Defining the Geopolitics of a Thirsty WorldSM
The Next Dust Bowl

Two interesting articles on threat of a coming Dust-Bowlification from Think Progress.

The first reflects on a recent IPCC study that – according to Joseph Romm – hints at Dust-Bowlification, but is mostly silent on global warming’s most grave threat to humanity -  food production:

A USA Today (not IPCC) chart emphasizes the risk of drought in heavily populated areas.

The IPCC Special Report “Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX)” is now online.  I had seen the previous draft and the changes to it, so I knew that it was a big missed opportunity, as I explained here.

Even so, since the media hasn’t been spending much time connecting the dots between extreme weather and climate change, the report has garnered some headlines:

There is definitely some good material in the report (I’ll do a separate post on that).  We should all appreciate the hard work that a great many scientists put into this report.  I’ve been highly supportive of IPCC scientists over the years, pushing back against the attacks by the deniers and confusionists — even as I have been critical of the IPCC process that tends to water down even the most obvious conclusions.

For instance, the report states:

It is virtually certain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in cold extremes will occur in the 21st century on the global scale. It is very likely that the length, frequency and/or intensity of warm spells, or heat waves, will increase over most land areas.

Virtually certain means “99-100% probability” while very likely means “90-100% probability.”  Is there really as much as a 10% chance that the length, frequency and/or intensity of warm spells, or heat waves, will NOT increase over most land areas over the next 90 years?

Then we have this line:

It is very likely that mean sea level rise will contribute to upward trends in extreme coastal high water levels in the future.

C’mon guys and gals.  You couldn’t put a “virtually certain” on that?  Note that the sentence is already hedged with “will contribute” and “upward trends” and even the vague “in the future.”  Precisely how could mean sea level rise — even sticking with the lowball estimate from the 2007 report — have as much as a 10% chance of NOT contributing toward an upwards trend in extreme coastal high level waters sometime in the future.

So you can see the effect of the IPCC process that waters down even the most innocuous conclusions.  And by the way, since this is a 2011 report, it ought to base such statements on the recent literature of sea level rise, which is considerably higher than the 2007 estimate (see the discussion in “Scientists withdraw low-ball estimate of sea level rise“).

My biggest problem with the report remains the short shrift it gives to the vast literature on drought that I reviewed in my recent Nature article.  As I wrote, “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.”

You can see from the chart above that USA Today (and Jeff Masters, who helped put it together) figured out that drought may be the biggest extreme weather danger in that it affects 5 heavily populated areas.

Reuters, in its story, states what should be obvious:

Droughts, perhaps the biggest worry for a world with a surging population to feed, were also expected to worsen.

The 29-page report itself has quite little on droughts, and the word “agriculture” appears only once in the main text, but it does have this blockbuster chart:

Figure SPM.5: Projected annual changes in dryness….  Changes in soil moisture (soil moisture anomalies, SMA). Increased dryness is indicated with yellow to red colors; decreased dryness with green to blue. Projected changes are expressed in units of standard deviation of the interannual variability in the three 20-year periods 1980-1999, 2046-2065 and 2081-2100. The figures show changes for two time horizons, 2046-2065 and 2081-2100, as compared to late-20th-century values (1980–1999), based on GCM [Global Climate Models] simulations under emissions scenario SRES A2 relative to corresponding simulations for the late-20th-century. Results are based on 17 (CDD) and 15 (SMA) GCMs contributing to the CMIP3. Colored shading is applied for areas where at least 66% (12 out of 17 for CDD, 10 out of 15 for SMA) of the models agree in the sign of the change; stippling is added for regions where at least 90% (16 out of 17 for CDD, 14 out of 15 for SMA) of all models agree in the sign of the change….

We can’t tell exactly how serious this is since they aren’t using a standard metric, like, say, the Palmer Drought Severity Index, and since the full report won’t be out until February!

But those large red patches around the global look pretty worrisome since they are where a great many people live and where a considerable amount of arable land is.  Indeed, the United States breadbasket looks to be headed for some very serious soil moisture drying in the second half the of the century if we stay anywhere near our current emissions path.

