Last week was something of a trial: bits of my little farm were being washed out to sea, tracks were eroding, and our road was closed by slips and rockfalls. Just another in a sequence of extreme weather events that have got the locals in North Canterbury wondering about the weird weather being inflicted on them. In my Daily Blog post this week — You Ain’t Seen Nothing Yet — I note that worse is on the way, and there’s little we can do beyond battening down the hatches.
Posts Tagged floods
After the usual run of late nights and argument, the IPCC has released the second part of its fifth report — the Working Group 2 report on climate impacts and risks management. Commenting on the report, VUW climate scientist Professor Tim Naish said “this latest report makes it quite clear that New Zealand is under-prepared and faces a significant ‘adaptation deficit’ in the context of the projected impacts and risks from global average warming of +2 to 4°C by the end of the century.”
The IPCC identifies eight key regional risks for New Zealand and Australia:
- significant impacts on coral reefs in Australia as oceans warm and acidify
- loss of montane ecosystems in Australia, as climate warms and snow lines rise
- increased frequency of and intensity of flooding in NZ and Australia
- water resources in Southern Australia will be under increased pressure
- more intense heatwaves will bring increased death rates and infrastructure damage
- increasing risks of damaging wildfires in New Zealand and southern Australia
- increased risks to coastal infrastructure and ecosystems from sea level rise
- risk of severe drying in parts of Australia could hit agricultural production
For New Zealand, extreme weather events such as flooding and heatwaves are expected to increase in frequency and severity, and rainfall is expected to increase on the already wet west coast and decrease in the east and north east. Sea level rise of up to one metre is expected to cause significant problems for coastal communities.
VUW’s Jim Renwick points to sea level rise as a big issue:
Every 10cm of rise triples the risk of a given inundation event, and we are expecting something like a metre of rise this century. That would mean today’s 1-in-100 year event occurs at least annually at many New Zealand coastal locations. New Zealand has a great deal of valuable property and infrastructure close to the coast that will be increasingly at risk as time goes on.
The Summary for Policymakers of the WG2 report is available here (pdf), and the final draft of the full report can be downloaded from this page. The Australia and New Zealand chapter (25) is here (pdf) and the Small Islands (Ch 29) here (pdf).
A huge amount of coverage of the report’s findings has already hit the net, and there will be more to come. Check out The Guardian‘s take on the five key points in the report, The Conversation’s examination of climate health risks, Graham Readfearn’s commentary on 25 years of IPCC warnings, and Peter Griffin’s look at the prospects for agriculture. I’ll have a post about the NZ political response to the report tomorrow.
That’s a climate model running on my iMac, thanks to BOINC, Climateprediction.net, and the new New Zealand and Australia modelling experiment launched yesterday. In this guest post, Dr Suzanne Rosier of NIWA explains what it’s all about…
A new citizen science experiment in which scientists will address possible links between climate change and extreme weather in Australia and New Zealand was launched on Wednesday. ANZ runs as part of the highly successful climateprediction.net project based at the University of Oxford, which makes state-of-the-art climate models available for anyone with a PC and an Internet connection to download and run on their computer. The global model contains within it a much more detailed model of the Australia/New Zealand region, detailed enough to model weather events properly, and the ‘2-in-1’ model needs to be run many thousands of times if scientists are to have a chance of capturing the very rarest weather events. This takes a huge amount of computing power – and you can help by volunteering your computer.
The model runs in the background on your machine, taking up any processing power that happens to be spare, but not interfering with your work. When your computer has finished crunching the results are automatically uploaded to a server at the University of Tasmania. If you take part in the project you also have the option to see how the model you are running on your machine is progressing. Many thousands of generous volunteers have already taken part in climateprediction.net, running global models, and , running regional models for other parts of the world. This is your chance to get involved and help scientists to gain a better understanding of what is happening to weather in Australia and New Zealand region as the climate changes.
The experiment launched today will produce many thousands of different simulations of how the weather in 2013 might have been, both with and without anthropogenic greenhouse gas emissions. This will enable scientists to put some hard numbers on how the risks of extreme weather events might — or might not — be changing as a result of the human contribution to global climate change. Scientists at NIWA will focus initially on the severe North Island drought of January to March 2013, but later the record-breaking warmth of last year’s winter will also come under scrutiny. Extreme rainfall events, such as that in Golden Bay and Nelson in December 2011 and the recent floods in Christchurch, will also be investigated as the ANZ experiment continues.
