Warming temperatures implicated in recent California droughts

drought
A photograph of a farmer showing his affected plot due to drought in Karnataka, India, 2012. Credit: Pushkarv/Wikipedia

California has experienced more frequent drought years in the last two decades than it has in the past several centuries. That observed uptick is primarily the result of rising temperatures in the region, which have climbed to record highs as a result of climate change, Stanford scientists say.

In a new study, published in the March 2 issue of the journal of the Proceedings of the National Academy of Sciences, researchers led by Stanford professor Noah Diffenbaugh, examined the role that temperature has played in California droughts over the past 120 years. They also examined the effect that human emissions of carbon dioxide and other greenhouse gases are having on temperature and , focusing on the influence of global warming upon California's past, present, and future drought risk.

The team found that the worst droughts in California have historically occurred when conditions were both dry and warm, and that global warming is increasing the probability that dry and warm years will coincide. The findings suggest that California could be entering an era when nearly every year that has low precipitation also has temperatures similar to or higher than 2013-2014, when the statewide average annual temperature was the warmest on record.

"Of course low precipitation is a prerequisite for drought, but less rain and snowfall alone don't ensure a drought will happen. It really matters if the lack of precipitation happens during a warm or cool year," Diffenbaugh said. "We've seen the effects of record heat on snow and soil moisture this year in California, and we know from this new research that climate change is increasing the probability of those warm and dry conditions occurring together."

Diffenbaugh and his team reached their conclusions by analyzing historical observations and computer climate change simulations. They took advantage of a recently released trove of monthly precipitation, temperature, and drought data for California that stretches back to 1895. Using this 120-year observed dataset, the scientists calculated the probability of drought years occurring in different temperature and precipitation conditions.

Their analysis revealed that the years that were both warm and dry were about twice as likely to produce a as years that were cool and dry. The scientists were also surprised to find that during the early and mid-20th century, temperature and precipitation were largely "uncoupled"-that is, they occurred more or less independently of one another.

"Imagine having two coins-one controls temperature, and the other precipitation," Diffenbaugh said. "In the past, when you flipped the coins, they each came up tails half the time, meaning that a quarter of the time both coins came up tails, representing a warm and dry year."

In the past two decades, however, nearly all of the years in California have been either warm or hot. "Now the temperature coin is coming up tails most years," Diffenbaugh said. "So, even though the precipitation coin is still coming up tails only half the time, it means that over the past two decades we have gotten two tails-warm and dry-in half the years, compared with only a quarter of years in the preceding century."

"When we look at the historical record, not only do we see a doubling of the odds of a warm-dry year, but we also see a doubling of the frequency of drought years," said Danielle Touma, a graduate student in Diffenbaugh's Climate and Earth System Dynamics research group and a coauthor on the study. "Warm conditions reduce snowfall, increase snowmelt, and increase water loss from soils and plants."

The team also used climate models to investigate the role of global warming in driving the observed warming trend, and the associated increase in drought. They analyzed simulations of California's temperature and precipitation levels over the 20th century both with and without human in the atmosphere.

The results were clear: even though to date has not substantially reduced yearly precipitation, human emissions are clearly implicated in California's statewide warming, and in the increased probability that dry years are also warm.

Assessment of climate model simulations that projected into the future also led the team to conclude that the risk of co-occurring warm and dry years will continue to increase in the coming decades. "We found that essentially all years are likely to be warm-or extremely warm-in California by the middle of the 21st century," said study coauthor Daniel Swain, who is also a graduate student in Diffenbaugh's lab. "This means that both drought frequency-and the potential intensity of those droughts which do occur-will likely increase as temperatures continue to rise."

More frequent warm years also increase the likelihood of multi-year droughts in the future. According to team's analyses, the current California drought, now entering its fourth year, is one of the longest consecutive periods in the historical record during which conditions were both severely dry and severely warm. The climate models also indicate that such conditions will become even more common if global warming continues in the future, as the state enters a regime in which there is nearly 100 percent risk that every year is warmer than conditions experienced during the 20th century.

The Stanford researchers say their findings could help California water managers and state officials plan for the future. "While our findings don't provide any particular recommendations," Diffenbaugh said, "they do provide very strong evidence that is already making it much more likely that California experiences conditions that are similar to what we have experienced during the current severe ."


