Megadroughts and the Arizona Daily Star

In the Sunday edition of the Arizona Daily Star we were treated with a scare story about megadroughts titled, “S. Ariz. closer to an epic drought .” The sub-headline of the story by Tony Davis (seen only in the print edition) reads, “If emissions are unchecked, upper risk is 50%, study says.” Trouble is, the study itself, does not mention “emissions.”

The lead line of the story reads (my emphasis): “The odds of a potentially devastating Southwestern ‘megadrought’ due to human-caused climate change are as high as 50 percent in this century, a new study finds.” This lead line is contradicted by a line later in the story: Toby Ault, one of the study authors is quoted: “We’re not saying that what’s happening now (with drought) is because of climate change.” The study, itself, does not mention “human-cause” climate change.

It appears that the Star is fabricating data and promoting propaganda. You can read the full study here.

Just for the record, here is a scan of the Star headline and story beginning:

Star drought headline

The study “Assessing the risk of persistent drought using climate model simulations and paleoclimate data” is an exercise in statistical manipulation and computer modeling. It does imply that warming predicted by computer models could cause drought. But we have seen that computer models have failed spectacularly in prediction of temperature (see my article: Failure of climate models shows that carbon dioxide does not drive global temperature).

Here is what the study says:

“In the current generation of global climate models, the risk of a decade-scale drought occurring this century is at least 50% for most of the greater southwestern US and may indeed be closer to 80%… The probability of multidecadal megadrought is also high: the likelihood of a 35 year event is between 10% and 50% depending on how much climate change is realized during the coming century. The probability of even longer events (> 50 year, or “permanent” megadrought) is non-negligible (5-10%) for the most intense warming scenario.”

But:

“An obvious limitation of our work is that it is ‘blind’ to certain aspects of dynamically-driven changes in prolonged drought risk. For instance, changes in the magnitude, frequency, or teleconnection patterns of El Nino and La Nina (e.g., Coats et al. 2013) may alter the statistics of interannual variability in ways that are not captured by our simple models. Further, megadrought statistics over the last millennium may be forcing-dependent, as suggested by Cook et al. (2004), for instance, which shows that megadroughts were more common during the medieval climate era of 850-1200 CE. Another very serious limitation is imposed by the reliability of the models themselves to make realistic predictions of changes in climatological precipitation for the end of the 21st century.”

And:

“Our estimates of risk are consequently only as accurate as climate model projections of changes in precipitation.”

Has global warming caused any drought conditions in the western U.S.? Let’s look at the data of drought conditions since 1900:

Drought trend

 

Let’s take a longer perspective on drought:

Drought since 800AD

Is it still as scary as the Star alleges? The study authors are free to do their modeling and speculations. It seems to me, however, the Arizona Daily Star is making up data, perhaps to fit an agenda, and thereby doing a dis-service to readers.

“The greatest challenge facing mankind is the challenge of distinguishing reality from fantasy, truth from propaganda. Perceiving the truth has always been a challenge to mankind, but in the information age (or as I think of it, the disinformation age) it takes on a special urgency and importance.” Michael Crichton.

 

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