We can all agree 2023 was a weird year for weather, right? The United States set a record for the number of billion dollar weather disasters. A major Amazon River tributary reached its lowest water levels in a century during extreme drought. Extreme rain in Libya caused two dams to break, destroying homes and killing over 4,000 people.

And then, of course, there was the heat. 2023 was the hottest year on record. Countries around the world saw heat records fall month after month. The Arctic was hot. The ocean was hot. And debates swirl on about whether we’ve already passed critical warming thresholds.

So how do we put 2023 in context of the greater trend of warming? Here’s what some of Woodwell Climate’s scientists have to say about last year’s record-breaking events.

Did the models predict this?

The dramatic scenes of heat and extreme weather last year prompted many to ask why temperatures had seemingly spiked way above the trend line. Was this unexpected? Was it out of the range of what scientists had modeled? Woodwell Senior Scientist, Dr. Jennifer Francis says not entirely.

“Almost exactly a year ago,” says Francis, “we had just come out of three years of La Niñas and we came close to breaking global temperature records then, even though La Niñas tend to be cooler than neutral or El Niño years. And then along came the strong El Niño of 2023.”

El Niño and La Niña are two extremes of a natural phenomenon that impacts weather patterns across the Pacific, and around the world. In an El Niño year, the prevailing trade winds that normally push warmer waters into the western tropical Pacific—allowing cooler water to well up along the western coast of the Americas—are reversed, resulting in hotter ocean surface temperatures in the eastern equatorial Pacific. When the ocean is hotter than the air above it, that heat is released into the atmosphere, often making El Niño years record breaking ones for global temperatures. 

“Last year’s spike looks a lot like the last big El Niño event in 2015-2016. It’s just that now the whole system is warmer. So to me, it wasn’t at all a surprise that we smashed the global temperature record in 2023,” says Francis.

The spike put global temperatures far above the average of climate model simulations, but that doesn’t mean the models didn’t account for it. Risk Program Associate Director, Dr. Zach Zobel, says that averages tend to smooth out natural year-to-year fluctuations, when in fact the upper and lower ranges of model predictions do encompass temperatures like the ones seen in 2023.

“It was well within the margin of error that you would expect for natural variations,” says Zobel.

How does ocean heat impact the climate?

One element of last year’s heat, one that wasn’t necessarily forecasted, was the simultaneous appearance of several ocean heat waves around the globe. The ocean absorbs the vast majority of heat trapped by greenhouse gasses, and that heat can be released under the right conditions. El Niño is one example, but in 2023 it coincided with other not-so-natural marine heat waves across the world.

“In pretty much every single ocean right now there are heat waves happening, which is something quite new,” says Francis.

A couple of dynamics could be driving this. One possibility is that, after three years of La Niñas, in which equatorial Pacific ocean temperatures were generally cooler than the air, the ocean simply absorbed a lot of heat, which was then primed to be released in an El Niño year. Another, Zobel suggests, could be recent shipping laws that required shipping vessels to eliminate sulfate emissions by 2023. Sulfates are a pollutant that may have been helping bounce back solar radiation, hiding the true extent of warming.

“Usually when there’s an El Niño, the eastern tropical Pacific is very warm, but it doesn’t actually drive up ocean temperatures everywhere,” says Zobel. “That was the biggest surprise to me: how warm the northern hemisphere of the Atlantic and Pacific were for most of last year and into 2024.” 

Ocean heat waves are typically long-lived phenomena, lasting many months, and so can be a useful tool for meteorologists looking to predict 2024’s extreme weather events.

“The good news is that it provides some kind of long-term predictability about weather patterns in the upcoming year,” says Francis. “The bad news is that they tend to be unusual weather patterns, because those ocean heat waves aren’t usually there.”

Will next year be hotter?

So are we in for another, hotter year after this one? Risk Program Director Dr. Christopher Schwalm says it’s likely.

“Warming predictions for 2024 from leading scientists all forecast a higher level of warming this year than last year,” says Schwalm. 

Already, March 2024, was the 10th month in a row to break temperature records. Zobel says it’s typical for the year following an El Niño peak to maintain high temperatures.

“Because the ocean spent a good amount of the year last year warmer than average, that energy is typically dispersed throughout the globe in the following year,” says Zobel. “So even though the tropical Pacific might return to normal, that energy is still in the system.”

