Brutal Droughts, Worsened By Global Warming, Threaten Food Production Around The World

Severe drought (or Dust-Bowlification) “is the most pressing problem caused by climate change.” As I wrote in the journal Nature last year, “Feeding some 9 billion people by mid-century in the face of a rapidly worsening climate may well be the greatest challenge the human race has ever faced.”

As far back as 1990, NASA scientists projected that severe to extreme drought in the United States, then occurring every 20 years or so, could become an every-other-year phenomenon by mid-century if temperatures kept rising. They did.

In fact, a major 2011 NOAA report concluded, human-caused climate change is already a major factor in more frequent Mediterranean droughts.

A comprehensive 2011 study of drought, by Aiguo Dai of the National Center for Atmospheric Research, looked at “Characteristics and trends in various forms of the Palmer Drought Severity Index during 1900–2008.” The PDSI is “the most prominent index of meteorological drought” used in the U.S. That study concluded:

All the four forms of the PDSI show widespread drying over Africa, East andSouth Asia, and other areas from 1950 to 2008, and most of this drying is due to recent warming. The global percentage of dry areas has increased by about 1.74% (of global land area) per decade from 1950 to 2008….

Thus, I believe that our main conclusion is robust that recent warming has caused widespread drying over land. And model predictions suggest that this drying is likely to become more severe in the coming decades.

A look at the headlines and ledes from just the last month make clear that drought is slamming the world right now:

And last week I reposted this story, “Syria: Climate Change, Drought and Social Unrest.”

While the Texas drought has gotten much of the attention in this country, what has happened in Mexico is equally devastating. Since Mexico is projected to suffer even worse warming-driven Dust-Bowlification in the coming decades — and that will certainly have consequences for the United States — it’s worth looking in a little more depth at what’s happening to our neighbor to the south:

The severe drought affecting 22 of Mexico’s 32 states has caused a 40 percent drop in agricultural production, opening the way for food shortages over the next few months, the National Peasants Confederation, or CNC, said….

The drought has ravaged Indian communities, destroying crops and forcing thousands of peasants to leave their ancestral lands and head to the cities.

“As of last November, corn production was at barely 42 percent of the volume projected for 2011, and bean production was only 41 percent,” CNC president Gerardo Sanchez said.

Corn and beans are staples in the Mexican diet and shortages could lead to speculation, sending the prices of these commodities soaring, the CNC said.

“Of the 4.2 million people who fell into food poverty from 2008 to 2010, nearly 75 percent (about 3 million)” live in rural areas, the CNC said.

That was the Latin American Herald Tribune. Here’s the AP from December:

North Mexico Drought Worst On Record

DURANGO, Mexico (AP) — The sun-baked northern states of Mexico are suffering under the worst drought since the government began recording rainfall 70 years ago. Crops of corn, beans and oats are withering in the fields. About 1.7 million cattle have died of starvation and thirst….

Mexican farmers have lost 2.2 million acres (900,000 hectares) of crops to dry conditions and 1.7 million farm animals have died this year from lack of water or forage, according to the nation’s Agriculture Department.

You can listen to the NPR story, “Drought Ravages Farms Across Wide Swath Of Mexico.” That story writes about “the central Mexican state of Zacatecas”:

This is an arid part of Mexico, but normally there’s a rainy season between June and September, allowing farmers to grow crops during the summer. They also tend cattle on the scrubby rolling hills dotted with cactuses.

Rodarte has lived here all his life and says this is the worst drought he’s ever seen.

“Now most people are leaving,” he says, “to the cities, the coasts where it rains, or to the United States. That’s where the people are going to work. And those who are abroad in the U.S. are the ones who are sustaining the families here. They send us a little bit of money.”

That is the classic “adaptation” strategy to prolong drought. As I wrote in the journal Nature:

Human adaptation to prolonged, extreme drought is difficult or impossible. Historically, the primary adaptation to dust-bowlification has been abandonment; the very word ‘desert’ comes from the Latin desertum for ‘an abandoned place’. During the relatively short-lived US Dust-Bowl era, hundreds of thousands of families fled the region.

So yes we should care about drought in Mexico and around the world — especially since these kind of droughts will almost certainly get worse and more frequent in the coming decades if we keep taking no action.


What does the future look like? Dai laid it out in a 2010 NCAR study, “Drought under global warming: a review,” the best review and analysis on the subject I’ve seen — see the figure below (click to enlarge, “a reading of -4 or below is considered extreme drought”):

The figure [click to enlarge] charts the PDSI where “a reading of -4 or below is considered extreme drought.” The PDSI in the Great Plains during the Dust Bowl spiked very briefly to -6, but otherwise rarely exceeded -3 for the decade (see here).

And it keeps getting worse — assuming we are so unpragmatic that we don’t start cutting emissions ASAP [click to enlarge]:

If we allow this to come to pass it would mean large parts of the currently habited and arable land of the planet would be all but uninhabitable and virtually impossible to farm. Dai explains:

The large-scale pattern shown in Figure 11 [of which the figures above are part] appears to be a robust response to increased GHGs. This is very alarming because if the drying is anything resembling Figure 11, a very large population will be severely affected in the coming decades over the whole United States, southern Europe, Southeast Asia, Brazil, Chile, Australia, and most of Africa.

The study notes “By the end of the century, many populated areas, including parts of the United States, could face readings in the range of -8 to -10, and much of the Mediterranean could fall to -15 to -20. Such readings would be almost unprecedented.”


For the record, the NCAR study merely models the IPCC’s “moderate” A1B scenario — atmospheric concentrations of CO2 around 520 ppm in 2050 and 700 in 2100. We’re currently on the A1FI pathway, which would takes us to 1000 ppm by century’s end, but I’m sure with an aggressive program of energy R&D we could keep that to, say 900 ppm.

It’s worth noting that the scientific literature says this could last a long, long time (see NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe).

The time to act is now.

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