August 29, 2024
Source: The Christian Science Monitor
Photo Source: Unsplash,
From Las Vegas to London, New England to New Delhi, the summer of 2024 shattered heat records. As recently as this week, more than 85 million people in the United States experienced extreme heat alerts, with many spots in the Midwest reaching heat indexes of more than 100 degrees Fahrenheit.
But heat isn’t the only extreme weather the world has faced over the past few months. Unusually massive wildfires swept across California and Greece, while sustained precipitation – including May’s deadly Cyclone Remal – led to widespread flooding and the displacement of some 700,000 people in Bangladesh. Fierce rains and resulting flooding also devastated communities from Brazil to Kenya.
It’s tempting to point to climate change as the culprit for all of this. After all, scientists are clear that the world is getting hotter because of human behavior, and most agree that more heat – aka energy – in the atmosphere can lead to a host of increasingly intense weather events.
Why We Wrote This
After a summer of brutal heat waves, hurricanes, and wildfires, it’s easy to assume that extreme weather is linked to climate change. That’s often true, but scientists are still learning more. Their findings impact decision-making in a variety of fields.
But the connection between extreme weather events and the increasing level of heat-trapping gases in our atmosphere remains scientifically complicated, thanks to the huge number of atmospheric and human factors involved. It also varies tremendously based on where and what, exactly, one is considering.
“We are seeing increases in many types of extreme weather, which is consistent with theory and predictions and modeling,” says Daniel Swain, a climate scientist with the Institute of the Environment and Sustainability at the University of California, Los Angeles. But what that means, he adds, “really does vary by the type of extreme weather we’re talking about.”
Scientists know a lot about the impact of global warming on temperature trends, for instance. Researchers know that Earth is warmer because of more heat-trapping gases in the atmosphere, and that this causes more extreme heat events and fewer extreme cold events.
We know less about how it impacts the frequency of hurricanes. Warmer air can hold more moisture, so the intensity of some storms has – and is expected to – increase. But globally, the number of tropical cyclones has decreased over the last century, although they have increased – and some research shows they get stronger, faster – in the North Atlantic.
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And when it comes to rain, the role of climate change can differ from place to place. While extreme precipitation events are increasing everywhere, some areas, like the northeastern U.S., are getting wetter, while others, such as the Mediterranean, are drying out.
This all might seem nuanced, and maybe even like “in the weeds” science. But understanding the details when it comes to climate change and extreme weather – where models work and where they don’t, where human behavior is the main culprit and where we still don’t know – matters tremendously, experts say. It has implications on everything from where houses are built to how to ensure humans have enough food.
What scientists know best
The clearest information we have about the warming atmosphere is on the global level. The Earth is clearly warmer than it once was, and scientists know – from studying carbon isotopes, historical patterns, and climate modeling – that the reason for this warming is the accumulation of heat-trapping, or greenhouse, gases, primarily from fossil fuels like coal or oil.
But those planetary-wide numbers don’t necessarily say what’s happening in your neighborhood – or let you predict what might happen next month.
Overall, Earth is about 2.45 F warmer now than the average temperature in the preindustrial 19th century. But the global mean temperature can seem abstract, without telling people much about what’s happening on the ground in a particular place and at a particular time, says Dr. Swain.
Margarita Salazar wipes sweat off her brow inside her home amid high heat in Veracruz, Mexico, June 16, 2024.
Even temperature can get complicated. The air over land has warmed faster than over the ocean. Temperature increases happen in both the winters and summers, nighttime and daytime. And because of the complex interactions among land and air and ocean, a few degrees of warming in some places can have cascading effects.
This is arguably best understood when it comes to extreme heat – and why a few degrees of warming can result in temperature spikes that go much higher than even the global land surface average. This is because as the temperature increases, the hotter air sucks moisture out of the soil. With less water in the soil, more of the energy from the sun goes to heating the earth as opposed to evaporating moisture. This creates an accelerating feedback cycle, as that hotter earth then heats up the surrounding air even more.