The more people who participate, the more science can be done. Please go to ‘weatherathome.net’ – sign up, and start crunching numbers.
Gareth adds: Suzanne does an excellent job of introducing the project in this video:
Read more about the project at Climateprediction.net, The Conversation, and NIWA. If anyone’s interested in running an NZ climate team, let me know. For some background to the difficult statistics of extreme weather events, I highly recommend this recent article by Stefan Rahmstorf at RealClimate. The ANZ models will run (via BOINC, the framework for distributed processing developed at Berkeley and used in a wide variety of distributed computing projects such as or ) on most recent releases of Windows, Mac OSX and Linux.
In this week’s post at The Daily Blog — Up a blind alley (without a paddle) — I ruminate further on the message to be gleaned from last week’s flooding in Christchurch, and how ignoring the shape of things to come makes for bad government and worse politics:
What happened in Christchurch was not a consequence of climate change (though the heavy rainfall is something expected to increase in a warming world), but an early warning of what will happen to coastal cities as sea level rise takes its toll over coming decades. With CO2 nudging 400 ppm, the planet can expect the sea to eventually stop rising when it is 15-20 metres higher than today. It might take a few hundred years to get there, but if we don’t act to reduce atmospheric carbon it’s not just a distant threat, it’s a long term certainty.
With another storm bearing down on the country from the tropics and severe weather on the cards for much of the country over the weekend, the government may well have to confront another flood emergency. We can only hope they learn something more than how to deploy the prime ministerial mop.
Lost in the flood Mar 09Join the conversation at Hot Topic
This morning’s NASA Earth Observatory image of the day shows the impact of last week’s heavy rain in Christchurch and Banks Peninsula on the sea around. The light blue colours show sediment washed off the land. If you visit the EO page, they provide a helpful reference image: the region snapped from space in late February, when there’s no sign of any sediment at all.
The heavy rain brought flooding to many parts of Christchurch, as NASA notes:
Christchurch’s flood control infrastructure has been under increasing pressure in recent years because a series of earthquakes struck the area in 2010 and 2011. According to University of Canterbury researchers, the quakes caused land in some areas to drop, while narrowing and uplifting certain river channels. The result is an increased risk of flooding.
This rainfall map from NIWA shows rainfall over the last 15 days (right) compared with the average for the same period (left) and the anomaly (centre). The rain event is immediately obvious as the blue thumb sticking out of the South Island east coast:
The Weather Underground’s Christopher Burt provides numbers for the storm:
The powerful storm pounded the Christchurch area between March 3-5 with wind gusts up to 119 km/h (74 mph) and rainfall of 151.6 mm (5.97”) as officially measured at Christchurch’s weather station. Of this amount 100 mm (3.94”) fell in just a single 24-hour period on March 4-5. The suburb of Lyttelton received 160 mm (6.30”) in 24 hours and other suburbs reported storm totals of 170 mm (6.70”). The normal monthly rainfall for Christchurch in March is just 45 mm (1.77”).
The severe flooding in parts of Christchurch – notably the “Flockton Basin” – was caused or made worse by a number of factors. The earthquake sequence caused ground levels to fall by up to half a metre in parts of the eastern suburbs and along the Avon River (see map here), raised and narrowed river and stream beds and damaged or destroyed storm water infrastructure. Add to that a heavy rainfall event that would have taxed the drainage system in pre-quake times, not to mention the tail end of a sequence of high spring tides causing water to back up in the estuary, and you have all the makings of a historic flood event.
Local and national politicians have rushed to promise action to address the flooding, but Christchurch’s problems will not be solved by a crash programme to defend homes that now flood every time there’s a rainstorm. Continuing sea level rise and increasing rainfall intensities — both already observed and projected to get much worse — suggest that serious consideration should be given to managed retreat in some areas, rather than rebuild and defend. How high should you make a stop bank when you expect sea level in a hundred years time to be a metre higher than now?
