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Portland's roads melted during last month's heatwave. So what does this extreme weather event tell us about climate change?

By North America correspondent Kathryn Diss, Saturday July 31, 2021 - 22:51 AEST

Ever imagined a city so hot that the road melts and parts of the transport system start to warp and twist?


What about an unprecedented cold snap that froze power lines in the usually balmy state of Texas? 


Or bushfire smoke travelling more than 4,000 kilometres from America's west coast to New York City, causing air pollution nine times the recommended level?


And Germany recording roughly double the amount of rain expected for the entire month of July in just two days.


This is now the lived reality for many parts of the world as severe weather events become more and more frequent.


And it's prompting many of these communities to now ask themselves: how do we adapt to the new normal?


According to climate scientist Bill Hare, it will require a dramatic shift in approach.


"Above all, it means future-proofing infrastructure and teaching people how to deal with extremes," he said.


"In some places, you're talking about simply giving up. In some places it will not work to build a seawall ? five years later, it will be gone."


But before we get deep into how communities are going to have to completely re-think how they interact with the world, let's take a closer look at what happened in Portland.


What really happened in Portland?


In short, it was very hot. The city's usually moderate summer broke records in June, literally melting through its hottest day ever.


And as it maxed out at 44 degrees Celsius, Portland's relatively modern, 20-year-old metro system started to warp.


A power cable twisted around some metal hardware and scorched, wires that run above the track expanded and sagged so much they risked touching train cars.


The trams, powered by 100 per cent renewable energy, are exactly what the United States needs to reduce carbon pollution, but they were clearly built for another age.


The heatwave was caused by an unusual weather phenomenon.


Usually, hot air expands and rises, which then cools the planet's surface or helps create thunderstorms.


But a high-pressure system sitting on the atmosphere trapped the hot air, causing a so-called heat dome.


When the air tries to rise, the system nudges it back to the surface ? and during that process, the air becomes denser and hotter.


It can't escape the cycle, so it just circulates up and down, getting hotter and hotter.


Could these events become more frequent?


According to experts, the Portland example is a rare phenomenon and considered a one in 1,000-year event.


But meteorologist Andrew Hoell from the National Oceanic and Atmospheric Administration said the question scientists were now trying to answer was whether climate change is making these kinds of extremes more frequent.


"There are really two considerations here when it comes to events like that," he said.


"The first one is, how will climate change affect the weather patterns? So, the specific pattern that produces that type of warmth.


"The other question is the background warming that climate change produces, which is on the order of maybe two or three and perhaps even four degrees Fahrenheit.


"That's really an emerging area right now, that the community is trying to understand, is whether a pattern like that is now more likely to happen in a changing climate."


There's little doubt extreme weather events are increasing in intensity and frequency, but scientists are still trying to determine how climate change could influence the anomalies.


"Some folks are arguing that the weather patterns are becoming stronger and more amplified because of climate change," Mr Hoell said.


"And they're linking that to changes in the Arctic, so changing sea ice cover and land ice cover, and also the temperatures in the Arctic, and how that may affect the weather pattern say over North America and over Europe.


"That right there needs a lot more vetting, it needs a lot more research, but there is that hypothesis, out there right now that we need to test more thoroughly."


Mr Hoell said scientists use their knowledge of the weather, climate observations and model simulations to determine if extreme events like what has happened in Texas and the Pacific northwest are becoming more likely.


"If a certain event is going to become more likely, whether it's a heat event or cold event or an extreme precipitation event, you want to be able to plan for that," he said.


"And we want to use our best information possible."


Are we seeing cities melt elsewhere?


Climate change isn't affecting all parts of the globe equally and the effects tend to be region-specific.


Australia's horror bushfire season last year was arguably the country's most recent display of the impacts of climate change.


"The bushfires in Australia were exceptional. Now they were linked to some forms of what we call natural variability," Mr Hoell said.


"So, there was a pattern of sea surface temperature anomalies in the Indian Ocean, that were very closely related to that."


