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Rise in blocking-patterns – hot or wet weather remaining stuck over regions for weeks – causing frequent heatwaves or floods.
By Damian Carrington.
A man hangs on to a trash can as rain water gushes towards Albuquerque in New Mexico, US. Heavy rains caused flash flooding and road closures in the city earlier this month. Photograph: Roberto E. Rosales/AP
The work shows so-called “blocking patterns”, where hot or wet weather remains stuck over a region for weeks causing heatwaves or floods, have more than doubled in summers over the last decade. The new study may also demonstrate a link between the UK’s recent flood-drenched winter and climate change.
Climate scientists in Germany noticed that since 2000 there have been an “exceptional number of summer weather extremes, some causing massive damage to society”. So they examined the huge meanders in the high-level jet stream winds that dominate the weather at mid-latitudes, by analysing 35 years of wind data amassed from satellites, ships, weather stations and meteorological balloons. They found that blocking patterns, which occur when these meanders slow down, have happened far more frequently.
“Since 2000, we have seen a cluster of these events. When these high-altitude waves become quasi-stationary, then we see more extreme weather at the surface,” said Dr Dim Coumou, at the Potsdam Institute for Climate Impact Research. “It is especially noticeable for heat extremes.” The intense heatwaves in Russia in 2010, which saw 50,000 people die and the wheat harvest hit hard, and in western Europe in 2003, which saw 30,000 deaths, were both the result of blocking patterns. The Intergovernmental Panel on Climate Change concluded in 2011 that extreme weather would become more common as global warming heats the planet, causing both heatwaves and increasingly severe rain storms.
In 2010, heatwaves caused hundreds of wildfires across Russia. Above, a man tries to stop a fire near Dolginino village. Photograph: Artyom Korotayev/AFP/Getty Images.
The rise in blocking patterns correlates closely with the extra heating being delivered to the Arctic by climate change, according to the research which is published in the journal Proceedings of the National Academies of Science (PNAS). Coumou and his colleagues argue there are good physical reasons to think there is a causal link, because the jet streams are driven by the difference in temperature between the poles and the equator. As the Arctic is warming more quickly than lower latitudes, that temperature difference is declining, providing less energy for the jet stream and its meanders, which are called Rossby waves.
Prof Ted Shepherd, a climate scientist at the University of Reading, UK, but not involved in the work, said the link between blocking patterns and extreme weather was very well established. He added that the increasing frequency shown in the new work indicated climate change could bring rapid and dramatic changes to weather, on top of a gradual heating of the planet. “Circulation changes can have much more non-linear effects. They may do nothing for a while, then there might be some kind of regime change.”
Shepherd said linking the rise in blocking events to Arctic warming remained “a bit speculative” at this stage, in particular because the difference between temperatures at the poles and equator is most pronounced in winter, not summer. But he noted that the succession of storms that caused England’s wettest winter in 250 years was a “very good example” of blocking patterns causing extreme weather during the coldest season. “The jet stream was stuck in one position for a long period, so a whole series of storms passed over England,” he said.
Flooding in Northmoor Green (Moorland) in Somerset, UK, in February this year. Photograph: David Levene for The Guardian.
Coumou acknowledges his study shows a correlation – not causation – between more frequent summer blocking patterns and Arctic warming. “To show causality, computer modelling studies are needed, but it is questionable how well current climate models can capture these effects,” he said.
Prof Tim Palmer, at the University of Oxford, wrote in a PNAS article in 2013 that understanding changes to blocking patterns may well be the key to understanding changes in extreme weather, and therefore to understanding the worst impacts of climate change on society. But he said climate models might have to run down to scales of 1km to do so. “Currently, national climate institutes do not have the high-performance computing capability to simulate climate with 20km resolution, let alone 1km,” he wrote. “I look forward to the day when governments make the same investment in climate prediction as they have made in finding the Higgs boson.”
Firefighters cross a flooded intersection on Route 110 in Farmingdale, N.Y., on New York’s Long Island, Wednesday, Aug. 13, 2014. Stranded Long Island drivers have been rescued after a storm slammed Islip, N.Y., with over 13 inches of rain — an entire summer’s worth. (AP Photo/Frank Eltman)
DEER PARK, N.Y. (AP) — A storm has slammed a suburban New York area with over 13 inches of rain — an entire summer’s worth — and trapped drivers on flooded roads around Long Island.
The staggering total was recorded Wednesday at an airport in the hamlet of Ronkonkoma (rahn-KAHN’-kuh-muh) in the town of Islip (EYE’-slip). Joe Pollina of the National Weather Service says the area’s normal total for June, July and August is 11.75 inches.
The Southern State Parkway was closed around Baldwin and about 20 miles east in Deer Park, where cars were stuck in a couple of feet of water.
WPIX says fire crews in boats rescued drivers in Nesconset (nehs-KAHN’-seht).
Central and eastern Long Island roads that were still open had bumper-to-bumper traffic Wednesday.
The rain started around 6 p.m. Tuesday. It tapered off Wednesday morning.
