Science News

Californian drought and climate change

Thu, 2nd Oct 2014

Timothy Revell

Extreme weather catastrophes could be as much as three times more likely as the global climate warms, researchers from Stanford University warned this week. 

Using California as a case study, Noah Diffenbaugh and his colleagues, writing in Bulletin of the American Meteorological Society, show how as temperatures rise the risk of droughts becomes more likely. 

The 2013 California droughts were the driest since records began. A state-level “drought emergency” was declared by California Governor Jerry Brown, and all 58 counties of California were declared “natural disaster areas,” with the economic costs estimated to be in the region of $2 billion. 

The droughts were caused by a large atmospheric ridge, a region of high pressure in the atmosphere, that prevented precipitation from reaching California, as well as Oregon and Washington.

“If you think of a large boulder in a stream,” says Noah Diffenbaugh, one of the authors of the paper, “the water is going to be diverted around the boulder, and that’s essentially what has been happening [in the atmosphere].” 

“As the air currents move across the Pacific, those that would normally make it to California have been blocked or steered northward.” 

The atmospheric ridge responsible for the Californian droughts was extraordinary for its size and longevity, which lead to it being named the Ridiculously Resilient Ridge, by Daniel Swain a graduate student in Diffenbaugh’s research group. 

To determine the role of climate change in the likelihood of the Californian droughts, the research group teamed up with Bala Rajaratnam, assistant professor of Statistics and of Environmental Earth System Science. Rajaratnam and his team used statistical techniques to analyse a variety of climate model simulations. They ran two sets of experiments, one where the greenhouse gas level in the atmosphere were set at today’s values, and the other set to levels before the industrial revolution.

According to Diffenbaugh, the research shows with a 95% confidence “the global warming that has already happened, has at least tripled the probability of this extreme atmospheric condition, relative to the probability without the human contribution.”


The blame for any individual climate event can never be fully attributed to climate change, but with an increased likelihood of extreme weather both in the US and around the globe we are going to need to learn to be better prepared.  

As Diffenbaugh puts it “there are a lot of opportunities to improve our resilience in the current climate and at the same time prepare for future events.”


Click to listen to the full interview with Noah Diffenbaugh:



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Usual bovine excrement. "Extreme" is undefined. "could be" is meaningless. 

"as much as three times more likely" is at least worth debating.  To qualify for "extreme", something has to be unlikely, otherwise it's just "normal". So exactly what is the probablity of something 3 times as much as very improbable? And if we are really talking about Poisson events, what is the confidence range of 3 times improbable?

Anyway surely the cart is being put before the horse here.  Climate is the longterm average of weather, so if weather changes, over an undefined period, so will climate.

Anyway it's not news

But I have no doubt that someone whose living depends on climatological scaremongering will say "a thousand years isn't climate, it's weather". Or maybe they will blame the 11th century drought on King Canute messing about with the tides - it's always the fault of the Brits.  alancalverd, Fri, 10th Oct 2014

"But I have no doubt that someone whose living depends on climatological scaremongering will say ......................."

Implying that there are no climate change deniers whose financial and corporate interests depend on convincing us that climate change is a myth? teragram, Mon, 13th Oct 2014

Climate has always changed, and always will, because the atmosphere is inherently unstable. Only a fool would deny that. But there are some who make a living by pretending that it is a recent phenomenon, caused by capitalism (why else would China be exempt from the Kyoto protocol?) and likely to be a disaster if you don't unplug your telephone charger, throw away your lightbulbs, and buy an expensive electricity meter.

There's far more money in scaremongering than in questioning the validity of the data and the robustness of the models. Governments make huge sums by imposing arbitrary "green" taxes, then redistribute the money to "consultants" and windmill manufacturers. And if anyone dares to ask a simple question like "how do you know what the global mean temperature was in 1800, when nobody had ever visited Antarctica, let alone measured its temperature"?  or "What exactly do you mean by "sea level"?" he faces execration and excommunication.

I guess my favourite example of mass gullibility was the way in which the recent discovery of 500-year-old bryophytes under a retreating glacier was reported. The headlines concentrated on the glacier retreating under "temperatures unprecedented in human history" and such bunkum, whereas the presence of the plants clearly indicates that it must have been hotter 500 years ago for them to have grown there in the first place. Written history goes back around 6000 years, and includes the time when Ur was a flourishing seaport, now 100 miles from the coast. Rising sea level? I think not.

My "financial and corporate interests" depend on sticking to the truth, and sticking the truth to others. Climate change is a fact, and we have to live with it because we have no control over it. Beware of false prophets. alancalverd, Mon, 13th Oct 2014

As far as I know China is not “exempt” from the Kyoto Protocol, it just didn’t sign up to it. If I remember correctly the U.S.A. had to be dragged into it after years of denial.
I’m glad that you accept the existence of climate change. My dreadful mistake was to omit the preface “Man made…..”
It has been known for about 120 years that CO2 in the atmosphere traps heat, and that burning fuels leads to an increase in the gas.
The scientific consensus is that climate change occurring since the industrial revolution is largely man made. Therefore we HAVE controlled the climate, but not to our benefit. By definition then we can (if it’s not too late) to some extent reduce the effect.
Incidentally, even the economics “scientists” now seem to think that it will cost far more to live with the consequences of man made climate change than to attempt to reduce it.
To say that  there is “far more money in scaremongering…” seems to imply that the vast majority of climate scientists are lying to us for their financial gain, rather than trying to warn us. So should we trust the repesentatives of non-renewable energy interests, or climate scientists? In other words, who are the “false prophets”?
teragram, Tue, 14th Oct 2014

When climate scientists get a prediction right, based on actual rather than "adjusted" data and arbitrary proxies, it will be time to listen to them. The fashionable view in the 1960's was that we are headed for an imminent ice age.