Where the science gets complicated
But it’s hard to definitively say if any given heat wave is because of climate change or normal weather fluctuations – and even more so when it comes to storms, wildfires, and droughts.
This summer, researchers using a relatively new tool called “attribution science” found that many of the world’s heat waves were made much more likely because of climate change.
But it’s important to recognize that attribution science deals in likelihoods, not in certainties. So July’s heat in the U.S., for instance, might have been three times more likely in a warmer world, according to attribution science – but it also could have happened without any global warming at all. It would have just been much less likely.
And even if climate change did cause those heat waves, the calculations are about the duration and peak temperatures. Climate change didn’t transform five 70-degree, low-humidity, lovely summer days into the 98-degree steam bath that many Americans experienced this summer. The change is in what scientists call the graph’s “tails”: As peak temperature goes up, hot weather lasts longer.
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Still, attribution science has allowed policymakers and advocates to more quickly, and clearly, identify the climate change fingerprint on events that directly impact humans. The science, says Jeff Masters, a meteorologist and co-founder of Weather Underground, is a remarkable but limited advance. “The tools they use are things we didn’t have 10 years ago,” he says. “But at the same time, they’re very crude tools.”
Attribution models, for instance, compare sea temperatures with and without human-caused climate change, and examine the difference. This provides a bare-bones estimate, says Dr. Masters, but is inconclusive about exactly how much of extreme weather is due to climate change or natural climate variability.
“You can get some crazy extremes ... without climate change,” he says. “So apportioning all that is a heroic task.”
Some who downplay the role of climate change use these unknowns to suggest that global warming isn’t actually causing extreme weather events. But Dr. Masters and many of his colleagues believe that models are underestimating the role of climate change. Just because there is variability, or because human behavior often ignites events like wildfires, it doesn’t diminish the fact that more energy in the atmosphere leads to surprises.
How this relates to everyday life
How we understand the connections between climate change and extreme weather events can impact a slew of individual, economic, and policy choices.
For one thing, experts in many fields make decisions based on climate science.
“There are certain people in the world, like people who work in insurance and reinsurance, people who build dams and manage water resources, people who plan for hurricane landfalls; they don’t have the luxury of believing whatever they want to believe,” says Roger Pielke Jr., a University of Colorado Boulder professor whose research is cited by the Intergovernmental Panel on Climate Change. “They need to stick to what we can and can’t say with the science.”
Dr. Pielke’s work, for instance, has found that much of the increase in financial damages regularly attributed to climate change storms is actually a result of more people with more valuable property located along coastlines.
Wildfires can be beneficial for ecosystems, but devastating when homes and infrastructure are in their paths.
And flooding is barely noticed if towns or roads are not in the water’s path.
“The issue really lies in the fact that humans are in the way, and we’ve built structures in the way of these riskier zones,” says Libby Zemaitis, senior manager for resilience programs and policy at the Center for Climate and Energy Solutions.
Communities must increasingly prepare for multiple, sequential extreme events – wildfires and landslides, for instance – that a decade or two ago would have been viewed as impossible, says Rebecca Carter, director of climate adaptation and resilience for the global and U.S. climate program at the World Resources Institute. (After all, not so long ago the Pacific Northwest was viewed as a climate haven. In recent years, it has endured triple-digit heat waves.)
Indeed, although it might be impossible to directly tie, with 100% certainty, any series of extreme weather events to climate change, a clear pattern of the unexpected – of floods, heat waves, and fires at unexpected times and in unexpected places – is emerging.
That idea that something is going to happen, even if we don’t know exactly what, concerns many climate scientists, even those who are more conservative about wanting to see a lot of proof, and over an extended period of time, before making the connection with specific extreme events.
“Climate change is always going to be a risk management problem,” says Dr. Pielke. “We’re changing the energy balance of the Earth system. It is going to have consequences.”
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