However, atmospheric scientists are already seeing signs that El Niño is slowing down and flipping to its counterpart, La Niña, adding another layer of complexity to predictions for 2024. 

“The 2024 hurricane season is a large concern,” says Zobel. “La Niña is a lot more conducive to tropical cyclone development. If we combine above average numbers with the amount of energy that storms have to feed on, it’ll be a shock to the system.”

What does this mean for 1.5?

In the discussions around 2023’s temperatures, one number dominates the conversation: 1.5 degrees C. This is the amount of warming countries around the world agreed to try to avoid surpassing, in accordance with the United Nations’ 2015 Paris Climate Agreement. Estimates from Berkeley Earth say that 2023 may have been the first year spent above that threshold. 

This assertion may take several years to verify— one year spent physically above 1.5 degrees of warming does not indicate the UN threshold has been permanently passed. What scientists are looking for is a clear average trend line rising above 1.5 degrees C without coming back down, and for that you need several years of data. That, regrettably, creates a lag time between climate impacts and updating climate policy. But, for many, the debate around the arbitrary 1.5 degree goal has become a distraction. Schwalm says scientists and policy-makers should be focusing on urgently combating climate change whatever the numbers say.

“We are already living in a post-Paris Agreement reality,” says Schwalm. “The sooner we admit that and reimagine climate policy, the better.”

“Actual real world impacts are going to be there, whether we’re at 1.48 or 1.52,” says Zobel.

And Francis agrees. “There are so many indicators telling us that big changes are underfoot, that we are experiencing major climate change, but reaching 1.5 isn’t going to all of a sudden make those things worse. It’s just one more reminder we’re still on the wrong track and we’d better hurry up and do something.”

Last month was hottest February ever recorded. It’s the ninth-straight broken record

snow melts next to a road, surrounded by evergreen trees

For the ninth straight month, Earth has obliterated global heat records — with February, the winter as a whole and the world’s oceans setting new high-temperature marks, according to the European Union climate agency Copernicus.

The latest record-breaking in this climate change-fueled global hot streak includes sea surface temperatures that weren’t just the hottest for February, but eclipsed any month on record, soaring past August 2023’s mark and still rising at the end of the month. And February, as well the previous two winter months, soared well past the internationally set threshold for long-term warming, Copernicus reported Wednesday.

Continue reading on Associated Press News.

Study pinpoints links between melting Arctic ice and summertime extreme weather in Europe

New research shows how last year’s warming melted ice in Greenland that increased flows of fresh, cold water into the North Atlantic, upsetting ocean currents in ways that lead to atmospheric changes.

Arctic ice floes

The Arctic Ocean is mostly enclosed by the coldest parts of the Northern Hemisphere’s continents, ringed in by Siberia, Alaska and the Canadian Arctic, with only a small opening to the Pacific through the Bering Strait, and some narrow channels through the labyrinth of Canada’s Arctic archipelago.

But east of Greenland, there’s a stretch of open water about 1,300 miles across where the Arctic can pour its icy heart out to the North Atlantic. Those flows include increasing surges of cold and fresh water from melted ice, and a new study in the journal Weather and Climate Dynamics shows how those pulses can set off a chain reaction from the ocean to the atmosphere that ends up causing summer heatwaves and droughts in Europe.

Read more on Inside Climate News.

If the summer of 2023 felt abnormally hot to you, that’s because it was. With heat waves making headlines month after month, this year saw a spike in temperatures that broke global records.

September 2023 followed in the footsteps of both August and July as the hottest each month has been since temperature record-keeping began, making the late summer of 2023 Earth’s hottest yet. Here’s how 2023’s sweltering heat compares to past years:

  1. Global average surface air temperature reached a record high in the summer of 2023.
  2. July 24th, 2022 was the hottest day of last year, at 62.5 degrees F.
  3. July 3rd, 2023 was the first day that was hotter than the hottest day in 2022.
  4. July 6th, 2023 was Earth’s hottest day on record.
  5. 42 days this year were hotter than the hottest day in 2022.

Record-breaking heat in 2023

In North America alone, 78 all time records for hottest temperature were broken over the course of June, July and August. In New Iberia, Louisiana, the temperature record was broken four times, peaking at 109 degrees F. Places as far north as Wainwright Airport in Alaska saw temperatures as high as 84 degrees.

