Read here. Global warming alarmists have claimed that an increase of central Pacific El Niño events and intensity are the direct result of human-induced global warming. Yeh et al. conducted extensive research using climate models (4,200 simulations) and determined that natural variability could be the cause of increased El Niño frequency and intensity instead of the claimed human cause.
"...they indicate there is evidence of "increasing intensity as well as occurrence frequency of the so-called Central Pacific (CP) El Niño events since the 1990s." And the question thus arises: Is the latter a consequence of global warming?...ran a multi-millennial CGCM (coupled general circulation model) simulation "to assess whether the natural changes in the frequency of CP El Niño occurrence simulated by the model are comparable to the observed changes over the last few decades," suggesting that "if the changes are similar then we cannot rule out the possibility that the recent changes are simply natural variability."..."we cannot exclude the possibility that an increasing of occurrence frequency of CP El Niño during recent decades in the observation could be a part of natural variability in the tropical climate system," providing one more piece of evidence for the likely benign nature of recent global warming." [Sang-Wook Yeh, Ben P. Kirtman, Jong-Seong Kug, Wonsun Park, and Mojib Latif 2011: Geophysical Research Letters]
Additional oscillation-mode and peer-reviewed postings.