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El Niño or Bust

Filed under: — mike @ 8 May 2014

Guest commentary from Michelle L’Heureux, NOAA Climate Prediction Center

Much media attention has been directed at the possibility of an El Niño brewing this year. Many outlets have drawn comparison with the 1997-98 super El Niño. So, what are the odds that El Niño will occur? And if it does, how strong will it be?

To track El Niño, meteorologists at the NOAA/NWS Climate Prediction Center (CPC) release weekly and monthly updates on the status of the El Niño-Southern Oscillation (ENSO). The International Research Institute (IRI) for Climate and Society partner with us on the monthly ENSO release and are also collaborators on a brand new “ENSO blog” which is part of www.climate.gov (co-sponsored by the NOAA Climate Programs Office).

Blogging ENSO is a first for operational ENSO forecasters, and we hope that it gives us another way to both inform and interact with our users on ENSO predictions and impacts. In addition, we will collaborate with other scientists to profile interesting ENSO research and delve into the societal dimensions of ENSO.

As far back as November 2013, the CPC and the IRI have predicted an elevated chance of El Niño (relative to historical chance or climatology) based on a combination of model predictions and general trends over the tropical Pacific Ocean. Once the chance of El Niño reached 50% in March 2014, an El Niño Watch was issued to alert the public that conditions are more favorable for the development of El Niño.
Current forecasts for the Nino-3.4 SST index (as of 5 May 2014) from the NCEP Climate Forecast System version 2 model.
Current forecasts for the Nino-3.4 SST index (as of 5 May 2014) from the NCEP Climate Forecast System version 2 model

More recently, on May 8th, the CPC/IRI ENSO team increased the chance that El Niño will develop, with a peak probability of ~80% during the late fall/early winter of this year. El Nino onset is currently favored sometime in the early summer (May-June-July). At this point, the team remains non-committal on the possible strength of El Niño preferring to watch the system for at least another month or more before trying to infer the intensity. But, could we get a super strong event? The range of possibilities implied by some models allude to such an outcome, but at this point the uncertainty is just too high. While subsurface heat content levels are well above average (March was the highest for that month since 1979 and April was the second highest), ENSO prediction relies on many other variables and factors. We also remain in the spring prediction barrier, which is a more uncertain time to be making ENSO predictions.

Could El Niño predictions fizzle? Yes, there is roughly a 2 in 10 chance at this point that this could happen. It happened in 2012 when an El Nino Watch was issued, chances became as high as 75% and El Niño never formed. Such is the nature of seasonal climate forecasting when there is enough forecast uncertainty that “busts” can and do occur. In fact, more strictly, if the forecast probabilities are “reliable,” an event with an 80% chance of occurring should only occur 80% of the time over a long historical record. Therefore, 20% of the time the event must NOT occur (click here for a description of verification techniques).

While folks might prefer total certainty in our forecasts, we live in an uncertain world. El Niño is most likely to occur this year, so please stay attentive to the various updates linked above and please visit our brand new ENSO blog.

Unforced variations: May 2014

Filed under: — group @ 2 May 2014

This month’s open thread. In order to give everyone a break, no discussion of mitigation options this month – that has been done to death in previous threads. Anything related to climate science is totally fine: Carbon dioxide levels maybe, or TED talks perhaps…

Faking it

Filed under: — gavin @ 30 April 2014

Every so often contrarians post old newspaper quotes with the implication that nothing being talked about now is unprecedented or even unusual. And frankly, there are lots of old articles that get things wrong, are sensationalist or made predictions without a solid basis. And those are just the articles about the economy.

However, there are plenty of science articles that are just interesting, reporting events and explorations in the Arctic and elsewhere that give a fascinating view into how early scientists were coming to an understanding about climate change and processes. In particular, in the Atlantic sector of the Arctic the summer of 1922 was (for the time) quite warm, and there were a number of reports that discussed some unprecedented (again, for the time) observations of open water. The most detailed report was in the Monthly Weather Review:
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Nenana Ice Classic: Update

Filed under: — gavin @ 25 April 2014

Somewhat randomly, my thoughts turned to the Nenana Ice Classic this evening, only to find that the ice break up had only just occurred (3:48 pm Alaskan Standard Time, April 25). This is quite early (the 7th earliest date, regardless of details associated with the vernal equinox or leap year issues), though perhaps unsurprising after the warm Alaskan winter this year (8th warmest on record). This is in strong contrast to the very late break up last year.



Break up dates accounting for leap years and variations in the vernal equinox.

As mentioned in my recent post, the Nenana break up date is a good indicator of Alaskan regional temperatures and despite last year’s late anomaly, the trends are very much towards a earlier spring. This is also true for trends in temperatures and ice break up mostly everywhere else too, despite individual years (like 2013/2014) being anomalously cold (for instance in the Great Lakes region). As we’ve often stressed, it is the trends that are important for judging climate change, not the individual years. Nonetheless, odds on dates as early as this years have more than doubled over the last century.

Labels for climate data

Filed under: — rasmus @ 24 April 2014

metadata-fig “These results are quite strange”, my colleague told me. He analysed some of the recent climate model results from an experiment known by the cryptic name ‘CMIP5‘. It turned out that the results were ok, but we had made an error when reading and processing the model output. The particular climate model that initially gave the strange results had used a different calendar set-up to the previous models we had examined.

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