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Wednesday, June 8, 2016

Different responses to Extreme rainfall and flooding from France and Australia

Updated: 10 June 2016: Details of climate attribution of French extreme rainfall and flood event

Over the last week we have seen extensive flooding around central France and southern Germany, and the impact of an East coast Low on Australia. They are different weather events but they share a certain commonality in being disastrous intensive rainfall and flood events resulting in death and damage.

The French extreme rain and flood event has recently been attributed to climate change, while the extreme nature of the East Coast Low has not yet been studied for event attribution. Attributing single events to climate change can be statistically difficult due to the range of climate variability. The damage and destruction of both events are consistent with increasing climate trends of greater intensity of rainfall and flood events around the world due to climate change.

While Prime Minister Turnbull and Opposition leader Shorten stayed well clear of mentioning climate change with regards to the extreme rainfall and flooding event in Australia, the French President was far less circumspect, exclaiming (fr) at a press conference that the extreme rainfall and flooding event in France emphasized the importance of the fight against global warming.

"When there are climatic phenomena of this severity, we must all be aware that it is across the world that we must act," he added. "The weather of this magnitude, with people who have been forcibly displaced with emergency relief interventions necessary, is not just a phenomenon that affects only France. It also concerns victims in Germany and Poland," he noted during a press statement with Chilean President Michelle Bachelet.

Malcolm Turnbull visited the flood affected area of Picton, south west of Sydney on Tuesday to investigate the flood damage and talk to Traders. "The resilience that you've shown and the rapidity of the response is a credit to your community," he said to assembled emergency services personnel, according to the Sydney Morning Herald.

"The national disaster relief and recovery arrangements enable the state government to provide support to low income households and businesses, half of the cost of which is borne by the federal government under those arrangements," Mr Turnbull said.

On the other side of town, Opposition leader Bill Shorten visited Coogee Beach Surf Lifesaving Club which was damaged by more than eight-metre tall waves on Sunday. He told the media: "We've seen the terrible damage done and I think all Australians, if they hadn't already heard of this lifesaving club, will recognise it now." Earlier on he urged insurance companies to treat customers fairly and to process claims quickly.

Unlike the French President neither Australian leader was willing to use this extreme weather event to emphasise the importance of greater climate action by Australia and globally.

Torrential rain produce floods in central France

May 2016 one of the wettest months on record for France according to Meteo France statement (fr).

The high intensity rain event started on the weekend of 28 and 29 May 2016. It was a result of an active disturbance centred on France and the south of Germany which brought wide area persistent rain across France. Many regions experienced particularly significant rainfall accumulations, with quite a few rainfall records broken, particularly the central region of Ile-de-France and Paris. This active disturbance, more common in winter, was fed with hot and moist spring air, producing torrential rain.

"As a whole, the month of May 2016 is exceptional. Many monthly rainfall records have indeed been broken: the Paris-Montsouris station, there have been since the beginning of 176 mm, or about 3 months of rainfall (old record: 133 mm in May 1992). In Orleans, there was 178 mm, also about 3 months of precipitation (old record: 148 mm in May 1985).

Across the region Ile-de-France [Paris] is the rainiest month of all months since 1960."

In a subsequent statement(fr) Meteo France said that it is not possible to attribute this type of event (only) to climate change, as it is a rare event mainly the result of a particular weather situation. They said it is questionable whether climate change has altered the probability for such an event to occurr, although aknowledging there are presently no specific attribution studies for intense rainfall or flooding in France. Meteo France do acknowledge the IPCC (Intergovernmental Panel on Climate Change) consensus that there is an intensification of heavy precipitation events in a warmer climate.

In Paris the River Seine reached 6.1 metres (20 feet) above normal, and tens of thousands of people fled their homes. Le Louvre closed so they could move thousands of artworks out of basement rooms for safety against the flood threat.

