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Posts Tagged extremes

Friday melts, weird weather and whales (it’s been a long time…) Gareth Renowden Aug 22

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It’s been a long time since my last post: apologies for that. You may blame a bad cold, an urgent need for root canal work, the peak of the truffle season (and truffle tours for culinary heroes1 ), the start of pruning and political distractions for the drop off in activity here. Normal service should resume in the near future, but meanwhile here are a few of the things that have caught my eye over the last week or two. You may therefore consider this an open thread – and given what follows, somewhat more open than usual…

The political distraction, of course, has been the response to Nicky Hager’s book, Dirty Politics. I haven’t yet read the book — it’s queued up on the iPad — but as everyone now knows, it concerns the sordid activities of right-wing attack blogger Cameron Slater, and in particular his close ties with senior government politicians. Slater has a long record of climate denial — often lifting material from µWatts or the Daily Mail to support his ignorant bluster — but the revelation that he published paid material for PR companies masquerading as his own opinion begs a question: was there a similar motivation for his climate denial posts?

As far as I can tell, Hager’s book only mentions climate once, in a discussion of Slater’s pet hates, but it will be interesting to see if the “raw data” now being drip fed into the public domain by the hacker2 who obtained Slater’s emails and Facebook chat messages contains any hints of another motivation — if it indeed it does go beyond the knee-jerk denial so common on the far right of NZ politics. For the record, I should note that Slater once used the words “twat” and “fraud” in close conjunction with my name. It would appear that both are likely to apply rather more aptly to him.

The real world, of course, obeys the laws of physics rather than the wishful thinking of political smear merchants, and out here the signs of continued warming are unmistakable. Europe’s Cryosat has detected a big increase in ice sheet melt at both poles, for example:

A new assessment from Europe’s CryoSat spacecraft shows Greenland to be losing about 375 cu km of ice each year.

Added to the discharges coming from Antarctica, it means Earth’s two big ice sheets are now dumping roughly 500 cu km of ice in the oceans annually.

“The contribution of both ice sheets together to sea level rise has doubled since 2009,” said Angelika Humbert from Germany’s Alfred Wegener Institute.

The atmosphere is also responding to energy accumulation by delivering an astonishing sequence of heavy rainfall events and flash floods. The BBC reports that 160 people have died in floods in Nepal and northern India, while in Hiroshima 36 people have died in landslides triggered by rain falling at rates of 100mm per hour (Japan Times). In Sweden, heavy rain is causing “catastrophic” flooding, while last month northern Italy bore the brunt of torrential downpours. Flash floods also hit parts of Arizona earlier this week. Nor should we forget the heavy rains that brought damaging floods to Northland in July. For a roundup of July’s weather, check out Chris Burt’s blog at Weather Underground.

Some of these rainfall extremes may be explained by the poleward expansion of the tropics, bringing warmer wetter air into the mid latitudes, as this new paper explains. Some of that tropical air may have been tickling Britain, which apart from experiencing some flash flooding has also just recorded its warmest January to July period since records began. And as a WMO conference found this week: “rising temperatures will have a “multiplying effect on weather events as we know them”.

Finally, and in brief: Earth Overshoot Day shot past this week – earlier than ever; warming may be hiding in the Atlantic; Choiseul in the Solomon Islands becomes the first town to relocate because of sea level rise; and The Wireless is running lots of good climate material this week.

  1. See also: why.
  2. @whaledump on Twitter, see here for why whale dumps are important for climate.

TDB Today: You ain’t seen nothing yet Gareth Renowden Jun 18

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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.

[Smashie & Nicey]

IPCC WG2 impacts report released: fire, floods and rising seas in all our futures Gareth Renowden Mar 31

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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.

Climate modelling on your PC: weather@home comes to NZ and Australia Gareth Renowden Mar 27

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Climateprediction

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.

WMO 2013 climate summary: laws of physics not negotiable, extremes to be expected on a warming planet Gareth Renowden Mar 25

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The World Meteorological Organisation’s (WMO) state of the climate report for 2013 was released on Sunday (pdf), and provides a very useful overview of last year’s weather and climate events. It confirms that 2013 was the 6th warmest year in the long term record (tied with 2007), that 13 of the 14 warmest years in that record have occurred this century1, and that the litany of extreme weather events that struck the planet is in line with what would be expected on a warming planet.