Explore further

Researchers offer new insights into predicting future droughts in California

More information: Anthropogenic warming has increased drought risk in California, Proceedings of the National Academy of Sciences, www.pnas.org/cgi/doi/10.1073/pnas.1422385112
Citation: Warming temperatures implicated in recent California droughts (2015, March 2) retrieved 22 May 2019 from https://phys.org/news/2015-03-temperatures-implicated-california-droughts.html
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Mar 03, 2015
Poor Cali. :(

I didn't understand until I was told to Google "california drought before and after".

Mar 03, 2015
Everything is due to AGW, everything! The science is settled!

Mar 03, 2015
Cantdrive,
This isn't going away, climate change by definition has some effect on the climate, droughts are a climate. It's important to understand our impacts so we can prepare for the future. Some places are going to get wetter.
NASA just launched a new climate monitoring satellite that's going to be able to measure soil moisture a few inches down anywhere on the earth, so we'll be able to get better measurements soon since that has a large impact on the weather.

Mar 03, 2015
Maybe it would help if, just like many other areas of the country, CA water providers enacted and enforced mandatory water rationing... I was very surprised to learn many areas in CA do not have restrictions, and people water 5+ days/week! Many, MANY other cities/towns/districts around the country have restrictions that limit irrigation to 2 days per week, sometimes even less. In the past 15 years, I have lived in 3 states, and 4 separate water authorities and all of them had restrictions. Additionally, high cost progressive fee schedules can also help curb usage. If you use an amount typical of household volume (<10,000g), your bill may be less than $50. But if you water a large yard with landscaping, and consume 30,000g+, you can easily top $500, one neighbor planted a lot of new flower beds and had a $1500 bill a few summers ago.

Mar 03, 2015
@MP3Car
Many water districts in CA do have mandatory water rationing and tiered billing is common.

Mar 24, 2015
@Vietvet

Okay, that's good to hear! I only mentioned it because I know two people in CA and neither one has rationing. One is in the bay area and the other is in so. cal, but I can't recall where. (Obviously two data points hardly reflects all the various water providers, but they both are in highly populated areas).

Mar 24, 2015
Any of you Chicken Littles believe this fella is worried about water?
http://content.us...h_Fw-Ct8

Mar 24, 2015
@MP3CAR

There 938 water districts in California, some are huge and others very small. Their policies can vary dramatically even when adjacent

I've lived with tiered pricing for years but some wealthy assholes in Orange County have challenged it in court and are likely to win do to the wording in state law. If they prevail it will take quick action by the state legislature to correct the situation.

Mar 29, 2015
Warming temperatures implicated in recent California droughts
This is just more AGWite scaremongering. The current drought, though a singular and significant event, is not unusual for California. In fact, except for the current low spike ever so slightly dragging it down, mean rainfall in California has been relatively steady for well over 100 years:

http://www.ncdc.n...binomial

Worsening droughts on the Palmer Drought Severity Index in California, are therefore man-made problems in regards to water resource use, not precipitation and climate.issues.


Mar 29, 2015
@unavontuba

Cherry picking at it's worst. You plotted one month, December, that doesn't show a decline, but plotting every other month of the rainy season does.

http://www.ncdc.n...binomial

Mar 29, 2015
[

Worsening droughts on the Palmer Drought Severity Index in California, are therefore man-made problems in regards to water resource use, not precipitation and climate.issues.

The biggest f**king lie (so far) by @unavontuba.

Mar 30, 2015
@Vietvet
Cherry picking at it's worst. You plotted one month, December, that doesn't show a decline,
Idiot. I posted ANNUAL precipitation. The "Annual" selection automatically defaults to Year-to-Date, December (meaning, the whole year).

Test it yourself. Switch "Time Scale" to Annual and submit. Then copy the link and paste it in another window. You will see it switches it automatically to "Year-to-Date, December," but the graph is identical.

but plotting every other month of the rainy season does.
LOL! And YOU accused ME of cherry picking!

Worsening droughts on the Palmer Drought Severity Index in California, are therefore man-made problems in regards to water resource use, not precipitation and climate.issues.
The biggest f**king lie (so far) by @unavontuba.
What is your problem? If you had concerns about the data I presented, you should have simply expressed them, rather than going off half-cocked and making an a** of yourself.


