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What we don't know about global warming

Upcoming global average temperature measurements are unlikely to yield surprises. The real question is how we adapt, says one scientist.

It's estimated that 2022 would finish as the fifth or sixth hottest year since the mid-19th century. (Pexels/Markus Spiske)
It's estimated that 2022 would finish as the fifth or sixth hottest year since the mid-19th century. (Pexels/Markus Spiske)

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It’s that time of year again, when climate scientists report that the 12 months that just passed are among the hottest in recorded history. If anything is surprising, it’s that annual rankings draw so much attention at all. 

Also read: How climate change can impact Indian Ocean dipole

Sight unseen, the results are somewhat predictable — and not just because the World Meteorological Organization previewed theirs in November. It estimated that 2022 would finish as the fifth or sixth hottest year since the mid-19th century. Several research groups are expected to release numbers soon, and they’re likely to tell a similar story. 

Climate is an average of weather over a long period of time, say, 30 years. And the last 15 decades or so show the world heating up. The temperature difference between 1922 and 2022 is mostly explainable by fossil-fuel burning. But what about between 2021 and 2022? Not as much as you’d think. That’s because consecutive years generally reveal more about natural, year-to-year weather variations than they do about human-driven warming.  

In years that have a La Niña cooling pattern in the equatorial Pacific, such as 2022, the global average may be slightly lower than it would be otherwise. When there’s an El Niño, the ocean instead churns out extra heat, sometimes leading to a new annual record, said Andrew Dessler, a professor of atmospheric sciences at Texas A&M University. Those ebbs and flows don’t change the fact that the world is steadily warming.

“We actually understand the physics of the climate system pretty well at this point,” Dessler said. “There hasn’t been a surprise in the global average physics since the 1960s or 70s.”

Dessler, an expert in climate physics and atmospheric chemistry, has been gradually shifting the focus of his work to reflect current problems in climate change — which for him increasingly have less to do directly with fundamental science and more to do with what he calls a “physics-human interface.”

“I basically decided that the stuff I was working on wasn't interesting anymore,” he said. “And so I've actually been shifting my research towards these other questions.”

Here are five questions that Dessler identified as increasingly critical as the world warms:  

How resilient are societies?

Countries built infrastructure to operate within the historical temperature range. Recent events suggest that the weather doesn’t have to go haywire for long before systems show strain. 

“The thing that blows me away continuously is how completely unprepared we are for very slight deviations outside of the temperature range we expect,” he said. 

More extreme or erratic weather is already revealing vulnerabilities in infrastructure all over the world, and in rich countries as well as poor. Colder than normal temperatures in the US state of Texas in February 2021 knocked out power and disabled natural gas infrastructure, leading to at least 246 deaths and $195 billion in damage. 

The surprising thing for Dessler is “it didn’t get that much colder than we get every year.” 

How can we get to 100% carbon-free energy?

The sun sets every night and the wind comes and goes. But the non-negotiable modern standard for an energy system is 100% reliability all day and all night. Intermittent renewable energy could solve the bulk of the energy transition, leaving perhaps 20% of the grid in need of a large, carbon-free power source that can be tapped whenever it’s needed. This could be nuclear reactors, natural gas plants fitted with carbon-capture equipment, geothermal energy or utility-scale battery arrays. 

Finance, permits and local buy-in will always be wildcards, the latter sometimes irrationally so, meaning the progression away from fossil fuels is rarely smooth or linear even when the technological solutions exist. “You drive under power lines all the time, you don't even see them, right?” he said. But “when you say we want to build a power line, people go ‘Oh, no. You can't do that. That's gonna destroy the landscape.’”

How fast will specific regions warm?

What rising thermometers mean for any particular region is still an active area of research. It’s hard to predict how regions will experience the combined effects of global warming and natural weather variability — the same changes that are also mostly responsible for the marginal dips and bumps in annual temperatures.  

Scientists used to think that climate change would bring more El Niño-driven heat events. But in the last 20 years, La Niñas have shown up with greater frequency. Until they have a better understanding of this influential element of the weather system, regional projections — something countries and companies are increasingly demanding — may remain fuzzier than anyone would like. 

How quickly could ice sheets go?

As the Greenland ice sheet melts, it loses altitude. And as it loses altitude, the surface comes into contact with warmer air, which melts more Arctic ice. On the other end of the world, as warming water eats into Antarctic ice at the sea floor, several glaciers are becoming vulnerable to “self-sustaining retreat.” While the time scale for total collapse is in the order of hundreds or thousands of years, sea-level rise is already faster than it’s been in at least 3,000 years and water temperatures are warmer than they’ve been in the last 11,000. How fast ice sheets melt could yet affect the rate of sea-level rise — and by extension the fate of coastlines and islands — in potentially unexpected ways. 

How do we stop uprooting natural systems?

Modern economies exist at the behest of natural systems that are now under huge strain. “We get an enormous value from nature,” Dessler said. It “does a lot of things for us basically for free.” 

International attention is growing on the twin risks of climate change and biodiversity loss, which is reaching critical levels. In December, 190 countries agreed to protect 30% of land and ocean by 2030. It remains far from clear if and how that will be achieved. 

Everybody loves lists, including of heat rankings, but for biodiversity loss, as for climate, the rising global average of temperatures is a lagging indicator. 

Also read: 4 podcasts on climate anxiety and the environment in 2023

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