November 2021 La Niña update: movie night

The limited record of reliable observations is definitely a challenge we often struggle to grapple with, especially, as Michelle's recent post discusses, since the climate system can have large, unpredictable variations (internal variability) over many decades. This is one reason why it is critical to have accurate computer models that capture the physical processes of ENSO, so we do not have to rely on the observed record alone. These models are pretty remarkable, but of course, we are always striving to get more observed data and to make better models. 

Thanks for your comment. Given that Climate.gov and the ENSO Blog support the mission of the U.S. National Oceanic and Atmospheric Administration, the blog will tend to have a U.S. focus. However, we do frequently discuss impacts that extend beyond the U.S. (see, for example, here, here, and here). We'll definitely keep an eye out around the globe for possible notable impacts of this La Nina. 

It's true that three of the NMME models are indicating a stronger La Nina this autumn and winter - the disagreement among the NMME models is a bit striking considering the short lead times. However, I note that the NASA model has been biased cold for many months now, so I would discount that forecast. Also, the ocean analysis used to initialize the CFSv2 (GODAS) has been a bit colder than other initializations, and it may be due to missing TAO array data - the CPC Monthly Ocean Briefing has some discussion of this. The bottom line is that I am skeptical of the very cold forecasts, but I agree that these possibilities should not be dismissed outright. 

Hi Edder, I can imagine how disruptive a 3rd La Nina in a row could be! Regarding the La Nina intensity, this webpage is a good resource for getting an idea about the likelihood of various intensity possibilities. For example, it currently shows a 14% probability of the Nino 3.4 SST anomaly being less than -1.5C from November through February, so that means a 14% probability of a strong La Nina. It's difficult to say how that will change in the coming months, but we can expect the uncertainty about the upcoming winter to diminish, which means the probabilities for a small number of bins will increase and the rest will decrease. 

Regarding the accuracy of the predictions, I think this article is a good resource. Specifically, the bottom right panels in Figures 9 and 10 (two different metrics) give a concise summary. The main features are (1) forecasts targeting boreal fall and winter are rather accurate about 5-10 months in advance (depending on your error tolerance), and (2) forecasts targeting boreal spring and summer are much less accurate, due in large part to the spring predictability barrier. 

Thanks for your question. Climate models do not incorporate any adjustments explicitly for ENSO in response to climate change, but rather the changes in ENSO emerge from the effects of greenhouse gas warming interacting with the physical laws encoded in the ocean and atmospheric models. In other words, climate models consist of equations that capture physical laws like conservation of energy and mass, and the various weather and climate phenomena like ENSO emerge as a result of the ability to simulate these basic physical processes in our climate system. Although the simulation of ENSO may be factored into the "tuning" of various parameterizations (parameterization is needed for processes that cannot be explicitly simulated by the climate model, mainly because grid cells are too large to simulate smaller-scale processes), climate models do not explicitly target the simulation of ENSO. It's actually reassuring that fairly realistic simulation of ENSO emerges without this explicit goal of simulating ENSO. This site provides a brief overview of climate modeling that may be helpful. 

The effects of increasing greenhouse gases are incorporated into the radiative transfer components of our climate models, and the resulting temperature changes in the atmosphere and ocean affect all sorts of phenomena like ENSO through the interaction of these temperature changes with the physical laws and parameterizations encoded in our atmosphere and ocean models. Therefore, the changes to ENSO again emerge from the basic physics captured by these models, but there are no ad hoc adjustments specifically for ENSO.

We have published several blog posts related to ENSO and climate change. You can find them here, here, here, here, and here. I hope that helps! 

Hi Kelley, that's a pretty good summary. I would just add the caveat that the impacts of La Nina are always in terms of probabilities; Mother Nature sometimes can have other ideas, like what we saw last winter. Regarding the colder solution for winter/spring, I will point out the peak of La Nina typically occurs around now (late November), so it's hard to imagine that we will suddenly turn much colder in December and January like some models indicate. However, that is my personal opinion and not an official NOAA position. :-)