Confirmation bias in climate predictions: El Niño and Arctic temperatures

Source: Danmarks Meteorologiske Institut

Source: Danmarks Meteorologiske Institut

Confirmation bias, also called confirmatory bias or myside bias, is the tendency to search for, interpret, favor, and recall information in a way that confirms one’s beliefs or hypotheses, while giving disproportionately less consideration to alternative possibilities.



This is one of the chief culprits of predictive failures in climate science.

Luckily, someone is more resistant to this bias than others.

SHAPIRO: OK. So El Nino plays a role. The Arctic oscillation plays a role. What about climate change? Is that playing a role?

HALPERT [Mike Halpert, NOAA’s deputy director of the Climate Prediction Center]: If it is, it’s probably fairly insignificant at this point. If it were to play a role, it would be more likely if, somehow, climate change is impacting either the Arctic oscillation or El Nino, and we’re not really aware that it is at this point. If you think about, maybe – the high temperature over the weekend was 70, so maybe without climate change, it would’ve been 69. I think it’s a fairly insignificant role, if any role at all.

Meteorologists have blamed El Niño and the polar vortex for record-breaking warm temperatures across the US this week, saying the pair of weather systems will likely keep 2015 warm enough to be the hottest year on record.

Climate scientists caution that the fluctuations of the weather – including systems like El Niño and the polar vortex – should not be conflated with climate change, which is the related but separate, long-term warming of the planet.


The Arctic Atlantic reconstruction features temperatures during the Roman Warm Period and Medieval Climate Anomaly that are comparable or even warmer than those of the twentieth century

Sami Hanhijärvi, Martin P. Tingley, Atte Korhola, Pairwise comparisons to reconstruct mean temperature in the Arctic Atlantic Region over the last 2,000 years, Climate Dynamics, October 2013, Volume 41, Issue 7, pp 2039-2060

Graphs of the actual and reconstructed Arctic temperatures over the past millennia, showing that today’s temperatures are no warmer than in the past and certainly not outside the range of natural variation:

Rinne et al, 2014:…/1-s2.0-S0921818114000253-gr4.jpg

Von Gunten et al., 2012:

Cook et al., 2008:

Gajewski, 2015:…/1-s2.0-S0921818115000417-gr3.jpg

Divine et al., 2011:…/view…/7379/html_187/26749

Arctic temperatures satellitetemperatures reconstruction Arctic 1temperatures reconstruction Arctic 2temperatures reconstruction Arctic 3temperatures reconstruction Arctic 4temperatures reconstruction Arctic 5doi:10.3402/polar.v30i0.7379

Godzilla El Niño: harbinger of some portentous changes in climate?


BEGINNING about 1,100 years ago, what is now California baked in two droughts, the first lasting 220 years and the second 140 years. Each was much more intense than the mere six-year dry spells that afflict modern California from time to time, new studies of past climates show. The findings suggest, in fact, that relatively wet periods like the 20th century have been the exception rather than the rule in California for at least the last 3,500 years, and that mega-droughts are likely to recur.

Severe Ancient Droughts: A Warning to California, NYT, 19 July 1994

This could be among the strongest El Niños in the historical record dating back to 1950

Mike Halpert, deputy director of the Climate Prediction Center, Latest forecast suggests ‘Godzilla El Niño’ may be coming to California, Los Angeles Times, 13 August 2015

El Niño Activity and Sea-Ice Extent in a South Pole Ice Core

Meyerson, E.A., Mayewski, P.A., Kreutz, K.J., Meeker, D., Whitlow, S.I. and Twickler, M.S.  2003.  The polar expression of ENSO and sea-ice variability as recorded in a South Pole ice core.  Annals of Glaciology 35: 430-436.

What was learned

Among other things, the authors noted a shift at about 1800 towards generally cooler conditions. This shift was concurrent with an increase in the frequency of El Niño events in the ice core proxy record, which is contrary to what is generally predicted by climate models, where cooling generally leads to less El Niño activity and warming leads to more (Timmermann et al., 1999). On the other hand, the authors’ findings were harmonious with the historical El Niño chronology of both South America (Quinn and Neal, 1992) and the Nile region (Quinn, 1992), which depict “increased El Niño activity during the period of the Little Ice Age (nominally 1400-1900) and decreased El Niño activity during the Medieval Warm Period (nominally 950-1250),” as per Anderson (1992) and de Putter et al., 1998).

Anderson, R.Y.  1992.  Long-term changes in the frequency of occurrence of El Niño events.  In: Diaz, H.F. and Markgraf, V. (Eds.), El Niño.  Historical and Paleoclimatic Aspects of the Southern Oscillation.  Cambridge University Press, Cambridge, UK, pp. 193-200.

de Putter, T., Loutre, M.-F. and Wansard, G.  1998.  Decadal periodicities of Nile River historical discharge (A.D. 622-1470) and climatic implications.  Geophysical Research Letters 25: 3195-3197.

Quinn, W.H.  1992.  A study of Southern Oscillation-related climatic activity for A.D. 622-1990 incorporating Nile River flood data.  In: Diaz, H.F. and Markgraf, V. (Eds.), El Niño.  Historical and Paleoclimatic Aspects of the Southern Oscillation.  Cambridge University Press, Cambridge, UK, pp. 119-149.

Quinn, W.H. and Neal, V.T.  1992.  The historical record of El Niño events.  In: Bradley, R.S. and Jones, P.D. (Eds.), Climate Since A.D. 1500.  Routledge, London, UK, pp. 623-648.

Timmermann, A., Oberhuber, J., Bacher, A., Esch, M., Latif, M. and Roeckner, E.  1999.  Increased El Niño frequency in a climate model forced by future greenhouse warming.  Nature 398: 694-696.