations in greenhouse gases. Our results now provide a guide to improve the accuracy of climate models and their projections of future ENSO activity. If this trend of increasing ENSO activity continues, we expect to see more weather extremes such as floods and droughts." Which is what we've expected, more or less—more extreme weather—but now we can at least expect it better.
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