24/07/2021

(Reuters) From China To Germany, Floods Expose Climate Vulnerability.

Reuters - Aradhana Aravindan | James Mackenzie

An aerial view shows a flooded road section following heavy rainfall in Zhengzhou, Henan province, July 21. China Daily via REUTERS/File Photo

Deadly floods that have upended life in both China and Germany have sent a stark reminder that climate change is making weather more extreme across the globe.

At least 25 people in the central Chinese province of Henan died on Tuesday, including a dozen trapped in a city subway as waters tore through the regional capital of Zhengzhou after days of torrential rain. read more

Coming after floods killed at least 160 people in Germany and another 31 in Belgium last week, the disaster has reinforced the message that significant changes will have to be made to prepare for similar events in future. read more

"Governments should first realize that the infrastructure they have built in the past or even recent ones are vulnerable to these extreme weather events," said Eduardo Araral, associate professor and co-director, Institute of Water Policy, at Singapore's Lee Kuan Yew School of Public Policy.

In Europe, climate change is likely to increase the number of large, slow-moving storms that can linger longer in one area and deliver deluges of the kind seen in Germany and Belgium, according to a study published June 30 in the journal Geophysical Research Letters.

As the atmosphere warms with climate change, it also holds more moisture, which means that when rainclouds break, more rain is released. By the end of the century, such storms could be 14 times more frequent, the researchers found in the study using computer simulations.

While the inundation that devastated wide swathes of western and southern Germany occurred thousands of kilometres from the events in Henan, both cases highlighted the vulnerability of heavily populated areas to catastrophic flooding and other natural disasters.

"You need technical measures, bolstering dikes and flood barriers. But we also need to remodel cities," said Fred Hattermann at the Potsdam Institute for Climate Impact Research. He said there was increasing focus on so-called "green-adaptation" measures, like polders and plains that can be flooded, to stop water running off too fast.

"But when there's really heavy rain, all that may not help, so we have to learn to live with it," he said.

Reinforcing dikes and climate-proofing housing, roads and urban infrastructure will cost billions. But the dramatic mobile phone footage of people struggling through subways submerged in chest-deep water in Zhengzhou or crying in fear as mud and debris swept through medieval German towns made clear the cost of doing nothing.

A man looks on outside a house in an area affected by floods caused by heavy rainfalls in Bad Muenstereifel, Germany, July 19, 2021. REUTERS/Wolfgang Rattay/File Photo

"It is shocking and I have to say it is scary," said John Butschkowski, a Red Cross driver who was involved in rescue work in western Germany this week. "It is ghostly, no people anywhere, just rubbish. And it is inconceivable that this is happening in Germany."

One year's rainfall in three days

Koh Tieh-Yong, a weather and climate scientist at Singapore University of Social Sciences, said an overall assessment of rivers and water systems would be needed in areas vulnerable to climate change, including cities and farmlands.

"Floods usually occur due to two factors combined: one, heavier-than-normal rainfall and two, insufficient capacity of rivers to discharge the additional rainwater collected," he said.

In both China and northwestern Europe, the disasters followed a period of unusually heavy rain, equivalent in the Chinese case to a year's rainfall being dumped in just three days, that completely overwhelmed flood defences.

Residents, holding umbrellas amid heavy rainfall, wade through floodwaters on a road in Zhengzhou, Henan province, July 20. cnsphoto via REUTERS/File Photo

After several severe floods over recent decades, buffers had been strengthened along major German rivers like the Rhine or the Elbe but last week's extreme rainfall also turned minor tributaries like the Ahr or the Swist into fearsome torrents.

In China, built-up urban areas with inadequate water evacuation and large dams that modified the natural discharge of the Yellow River basin may also have contributed to the disaster, scientists said.

Rescuers carry children to safety in flood-stricken Anyang

But measures such as improving the resilience of buildings and raising riverbanks and improving drainage are unlikely to be enough on their own to avert the effects of severe flooding. As a last resort, warning systems, which were heavily criticized in Germany for leaving people insufficient time to react, will have to be improved.

"It really needs to be embedded in practical knowledge that people have so they know what to do," said Christian Kuhlicke, head of a working group on environmental risks and extreme events at the Helmholtz Centre for Environmental Research.

"If you can't keep the water back, if you can't save your buildings then at least make sure that all vulnerable people are moved out of these places."

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(UK The Guardian) John Kerry: World Leaders Must Step Up To Avoid Worst Impacts Of Climate Crisis

The Guardian - 

US envoy uses landmark speech in London to make impassioned plea for unified global effort

‘The climate crisis is the test of our times’: John Kerry speaks at Kew Gardens – video

The world still has a chance of staving off the worst impacts of climate breakdown but only if governments step up in the next few months with stronger commitments on cutting greenhouse gas emissions, the US envoy for climate change has said.

John Kerry, appointed by Joe Biden to spearhead the US’s international efforts to tackle the crisis, urged all large economies to come forward with new plans to cut emissions before the Cop26 UN climate talks in Glasgow this November.

