Climatologist Ben Santer on the attribution of extreme weather events to climate change

When you warm up the planet, you experience that through changes in weather that makes up the climate,” says Dr. Benjamin Santer at the Lawrence Livermore National Lab. In a video interview with Climate Science Watch, Santer answers the questions: What is the most appropriate way for reporters and scientists to make a distinction between climate and weather when discussing the attribution of specific weather events, such as heat waves, droughts, and intense precipitation to climate change? What do you think is the most important message for the public to take away from witnessing these events?

Reinsurer Munich Re, whose natural catastrophe database is “the most comprehensive of its kind in the world,” has said “The only plausible explanation for the rise in weather-related catastrophes is climate change.”  A recent Journal of Climate Study found global warming is driving increased frequency of extreme wet or dry summer weather in southeast, so droughts and deluges are likely to get worse.  And it remains an amazing, though clearly little-known, scientific fact:  We get more snow storms in warm years!

What follows is re-post from Climate Science Watch, starting with the video interview of Santer:

We conducted the interview on August 27, 2010.

Santer’s written testimony before the House Committee on Science and Technology, Subcommittee on Energy and Environment, held in Washington, D.C. on November 17 includes the following within its 19 pages:

Assessing Risks of Changes in Extreme Events

We are now capable of making informed scientific statements regarding the influence of human activities on the likelihood of extreme events (75, 76, 77).

As noted previously, computer models can be used to perform the control experiment (no human effects on climate) that we cannot perform in the real world. Using the “unforced” climate variability from a multi-century control run, it is possible to determine how many times an extreme event of a given magnitude should have been observed in the absence of human interference.  The probability of obtaining the same extreme event is then calculated in a perturbed climate – for example, in a model experiment with historical or future increases in greenhouse gases, or under some specified change in mean climate (78). Comparison of the frequencies of extremes in the control and perturbed experiments allows climate scientists to make probabilistic statements about how human-induced climate change may have altered the likelihood of the extreme event (53, 78, 79). This is sometimes referred to as an assessment of “fractional attributable risk” (78).

Recently, a “fractional attributable risk” study of the 2003 European summer heat wave concluded that “there is a greater than 90% chance that over half the risk of European summer temperatures exceeding a threshold of 1.6 K is attributable to human influence on climate” (78).

This study (and related work) illustrates that the “D&A” [detection and attribution] community has moved beyond analysis of changes in the mean state of the climate. We now apply rigorous statistical methods to the problem of estimating how human activities may alter the probability of occurrence extreme events. The demonstration of human culpability in changing these risks is likely to have significant implications for the debate on policy responses to climate change.

Also see the discussion of climate and weather extremes in the written testimony (pp. 10-13) submitted for the hearing record by Dr. Heidi Cullen and the written testimony (pp. 6-9) of Dr. Gerald Meehl.

Climate Science Watch

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25 Responses to Climatologist Ben Santer on the attribution of extreme weather events to climate change

  1. catman306 says:

    “You can’t attribute a single event to climate change” has always bothered me. Averages can only move with a multitude of small events in the same direction or with far fewer extreme events.
    Think of your favorite example from sports statistics. If a player ‘gets hot’ for a month, we can expect his averages will rise dramatically. No single hit, pass, or game score can be attributed to the players rising star, because a lesser player can also have a good day, but the frequency of those events easily shows the direction that the star player’s averages will be moving. Same with climate statistics.

    Since Fox News viewers probably also watch televised sports, (and MEMORIZE the sports statistics!) developing this example might just convince some that the frequency of these extreme weather events mean something to them in their lives and that maybe something must be done.

  2. Jeffrey Davis says:

    There are no discrete weather events. That’s a newspaper/folk idea. All weather is now influenced by the increase in temps the same way the sun illuminates a landscape.

  3. MapleLeaf says:

    Kudos to Dr. Santer for doing more and more outreach.

    Note how he chooses his words incredibly carefully, how his responses are measured and thought out logically,also note how he doesn’t speak too fast etc. Santer is an incredibly bright man and excellent scientists.

    Now we just need to hold an image of some silly contrarian or denier of AGW in the room to make Ben sound more passionate, and he’ll be a fantastic and captivating orator.

  4. Paulm says:

    Planet Eaarth….
    This community will soon have to be abandoned.

    ‎”We lost our wharf, breakwater and road, and again this year [we have] the same high tides and surges,” Paul told CBC News.

    Paul said the storms prove Ferryland needs a breakwater to protect the community, about 75 kilometres south of St. John’s. Paul said the work would cost well over $1 million.

  5. Paulm says:

    “When you look just at the shift in temperature … it looks favourable for Canada,…. But that’s not the problem.

    The problem is not the shift in the average, it’s the shift in the extremes. And that’s going to be the most challenging consequence of global warming in our region.”
    Welcome to the New Normal, courtesy of Climate Change. « Climate Denial Crock of the Week

  6. apeescape says:

    You can’t attribute a single extreme event to climate change, but single extreme events do not exist in a vacuum.

    It’s like saying if you increase CO2 while holding everything else constant, you get a climate sensitivity of 1C.

    With sports analogies, we can say that Barry Bonds hit 73 homeruns thanks much to (anthropogenic!) steroids because we know his performance pre-steroids and that steroids should bump up the average power output of a player.

    Generally, small increase in the temperature should result in a large increase in the frequency of extremes.

  7. Michael Tucker says:

    “an amazing, though clearly little-known, scientific fact: We get more snow storms in warm years!”

    THAT is absolutely true! Why is it “little-known”?