Christchurch is facing the sort of problems that all coastal cities are going to have to confront over coming decades, brought forward by the earthquake sequence that caused so much death and destruction. Unfortunately for the citizens of the city, the earthquake recovery programme is being overseen by Gerry Brownlee, a cabinet minister who is on the record as a climate sceptic. If he fails to consider the big picture, and neglects to plan for a future when the waters have risen far above today’s levels, then Christchurch will be even deeper trouble every time it rains old women and sticks1.
[Brooce, at his best.]
- Mae hi’n bwrw hen wragedd a ffyn – It’s raining old ladies and sticks: Welsh idiom.
The first major study to look at the impact of sea level rise on Christchurch and Banks Peninsula following the 2010/11 earthquake sequence projects a watery future for many parts of the city and its surrounding shorelines. The image above1 shows changes in ground elevation between 2003 and 2011 in the Christchurch region. Areas in green/blue have moved upwards by half a metre – particularly noticeable to the west of the estuary – and areas in red and yellow down, in many places along the Avon and subsidiary streams by a metre or more.
The report, Effects of Sea Level Rise on Christchurch City (pdf), by consultants Tonkin & Taylor was released last week and suggests that as a minimum planners should take into account a 1m rise in sea level over the next 100 years. Combined with the elevations changes caused by the earthquakes, this would mean significant shoreline retreats, increased flooding in many areas and the loss of hundreds of hectares of land to the sea. It’s well worth digging into the report to get the full picture, and it will make uncomfortable reading for many in the city.
Tonkin & Taylor prepared their study before the IPCC’s AR5 Working Group One report was released, and so based their SLR numbers on a literature search and the Royal Society of NZ’s 2010 paper. They suggest a “plausible upper range” of 2m over the next 100 years, with the behaviour of the West Antarctic and Greenland ice sheets in a warming world “probably the largest uncertainty in sea level rise projections”.
And now the bad news…
The Pine Island Glacier (PIG) in West Antarctica — responsible for 25% of the ice loss from the region — is now probably beyond the point of no return, committed to melt back well inland from its current position even if the local climate cools strongly. In a new study published in Nature Climate Change this week2 an international team of scientists used detailed models of the glacier and its bed, combined with field observations, to track how the ice would behave. It suggests that the PIG could contribute as much as 10mm to sea level over the next 20 years, with the potential for much more in the longer term, as one of the authors, Dr Hilmar Gudmundsson of the British Antarctic Survey points out:
“Pine Island Glacier shows the biggest changes in this area at the moment, but if it is unstable it may have implications for the entire West Antarctic Ice Sheet. Currently we see around three millimeters of sea level rise a year, and the Pine Island Glacier retreat could contribute an additional 3.5 – 10 millimeters in the next twenty years, so it would lead to a considerable increase from this area alone. But the potential is much larger. At the Pine Island Glacier we have seen that not only is more ice flowing from the glacier into the ocean, but it’s also flowing faster across the grounding line — the boundary between the grounded ice and the floating ice. We also can see this boundary is migrating further inland.”
If the PIG is already doomed to major retreat over the next century, then stability of the whole West Antarctic Ice Sheet could be threatened. Paleoclimate studies have shown that the WAIS collapsed repeatedly in earlier warm periods, though it is thought to have taken 500 – 1,000 years to melt. During the last interglacial 125,000 years ago, sea level peaked at about 6m above present with significant melt contributions likely from the WAIS and Greenland. That was with CO2 at 300ppm. We’re now nudging 400ppm.
Ice sheet behaviour in a rapidly warming world is not something we understand well, and that means that any sensible analysis of the risks of sea level rise has to consider worst cases in both the near and long term. We can get a good idea of the long term sea level rise — where the sea level will stop rising when the climate comes into equilibrium with the ice sheets — by looking at climate history. 400ppm CO2 probably means an eventual 20m of sea level rise.
In the short term — over the next few decades — unless something truly astounding happens to the WAIS or Greenland, the impacts of sea level rise are likely to be modest and manageable — at least if affected communities take the problem seriously. But when planning infrastructure that has a longer lifespan — like rebuilding a city — then the multi-metre rises we are likely to see over the next hundred years become a critical consideration. As yet there’s little sign — Tonkin & Taylor’s thorough report included — that anyone is thinking in those terms.