“The climate crisis is the test of our own times and, while it may be unfolding in slow motion to some, this test is as acute and as existential as any previous one. Time is running out,” he said.

He called Cop26 “a pivotal moment” and 2021 “a decisive year”, as the world must get to grips with the climate crisis and rapidly slash emissions in the 2020s to have a chance of a safe future.

Speaking as floods have devastated parts of Europe and heatwaves and wildfires swept North America, Kerry drew a parallel between the ruins of Europe after the second world war and the ravages of the climate crisis.

“The world order that exists today didn’t just emerge on a whim. It was built by leaders and nations determined to makes sure that never – never – again would we come so close to the edge of the abyss,” he said.

US seeks cooperation with China on climate but not at any price. Read more
Kerry said his earliest memory, aged four, was of the ruined skeleton of a burned-out building in Europe, where he had been taken by his mother, who fled the Nazis.

“That journey has always given me the bedrock confidence that we can solve humanity’s biggest threats together.”

Staying within 1.5C of global heating, the aspirational goal of the 2015 Paris climate agreement, was still possible, he insisted.

“There is still time to put a safer 1.5C future back within reach. But only if every major economy commits to meaningful absolute reductions in emissions by 2030. That is the only way to put the world on a credible track to global net zero by mid-century,” he said.

The Paris agreement targets an upper limit of holding global temperature rises to well below 2C above pre-industrial levels, with an aspirational lower limit of 1.5C.

Kerry made it clear that the Cop26 summit must aim for the lower threshold, and warned that current government pledges on emission cuts would lead to 2.5C or 3C rises.

“We’re already seeing dramatic consequences with 1.2C of warming. To contemplate doubling that is to invite catastrophe,” he said.

Kerry used his landmark speech at the Royal Botanic Gardens, Kew, in London, with just over 100 days to go before Cop26, to make an impassioned plea for a unified global effort. “We can’t afford a world so divided in its response to climate change when the evidence for compelling action is so strong.”

He singled out China, the world’s biggest emitter and second largest economy, which has yet to submit to the UN a national plan for emissions cuts before 2030. “It’s imperative that we and China, and the rest of the world, are pulling in the same direction on this critical effort,” he said.

Kerry told the Guardian in an interview after his speech that he was hopeful China would realise the need to act quickly. “When China has set targets before, it has outperformed them, so that is very hopeful,” he said.

But he made it clear he also had other countries in his sights. He said the US was working with “allies, partners, competitors and even adversaries all too aware that some things happening today threaten to erase the very progress so many are struggling to advance”.

UN climate summits proceed by consensus so recalcitrant counties can thwart agreement. For Cop26 to be a success, countries such as Russia, Brazil and Saudi Arabia will need to acquiesce at least – Kerry’s remarks will be seen as warning them not to disrupt the process.

Climate experts and campaigners told the Guardian the US was still lagging behind in providing finance for poor countries, to help them cut emissions and cope with the impacts of extreme weather. Rich countries promised a decade ago to provide at least $100bn a year in climate finance by 2020, a pledge that has not been met.

“The US is not pulling its weight – it’s the only country holding up the $100bn pledge,” said John Sauven, executive director of Greenpeace UK. “If the US does not put its hands in its pockets and make up the shortfall, Glasgow will be in jeopardy.”

Kerry told the Guardian in response that the Biden administration was “working hard” on finding more financial assistance for poor countries. “It’s very important that the US should provide finance. Our internal process on this is not complete yet.”

He added: “We are very conscious of the sensitivities around this. The US obviously plays a key role, and our absence in the last four years [from climate action] heightens that sense of responsibility and the imperative to find a way.”

Ed Miliband, the shadow business secretary, who was at the speech – which no government ministers attended – said Kerry had shown the US was determined to lead the way on climate action. “He made it clear he is focused on 1.5C – and he’s absolutely right, that’s ambitious but essential,” he said.

Kerry also called on governments to invest in clean energy, holding out the prospect of a clean energy boom worth $4tn a year by 2030, and said new technologies such as hydrogen and carbon capture and storage would also be needed.

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(ABC) No Scientific Consensus Yet On Whether Warming Arctic May Lead To More Extreme Weather

 ABC Weather - Ben Deacon

Predicting the impact of global warming on the jet stream is at the frontier of climate science. (Supplied: NASA)

Key Points
  • Climate change is leading to an increase in the frequency and intensity of extreme weather events
  • The warming Arctic may be leading to a slowing of the jet stream in the Northern Hemisphere, causing more extreme weather
  • The slowing jet stream theory is an area of ongoing research
In the past month alone, Germany, Belgium and the Netherlands have suffered horrific flooding, Siberia caught fire, and the Arctic Sea suffered near-record melting. 

 Meanwhile, in North America, after record-high temperatures, formerly rare fire thunderstorms have become near-daily events.

There is one big theory connecting climate change to the weather patterns behind events as disparate as fire and floods, heatwaves and melting ice, across three different continents. 