It is not only high rainfall that exacerbates flood events, but the way we have modified the landscape increasing hard surfaces for rapid runoff of water, and reducing the number of floodplains and wetlands that soak up water and then slow release it for river systems.

This French animation articulates that 50 percent of wetlands in France are disappearing under development.

In the west of France there are plans to build a new airport at Notre Dame Des Landes north of Nantes. This area has important wetlands with significant biodiversity and threatened species. You can read the scientific and ecological assessments in a 140 page PDF document at NATURALISTES EN LUTTE: Second numéro spécial de la revue Penn ar Bed consacré à NOTRE-DAME-DES-LANDES vient de paraître (fr)

A referendum in the Loire Atlantique region will take place on 26 June to determine if the airport construction will proceed. Climate activists and scientists have campaigned strongly against the airport for many years, including a 20,000 protest in January 2016, and 60,000 on the Nantes ring road late February this year.

Of course there was also substantial media silence in France on climate change with regard to the torrential rain and floods (fr), reports Young Friends of the Earth.

Event attribution study finds climate change increased risk in French Flood event

Update: 10 June 2016 Near real time climate event attribution study by the World Weather attribution team co-ordinated by Climate Central, has found at least a 40 percent increase in risk from climate change across France from extreme rainfall, with this increasing to 80 percent more for the Seine River basin and 90 percent more for the Loire river basin in France.

Map of mean rainfall (in mm) for the period from
May 29-31, 2016, over France
Image: Climate Central

Results: Overall, the probability of 3-day extreme rainfall in this season has increased by at least 40 percent in France, with the best estimate of about 80 percent on the Seine and about 90 percent on the Loire. All four climate model ensembles that simulated the statistical properties of the extremes are in good overall agreement. Results for Germany were inconclusive.

Changing Risk: By comparing recent 3-day precipitation extremes in April-June with the historical record and climate model simulations, the team found that an event like this now expected to occur roughly 80 percent more often due to climate change than it was in the past for the Seine River Basin. For the Loire River Basin 3-day precipitation extremes in April-June, the team found that an event like this is now expected roughly 90 percent more often due to climate change than it was in the past. In both cases, the increases are at least 40 percent.

Sydney storm highlights Coastal erosion and sea level rise threat

Photo: UNSW Water Research Lab showing undermining of beachfront houses and a concrete swimming pool stranded on the beach

Back to Australia, the East Coast Low, packing the power of a tropical cyclone, sequentially pounded the east Australian coast from Southern Queensland on 3 June heading south. The whole east Coast of Australia from southern Queensland to Tasmania was on alert for intense rain, flash flooding and storm surge. The Bureau of Meteorology urged Southeast Qld and eastern NSW to prepare for a wet and windy weekend.

Several people are either dead or missing in NSW and Tasmania as a result of flooding.

Why so much rain? According to the BOM Tropical moisture from Coral & Tasman Seas was feeding into the East Coast Low. If you remember sea surface temperatures have been at record levels in the Coral sea causing extensive coral bleaching of the Great Barrier Reef over summer.

In the 24 hour period to 9am Sunday 5 June, 2016 rainfall measurements along the entire NSW coast were recording totals over 100mm in the 24 hour period.

Here is a report of flooded coal seem gas wells and a gas holding tank on it's side in flood waters on the flood plain of the Nepean River in the Sydeny basin. Methane gas is now bubbling in the Nepean river adding to the greenhouse gas emissions.

In NSW the storm combined with a king tide to bring widespread coastal erosion and destruction, forcing people to flee homes.

Much attention has focussed on the storm surge impact and coastal erosion on Sydney's beaches. The Coogee surf club sustained substantial damage and innundation from the 13 metre storm surge that was also associated with a King tide.

Houses at Collaroy on Sydney northern beaches were undermined from the king tide and storm surge on Sunday night. Houses saw their backyards crumble into the ocean, including one house losing it's concrete inground swimming pool. Many houses are now tottering on the edge, the sand footings undermined by the surging waves.

