Our family took a trip to San Diego to visit friends. We got to spend some time in the warm Southern California water at a time when the news was filled with stories about sensational oceanic anomalies. Was the warm water we felt an anomaly? How certain could I be and how certain can anyone be about climatic statistical anomalies?
Let’s unpack it.
BOOGIE WOOGIE FREAK OUT
I felt the current sucking my legs out to sea as a wave formed behind me. I struggled to hurl myself, and my boogie board, toward the beach to meet the momentum of the rising wave. “KICK, KICK, KICK”, I yelled to my son who was next to me.
Then came the welling and humbling sensation born out of the magnitude of a swelling ocean wave. As it crested a smile crossed my face and the force propelled me down the wave’s sloping curve. I looked over and realized not only had my son caught the wave, but my daughter and wife had too. The whole family was giggling and kicking amidst the seafoam of an exhausted but rewarding wave.
I’d forgotten how exhilarating boogie boarding is. I was first introduced to it when I lived in Hermosa Beach, California in the mid-eighties. I’m kicking myself for not learning to surf that year. I didn’t even try until a few years later at the very beach we found ourselves boogie boarding – Moonlight Beach in Encinitas, California.
I spent a summer working at a newspaper there in 1987 laying out ads on their newly purchased Mac SE alongside the art director and one full-time designer. They were both surfers and decided to take me out one day. I remember my shoulders being sore for a week from paddling. Let’s just say I paddled more than I surfed.
The water is relatively warm in San Diego which makes it a nice place to surf and boogie board. Not only is it the southern most major city in California and thus the warmest, it can also be the recipient of warm water flowing up the coast from Mexico.
It was cloudy, cool, and a little rainy the day we were boogie boarding with friends making the water feel particularly warm. I wondered how much warmer the water there might be compared to when I was feebly attempting to stand on a surfboard for the first time. I wondered if climate change had demonstrably warmed the surface water after all these years.
Ocean flow and temperatures have been all over the news in the last week or so. Take, for example, this ABC news story that was amplified by a post from John Gibbons, aka @thinkorswim, on that site we’ll all continue to call Twitter. According to John’s profile he likes to ‘freak out and speak out’ on the ‘climate emergency’ but warned he didn’t want to sound ‘alarmist’ when he shared a graph one scientist called ‘gobsmacking’.
It’s a chart of a set of standard deviations — the number of points a number falls above or below an average number. How much it deviates from an average. In this case the number represents the average extent ice has covered a particular area in the Antarctic Sea from 1989 to 2023 as compared to the average between the years 1991-2020.
From 1989 to 2022 the number didn’t deviate from the average much more than 3 or -3 standard deviations, but by June of 2023 it deviated well below -6, or ~6.4 standard deviations.
It makes 2023 look like an exceptionally bad year thus far for a really important element of our climate system: sea ice. These sheets of ice play a significant role in how the Earth's climate behaves. For example, we know it affects how much sunlight is reflected into space (planetary albedo), how the atmosphere moves (atmospheric circulation), the productivity of ocean life, and how heat and salt circulate in the ocean (thermohaline circulation).
Which gets us to another big piece of oceanic news this week; the fate of AMOC (pronounced “AY-mock). The Atlantic Meridional Overturning Circulation is a large-scale ocean current system in the Atlantic Ocean and Danish scientists predicted it’s flow will slow or even stall before the end of the century.
Like polar ice sheets, AMOC is also a critical component of the Earth's climate system. It’s responsible for transporting warm, salty water from the tropics to the northern latitudes and then returning cold, less salty water southward through currents deep in the ocean. This circulation pattern helps regulate the climate by redistributing heat while also influencing weather patterns across the North Atlantic region and beyond.
One of the authors of the study, Susanne Ditlevsen, is a professor of statistics at the University of Copenhagen. She told the New York Times that “climate scientists generally agree that the Atlantic circulation will decline this century, but there’s no consensus on whether it will stall out before 2100.” Given this, she was surprised they could predict the timing of a collapse.
Should we be shocked by statistics yielding whacky numbers or suspicious of the models that produce them? Some scientists are calling for scrutiny of climatic models, encouraging more nuanced discussion of these alarming predictions.
While there is reason to be scared, we should not be scared to reason.
‘Gobsmacking’ numbers from scientists and mathematicians make for good click bait, and indeed can offer legitimate alarm bells, but they also can give the illusion of certainty and can distract us from all that remains uncertain, nuanced, or all together unknowable.
This view was expressed by the climate scientist John Kennedy who scrutinizes the mythology of mathematical certainty and lionizes the phraseology of scientific humility. He called out the gobsmacked scientist ABC quoted about the ‘six-sigma event’ in the Antarctic who was quoted as such,
“To say unprecedented isn’t strong enough,” Dr Doddridge said, “For those of you who are interested in statistics, this is a five-sigma event. So it’s five standard deviations beyond the mean. Which means that if nothing had changed, we’d expect to see a winter like this about once every 7.5 million years. It’s gobsmacking.”
To show just how cautious we should be with these numbers, while Dr. Doddridge translated the standard deviations into a 1 in 7.5-million-year event, another math professor and climate watcher noted “6.4 standard deviations would correspond to odds of about 1-in-13,000,000,000 (1-in-13 billion).”
Kennedy, who is decidedly not a climate denialist, also cautions that tracking ice extent in Antarctica has only been occurring for 45 years. This doesn’t mean the once-in-the-lifetime-of-the-Earth’s-existence event isn’t happening, but that it’s derived from a relatively miniscule time span. He suggests we might be better served to let people know that there is much more we don’t know about trends of the ice extent around Antarctica than we do know.