WMO Secretary-General Michel Jarraud said:

There is no standstill in global warming. The warming of our oceans has accelerated, and at lower depths. More than 90 percent of the excess energy trapped by greenhouse gases is stored in the oceans. Levels of these greenhouse gases are at record levels, meaning that our atmosphere and oceans will continue to warm for centuries to come. The laws of physics are non-negotiable.

On extremes, Jarraud was equally direct:

…many of the extreme events of 2013 were consistent with what we would expect as a result of human-induced climate change. We saw heavier precipitation, more intense heat, and more damage from storm surges and coastal flooding as a result of sea level rise – as Typhoon Haiyan so tragically demonstrated in the Philippines.

Here’s the full list of the WMO’s key climate events of 2013:

  • Typhoon Haiyan (Yolanda), one of the strongest storms to ever make landfall, devastated parts of the central Philippines.
  • Surface air temperatures over land in the Southern Hemisphere were very warm, with widespread heat waves; Australia saw record warmth for the year, and Argentina its second warmest year and New Zealand its third warmest.
  • Frigid polar air plummeted into parts of Europe and the southeast United States.
  • Angola, Botswana and Namibia were gripped by severe drought.
  • Heavy monsoon rains led to severe floods on the India-Nepal border.
  • Heavy rains and floods impacted northeast China and the eastern Russian Federation.
  • Heavy rains and floods affected Sudan and Somalia.
  • Major drought affected southern China.
  • Northeastern Brazil experienced its worst drought in the past 50 years.
  • The widest tornado ever observed struck El Reno, Oklahoma in the United States.
  • Extreme precipitation led to severe floods in Europe’s Alpine region and in Austria, Czech Republic, Germany, Poland, and Switzerland.
  • Israel, Jordan, and Syria were struck by unprecedented snowfall.
  • Greenhouse gas concentrations in the atmosphere reached record highs.
  • The global oceans reached new record high sea levels.
  • The Antarctic sea ice extent reached a record daily maximum.

The WMO has published a very nifty interactive map of the year’s notable events here (requires Flash). Clicking on individual events brings up a pop-up with details of what happened. Well worth exploring.

Meanwhile, the prospects for 2014 and 2015 are becoming more “interesting” with each passing week. The chances of the tropical Pacific slipping into El Niño mode are increasing according the Bureau of Meteorology in Australia and NOAA in the US. El Niño years are generally associated with a spike in global temperature and increased extreme weather events.

See also: The Conversation, The Guardian, Climate Progress.

  1. The 15 warmest years have all happened since 1998.

NZ government climate policy: look, a squirrel! Gareth Renowden Dec 16

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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?

  1. From p126 of the report
  2. 88 Gg CO2e without measures, 84 Gg with.

Poland or Coaland? Climate talks about to begin in Warsaw cindy Nov 10

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Will the sun rise over progress at the climate talks (is that a coal fired power station in the distance?)
Will the sun rise over progress at the climate talks (is that a coal fired power station in the distance?)

Another year, another round of climate talks.  It’s the 19th Conference of Parties to the UN Climate Convention and we’re back in Poland, the scene of an almost complete non-event in 2008, the year before Copenhagen.

It’s Eastern Europe’s turn to host another meeting, and nobody else was prepared to put their hand up, so we’re back in the land of coal, in the country that has rallied their biggest coal companies to sponsor the conference, and which is dragging the whole of the EU down to their level as they refuse to accept stronger targets.  I suspect #coaland will be a well-used hashtag by the end of this.

Usually when you come to a meeting like this, the town is full of banners and signs that a climate meeting is being hosted, but there’s not much sign of it here in Warsaw, except this rather confusing industry advertisement at the airport.

Next weekend there’s a World Coal Association conference in town, being addressed by UNFCCC Executive Secretary Christian Figueres, who turned down a talk to youth at the Powershift conference in favour of talking with Big Coal.  She’s assured them it’s because she wants to “talk frankly” – let’s hope she does.