Here is Matt Kemp's video of houses on Ramsay street being undermined. Matt described the situation: "you can see a backyard pool washing into sea in front of our place. I also saw power poles, wheelie bins and roofs and heaps of garden furniture washing past. Pretty crazy. No rain for ages and then whoosh, have a bit of that!!! The coloured lights are the police and SES. They are busy securing a sink hole."

Drone footage of severe coastal erosion on Sydney's Northern Beaches by UNSW Water Research Laboratory on Youtube:

National coastline Observatory needed say scientists

Narabeen and Collaroy beaches have been monitored for beach erosion for the last 40 years by the Water Research Laboratory at the University of New South Wales. The research is currently lead by Professor Ian Turner who described to the ABC the extent of the erosion seen.

"At Collaroy, Narrabeen, we've seen the beach come back by about 40 metres in two days."

"We are a uniquely coastal nation, 85 per cent (of the population) on the coast, yet there is only this one location in Sydney where we have a long-term record of how that beach has changed over time," he said.

"We need to establish a national coastline observatory, with similar sites along the whole coastline."

He said that sort of monitoring would help contain future damage.

"I think we are more cognisant, we don't build homes so close to the beach, but we have a lot of infrastructure, not just homes, cable lines, gas lines, sewers, very exposed along the coastline and we need to come up with solutions."

This is how we will experience accelerating sea level rise. With storm surge events such as this East Coast low, beach erosion will continue to redraw our coastline and the buildings and road infrastructure on the edge. Allowing buildings on coastal sand dunes is problematic. Sand dunes are a longterm repository of beach sand that can be used to replenish beaches during storms. They are part of our natural coastal defence systems which we ignore when we build upon them.

Rock retaining walls may provide a solution, but ultimately these will be temporary solutions with conservative estimates of sea level rise of up to 1 metre by the end of the century, and some studies suggesting sea level rise may be 2 metres or more and accelerating.

Climate Council: more moisture and higher sea levels in a climate changed world

Professor Lesley Hughes said at the Climate Council website that coastal flooding events had tripled in Sydney in the 20th century, and on present levels of climate change, today’s 1-in-100 year flood will occur every day or so by 2100.

“These storm surges are now riding in on a sea level that is much higher than it was before climate change really started to take hold,” she said.

“These east coast lows, while they’ve also been around for some time and often deliver intense rainfall, are occurring in an atmosphere that has about 7% more water vapour than it did fifty years ago. This increases the risk of more intense rainfall.

“More intense rainfall and higher sea levels have combined are making these kinds of storms more damaging. Australia is seeing the impacts of climate change right now, which only underpins how critical it is to phase out coal and move to renewable sources of energy.

In a nutshell, climate change is producing intense rainfall and higher sea levels which combined make these kinds of storms more damaging.

Climate Council CEO Amanda McKenzie highlighted why cuts to the CSIRO would damage Australia’s ability to understand, respond to and plan for a changing climate.

“Flights this week have been thrown into chaos by the flooding at Sydney Airport,” she said. Yet the disruption is insignificant when you look at the flooding projected in the future for Sydney airport in business as usual or rapid emission cuts scenarios.

Image: Climate Central sea level rise floodmap of Sydney Airport comparing business as usual scenario with emissions reduction scenario.

“We now live in a new and changing climate. Research is critical to ensure that we can prepare for the future, particularly our emergency and health services who are first responders to these types of events. If we don’t tackle climate change then more than $226 billion in commercial, industrial, road, rail and residential assets in Australia are at risk from rising sea levels," said McKenzie.

“Governments and business rely on climate science to make billion-dollar decisions. Without it, they will be relying on guesswork. Climate modelling is the backbone of our ability to understand changes to the climate system. The information that is vital to coping with climate change and building preparedness for our worsening extreme weather events. Cutting further model development will leave us dangerously exposed to the escalating risks of climate change.”

