Sunday, June 30, 2013
El Nino - Global Warming Link Found
The El Nino - Southern Oscillation (ENSO) has, for the first time, been linked to global warming.
A team of researchers examining tree ring evidence from the past seven hundred years finds that ENSO events have increased in frequency since the onset of global warming.
Spawning droughts, floods, and other weather disturbances world-wide, the El Niño – Southern Oscillation (ENSO) impacts the daily life of millions of people. During El Niño, Atlantic hurricane activity wanes and rainfall in Hawaii decreases while Pacific winter storms shift southward, elevating the risk of floods in California.
These proxy records all indicate that ENSO was unusually active in the late 20th century compared to the past seven centuries, implying that this climate phenomenon is responding to ongoing global warming.
"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" explains lead author Jinbao Li.
"Many climate models do not reflect the strong ENSO response to global warming that we found," says co-author Shang-Ping Xie, meteorology professor at the International Pacific Research Center, University of Hawaii at Manoa and Roger Revelle Professor at Scripps Institution of Oceanography, University of California at San Diego. "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."
Their study is published in today's issue of Nature Climate Change.
After reading this report I contacted the study's lead author, Jinbao Li, to enquire about how the newly energized polar jet stream may interact with the more active El Nino-Southern Oscillation. His reply:
Many thanks for your interest in our work. Scientists generally believe that there is strong influence of the ENSO on the position of jet stream, as summarized here (http://www.srh.noaa.gov/jetstream/tropics/enso_impacts.htm). This year's unusual behavior of jet stream is challenging our current knowledge on this phenomenon. I myself haven't do much study on the interaction between ENSO and jet stream. But our current research suggests that ENSO will very likely get more extreme with global warming, which implicates that unusual jet stream will also become more frequent. I hope there will be solid studies on this topic soon.