- Fig 3-4, p15 in the report.
- The retreat of Pine Island Glacier controlled by marine ice-sheet instability by L Favier, G Durand, S L Cornford, G.H. Gudmundsson, O. Gagliardini, F. Gillet-Chaulet, T. Zwinger, A. J. Payne and A.M. le Brocq, Nature Climate Change, doi:10.1038/nclimate2094
Two major new government reports on New Zealand’s emissions projections and the expected impacts of four degrees of warming on NZ agriculture were released without fanfare last Friday — the timing clearly designed to minimise media fallout from reports that highlight the paucity and ineffectiveness of current climate policy settings.
Climate change minister Tim Groser dutifully issued a press release welcoming the release of New Zealand’s Sixth National Communication under the United Nations Framework Convention on Climate Change and Kyoto Protocol, the first such report since 2009. Groser praised government policies, but failed to draw attention to the fact that his own report shows NZ emissions failing to meet the government’s targeted cuts, or that current policy settings will do little to reduce them — let alone achieve reductions by comparison with 1990 levels. This graph1 of actual and projected net emissions out to 2030 tells the story of the Key government’s abject policy failure:
The blue line is actual emissions up to 2008, “with measures” — that is, as affected by policies to reduce emissions. The red line is emissions projected out to 2030 assuming no action to reduce emissions, the green line the emissions that will result after current policy settings are taken into account. Both green and red lines rise substantially up to 2030, and end up at the virtually the same point2 — more than double NZ’s net emissions in 1990.
In other words, Tim Groser and his cabinet colleagues have created a suite of policies designed to increase New Zealand’s emissions at a time when they are supposed to be being reduced, and which will miserably fail to meet the government’s own target of a 5% reduction in emissions (using the 1990 baseline) by 2020.
The second report released last week is much the more interesting of the two, and makes grim reading for anyone trying to play down the seriousness of the likely changes that confront NZ and its farmers and growers. Four Degrees of Global Warming: Effects on the New Zealand Primary Sector (full report and summary available here) was placed on the Ministry of Primary Industries web site last Friday, but was spotted by TV3 News today.
The report is the first study to consider the likely impacts of warming at the upper end of global expectations, and projects climate impacts across the country and on pasture and forest productivity based on two different climate model projections. The pattern of changes is much as described in previous studies — warming spreading down from the north, wetter in the west and drier in the east, greater rainfall intensities, bigger floods and longer droughts — but with much sharper increases in these parameters.
Under the four degrees of warming scenario:
- frosts are expected to disappear from all but the highest parts of the North Island and much of the coastal South Island
- the amount of rain falling in extreme events is expected to increase by 32%
- river flows will experience seasonal changes as snowfall declines
- periods of maximum irrigation demand are likely to coincide with extended periods of low flows in major catchments
- a massive increase in the growing degree days experienced in all regions, with Canterbury almost as warm as Northland
- fruit crops requiring winter chilling (apricots, kiwi) will have to move south
- wine growing regions will move and different grape varietals will be required
- significant increase in heat stress on dairy cattle
The report finds that the most positive impact will be on forestry, where a combination of warming and CO2 fertilisation is expected to increase yields in both Pinus radiata and eucalyptus plantations.
This is more than a little ironic, given that the Emissions Trading Scheme policy settings and low carbon price have reduced the attractiveness of forestry planting as a carbon sink. The one thing that might do well in a warmer NZ is the one thing the government seems unable to incentivise with a handout. Perhaps James Cameron could make a film about it?
- From p126 of the report
- 88 Gg CO2e without measures, 84 Gg with.