The CSIRO management under the Current government is intent in cutting many of its climate research programs, including climate modelling, which is likely to have a detrimental impact on long term planning decision making.

Increased Intensity of rainfall with climate change

The increased intensity of rainfall is confirmed by a number of scientific studies. Heavy rainfall events are setting ever new records have been increasing, especially in the past thirty years. Scientists of the Potsdam Institute for Climate Impact Research detected a clear upward trend in the past few decades towards more unprecedented daily rainfall events.

“One out of ten record-breaking rainfall events observed globally in the past thirty years can only be explained if the long-term warming is taken into account,” says co-author Dim Coumou. “For the last year studied, 2010, it is even one event out of four, as the trend is upward”.

“The pronounced recent increase in record-breaking rainfall events is of course worrying,” Coumou concludes. “Yet since it is consistent with human-caused global warming, it can also be curbed if greenhouse gas emissions from fossil fuels are substantially reduced.”

The study - Increased record-breaking precipitation events under global warming (abstract) - by Jascha Lehmann, Dim Coumou, Katja Frieler, was published in Climatic Change in July 2015. The abstract states in full:

    In the last decade record-breaking rainfall events have occurred in many places around the world causing severe impacts to human society and the environment including agricultural losses and floodings. There is now medium confidence that human-induced greenhouse gases have contributed to changes in heavy precipitation events at the global scale. Here, we present the first analysis of record-breaking daily rainfall events using observational data. We show that over the last three decades the number of record-breaking events has significantly increased in the global mean. Globally, this increase has led to 12 % more record-breaking rainfall events over 1981–2010 compared to those expected in stationary time series. The number of record-breaking rainfall events peaked in 2010 with an estimated 26 % chance that a new rainfall record is due to long-term climate change. This increase in record-breaking rainfall is explained by a statistical model which accounts for the warming of air and associated increasing water holding capacity only. Our results suggest that whilst the number of rainfall record-breaking events can be related to natural multi-decadal variability over the period from 1901 to 1980, observed record-breaking rainfall events significantly increased afterwards consistent with rising temperatures.

This graph shows the increasing global trend for extreme rainfall events:

An earlier study in 2013 by Seth Westra, Lisa V. Alexander, and Francis W. Zwiers highlighted Global Increasing Trends in Annual Maximum Daily Precipitation.

"When we looked at the association between the intensity of rainfall extremes and a record of global mean near-surface atmospheric temperature, rainfall intensity was found to increase at a rate of between 5.9% and 7.7% for each degree, depending on the method of analysis." explained Seth Westra at The Conversation.

Acacia Pepler, a PhD student at UNSW Australia explains the role of climate change in eastern Australia’s wild storms. Once again, Pepler identifies the major climate link are record warm sea surface temperatures and atmosphere increasing moisture carrying capacity for more intense rainfall, and higher sea levels for the storm surge to flood coastal areas and cause erosion.

Law lecturer Justine Bell-James identifies that Our institutions are ill-prepared for a potential increase in the frequency and severity of such storm events.

"Even if emissions are immediately reduced, a global sea-level rise of 0.28-0.60m by 2100 is still possible. This will be especially problematic in Australia, with an estimated 711,000 residential addresses located within 3km of the shore and less than 6m above sea level – not to mention the billions of dollars' worth of government infrastructure also located in these regions." said Bell-James at the Conversation.

He identifies that "the pictures from Collaroy should prompt a discussion about how we, as a society, can deal with the potential impacts of coastal hazards on existing developments", particularly in regards to insurance and disaster assistance.

And we must also be mindful in our urban areas how Massive storms are pumping pollution into our oceans: time to clean up our cities through water sensitive urban design. Putting in rain tanks, rainwater traps and gardens, and incorporating wetlands in development can reduce flooding and help filter our urban detritus from reaching and polluting the ocean.


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