Furthermore, there isn’t a scientist out there who will say what this all means, how it happened, and when it might happen again. For all we know, within the next few years we may see an equally anomalous event in the other direction. After all, Kennedy points out,
“Up to around 2014, extent had been trending gradually upwards. Not by a huge amount, but it definitely wasn’t dropping. It hit a record high in 2014. Then it dropped off a cliff. By 2017, it was record low. It bounced back to “normal” in 2020 and now we are where we are.
He goes on to note the cautious language the IPCC uses to describe these changes.
“In conclusion, the observed small increase in Antarctic sea ice extent during the satellite era is not generally captured by global climate models, and there is low confidence in attributing the causes of the change.“
“For Antarctic sea ice, there is no significant trend in satellite-observed sea ice area from 1979 to 2020 in both winter and summer, due to regionally opposing trends and large internal variability. Due to mismatches between model simulations and observations, combined with a lack of understanding of reasons for substantial inter-model spread, there is low confidence in model projections of future Antarctic sea ice changes, particularly at the regional level.“
“There remains low confidence in all aspects of Antarctic sea ice prior to the satellite era owing to a paucity of records that are highly regional in nature and often seemingly contradictory.”
Kennedy concludes that,
“My concern is that because Antarctic sea ice has suddenly dropped, a lot of people have forgotten what we don’t know. This feeds into the alarmingly large, shonky, yet definitive-sounding numbers like one in 7.5 million years, which then get into headlines, and spread across social media like the clappers. When Antarctic sea ice inevitably does its next weird thing, everyone will suddenly remember what we don’t know and that isn’t, it must be said, a great look.”
He's got a point.
So, what of the warming waters of San Diego? Has the temperature demonstrably changed since I was swimming there 36 years ago? Like all ocean water, it is warming. However, on any given day it may be warmer or cooler relative to past years. It’s this cyclical variability of complex systems coupled with spotty, uncertain, and incomplete data that makes predictions and smoking guns so hard to pin down.
It’s hard to tell what pattern is emerging from this chart dating back to 2000. The peak temperature in 2016 was due a record heat wave, but as you see it was followed up a year later with a significant drop. However, there were measurements in June that indicated “a weak El Niño was associated with above-average sea surface temperatures (SSTs) across the equatorial Pacific Ocean” as part of another oceanic circulation pattern known as the El Niño Southern Oscillation (ENSO). So, it’s possible these warm waters made their way to Encinitas. It’s hard to tell.
It's also possible ENSO is partially responsible for Antarctica’s sea ice variability. Climate scientist Zack Labe writes that,
“These patterns of climate variability modulate the transport of heat in the Southern Ocean, storm activity, and patterns of low-level surface winds – all of which significantly affect Antarctic sea ice (a lot more than air temperature does).”
“If we see a dramatic change in the large-scale atmospheric circulation in the next few weeks/months, it is very possible that sea ice levels could return closer to average. This is good news, as it implies that we are not necessarily guaranteed to see another new minimum record at the end of next summer.”
But Zack is one the of scientists John Kennedy praises for his humility and willingness to not have definitive answers no matter how attractive they may be to media outlets and their consumers. He writes,
“…even though many scientists (including myself) are often responding with I don’t know for why Antarctic sea ice is so low right now, we do know quite a bit. It’s just that this is very complicated to disentangle so quickly, and there is no simple one-way causal factor to communicate. We have many clues, but scientists need more data and experiments to state their conclusions more confidently (“we” are cautious to avoid making sweeping conclusions by nature of training).
Attributing the why is also very challenging in real-time, especially for understanding the role of climate change in the Antarctic. The normal scientific research process is so much longer than the media cycle. Studies just focusing on 2023’s Antarctic sea ice levels, for instance, will likely be published for at least the next five years or more.”
This much we do know:Antarctic sea ice has been gradually increasing over the past four decades, but there have been some record low levels of sea ice. As we’re seeing now. These changes vary in different regions of Antarctica, with some areas experiencing more ice while others have seen decreases. Wind patterns play a significant role in driving these changes, but the observations are limited, and climate models still struggle to fully explain them.
The annual growth and melting of Antarctic sea ice is a unique and regular phenomenon amidst the year-to-year variations. It plays a crucial role in the exchange between the atmosphere and the ocean, providing a habitat for the diverse ocean ecosystems. Including the habitats I was swimming in last week. Understanding and modeling these processes is essential given their significance but doing so is admittedly very tricky.
The factors contributing to extreme sea ice events include both atmospheric and oceanic drivers. They’re influenced by local changes within Antarctica and remote impacts from other regions like the Pacific Ocean. The combination of anomalous winds and upper ocean heat can lead to significant sea ice deviations and records at specific times. While predicting summer sea ice conditions based solely on the previous winter is challenging, changes in large-scale atmospheric circulation might bring sea ice levels closer to average, offering hope to avoid new minimum records.
Researchers will obviously continue to study sea ice trends to better determine if it's driven by internal variability or unexpected responses to circulation trends in the Northern Hemisphere. But given all these anomalies and uncertainties, it's important to dig into reliable sources, seek knowledge of our complex ecosystems, and be cautious of, or avoid all together, unnecessary hype.
It’s a bit like trying to catch every wave you see. It can become exhausting, disappointing, and with time…depressing. But when you learn to read the ocean from experts, gain some experience, and have some patience, rewards – sometimes exhilarating – do come.
Understanding the Seasonal Cycle of Antarctic Sea Ice Extent in the Context of Longer-Term Variability. Clare Eayrs, et al. Reviews of Geophysics. 2019.