Guest Post by Willis Eschenbach
I keep reading all kinds of claims that the slight warming we’ve been experiencing over the last century has already led to an increase in droughts. A few years ago there were a couple of very dry years here in California, and the alarmists were claiming that “global warming” had put us into “permanent drought”.
Of course, the rains returned. This season we’re at about 120% of normal … it’s called “weather”.
In any case, I thought I’d take a look at the severity of droughts in the US over the last century. I always like to take a look at the longest dataset I can find. In this case, I got the data from NOAA’s CLIMDIV dataset. Figure 1 shows the monthly variations from 1895 to the present. Note that I’ve inverted the Y-axis on the graph, so higher on the graph is dryer, and down near the bottom is wetter.
We can see a few interesting things in this graph. As you might expect, the worst droughts were in the 1930s, the time of the “Dust Bowl”. There were also droughts in the 1950s, although somewhat smaller and shorter.
Then for about thirty years, from 1970 to 2000, times were generally wetter … followed by drier times up to 2010, and wetter times since then.
Next, overall there is a very slight and not statistically significant linear trend toward a bit more wetness.
Finally, it’s worth noting that if our data had started in say 1930, it would have a statistically significant trend toward wetter times … which shows that even 80 years of data may give a very different answer than we get from the 125 years of data shown above. This is why I use the longest dataset available.
In any case, according to NOAA, there’s been no increase in either droughts or wet periods in the US since 1895 …
And meanwhile, here on the northern California coast, it’s Christmas Eve, and a gentle rain has just begun falling … best of the season to everyone.
w.
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w. ==> While I appreciate the analysis, Continental US drought data does not capture the problems of precipitation levels where it matters.
Rainfall is always a local (or local/regional) problem. California does not benefit from lack of drought in Florida. Lots of snow pack in Washington State does not keep reservoirs full in California’s Central Valley.
This is a major failing of Climate Science in general — the use of computational power to crunch numbers on global or continental level leads to useless (or, worse, misleading) analyses.
California, for instance, needs deep snow pack in the Sierras that melts slowly over the rest of the year, a good monsoon across the southern reaches, and could use fewer atmospheric rivers washing the hills of southern California into the sea.
All this comes under Climatically Important Differences. In New York State, a 10% shortfall of rainfall during a summer hardly makes an effect, whereas the same in Georgia creates water supply problems for Atlanta.
California needs to build many more reservoirs — and the infrastructure to deliver the water where it is needed. The insanity of building tens of thousands of new homes every year without requiring developers to guarantee water supply is almost beyond belief.
Kip Hansen December 27, 2019 at 7:36 am
Mmm … mixed feelings on that one. It’s true, but remember that the claim is that this is GLOBAL warming, and that ON AVERAGE droughts either are or will soon be increasing.
That’s the claim that I’m refuting, and so I have no choice but to look at wide-area averages.
Regards,
w.
Do you have a reference to such a claim (that droughts, globally, will increase)? Regardless, you didn’t provide global data, only continental US data. But if regional weather (wetter areas becoming wetter and drier areas becoming drier) is following projections, why completely ignore that?
Mike Roberts December 31, 2019 at 1:22 am
Mike, I discussed this upthread.
The data for the US is the biggest and best that I can find. I don’t know of any larger area with good long-term drought information.
Best regards,
w.
Thanks for that, Willis. Indeed, it is projected that droughts will increase but your post didn’t look at droughts, it looked at the US PDSI. As TheFinalNail mentioned, regional effects are more pronounced and we can see the increase in droughts for drier areas, which was projected. However, looking at the PDSI doesn’t tell us about droughts, even in the US (which is a small fraction of the earth), it tells us about the dryness overall which, as you point out, hasn’t changed much.
Mike Roberts December 31, 2019 at 9:12 pm
It didn’t look at droughts, it looked at the Palmer Drought Severity Index???
I have absolutely no clue what that means. How else would you measure droughts?
w.
Willis,
You mentioned droughts and the severity of droughts. You clearly made the link between PDSI and droughts. That was wrong.
Climate Change activists have many scare stories. Sea level, polar bears, heat waves, and so on. The problem is, they are not scary. If Al Gore and Obama don’t believe sea level will flood their mansions, why should I worry?
The real scare in climate change (that is, really scary, but not necessarily real) is drought. It is scary because climate change is not even needed. The dust bowl happened, the Anasazi suffered droughts, as did other pre-Columbian civilizations. Long term droughts happen, naturally. It could happen again.
California is not the only desert region with large and growing populations. Insane.
But the claim that “that this is GLOBAL warming, and that ON AVERAGE droughts either are or will soon be increasing” is impossible to prove or disprove. Average global temperature is hard enough to measure. Drought by region makes somewhat more sense, but predicting that is more in the realm of weather prediction than climate prediction. We might as well predict where the jet stream will be in 2100.
Cliff Mass says:
Take a look at the graph of those simulations.
https://cliffmass.blogspot.com/2019/12/a-dry-year-with-twist-and-few-major.html
None of those individual simulations show any trend, except maybe drought after 2090!
“We can see a few interesting things in this graph. As you might expect, the worst droughts were in the 1930s, the time of the “Dust Bowl”. There were also droughts in the 1950s, although somewhat smaller and shorter.”
____________________________________
Dust bowl: they shoot horses, don’t they.
https://www.google.com/search?q=dust+bowl+they+shoot+horses%2C+don%27t+they&oq=dust+bowl+they+shoot+horses%2C+don%27t+they+&aqs=chrome.
“We can see a few interesting things in this graph. As you might expect, the worst droughts were in the 1930s, the time of the “Dust Bowl”. There were also droughts in the 1950s, although somewhat smaller and shorter.”
____________________________________
Dust bowl: they shoot horses, don’t they.
https://www.google.com/search?q=dust+bowl+they+shoot+horses%2C+don%27t+they&oq=dust+bowl+they+shoot+horses%2C+don%27t+they+&aqs=chrome.
https://www.google.com/search?client=ms-android-huawei&sxsrf=ACYBGNRdDrdPHHzto-pasatbu9bbPWzNZQ%3A1578402623588&ei=P4MUXr-4I4eAk74Pl4-10A0&q=Dust+bowl+route+66&oq=Dust+bowl+route+66&gs_l=mobile-gws-wiz-serp.
https://www.google.com/search?q=dust+bowl+oakis+california+migration&oq=dust+bowl+oakis+California+&aqs=chrome.