This week we talk about ENSO, El Niño, and attribution science.

We also discuss climate change, natural disasters, and the trade winds.

Recommended Book: Titanium Noir by Nick Harkaway

Transcript

The field of attribution science, sometimes referred to as "extreme event attribution," focuses on figuring out whether and to what degree a particular weather event—especially rare weather disasters—are attributable to climate change.

Severe floods and tornadoes and hurricanes all happen from time to time, which is why such events are sometimes referred to as once in a decade or once in a century disasters: the right natural variables align in the right way, and you have a disaster that is rare to the point that it's only likely to happen once every 10 or 100 years, but such rare events still happen, and sometimes more frequently than those numbers would imply; they're not impossible. And they're not necessarily the result of climate change.

Folks working in this space, which is a blend of meteorology and the rapidly evolving field of climate science, do their best to figure out what causes what, and how those odds might have been impacted by the shifts we're seeing in global average temperatures in particular, and the knock-on effects of that warming, like shifts in the global water cycle; both of which influence all sorts of other planetary variables.

The most common means of achieving this end is to run simulations based on historical climate data and extrapolating those trend-lines forward, allowing for natural variation, but otherwise sticking with the range of normal fluctuations that would have been expected, had we not started to churn so much CO2 and other greenhouse gases into the atmosphere beginning with the industrial revolution.

So if we hadn't done the Industrial Revolution the way we did it, what would our global climate and weather systems look like? They have a bunch of models with different assumptions baked into them that they have running, and they can simulate conditions, today, based on those models, and compare them with the reality of how things actually are in the real world, a world in which we did start to burn fossil fuels at a frantic rate, with all the pros and cons of that decision aggregating into our current climactic circumstances.

This comparison, between a baseline, non-climate-change-impacted Earth, and what we see happening on real Earth, allows us to gauge the different in likelihoods for various weather systems and increasingly even specific weather events, like massive floods or hurricanes.

It also allows us to ascertain what elements of a disaster or system are more or less likely, or the same, compared to that baseline Earth; so maybe we look at a regional heat wave and discover that it was a rare event made more likely by climate change, but that the intensity of the heat wasn't impacted—as was the case with a heat wave in Russia in 2010; climate change made the heat wave more likely, but had such a heat wave occurred, despite its low likelihood, in that non-industrial revolution scenario, the heat would have been roughly the same intensity as it was in real life.

Both components of this system, attributing events and patterns to climate change, and confirming that they were not impacted, that they were just run of the mill bad luck, the consequence of natural systems, are arguably important, as while the former provides data for folks wanting to predict future climate change-related outcomes, and provides some degree of ammunition for the argument that climate change is making these sorts of things worse, which helps put a price tag on not moving faster to shift away from fossil fuels, it's also vital that we understand how climate and weather systems work, in general, and that we are able to set proper expectations as to what will change and how, as the atmosphere's composition continues to change, while also understanding what will remain the same, what various regions around the world need to be prepared for in a vacuum, leaving climate change out of it, and how our global weather systems work on a granular level, so that as outside influences like climate change, but not limited to climate change, act upon them, we can make better predictions about how that will adjust or overhaul the practical reality for people and ecosystems impacted by them.

What I'd like to talk about today is a natural weather phenomenon that is expected to return soon, and how this phenomenon might change our latent, global weather patterns, for the better, for the worse, and for the neutral, and in turn how it might be changed by the climactic adjustments we're tracking using these simulations.

—

The El Niño-Southern Oscillation, or ENSO phenomenon, is the monicker we've given to a collection of sea surface temperature and wind variations in the Pacific Ocean that, largely unpredictably, tweak the patterns of these systems from time to time, influenced by and influencing a large number of other, micro- and macro-scale systems around the world.

Most directly, ENSO dictates how warm it will be across the tropics and subtropics, El Niño bringing warm waters to the surface of the relevant oceans and the Southern Oscillation referring to air pressure variations spanning the ocean between Tahiti and Darwin, Australia, low pressure tending to occur over warm bodies of water, and higher pressure over colder bodies of water.

