Don’t Hang Your Hat on This One

by Carl Wolk on August 6, 2009

When it comes to understanding climate change, the El Nino/Southern Oscillation (ENSO) is one of the least understood but most important aspects of the climate system. Dynamics related to ENSO, like the Madden-Julian Oscillation, Pacific Decadal Oscillation, and Meridional Overturning Circulation, dominate the Indian, Pacific, and North Atlantic Oceans. With that said, a recent paper published in the Journal of Geophysical Research titled “Influence of the Southern Oscillation on tropospheric temperature” represents a misinterpretation of ENSO.

The new paper by McLean, De Freitas, and Carter blames global warming on ENSO and has garnered a lot of attention and enthusiasm from the skeptical community.  Their conclusion may indeed hold water, but not for the reasons they claim.

ENSO describes a pattern of sea surface temperatures, pressure, and wind in the Equatorial Pacific. During El Nino events, the pressure differential between the East and West Pacific falls, trade winds slow, and warm water sloshes upward and eastward until it appears in the temperature record in the Cold Tongue of the Pacific. During La Nina events, the opposite happens.

ENSO is classically defined as heat redistribution; no heat enters the system during El Nino events or leaves the system during La Nina events. The heat is merely moved from the subsurface (hidden from the temperature record) to the surface (included in the temperature record). Behind all the math used in the paper, the fact remains that ENSO has been falling since 1976, while temperatures have risen. If they accept the classical definition of ENSO as non-radiative (which one can only assume they do), then they cannot blame ENSO for global warming.

It is for this reason that the conclusions of the paper are not supported by the work in their paper. All they establish is that ENSO drives global temperatures over the short-term; they do nothing to show it would explain the trend. Unless they challenged the conventional view of ENSO as non-radiative, their case holds no water. With that said, there is significant evidence that ENSO may in fact be radiative, particularly the 1976/7, 1986/7, and 1997/8 events. For more information on how the data demonstrate that ENSO is a radiative oscillation, visit my blog, here.

In conclusion, McLean, De Freitas, and Carter’s research is a reminder that the alarmists have no monopoly on papers that prove less than the authors claim; the alarmists just publish most of them.

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