Humidity makes the heat deadly

Extreme heat events like these present a serious danger to human health. That threat is multiplied when instances of high temperature coincide with high humidity— interrupting the ability of the human body to cool off through evaporating sweat. A recent paper, co-authored by Woodwell Climate Risk Program director, Dr. Christopher Schwalm, defines “lethal heat” as a wet bulb temperature (a measure combining heat and humidity) of 35 degrees C (95 degrees F). Prolonged exposure— over 6 hours— to temperatures exceeding this can result in death even for a healthy person keeping hydrated in the shade

According to the paper, instances of deadly heat waves are increasing with climate change. Already, with over a degree of warming, parts of Northern India are seeing annual heat events. By just two degrees of warming— a milestone we are currently on track to hit by mid-century— a quarter of the world is expected to experience a lethal heat event at least once in a decade. A significant subset of the world, particularly regions of India, Africa, South America, and the Southeastern US, can expect deadly heat conditions at least once a year at that point, and the area will expand wider with each half degree of warming.

It’s a forecast that highlights the urgency of acting to mitigate warming and developing local and regional strategies to prepare communities to handle high heat and humidity events when they do come. 

“It puts this past year’s heat waves into somber perspective,” says Dr. Schwalm. “Without action, we put a lot more, potentially billions, of people at risk of heat stress or death on an annual basis. It’s a significant public health concern.”

“It’s been around a long time, actually,” muses Senior Scientist, Dr. Jennifer Francis. “It’s gotten more sophisticated, sure, and a lot of the applications are new. But the concept of artificial intelligence is not.”

Dr. Francis has been working with it for almost two decades, in fact. Although, back when she started working with a research tool called “neural networks,” they were less widely known in climate science and weren’t generally referred to as artificial intelligence.

But recently, AI seems to have come suddenly out of the woodwork, infusing nearly every field of research, analysis, and communication. Climate science is no exception. From mapping thawing Arctic tundra, to tracking atmospheric variation, and even transcribing audio interviews into text for use in this story, AI in varying forms is woven into the framework of how Woodwell Climate creates new knowledge.

AI helps climate scientists track trends and patterns

The umbrella term of artificial intelligence encompasses a diverse set of tools that can be trained to do tasks as diverse as imitating human language (à la ChatGPT), playing chess, categorizing images, solving puzzles, and even restoring damaged ancient texts.

Dr. Francis uses AI to study variations in atmospheric conditions, most recently weather whiplash events— when one stable weather pattern suddenly snaps to a very different one (think months-long drought in the west disrupted by torrential rain). Her particular method is called self-organizing maps which, as the name suggests, automatically generates a matrix of maps showing atmospheric data organized so Dr. Francis can detect these sudden snapping patterns.

“This method is perfect for what we’re looking for because it removes the human biases. We can feed it daily maps of, say, what the jetstream looks like, and then the neural network finds characteristic patterns and tells us exactly which days the atmosphere is similar to each pattern. There are no assumptions,” says Dr. Francis.

This aptitude for pattern recognition is a core function of many types of neural networks. In the Arctic program, AI is used to churn through thousands of satellite images to detect patterns that indicate specific features in the landscape using a technique originally honed for use in the medical industry to read CT scan images.

Data science specialist, Dr. Yili Yang, uses AI models trained to identify features called retrogressive thaw slumps (RTS) in permafrost-rich regions of the Arctic. Thaw slumps form in response to subsiding permafrost and can be indicators of greater thawing on the landscape, but they are hard to identify in images.

“Finding one RTS is like finding a single building in a city,” Dr. Yang says. It’s time consuming, and it really helps if you already know what you’re looking for. Their trained neural network can pick the features out of high-resolution satellite imagery with fairly high accuracy.

Research Assistant Andrew Mullen uses a similar tool to find and map millions of small water bodies across the Arctic. A neural network generated a dataset of these lakes and ponds so that Mullen and other researchers could track seasonal changes in their area.

And there are opportunities to use AI not just for the data creation side of research, but trend analysis as well. Associate Scientist Dr. Anna Liljedahl leads the Permafrost Discovery Gateway project which used neural networks to create a pan-Arctic map of ice wedge polygons—another feature that indicates ice-rich permafrost in the ground below and, if altered over time, could suggest permafrost thaw.

“Our future goals for the Gateway would utilize new AI models to identify trends or patterns or relationships between ice wedge polygons and elevation, soil or climate data,” says Dr. Liljedahl.