Mr Hoell said it also sparks a number of questions, such as whether that pattern of sea surface temperatures is now more likely in the changing climate.


"So did that feed into the exceptional fires but also, when it came to those fires, was the ground more arid because of climate change?" he asked.


Mr Hoell said the bushfires which transpired in Australia and the heatwave in Portland were events which only occur every 500 to 2,000 years but that was changing.


He said if climate change is going to make some events twice as likely ? for example, a one in 100-year event becoming a one in 50-year event ? then that could have serious implications for current infrastructure.


Take a bridge, for example. Instead of experiencing a rare weather event once during its lifetime, Mr Hoell said going by that model, it could now expect to experience it twice.


"So now it's twice going to have twice as much stress on it just because it's two events as opposed to one," he said.


So how are cities preparing for a new normal?


In North America, millions are being forced to confront a string of inescapable disasters as the nation endures a summer of record-breaking drought, heatwaves and megafires exacerbated by climate change.


Groundwater and streams vital to both farmers and cities are drying up and fires are devouring entire neighbourhoods and livelihoods on an ever-increasing scale.


While summer monsoon rains have brought some relief to the south-west, 99.9 per cent of Utah is locked in severe drought and reservoirs are less than half full.


US President Joe Biden recently announced a mega $3.3 trillion dollar infrastructure plan designed to future-proof the nation's homes for weather extremes while also reducing carbon emissions by investing in clean technology.


It's part of his plan to undertake the gigantic task of shifting the United States to net zero greenhouse gas emissions by 2050.


"It's actually a pretty intelligent thing to do, just because you're trying to use your best possible information to inform certain infrastructure," Mr Hoell said.


"Because if you don't do that, then you may experience a weather event or climate event that will ruin your infrastructure, then you have to do it all over again.


"The reason why this is such a priority with this administration and even was a priority with the Trump administration is because all the infrastructure that was built was built 50 to 100 years ago, [and it] needs to be replaced.


"So that's why this is really at the forefront of his agenda, is to try to make more informed decisions so the infrastructure will last."


Some states are also doing their part to weatherproof communities as well.


California's largest electricity provider, Pacific Gas and Electric, plans to spend tens of billions, putting 16,000 kilometres of powerlines underground to prevent future bushfires.


Parts of the state, which typically swelter through hot summers, have also set up cool rooms to house homeless people unable to escape the heat.


Even Seattle, which is home to a far milder climate, set them up this year.


"Heatwaves kill people, as everyone says, silently, but they kill more if you don't understand them," Dr Hare said.


"If you're prepared ? there's warning systems, there's welfare services in place ? then you can get more people through the extreme heatwaves."


Governments will also have to start retrofitting buildings or replacing infrastructure better able to handle extremes on both ends of the climate spectrum.


"That's making sure cities are greener. You can lower the peak temperature by a number of degrees by focusing on that," Dr Hare said.


"Adaptation resilience sort of issues are labour-intensive, right, you've got to retrofit housings and buildings, you are spending money that's ultimately spent on labour and then you also impose the economic capacity of a country when things get too hot.


"Hot places have lower productivity, when it gets hot, people slow down.


"You're also trying to build economic resilience, the same with floods. If you can limit the infrastructure damages, then you're also building economic resilience to climate extremes."


What else can be done?


Most scientists will tell you mitigating the effects of climate change by reducing our impact on carbon emissions is the best path forward.


That's because continually adapting the world to ever-changing weather conditions will be expensive and inefficient.


But Dr Hare seriously doubts many governments have the will to do it.


"You're talking about making hard decisions and very few governments are equipped to do that," he said.


"I'm hard-pressed to think of any governments who have serious approaches to this.


"It's a tough thing for governments because you're up against everyone."


He gives the example of governments being forced to determine whether parts of the planet are no longer habitable, even if it means moving a village that has existed for 500 years.


"It means looking at all infrastructure and slowly future-proofing it, when it's due for replacement or before," he said.


"It also means basically deciding that some places are not places for people to live safely."







- ABC

© ABC 2021

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