It is elegant, reasonably easy to understand and has profound implications — but because it is at the frontier of climate science, not all researchers are yet convinced.

Warmer world, hotter heatwaves

 In one respect, the influence of climate change on heatwaves is relatively straightforward, according to Andrew King from the ARC Centre of Excellence for Climate Extremes at The University of Melbourne.

Smoke from Oregon's Bootleg fire rises behind the town of Bonanza. (AP: Bootleg Fire Incident Command)

"We've warmed the planet by about 1.2 degrees Celsius and the land has warmed faster than the ocean," Dr King said.
"So, this allows heatwaves to be that bit hotter than they would be otherwise."
Lytton, in Canada's British Columbia, recorded a record high temperature of 49.6C on June 29. (Supplied: Andybremner2012 CC BY-SA 4.0)

 Dr King said a warmer atmosphere could also hold about 7 per cent more moisture for every degree Celsius of warming.
"That means storms that occur on very short timescales can rain out more than they would be able to in a world without global warming," he said.
Heavy rainfall in central China's Henan province caused deadly flooding this week. (Supplied: AP)

Climate change and weather patterns

 Instances of extreme weather can be driven by distinct weather patterns that allow rain or heat to build up over time because weather systems stall in one place instead of moving on.

If climate change is causing weather systems to stall for longer, they may build to more intense levels.

This visualisation of high-altitude winds over North America on the day it reached 49.6 degrees Celsius in Canada shows the meandering jet stream. (Supplied: Earth.nullschool.net)
Late last month in Canada, a horseshoe-shaped high-pressure system called an Omega Block saw heat build up for days, leading to off-the-chart temperatures. In Europe last week, a cut-off low pressure system stalled over Germany, dumping a month's worth of rain in a day.
Limit of science

The impact of climate change on how such individual weather patterns move is at the very limit of science.

"It's kind of like having a jigsaw but most of the pieces are missing," Dr King said.
"We have really incomplete observations in many parts of the world and they don't go back long enough in time to really track the climate for long enough."
A lack of weather observations from remote regions like the Arctic makes it difficult to predict the precise behaviour of weather systems. (Supplied: Polar Bears International)

That missing data — often from remote places like the Arctic — is needed to build computer models of unprecedented detail that can better predict weather patterns. 

"We really need high-resolution simulations," Dr King said. 

"We have a few studies with regional, high-resolution simulations that point to a climate change-caused intensification of short-duration extreme rainfall, including in Europe.

"That's quite a powerful line of evidence to suggest that climate change is [enhancing] — or has likely enhanced — the recent extreme rainfall we saw in Germany, the Netherlands and elsewhere.
"But we just don't have enough data to really make conclusive statements."
The missing data is crucial to answering one of the biggest questions in climate science: Are weather systems sticking around for longer in the Northern Hemisphere because of climate change?

The answer — which would connect heat, floods and fire — has everything to do with the jet stream.

The jetstream circling the North Pole, reaching down into North America.

Wavy jet stream theory

Dr King says there is a belt of high-altitude winds that encircle the Northern Hemisphere, called the jet stream, and weather systems often follow that track.

Those winds are related to temperature differences between the cold polar regions and the warm tropics. 

"In a warming world, we're seeing a bit more warming over higher latitudes in the polar regions than we see over the equator," Dr King said.

"And that reduces the temperature difference between the equator and the poles.
"The idea is that, if you reduce that temperature difference between the equator and the poles, both near the surface and higher up in the atmosphere, you might reduce the strength of the jet stream. And you might make it wavier or slower," he said.
A slower, wavier jet stream may allow storms to stick around longer, leading to more extreme weather. 

But there is no conclusive evidence that the jet stream is slowing due to climate change.

"There are a variety of studies looking into this, some of which find evidence to suggest this is happening, particularly from the model-based studies, [and[ others, which suggest this isn't really happening,"  Dr King said. 

How the warming Arctic affects weather patterns in the Northern Hemisphere is an active area of research. (Supplied: Alfred-Wegener-Institut/Mario Hoppmann)

One recent study used detailed computer modelling to show a warmer world would lead not only to more intense rain in Europe but also to slower storm movement. 

However, its lead author — Abdullah Kahraman from Newcastle University in the United Kingdom — was at pains to qualify the limits of the study, saying it related to one very detailed computer simulation.

"This study does not really tell you that this will definitely be happening like that, because this is one scenario," Dr Kahraman said.
"However, when it comes to the jet stream issue, this is not the only simulation that is projecting some kind of decreasing of wind speed in the higher atmosphere."
Other scientists have recently shown there may only be a modest decrease in high altitude winds due to a warming Arctic. 

"It's basically an area of very active research, there are quite a few people around the world looking into this. And there is a diversity of views among scientists," Dr King said.
"At the very least, I think we can say that we don't have a great deal of confidence that this is a clear effect of climate change.
"But there is some indication that there might be more persistence of weather systems, as the jet stream may be allowing them to remain in place for longer.

"This could be contributing to some extreme weather events."

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