How do neural networks work?

The projects above are examples of neural-network-based AI. But how do they actually work?

The comparison to human brains is apt. The networks are composed of interconnected, mathematical components called “neurons.” Also like a brain, the system is a web of billions upon billions of these neurons. Each neuron carries a fragment of information into the next, and the way those neurons are organized determines the kind of tasks the model can be trained to do.

“How AI models are built is based on a really simple structure—but a ton of these really simple structures stacked on top of each other. This makes them complex and highly capable of accomplishing different tasks,” says Mullen.

In order to accomplish these highly specific tasks, the model has to be trained. Training involves feeding the AI input data, and then telling it what the correct output should look like. The process is called supervised learning, and it’s functionally similar to teaching a student by showing it the correct answers to the quiz ahead of time, then testing them, and repeating this cycle over and over until they can reliably ace each test.

In the case of Dr. Yang’s work, the model was trained using input satellite images of the Arctic tundra with known retrogressive thaw slump features. The model outputs possible thaw slumps which are then compared to the RTS labels hand-drawn by Research Assistant Tiffany Windholz. It then assesses the similarity between the prediction and the true slump, and automatically adjusts its billions of neurons to improve the similarity. Do this a thousand times and the internal structure of the AI starts to learn what to look for in an image. Sharp change in elevation? Destroyed vegetation and no pond? Right geometry? That’s a potential thaw slump.

Just as it would be impossible to pull out any single neuron from a human brain and determine its function, the complexity of a neural network makes the internal workings of AI difficult to detail—Mullen calls it a “black box”—but with a large enough training set you can refine the output without ever having to worry about the internal workings of the machine.

Speeding up and scaling up

Despite its reputation in pop culture, and the uncannily human way these algorithms can learn, AI models are not replacing human researchers. In their present form, neural networks aren’t capable of constructing novel ideas from the information they receive—a defining characteristic of human intelligence. The information that comes out of them is limited by the information they were trained on, in both scope and accuracy.

But once a model is trained with enough accurate data, it can perform in seconds a task that might take a human half an hour. Multiply that across a dataset of 10,000 individual images and it can condense months of image processing into a few hours. And that’s where neural networks become crucial for climate research.

“They’re able to do that tedious, somewhat simple work really fast,” Mullen says. “Which allows us to do more science and focus on the bigger picture.”

Dr. Francis adds, “they can also elucidate patterns and connections that humans can’t see by gazing at thousands of maps or images.”

Another superpower of these AI models is their capability for generalization. Train a model to recognize ponds or ice wedges or thaw slumps with enough representative images and you can use it to identify the water bodies across the Arctic—even in places that would be hard to reach for field data collection.

All these qualities dramatically speed up the pace of research, which is critical as the pace of climate change itself accelerates. The faster scientists can analyze and understand changes in our environment, the better we’ll be able to predict, adapt to, and maybe lessen the impacts to come.

Canada’s fire season has barely started and it’s already on track to break records. So far, NOAA has documented more than 2,000 wildfires that have resulted in the forced evacuation of over 100,000 people across Canada. The most recent bout of fires burning in Ontario and Quebec has sent smoke southward into the Eastern U.S., causing record levels of air pollution in New York and warnings against outside activity as far south as Virginia.

Only a little over a month into the wildfire season, fires have already burned 13 times more land area than the 110-year average for this time of year, and they show no sign of stopping, according to Canadian publication The Star. Indigenous communities, some of whom live year-round in remote bush cabins, have been particularly harmed by the blazes.

According to Woodwell Climate Senior Scientist Dr. Jennifer Francis, the phenomenon of winds pushing smoke down to the northeastern U.S. has been linked to rapid Arctic warming caused by climate change.

In the upper atmosphere, a fast wind current called the jet stream flows from west to east in undulating waves, caused by the interaction of air masses with different temperatures and pressures, particularly between the Arctic and temperate latitudes.

As global temperatures have risen, the Arctic has warmed two to four times faster than the average global rate. Dr. Francis stated in an interview in the Boston Globe that the lessening of the temperature differences between the middle latitudes and the Arctic has slowed down the jet stream, which results in a more frequent occurrence of a wavy path.
Another factor contributing to the widespread smoke is an ongoing oceanic heat wave in the North Pacific Ocean. The blob of much-above-normal sea water tends to create a northward bulge in the jet stream, which creates a pattern that sends cooler air down to California and warm air northward into central Canada—resulting in the persistent heat wave there in recent weeks. Farther east, the jet stream then bends southward and brings the wildfire smoke down to the Northeast.