Consensus in science is a dangerous thing. Understanding comes from mavericks like Galileo and Einstein. If we relied on consensus we'd still be suffering from cholera, typhoid, smallpox and malaria. The American Academy of Sciences famously told the Wright Brothers in 1910 that "there is no conceivable military use for the airplane" and two airborne wars later the British Association decreed that "about five computers will suffice for the UK's needs".

Climate change is, by consensus, due to the interaction of phlogiston with caloric, though my bet is on water, which the IPCC generously admitted (in its very first report) was clearly the most important greenhouse gas but far too difficult to quantify, so they ignored it.

China was indeed an early signatory to Kyoto, but, along with India, has no commitment to do anything about it. alancalverd, Tue, 14th Oct 2014

To be fair, China is closing some coal fired power stations and banning the use of the more pollutive types of coal in large areas. The aim is to improve air quality.

I would say the relevant maverick here is Jim Hansen, ex NASA, first, I think, of the modern visionaries to warn us in 1988 of the dangers of human-induced climate change.
Are Galileo and Einstein still mavericks?

Water vapour, as you say, is a great contributor to global warming. Remember that the production of CO2 from burning fossil fuel is accompanied by a proportionate production of water vapour.
As for phlogiston, I’ve still got a few bottles left. Out of caloric though.
teragram, Thu, 16th Oct 2014

Which makes coal the least climate-change-inducing fuel of all! alancalverd, Tue, 21st Oct 2014

Which makes coal the least climate-change-inducing fuel of all!

It says 'ere...
Water vapour feedback loop amplifies the temperature change caused by CO2. peppercorn, Wed, 22nd Oct 2014

Yeah, that's the usual bunkum put about by the CO2 lobby. It doesn't explain why the prehistoric CO2 curve follows rather than leads the temperature curve, unless you believe that the laws of physics changed in 1900. The simple explanation is that water is the driver and the CO2 balance between plants and animals is temperature dependent - as any insect will tell you.

Why the non-science? Because you can tax carbon.  alancalverd, Wed, 22nd Oct 2014

I agree Alan,'s all about the Globalists control of wealth redistribution...................Ethos Ethos_, Wed, 22nd Oct 2014

Why do CO2 deniers speak  disparagingly about the “CO2 lobby”? Is it because it is such a tiny movement compared to the fossil fuel lobby?
Anyway, even if you believe that CO2 is irrelevant in climate change, the fact that water vapour is relevant indicates that burning fossil fuels is undesirable.
The argument re. the CO2 curve following, not leading, the temperature curve, was I think anticipated by James Hansen (see above) and others, many years ago. The key phrase is I think “the prehistoric CO2 curve”. In more recent times man-made CO2 has risen beyond the point where it becomes a significant contributor.
See Peppercorn’s link above.

teragram, Tue, 28th Oct 2014

It's not just "prehistoric" data that makes one doubt the importance of anthropogenic CO2. We now have evidence from a retreating glacier that the planet, or at least Canada, was warmer 500 years ago than it is now, well within recorded history but way before the industrial revolution.

There are many good reasons to reduce or eliminate our dependence on fossil fuel, but lies and bad science aren't among them. alancalverd, Wed, 29th Oct 2014

"CO2 causes warming AND rising temperature causes CO2 rise when the Earth comes out of an ice age.
Here, the warming is not initiated by CO2 but by changes in the Earth's orbit. " peppercorn, Sat, 1st Nov 2014

And not just an ice age. The famous Mauna Loa data shows an annual cycle of CO2 concentration that (a) lags behind the temperature graph and (b) reaches a minimum in late winter when anthropogenic CO2 emission is at a maximum. Indeed all the evidence I have seen, points towards CO2 being the thermometer, not the thermostat. alancalverd, Sun, 2nd Nov 2014

As in this: Mauna Loa Carbon Dioxide... ?

The fluctuations are explained by forest 'breathing' - ie. growth through the summer (most forest is concentrated in the Northern Hemisphere). peppercorn, Mon, 3rd Nov 2014

Forest growth should reduce the CO2 level in summer. The data shows the opposite. alancalverd, Tue, 4th Nov 2014

The 'annual cycle' data shown fits perfectly with that assertion. Drop off starts in May and continues until September. peppercorn, Tue, 4th Nov 2014

I think we live on a different planet, or at least we till different soils. Fastest growth occurs in the period February-July. Once the days start getting shorter, deciduous forests and grasslands think about seeding, not competing for sunlight, and the leaves start falling in September, with most trees and grasses virtually dormant by the end of October. Something to do with "fall" and "harvest".

As for conifers, here's what happens to the Douglas Fir - surely a typical northern hemisphere wild and farmed species.

So what is actually going on? A simple suggestion is that insect activity determines the equilibrium between atmospheric and sequestered CO2. Plants grow by turning CO2 into structural materials, and insects get their energy by oxidising plant material back to CO2. Insect activity is profoundly temperature-dependent with grubs eating themselves to the limit in spring, then hatching and mating at the height of summer. Many insects don't eat at all after mating, and eventually the trees outgrow their pests (otherwise the entire ecosystem would collapse) so around July the rate of CO2 absorption exceeds production, and by September the insects have pretty much given up and the CO2 level plummets. However as the mean temperature increases year by year, so the mean atmospheric CO2 concentration is gradually increasing - the insects are winning the long war,if not the annual battle.      alancalverd, Wed, 5th Nov 2014

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