When the water in this part of the Pacific, the central and east-central equatorial pacific, is warmer, on the surface, that reduces atmospheric pressure thereabouts, which in turn reduces the strength of the Pacific trade winds. That reduction, among other things, decreases rainfall over parts of Australia, India, and Indonesia, while upping the same, while also stoking additional cyclone risk, in the tropical Pacific Ocean.

Fundamental to understanding why this is a big deal is understanding that this tweak in water and atmospheric conditions causes low level surface trade winds, which usually blow from east to west, to either stop blowing or barely blow, or in some cases to reverse direction.

If you think about how weather patterns form, determining everything from who gets rain and how much, to what temperatures are like in a given area—because those winds pull warm or cold air along with them as they pass over warmer or cooler parts of the planet, like mountains and glaciers, but also deserts and tropical rain forests—it becomes clear why this change-up is such a big deal.

There's a neutral phase of this phenomenon that typically occur between warmer and colder phases, and during that neutral phase, we usually see other, similar systems that are interconnected and predicated on still other geographic and atmospheric variables, like the Pacific-North American teleconnection pattern, and the North Atlantic Oscillation, having more of an impact on global weather and water cycle patterns.

When this system is in a warmer El Niño state, though, that tends to cause a lot of heat waves throughout tropical regions in particular, while also spiking global surface temperatures for around a year, with all the secondary consequences of suddenly jolting the global thermostat higher: melting glaciers and ice caps, increasing the range of disease-carrying pests, messing with planting seasons; things like that.

The opposite side of this coin, La Niña, can also be quite disruptive though, its influence defined by cooler waters rising to the surface in that part of the Pacific, warmer waters headed westward where they have less influence on this component of the world's thermostat and weather machine, and that drop in water temperature in this part of the ocean tends to reset many of the dials that are turned up by El Niño, moderating some of the weather patterns that are amplified by those warmer waters and returning the trade winds to their normal settings, while also reducing global temperatures to what we might think of as their default.

But the next La Niña phenomenon—which experts in this space say will likely arrive sometime in the next few months, June or July of 2024, marking a quick transition away from the record-setting El Niño system we've been living through since July of 2023, which has been designated the fourth most extreme in recorded history—this anticipated new La Niña setup will follow a truly intense opposite pattern, which means if it's not strong enough, it may not counteract all of the warming brought about by its precursor El Niño system, which means the next El Niño system could compound upon this outgoing one, in terms of its globe-heating effects.

There are also concerns that, because of that strong El Niño, and it arriving at a period of human-caused warming—two forces raising the temperature on the thermostat simultaneously, basically—there's a chance that the moderating force of this La Niña might run up against an insurmountable variable adjustment, even if it is otherwise powerful enough; meaning, this ENSO phenomenon could contribute to a long term, even permanent increase in global temperatures because its warming effects are mirroring another, external warming effect caused by us and our greenhouse gas emissions.

We don't know exactly what that would mean in practice and long-term, but it could lead to more. and more extreme versions of what we've seen this past year: namely a surge in weather disasters like extreme droughts and floods and wildfires that never really end; just bigger and bigger surges, combined with higher and higher temperatures.

And again, that's possible even if the La Niña pattern that's set to arrive is of a normal, non-weak strength, because of how potent this outgoing El Niño has been, and because its effects may be compounded by climate change.

If the new La Niña does prove potent enough to counteract this outgoing El Niño, that may help with short-term temperature changes, but we're then likely to see a substantially more severe hurricane season; which is normally what happens during these periods of change, La Niña conditions making hurricanes more likely, but it could be even more severe than usual because of lingering oceanic heat from the El Niño, which popped temperatures in the Atlantic to 2 degrees Fahrenheit higher than the average temperature from the past three decades—and oceanic heat is what powers hurricanes, informing how big and destructive they can become.

Last year's Atlantic Ocean hurricane season was already above-average in terms of the number of hurricanes and their strength because of that heat, but the amalgamation of variable-tweaks inherent in a La Niña transition make hurricanes more likely, whatever the ocean's temperature, so the combination of, likely, more hurricanes, plus far warmer than usual oceanic temperatures, means more, but also potentially a lot more powerful, hurricanes this season.