Mar 30, 2015
@unavontuba

Are you claiming this map is a work of fiction?

http://droughtmonitor.unl.edu/

Mar 30, 2015
@Vietvet:

P.S. You were wrong about that every other month thing too.

Here they are, month by month:

October:

http://www.ncdc.n...binomial

November:

http://www.ncdc.n...binomial

December:

http://www.ncdc.n...binomial

cont...



Mar 30, 2015
Drought Defined

A drought is a period of drier-than-normal conditions that results in water-related problems. When rainfall is less than normal for several weeks, months, or years, the flow of streams and rivers declines, water levels in lakes and reservoirs fall, and the depth to water in wells increases. If dry weather persists and water-supply problems develop, the dry period can become a drought.

"The term "drought" can have different meanings to different people, depending on how a water deficiency affects them. Droughts have been classified into different types such as:

meteorological drought - lack of precipitation
agricultural drought - lack of soil moisture, or
hydrologic drought -reduced streamflow or groundwater levels"

http://ca.water.u...drought/

@unavontuba

Nothing in that definition is man-made.

Mar 30, 2015
@unavontuba

Are you claiming this map is a work of fiction?

http://droughtmonitor.unl.edu/
Of course not. Did you not see where I wrote, "The current drought, though a singular and significant event, is not unusual for California."

But "drought" is measured in more ways than just precipitation. It's mostly about water resources.

You're generally more perceptive than this. I'm starting to worry a little about you. Are you okay?


Mar 30, 2015
@Vietvet
Nothing in that definition is man-made.
Agriculture is not a man-made concern? Hydrology is not a man-made concern? Groundwater pumping and groundwater levels are not man-made concerns? Really?

Do you not see it?

If supply (precipitation) is relatively steady, but demand increases, shortages arise. Ergo: Increasing drought.


Mar 30, 2015
Drought Defined

A drought is a period of drier-than-normal conditions that results in water-related problems. When rainfall is less than normal for several weeks, months, or years, the flow of streams and rivers declines, water levels in lakes and reservoirs fall, and the depth to water in wells increases. If dry weather persists and water-supply problems develop, the dry period can become a drought.

"The term "drought" can have different meanings to different people, depending on how a water deficiency affects them. Droughts have been classified into different types such as:

meteorological drought - lack of precipitation
agricultural drought - lack of soil moisture, or
hydrologic drought -reduced streamflow or groundwater levels"

http://ca.water.u...drought/

@unavontuba

Nothing in that definition is man-made.

You have to remember, ubamoron thinks you can grow food in a desert!

Mar 30, 2015
@Maggnus
You have to remember, ubamoron thinks you can grow food in a desert!
Really? Do you really want to be admitting you're still this ignorant? How is anyone supposed to believe anything else you write then?

And speaking of deserts, it appears Vietvet has run off to bury his head in the sand to hide his shame..

Why do AGWites deny both reality and science?


Mar 30, 2015
[

And speaking of deserts, it appears Vietvet has run off to bury his head in the sand to hide his shame..



I'm not hiding anywhere, you'll get my response in due time. There is more to life than arguing with the willfully ignorant.

Mar 31, 2015
@Vietvet
Nothing in that definition is man-made.
Agriculture is not a man-made concern? Hydrology is not a man-made concern? Groundwater pumping and groundwater levels are not man-made concerns? Really?

Do you not see it?

If supply (precipitation) is relatively steady, but demand increases, shortages arise. Ergo: Increasing drought.



Well allrighty then ubibbittymaroony,

Let's see some hard, well-qualified, and well-quantified figures for your claimed increased demand/decreased supply scenario, which are sufficient to tip a very-nearly-normal, only-slightly-less-than-normal, virtually-indistiguishable-from-normal, hell--may-as-well-just say-normal ---or whatever other minimizing the difference phrasing you would prefer, ever-so-slight decrease in annual average precipitation into a HUMAN CONSUMPTION-INDUCED, BONA FIDE, MULTI-YEAR , REGIONAL DROUGHT.

With no waffling or prevarication.

You've made the claim --now substantiate it.



