The El Nino/La Nina cycle, more formally known as the El Nino/Southern Oscillation (ENSO) is an irregular cycle of sea surface temperature, atmospheric pressure, and wind direction in the tropical Pacific Ocean which has a profound affect on global weather. Both floods and droughts are associated with phases of ENSO.
El Nino (warm phase)
In South America, this warm phase suppresses the normally cold upwelling currents that bring fish to the coasts of Peru and Ecuador. This phase brings unusually warm and wet weather during the South American winter.
In North America, El Nino brings warm, dry winters and wet summers to the northern region, and much wetter winters to the southwestern U.S. and northern Mexico.
Australia can experience droughts.
La Nina (cool phase)
In South America, La Nina brings drought to Peru and Chile but more rain to northern Brazil. In North America, La Nina brings above average precipitation to the north (hence our heavy snowfall during the winter of 2010-2011) and average to much below average precipitation to the southern U.S.
The influence of La Nina reaches Africa and produces more precipitation in south Africa and dryer conditions in equatorial Africa.
Climate models fail
Climate models, which are based on the assumption that carbon dioxide has a positive feedback, i.e., that carbon dioxide causes significant warming, make predictions on the behavior of ENSO. An analysis of those predictions versus what actually happened shows that the climate models predicted almost the exact opposite of what really happened.
Citation: McPhaden, M. J., T. Lee, and D. McClurg (2011), El Niño and its relationship to changing background conditions in the tropical Pacific Ocean, Geophys. Res. Lett., 38, L15709, doi:10.1029/2011GL048275
The abstract reads:
This paper addresses the question of whether the increased occurrence of central Pacific (CP) versus Eastern Pacific (EP) El Niños is consistent with greenhouse gas forced changes in the background state of the tropical Pacific as inferred from global climate change models. Our analysis uses high-quality satellite and in situ ocean data combined with wind data from atmospheric reanalyses for the past 31 years (1980–2010). We find changes in background conditions that are opposite to those expected from greenhouse gas forcing in climate models and opposite to what is expected if changes in the background state are mediating more frequent occurrences of CP El Niños. A plausible interpretation of these results is that the character of El Niño over the past 31 years has varied naturally and that these variations projected onto changes in the background state because of the asymmetric spatial structures of CP and EP El Niños.
In another paper:
Wolter, K. and Timlin, M.S. 2011. El Niño/Southern Oscillation behavior since 1871 as diagnosed in an extended multivariate ENSO index (MEI.ext). International Journal of Climatology 31: 1074-1087.
The researchers were able to extend analysis of ENSO events back to 1871 and found: “none of the behavior of recent ENSO events appears unprecedented, including duration, onset timing, and spacing in the last few decades compared to a full century before then.” Climate models predict that ENSO events should become more frequent and intense with global warming.
In other words, the climate model assumption of a positive feedback for carbon dioxide is wrong. And once again there is evidence that our carbon dioxide emissions have little actual effect on global temperature, and, there is still no physical evidence that carbon dioxide does have a significant effect. We, therefore, should not be basing policy decisions on flawed model scenarios.
ENSO is just one of several recognized oscillations driven by the sun and the earth’s position relative to the sun. To see other oscillations go here.
See Tisdales guide: An Illustrated Guide to El Nino and La Nina