    Many think that when journalists (science or otherwise) talk about how global warming will cause warmer winters that means very little or no snow and much warmer weather. The messaging is terrible. No one really knows what to expect when the average temperature increase reaches 2 deg C. Will we still have cold winters in the northern hemisphere? Will it still snow in winter? When the average reaches 4 deg C will palm trees grow on the shores of Hudson Bay? Many expect winters will be like summers and summers will be unbearably hot.

    Since most will attribute the increase in heat waves, droughts, and heavy rainfall events to global climate disruption BUT rarely mention the blizzards, it is natural that the science illiterates would seize on this and use blizzards as evidence that global warming is not happening.

  8. Leif says:

    Good analogy catman306, @1. An average ball player can indeed have an exceptional play from time to time, as the skill level of all professional players is way above the average human. However above average skills of individual players quickly manifest themselves when broken down to individual categories. Clearly you cannot say that any single base hit shows exceptional talent but a player that has a record of 9 out of 10 base hits for the season? That is a player that get the lead off batter position in any club.

    Similarly, when extreme warming events exceed extreme cold events by two to one for a ten year average,

    a change from ~1::1, ~50 years ago, it is clear that every other event can be attributed to above average influence. If not Climatic Disruption, what?

  9. Colorado Bob says:

    Clean up begins after storm inflicts worst flooding in 150 years

    One site in the Marlborough Sounds measured 230mm (9 inches) of rain in 24 hours, Mr Wheeler said,

  10. Colorado Bob says:

    Queensland’s floods have cost grain farmers an estimated $400 million and the bill will certainly rise, AgForce says.

    This latest round of rains has moved sugar, coal , and cotton prices again.

  11. Colorado Bob says:

    Australian floods send coal prices soaring
    The wettest Australian summer since records began has resulted in the price of coal rising as fast as the stock of the English cricket team.

  12. Colorado Bob says:

    4,000 evacuated after flash floods in Philippine region

    The rainy season which began in June should have ended in November.

  13. Colorado Bob says:

    Dec 29, Colombo: Sri Lanka’s national economy has suffered losses of 6 billion rupees ($54,102,000.00) due to the floods ravaging many parts of the island in recent weeks, the government revealed.

  14. Colorado Bob says:

    New Zealand.

    Golden Bay was hit particularly hard, with the latest flood being the third this month; the area has received over 500 millimetres (19.68 inches) of rain in December.,nrhl

  15. Arkitkt says:

    Meanwhile in South America, the hottest summer in record.

  16. Colorado Bob says:

    Arkitkt’s page translated :

    Buenos Aires “burns” with a heat wave, you power shutdown and lack of fuel

    Added to the exhausting heat, that is hoped that it begins to decrease this Wednesday, the climatic phenomenon “the girl” has caused to drought in vast zones of the provinces of Buenos Aires and Pampas, in the richest agricultural region of Argentina, one of the global producing grain majors.

    Sources of the farming sector think that the lack of rains can be extended until next March, with the consequent loss of cultures of soybean and maize.

    The heat wave untied, in addition, a “historical record” of the electrical energy demand, according to agreed companies of the sector, to the point that in numerous districts of Buenos Aires and their urban belt were in the last days you cut of provision which they brought about rough protests of the users.

  17. dhogaza says:

    climatic phenomenon “the girl”

    In plain English, La Niña … :)

  18. American_Idle says:

    In all probability, the denial machine is having second thoughts about having picked a fight with Dr. Santer. A link to his written testimony that was submitted to the November House Committee hearing is copied from above.

  19. catman306 says:

    I dare any farmer from anywhere to brag about how their local climate is quite normal, exactly the way it’s been in the past.

    Warning! Gaia has eyes and ears, a sense of smell to shame a bloodhound, is smarter and mightier than any of us, or even all of us, has all the time in the world, and won’t trifle with infidels.

  20. George Ennis says:

    Here is the cost to one of Canada’s eastern provinces of the current winter extreme weather events.

    You will note that they are planning for a SLR of 20 centimeters. It would seem that they have not heard the more recent forecasts for SLR which if true will be nothing short of devastating to the province.

  21. Rabid Doomsayer says:

    What is going to happen to the price of food over the next 6 months? Around the world disaster after disaster.

  22. Mulga Mumblebrain says:

    Well Argentina is out because of drought, Queensland, New South Wales and Victoria in Australia out because of unprecedented flooding, West Australia ‘rooned’ by drought, Pakistan still effected by floods, and record floods raging or have been just recently in Sri Lanka, New Zealand, Colombia, Venezuela, the Philippines, Vietnam, Thailand etc. Yes and La Nina cycles into El Nino some time soon, as the solar cycle picks up steam. 2012 looks more and more ominous, and the Mayans knew a thing or two about drought and starvation, from incredibly bitter experience. Could it be time to bring back human sacrifice, because I could nominate a few delectable offerings for the Gods.

  23. Adding to comment 14
    Yes here in Golden Bay we have had a December with a high rainfall (mostly due to the one event) but we had a very dry October and November. I dont understand the science that supposedly links this to carbon emissions?

  24. Chris Winter says:

    I’ve lately found Google Translate (translate dot google dot com) to be superior to Babel Fish. On that Argentinian page, it does a very good job, even gets “La Niña” right.

  25. Solar Jim says:

    So, does fractional attributable risk mean the insurance companies should start suing the petroleum and coal companies for damages? They have been looking at the climate contamination situation for over a decade. Or perhaps they will be the last to be bought off, especially since some insurance companies are owned by investment banks (oxymoron) which own parts of the world petroleum industry along with their fossil reserve valuations. It is all so complicated, isn’t it?

    Note: petroleum is not an “energy” resource, and neither is uranium. (Hint: they are explosives)

    Anyone seen the Arctic Vortex lately?