We've been watching these systems and transitions for a while now, and our science related to them—including our ability to predict what they're going to do, and how much—has gotten pretty good over the last few decades.

But all of these systems and all of their variables are interconnected, each and every piece touching each and every other piece of the planet's cycles and ecosystems and compositions; so there's a lot we're not tracking, a lot we're not tracking with the resolution we'd need for it to be valuable in this regard, and a lot of entanglements and relationships we're not even aware of, yet.

In particular, the impact that climate change is having on these systems, directly and indirectly, is a big question mark in all these computations.

Yes, we understand all of this better than a few decades ago, and yes, our simulations and models have gotten pretty solid, and are getting better by the day as we develop better formulae and software, and deploy more fancy satellites and other tracking tools that allow us to keep tabs on the relevant variables in an up-to-the-second manner.

But because of how complex all of this is, it's a truly chaotic jumble of systems, and because of how we're scrambling to play catch-up, the world changing around us faster than we're learning about those changes—these sorts of systems are evolving even as we come to understand how they work; so our most up to date information is always a little bit out of date, leaving us prone to new unknowns and larger shifts than we'd anticipated based on our existing data.

Human-amplified climate change, then, is fiddling with all the knobs and switches, changing how these phenomena work right before our eyes, and each new system and cycle is part known, part complete surprise because of how even tiny changes can make huge differences when compounded by these spirals and cascades of cause and large-scale, multifaceted effect.

In other words, we have a good sense of what we need to be worried about and watching for during this probable upcoming transition, and we maybe have some things to look forward to, alongside a few other things to worry about and prepare for.

We'll also be watching to see how much global temperatures come down, as that will tell us to what degree this outgoing El Niño has been tweaking those temperatures, and to what degree climate change is to blame for the disconcerting numbers we've been seeing in this regard.

But we'll also be watching to see how everything is being amplified and compounded by all of these interconnected effects, as it may be, still allowing for ups and downs and other variations year to year, that these patterns, and others like them, will lead to wider, broader, more dramatic swings for the foreseeable future because of all those changes, natural and human-caused.

Show Notes

https://www.reuters.com/business/environment/el-nino-end-by-june-la-nina-seen-second-half-2024-says-us-forecaster-2024-05-09/

https://www.axios.com/2024/05/09/el-nino-la-nina-hurricane-season

https://www.vox.com/climate/24145756/la-nina-2024-el-nino-heat-hurricane-record-temperature-pacific

https://oceanservice.noaa.gov/facts/ninonina.html

https://theconversation.com/la-nina-is-coming-raising-the-chances-of-a-dangerous-atlantic-hurricane-season-an-atmospheric-scientist-explains-this-climate-phenomenon-228595

https://en.wikipedia.org/wiki/El_Ni%C3%B1o%E2%80%93Southern_Oscillation

https://en.wikipedia.org/wiki/2020%E2%80%932023_La_Ni%C3%B1a_event

https://en.wikipedia.org/wiki/Extreme_event_attribution

https://www.usgs.gov/faqs/how-can-climate-change-affect-natural-disasters

https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch9s9-1-2.html

https://crsreports.congress.gov/product/pdf/R/R47583

https://www.scientificamerican.com/article/scientists-can-now-blame-individual-natural-disasters-on-climate-change/

https://www.vox.com/climate/2024/2/28/24085691/atlantic-ocean-warming-climate-change-hurricanes-coral-reefs-bleaching

https://en.wikipedia.org/wiki/El_Ni%C3%B1o%E2%80%93Southern_Oscillation

https://en.wikipedia.org/wiki/2020%E2%80%932023_La_Ni%C3%B1a_event

https://theconversation.com/is-climate-change-to-blame-for-extreme-weather-events-attribution-science-says-yes-for-some-heres-how-it-works-164941

This is a public episode. If you’d like to discuss this with other subscribers or get access to bonus episodes, visit letsknowthings.substack.com/subscribe

Get the future of podcasts.