Vehicles are submerged on a flooded section of the Northern State Parkway, near Route 107, in Jericho, N.Y., on New York’s Long Island, Wednesday Aug. 13, 2014. Stranded Long Island drivers have been rescued after a storm slammed Islip, N.Y., with over 12 inches of rain — an entire summer’s worth. (AP Photo/Newsday, Howard Schnapp) NYC LOCALS OUT
Power plants and electricity distribution networks are particularly vulnerable to droughts and floods. Photograph: Stephen Hird/Reuters
Rising sea levels, extremes of weather and an increase in the frequency of droughts and floods will all play havoc with the world’s energy systems as climate change takes hold, a new report has found.
Energy companies are more often cited as part of the problem of climate change, generating the lion’s share of the world’s greenhouse gas emissions, amounting to around 40% of the total. But they will also suffer as global warming picks up pace, as generators – from nuclear reactors to coal-fired power plants – feel the brunt of the weather changes.
Many large plants are particularly at risk from droughts, because they need water to cool their facilities, and floods, because they lack protection from sudden storms. Electricity distribution networks are also likely to be affected.
The vulnerability of energy systems to natural shocks was shown starkly when the Fukushima nuclear plant in Japan had to be closed down following the 2011 tsunami, which prompted governments around the world to review their nuclear policies.
The World Energy Council (WEC), which compiled the study along with Cambridge University and the European Climate Foundation, urged generators to examine their vulnerability to climate change, saying that with suitable adaptations – such as protecting power plants from water shortages and building resilience into power networks – the worst of the problems could be avoided. (more…)
Met Office and Newcastle University study is first to draw direct link between climate change and rise in summer downpours.
Flood damage in Boscastle, Cornwall, in 2004. Photograph: Graeme Robertson/Getty Images
Flash flooding in summer is likely to become much more frequent across the UK as a result of climate change, with potentially devastating results in vulnerable areas, according to new research.
The study, published in the peer-review journal Nature Climate Change, is the first to draw a direct link between climate change and an increase in summer downpours.
The research, a result of a collaboration between the Met Office and Newcastle University, used climate change computer models and standard weather prediction models of the type used for short-term weather forecasts. It found that summers would be drier overall, but punctuated by more extreme downpours.
These can have a much worse effect than the steady rainfall typical of winter, because the dry land is less capable of absorbing water, and when too much falls in a short period it runs off, causing flash floods of the type that struck Boscastle in 2004, one of the worst examples of sudden localised flooding in recent years.
Whether any given area is subject to flash flooding will depend heavily on its topography, such as the proximity of uplands and rivers, but vulnerable areas are likely to experience far more incidents than they did in the past.
It is not possible to say exactly how many more floods are likely, but the researchers said instances of particularly heavy summer rainfall – defined as more than 28mm in an hour – would be about five times more probable.
Elizabeth Kendon of the Met Office, the lead author of the study, said that the research was groundbreaking in using a high-resolution weather forecasting model to translate the likely effects of climate change into a detailed prediction of future UK summer weather.
“Until now, we haven’t been able to do it in this way,” she said. “This should help people to understand what is likely to happen in the summer in future. It’s very important that we’ve detected this signal for heavier downpours in the UK. It’s now for policymakers to decide what to do about it.”
Some of the worst results could still be a few decades away, but the effects are already being felt and are likely to grow more severe, according to the models. But Kendon said more accurate predictions would depend on more scientific research being undertaken.
Summer rainfall is different to that typical of winter, when long-lasting steady bouts of heavy rain are common. These can cause their own flooding problems, as seen early this year when heavy rain caused widespread devastation in the UK with thousands of people forced to flee their homes.
Climate models suggest heavier winter rainfall for the UK. Summer downpours, such as those seen in 2012 when heavy rainfall followed a long period of drought, with disastrous results, are harder to predict but can take a greater toll as they are more sudden, and crops are ruined and tourism disrupted.
Kendon said: “It’s the hourly rainfall rates that you look at in summer.” The rain tends to fall in shorter but more intense bursts, caused by convective storms, but this has been difficult for climate models to simulate, because they lack the ability to home in on such brief events. It took the Met Office supercomputer, one of the most powerful in the world, nine months to run the necessary simulations.
Editors Note: This will either push insurance premiums through the roof or else make it impossible to get any kind of insurance cover for your property.
Flooding is predicted for parts of England as heavy rain persists. Photograph: Charlie Crowhurst/Getty Images
Heavy rain across the east of England could cause flooding over the coming days, forecasters have warned.
The Met Office issued a yellow weather warning of rain for the region, predicting localised flooding that could cause disruption to travel.
The wet weather would persist until Wednesday night, the Met said, with up to 70mm (2.76in) of rain expected in worst-hit areas including parts of Lincolnshire, South Yorkshire and the Humber.
The Environment Agency (EA) warned of a flood risk in the east, mainly from surface water and low-lying rivers.
It said: “There may be some flooding of low-lying land and roads, some disruption to travel and possibly flooding to individual properties.”
Meteo Group forecaster Gareth Harvey said: “An area of prolonged rain is moving up over the eastern region and it’s not going to shift until Wednesday night.
“The rain is not exclusive to the east region but that’s where the persistent and largest rainfall totals of between 50 and 70mm will be.
“Pretty much the whole of Great Britain will see rain at some point over the next 48 hours.
“This means there could be some localised flooding.”
The EA has issued 10 low-level flood alerts in the south-east and the Midlands, mainly warning of groundwater flooding close to rivers.