It’s been almost half a year since Glenn, Gareth and John last met over the intertubes to discuss climate news — but we’re 97% sure we’re back, catching up on all the recent climate news. John discusses the recent Cook et al (where al is the Skeptical Science team) paper on the 97% consensus on climate science and the accompanying Consensus Project web site, “sticky” facts like using Hiroshima bombs as a unit of warming. Plus all the news on recent weather extremes — flooding in India, Canada, and Europe, climate impacts on the wine business, and Gareth’s recent interview with Bill McKibben. Show notes below the fold…
The Consensus Project
Peer-reviewed paper: http://iopscience.iop.org/1748-9326/8/2/024024
Graphics available at: http://sks.to/consensuspics
I took Rosie the truffle machine for a walk around the farm just before dark yesterday. We were both a bit stir-crazy after four days of cold, cold rain and a couple of days of screaming southerlies that brought snow to our hills. The ground passed field capacity at the beginning of last week, when an atmospheric river brought torrential downpours and flooding to much of the South Island. Now the soil is sodden, quivering with water and oozing mud at every footstep. Every drop of extra rain is taking that mud and sluicing it down to the river. A stream runs through my black truffle plantation. I spent this afternoon digging a drainage trench. Truffles don’t enjoy sitting in water. My crop might rot. The Waipara is roaring along at the bottom of our cliff at about 50 cumecs1, an impressive sight for a river that normally dribbles down to the sea at under a cumec. It peaked last week at about 110 cumecs. The riverbed will have been reshaped. But we got off lightly.
Over the last couple of days the New Zealand news has been dominated by extreme weather. The southerly storm that soaked us also battered Wellington and brought deep snow2 to much of the South Island. It made for compelling pictures. But what’s going on elsewhere in the world is even more dramatic:
The early arrival of particularly intense monsoon rain has brought flooding and chaos to northern India. At the time of writing, it is estimated that 600 people have died and 40,000 are stranded by rivers and landslides [BBC, NASA Earth Observatory, Jeff Masters.]. In The Times of India, government earth sciences secretary Shailesh Nayak was reported as saying that climate change played a role in the flooding:
The catastrophic rainfall in Uttarakhand was most likely a climate change event as it is in keeping with a pattern of increasing incidents of extreme weather events that often cause phenomenal damage as was seen in the hill state…
In Alberta, Calgary — Canada’s fourth largest city — has been flooded by torrential rains in the catchments of the Elbow and Bow rivers. Three people have died and 100,000 have been displaced. [Christopher Burt at Weather Underground, Calgary Herald, National Post, podcast: interview with Robert Sandford, ]
Meanwhile, Alaska has been experiencing a heatwave of record proportions as a slow moving giant loop in the jet stream has allowed a dome of high pressure to linger over the state.
New Zealand’s recent extreme weather was also down to a large excursion the in the southern hemisphere jet stream, as Jim Renwick told the Science Media Centre:
To get an event like this, which is pretty extreme, we need the westerly wind that normally blow across New Zealand and the southern oceans to slow down and to buckle into a series of big meanders, north-south waves around the hemisphere. […] Right now we have a series of large-scale waves around the southern hemisphere, with big southerlies near New Zealand, over the central Pacific, off the eastern South American coast, over the eastern South Atlantic, and over the central Indian Ocean. The southerly flow over/near New Zealand is the most impressive, as it reaches all the way south to south of 60S […] which is almost down to the edge of the sea ice at this time of year.
So where’s the climate change in all this? In India, Canada, Alaska and Europe we have extreme weather events happening more or less simultaneously, with a common factor — jet stream meanders — playing a significant role. Those meanders are most likely a symptom of a reduced equator to Arctic temperature differential, as Jennifer Francis and Stu Ostro explain in this recent Climate Desk event. We also have to consider the fact that the climate system is now operating at higher energy levels than before — a warmer atmosphere can carry more water vapour, and water vapour is the fuel for weather systems. More water vapour, more rain — and more intense rainfall.
Weather extremes are where the climate change rubber hits the road3. We might think that our future is described by the smoothly rising curves we see in multi-model means of global temperature projections over the next 100 years, but we don’t live in a multi-model world. We only have the one climate system, and we all live in regions, not in a notional global average.
We have to live through the noise — the bumps, the lumps, and the jumps that go with energy accumulating in the planet’s climate system. There will be more floods, more lives lost to climate instability. It’s happening now, and it’s going to get worse.
In my column at The Daily Blog today, I ruminate on the links between the historic and damaging floods in central Europe and the rapid warming of the Arctic. What will it take to make the world’s leaders wake up to the rapid changes that are happening now? Comments at TDB, please…