“Big waves in the jet stream tend to hang around a long time, and so the weather that they create is going to be very persistent,” Dr. Francis said. “If you are in the part of the wave in the jet stream that creates heat and drought, then you can expect it to last a long time and raise the risk of wildfire.”

The wildfires are also decimating North American and Canadian boreal forests, the latter of which holds 12 percent of the “world’s land-based carbon reserves,” according to the Audubon Society<./a> And three quarters of Canada’s woodlands and forests are in the boreal zone according to the Canadian government.

“The surface vegetation and the soil can dry out pretty dramatically given the right weather conditions. For this fuel, as we call it in fire science, it often just takes one single ignition source to generate a large wildfire,” said Woodwell Climate Associate Scientist Dr. Brendan Rogers.

As the climate continues to warm, Dr. Rogers said the weather conditions that lead to fuel drying and out-of-control wildfires also increase. This creates a feedback loop. Heat waves caused by greenhouse gas emissions increase the prevalence of wildfires. The fires in turn destroy these natural carbon sinks and, in turn, speed up climate change.

While the ultimate solution to breaking this feedback loop lies in reducing emissions and curbing climate change, Dr. Rogers and other researchers at Woodwell Climate have conducted research into fire suppression strategies that could help prevent large boreal fires from spreading and help keep carbon in the ground.

A study conducted in collaboration with Woodwell and other institutions found that suppressing fires early may be a cost-effective way to carbon mitigation. Woodwell Climate’s efforts also include mapping fires, using geospatial data and models to estimate carbon emissions across large scales, and looking at the interplay between fires and logging.

“Reducing boreal forest fires to near-historic levels and keeping carbon in the ground will require substantial investments. Nevertheless, these funds pale in comparison to the costs countries will face to cope with the growing health consequences exacerbated by worsening air quality and more frequent and intense climate impacts expected if emissions continue to rise unabated. Increased resources, flexibility, and carbon-focused fire management can also ensure wildlife, tourism, jobs, and many other facets of our society can persevere in a warming world,” Dr. Rogers said.

oncoming storm front
A sudden flip in weather conditions—from a long hot and dry period to a parade of storms, for example, or from abnormally mild winter temperatures to extreme cold—can cause major disruptions to human activities, energy supplies, agriculture, and ecosystems. These shifts, dubbed “weather whiplash” events, are challenging to measure and define because of a lack of consistent definition. A new study demonstrates an approach to measuring the frequency of these events based on rapid changes in continent-wide weather regimes.

The study indicates that, while the frequency of whiplash events in recent decades has not changed substantially, future model projections indicate increases will occur as the globe continues to warm under a thicker blanket of greenhouse gasses. In particular, the researchers find whiplash will increase most during times when the Arctic is abnormally warm, and decrease when the Arctic is in a cold regime—something that will occur less often as the planet warms.

Examples of weather whiplash during 2022 so far include a long, hot, drought in western U.S. states during early summer that was broken by record-breaking flash flooding; exceptionally wet and cool conditions during June in the Pacific Northwest replaced by a heat wave in July; a record-warm early winter for most south-central states followed by a cooler-than-average January and February; and a spell of 67 consecutive hot, dry days in Dallas, TX, broken by the heaviest rains in a century.

“The spring and summer of 2022 have been plagued by weather whiplash events,” said lead author, Dr. Jennifer Francis, Senior Scientist at the Woodwell Climate Research Center. “A warming planet increases the likelihood of longer, more intense droughts and heat waves, and we’re also seeing these spells broken suddenly by heavy bouts of precipitation, which are also fueled by the climate crisis. These sudden shifts are highly disruptive to all sorts of human activities and wildlife, and our study indicates they’ll occur more frequently as we continue to burn fossil fuels and clear-cut forests, causing greenhouse gas concentrations to rise further.”

Co-author Judah Cohen, Principal Scientist at Verisk AER noted that these phenomena are tightly linked to regional warming in the Arctic.

“We know the Arctic region is experiencing the most rapid changes in the global climate system. Evidence is growing that these profound changes are contributing to more extreme weather events outside the Arctic, and this influence will only increase in the future,” said Dr. Cohen.