Last month the Polish hosts were caught posting a news piece heralding the melting of the Arctic as a new opportunity to explore for yet more fossil fuels.  While The YesMen (in a specacular own-goal, in my opinion) tried to claim the piece as their own, it was indeed the Polish Government’s own work. Given this government is chairing the talks, it’s not looking terribly hopeful.

Meanwhile in the Philippines, Cyclone Haiyan, the strongest tropical cyclone ever recorded, has caused a terrible loss of life that’s still being counted – and major damage.  With winds at 195mph as it made landfall, it beat the 1969 record,  according to Jeff Masters’ blog.  Sea surface temperatures were up to 1.5degC above normal.

What role will the science have in these talks?  Will the IPCC’s recent working group 1 conclusions make a difference?  Figueres has already confirmed the IPCC’s carbon budget figures will not be on the agenda.

Finance for the poorest

This meeting is supposed to be the “Finance meeting” where governments are expected to make progress on committing money to the Green Climate Fund. They’ve promised $100bn a year by 2020 to help the world’s poorest countries adapt to climate change and shift to renewable energy, but so far there’s little to show for it in the fund.

And a programme to get to 2015

Governments agreed last year that this year would be when they set up the roadmap to get to a global agreement on climate to be agreed in Paris, 2015.  This should include a timetable for when they all put their increased targets on the table (early next year would be good) and that they will have a full draft negotiating text sorted out by next year, to be finalised by 2015.   But of course that 2015 agreement, even if it does get finished on time, wouldn’t come into force until 2020.  If the world does nothing except the Copenhagen pledges between now and 2020, it’s not going to be pretty. So there’s a strong call from many quarters for better 2020 targets to be put on the table as soon as possible.

How will New Zealand stack up?  During the course of the next two weeks, expect information to come out that will make it clear what New Zealand’s “fair share” of climate action actually is.  Given our walking away from Kyoto and the Ministry for the Environment’s recent admission that our emissions are set to soar, I don’t hold out much hope.

The Australians have made a spectacular start, announcing that for the first time in 16 years, no Minister will make it to the conference. Environment Minister Greg Hunt, recently famous for declaring there was no evidence of a link between climate change and bush fires (using the solid source of Wikipedia) is instead staying at home to dismantle the Australian climate legislation.  That’s a Fossil of the Day right there.

Then of course there’s the Russians.  What will they do?  Will they continue to throw their toys out of the cot about decisions being made in Doha without their agreement?  Will they actually start negotiating and be good global citizens?  (hint: releasing the 30 Greenpeace activists from the Murmansk prison would be a good start).

More to come, as it happens.   From both myself and from David Tong with the Adopt A Negotiator team.

The Climate Show #35: elections, extremes and a big wind Gareth Renowden Sep 19

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We’re running a bit late with this one: recorded last week before the big wind left Gareth powerless for six days (a bit like Glenn’s PC), John Cook ruminates on the result of the Australian election, the boys marvel at the Mail’s myth making about Arctic sea ice, and look forward to the release of the first part of the next IPCC report. And much, much more. Show notes below the fold…

Watch The Climate Show on our Youtube channel, subscribe to the podcast via iTunes, listen to us via Stitcher on your smartphone or listen direct/download from the link below the fold.

Follow The Climate Show on Facebook and Twitter.

The Climate Show

Show notes

News

Australian election, and prospects for climate policy:

Australia’s new government is likely to repeal the carbon price, by striking a deal with crossbenchers in the Senate after July 2014, or possibly going to a special election if it looks electorally attractive. Still, carbon pricing remains the logical choice for Australia’s longer term climate policy.

http://theconversation.com/what-next-for-australias-climate-policy-17991

In the run up to AR5, British right wing media up the ante by claiming that Arctic sea ice in “recovery” and cooling’s on the way:

Mail: http://www.dailymail.co.uk/news/article-2415191/Global-cooling-Arctic-ice-caps-grows-60-global-warming-predictions.html

Express: http://www.express.co.uk/news/world/427980/Global-warming-No-the-planet-is-getting-cooler

Telegraph: http://www.telegraph.co.uk/earth/environment/climatechange/10294082/Global-warming-No-actually-were-cooling-claim-scientists.html

MSN: http://now.msn.com/global-warming-may-be-pausing-for-a-period-of-global-cooling

But the truth is:

http://www.theguardian.com/environment/climate-consensus-97-per-cent/2013/sep/09/climate-change-arctic-sea-ice-delusions

AR5 WG1 summary for policymakers due at end of month:

The Twelfth Session of Working Group I (WGI-12) will take place from 23 to 26 September 2013 in Stockholm, Sweden. This Session of WGI is being convened to approve the Summary for Policymakers (SPM) of the Working Group I contribution to the IPCC Fifth Assessment Report (WGI AR5) and accept the underlying scientific and technical assessment.