Mar 31, 2015
Let's see some hard, well-qualified, and well-quantified figures for your claimed increased demand/decreased supply scenario, which are sufficient to tip a ...slight decrease in annual average precipitation into a MULTI-YEAR , REGIONAL DROUGHT.
First, that's not quite the scenario I portrayed. Second, I already provided the necessary data. And third, you only believe what you want to believe anyway.

Is it even possible for an AGWite to have a civil and rational discussion? It seems doubtful. Just look at Vietvet. He blew a gasket based upon his own misconception of the data, and immediately resorted to personal attacks.


Mar 31, 2015
There is more to life than arguing with the willfully ignorant.
Indeed. Which begs the question: Why do you and your fellow AGWites choose to remain so willfully ignorant? ...to such a degree you even deny the very definition of the concept to which you are supporting! It's about as irrational as arguing the sun is the moon.


Apr 01, 2015
Let's see some hard, well-qualified, and well-quantified figures for your claimed increased demand/decreased supply scenario, which are sufficient to tip a ...slight decrease in annual average precipitation into a MULTI-YEAR , REGIONAL DROUGHT.
First, that's not quite the scenario I portrayed. Second, I already provided the necessary data. And third, you only believe what you want to believe anyway.

Is it even possible for an AGWite to have a civil and rational discussion? It seems doubtful. Just look at Vietvet. He blew a gasket based upon his own misconception of the data, and immediately resorted to personal attacks.


Uh huh --nothing but waffling, backpedalling horseshit from ubibbitymaroonyMORON.

That was EXACTLY the scenario you fronted, troll.

Nothing quite like watching a troll prove its own pudding, and in such exemplary fashion.

Detestable tergiversation, thy name is ubibbitymaroonyMORON.


Apr 06, 2015
First, that's not quite the scenario I portrayed. Second, I already provided the necessary data. And third, you only believe what you want to believe anyway.

Is it even possible for an AGWite to have a civil and rational discussion? It seems doubtful. Just look at Vietvet. He blew a gasket based upon his own misconception of the data, and immediately resorted to personal attacks.
Uh huh --nothing but waffling, backpedalling horseshit from ubibbitymaroonyMORON.

That was EXACTLY the scenario you fronted, troll.

Nothing quite like watching a troll prove its own pudding, and in such exemplary fashion.

Detestable tergiversation, thy name is ubibbitymaroonyMORON.
Thank you, Caliban, for validating everything I wrote.


Apr 07, 2015
And speaking of deserts, it appears Vietvet has run off to bury his head in the sand to hide his shame..
I'm not hiding anywhere, you'll get my response in due time. There is more to life than arguing with the willfully ignorant.
Hmm. It's been more than a week, and still no response ...yet Vietvet has appeared to downrank me.

What's the matter, Vietvet? Are you having trouble coming up with a plausible rationalization for your blunder?


Apr 07, 2015
ubavontuba FAILED in his claim
Why do AGWites deny both reality and science?
ubavontuba has already confirmed he has NO physics education so his hypocrisy is immense and especially so when he CANNOT address this straightforward question:-

"How can adding a greenhouse gas to the atmosphere, such as CO2 with known & irrefutable properties, somehow NOT increase thermal resistivity?"

The evidence for distribution of heat is clear from latest data:-
http://images.rem...ies.html

ubavontuba's FAILURE to understand the temperature distribution is telling of his lack of education.

IOW: ubavontuba FAILS yet again !

Apr 07, 2015
Vietvet offered
@MP3Car
Many water districts in CA do have mandatory water rationing and tiered billing is common.
In Perth, Western Australia we have had water rationing for about 20yrs or so but, only last 10yrs or so it includes winter as well iirc.

Although Perth is on edge of a large desert & we have less rainfall than 1980's, in general we have approx twice the annual rainfall of London, though with us it comes down in large amounts over generally short periods whereas London seems to be more long term drizzle/fog.

Since I moved from northern hemisphere in 1969, notice we have more humid days & especially so in last 30 yrs along with Ultraviolet (UV) warnings ie Threat of sunburn if out in the sun unprotected for more than 7mins yes Seven minutes at height of summer (on TV & notice boards) when our xmas daily temps may be 46 deg C !

Rainfall has also reduced over that same 30yrs or so whilst Perth is growing, we now have an expensive desal plant !

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