The WGI AR5 Summary for Policymakers will be available on 27 September 2013.

AR5 web site: http://www.climatechange2013.org

NOAA/BAMS State of the Climate 2012:

2012 was one of the 10 warmest years on record globally. The end of weak La Niña, and unprecedented Arctic warmth influenced 2012 climate conditions.

http://www.noaanews.noaa.gov/stories2013/20130806_stateoftheclimate.html

http://www.ncdc.noaa.gov/bams-state-of-the-climate/2012.php

NOAA/BAMS extremes report:

New analyses find evidence of human-caused climate change in half of the 12 extreme weather and climate events analysed from 2012.

http://www.climatecentral.org/news/report-ties-climate-to-extreme-events-but-shows-hurdles-16438

http://www.theguardian.com/environment/2013/sep/05/climate-change-partially-caused-extreme-weather-2012

http://www.noaanews.noaa.gov/stories2013/20130905-extremeweatherandclimateevents.html

Auckland Anglican Church votes to get out of any fossil fuel investments:

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11121968

A link for the bit about the “Walkie Scorchie”

http://www.telegraph.co.uk/culture/art/architecture/10283702/Whats-frying-at-Walkie-Scorchie.html

Rooftop solar becoming so attractive in US that some power utilities are lobbying against incentives/wider adoption

http://e360.yale.edu/feature/with_rooftop_solar_on_rise_us_utilities_are_striking_back/2687/

ClimatePrediction Dot Net celebrates 10 years this week:

http://www.climateprediction.net/10-years-of-cpdn-and-you-are-invited-to-celebrate-with-us/

(Will be in Aus and NZ soon).

Beatin’ the heat: cut carbon or we’re cooked Gareth Renowden Aug 23

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The area of land affected by extreme heatwaves is expected to double by 2020 and quadruple by 2040, and there’s no way we can stop it happening according to a new paper by Dim Coumou and Alexander Robinson – Historic and future increase in the global land area affected by monthly heat extremes (Environmental Research Letters, open access). However, the researchers find that action to cut emissions can prevent further dramatic increases in heat extremes out to the end of the century.

The paper’s made headlines around the world — see The Guardian, Independent, and Climate Central — most focussing on the inevitability of more, and more intense, heat events in the near future. Dana Nuccitelli at The Guardian provides an excellent discussion of the science behind the new paper so, to avoid reinventing the wheel, I’m going to focus on a fascinating chart from the paper, and then ponder the implications for climate policy.

Coumou and Robinson define heat events in terms of their departure from the statistical distribution of all temperatures for any given part of the earth’s surface. If, like me, it’s a long time since that stats course at uni, you might need reminding that for things — like temperatures at any given place — that are “normally distributed”, then the frequency of given events is described by a bell curve. Here’s Wikipedia’s explanation, and graph:

Standard deviation diagram

The standard deviation — given the greek letter sigma — of a normal distribution is a measure of the variation, or spread, of events — how often they are likely to happen. By definition, 68% of events will fall in one standard deviation, 95% within 2-sigma, and 99.8% within 3-sigma. For temperatures, high temperature events fall under the right hand end of the curve, and cold under the left. Coumou and Robinson worked out how often 3-sigma heat events occurred during a period when the climate was relatively stable — from 1950 to 1980 — and then worked out how it has changed since then, and how an ensemble of models suggest it will change in the future. They found that the frequency and area of earth’s surface covered by 3-sigma events increased significantly over the last 30 years1, and then how they are likely to change in the future under two emissions scenarios — one low, one “business as usual”.

The effect of warming is to move the whole bell curve towards the right, so that very rare events — greater than 3-sigma — become much more common. Here’s what the paper says:

The projections show that in the near-term such heat extremes become much more common, irrespective of the emission scenario. By 2020, the global land area experiencing temperatures of 3-sigma or more will have doubled (covering ~10%) and by 2040 quadrupled (covering ~20%). Over the same period, more-extreme events will emerge: 5-sigma events, which are now essentially absent, will cover a small but significant fraction (~3%) of the global land surface by 2040. These near-term projections are practically independent of emission scenario. [my emphasis]

5-sigma events are very rare — “essentially absent” — in an unchanging climate, but as heat accumulating in the system stacks the dice (pace Hansen), they begin to happen – infrequently at first, but then more and more often as warming progresses. In a high emissions scenario:

By 2100, 3-sigma heat covers about 85% and 5-sigma heat about 60% of the global land area. The occurrence-probability of months warmer than 5-sigma reaches up to 100% in some tropical regions. Over extended areas in the extra-tropics (Mediterranean, Middle East, parts of western Europe, central Asia and the US) most (>70%) summer months will be beyond 3-sigma, and 5-sigma events will be common.

Figure 4 from the paper summarises the findings very nicely:

Coumouheat13

Land area is plotted on the vertical axis, and mean summer temperature across the bottom. Global temperature anomaly corresponding to those summer temps is given across the top. The black circles/triangles/crosses show the measured increase in land surface area for 1, 2 and 3-sigma events, and the coloured versions the modelled projections. We’re already seeing an increase in 3-sigma events, and it won’t be long before 5-sigma events start to show up.

So far, so technical. What does this mean in practical, policy-relevant terms?

Heatwaves are going to happen more often, they are going to become more widespread, and they are going to become more intense — unimaginably hot, for those of us who grew up in the 1950s to 1980s, the reference period for this work.

We’re already seeing this happen, and we can expect it to get much worse over the next few decades. In other words, this is not a hypothetical problem for another generation to deal with.

It is going to be very important to plan at a personal, local, regional and national level to be able to cope with extreme heat when it happens. This will be particularly important in parts of the world where extreme summer heat is not currently common. Increasing heat will worsen droughts and increase pressures on water supplies.

Developing resilience to heat extremes is something that needs to be done now, because what happens over the next 30 years is already baked in2. The climate commitment is going to bite hard, before we can do anything to prevent things getting even worse.

There is good news, however, and that is that if the global community manages to cut emissions steeply — the scenario modelled by Coumou and Alexander (RCP 2.6) effectively means transitioning to zero emissions by 2070 — then we can avoid the worst impacts.

These are the classic dimensions of planning to deal with climate change: we have to cut emissions (mitigate) and prepare for the worst (adapt). One without the other is policy madness. We can also see that the longer we delay both approaches, the costlier it will be to deal with the results.

[Dan Hicks scares himself]

  1. Confirming Jim Hansen’s findings from last year, although using different statistical techniques (see RealClimate for more discussion).
  2. Ahem. Sorry.

Planet waves, and the big heat Gareth Renowden Jul 02

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It’s certainly hot in the southwestern USA at the moment — a dome of heat has established itself under a persistent high pressure ridge, and temperatures are pushing up towards all-time highs. Wildfires are running out of control. One caused the tragic death of 19 firefighters at Yarnell Hill in Arizona yesterday. One more extreme weather event to add to this year’s growing list, and as with most of the others, there’s a clear sign of a link with rapid climate change. That heat dome is being held in place by a large, slow-moving northward loop in the jetstream — and that jetstream pattern is beginning to look very much like the characteristic fingerprint of rapid warming in the northern hemisphere, as Jennifer Francis explains in this video, recorded at a Climate Desk event in Washington last month. It’s just about the clearest explanation of what’s going on that I’ve encountered — particularly in her description of why the jetstream exists in the first place, and why warming is changing the way it behaves. If you want to understand what’s going on, you have to watch this.

There’s a full recording of the Climate Desk event here, including a talk by Weather Channel meteorologist Stu Ostro. Ostro used to be a confirmed sceptic, but began to see changes in weather patterns that he traced back to the effects of warming — specifically, an increase in the “thickness” of the atmosphere, the very thing that’s driving the changes in jetstream behaviour.

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