The IPCC has but one paragraph on this (plus the chart and a table):

There is medium confidence that droughts will intensify in the 21st century in some seasons and areas, due to reduced precipitation and/or increased evapotranspiration. This applies to regions including southern Europe and the Mediterranean region, central Europe, central North America, Central America and Mexico, northeast Brazil, and southern Africa. Elsewhere there is overall low confidence because of inconsistent projections of drought changes (dependent both on model and dryness index). Definitional issues, lack of observational data, and the inability of models to include all the factors that influence droughts preclude stronger confidence than medium in drought projections. See Figure SPM.5. [3.5.1, Table 3.3, Box 3.3]

The Table simply focuses on “Droughts in the context of food security in West Africa,” which is certainly important subject but only one of many, many areas around the world threatened by every-worsening droughts.

You would never know from this summary report that there is in fact a large literature just on the drying projected for the U.S. Southwest (which I reviewed here).  Heck, 3 years ago, the Bush Administration (!) released a US Geological Survey report that found:

The serious hydrological changes and impacts known to have occurred in both historic and prehistoric times over North America reflect large-scale changes in the climate system that can develop in a matter of years and, in the case of the more severe past megadroughts, persist for decades. Such hydrological changes fit the definition of abrupt change because they occur faster than the time scales needed for human and natural systems to adapt, leading to substantial disruptions in those systems. In the Southwest, for example, the models project a permanent drying by the mid-21st century that reaches the level of aridity seen in historical droughts, and a quarter of the projections may reach this level of aridity much earlier.

And there have been another half a dozen major studies covering the SW since then.

So yes the report was a missed opportunity to review this literature and highlight the  very real threat to food security.  The most comprehensive published literature review to date remains the must-read study from the National Center for Atmospheric Research, “Drought under global warming: a review,” which I discussed here.

The second presents Mr. Romm’s own thoughts on the threat of drought and its impact on food supplies:

The journal Nature asked me to write a Comment piece after they read one of my posts on prolonged drought and “Dust-Bowlification.”  The article is here (subs. req’d).

This is my first piece ever in the journal itself.  I did have an online piece, “Nature publishes my climate analysis and solution.”  This is not a peer-reviewed article but rather a “Comment” piece.

I sent it to five of the world’s leading authorities on climate change and drought and the hydrological cycle:  Kevin Trenberth, Aiguo Dai, Michael Mann, Peter Gleick and Jonathan Overpeck.  I endeavored to incorporate their comments, but unfortunately Nature has a 10-reference limit for their Comment pieces so I wasn’t able to include as many references as they suggested or as I would have liked.  I will probably do a later piece with more references.  If you want links to most of the articles I refer to, go here.

I was particularly delighted that Overpeck liked the term “Dust-Bowlification.”  He really was an inspiration for me to begin studying this topic many years ago when I saw a 2005 presentation of his, “Warm climate abrupt change–paleo-perspectives,” that concluded “climate change seldom occurs gradually” (see The “global-change-type drought” and the future of extreme weather).

I am equally delighted Nature has basically endorsed this term through its multiple appearances in this article and felt that the overall issue warranted more attention.

I do not believe that most Americans — and that includes most policymakers and the media — understand the convergence of the recent scientific literature on the extreme threat posed directly to this country of Dust-Bowlification.

During the last Dust Bowl era, hundreds of thousands of American families fled the impacted regions. Now, those same type of arid conditions could stretch all the way from Kansas to California within the next forty years.  America’s financial future and the health and safety of our people are at serious risk if greenhouse gas pollution is not brought under control.  The food security of all of humanity is at risk. Denial is simply not an option, the time for action is now.

Here are some key excerpts:

CLICK HERE TO READ MORE OR COMMENT

Which impact of anthropogenic global warming will harm the most people in the coming decades? I believe that the answer is extended or permanent drought over large parts of currently habitable or arable land — a drastic change in climate that will threaten food security and may be irreversible over centuries.

A basic prediction of climate science is that many parts of the world will experience longer and deeper droughts, thanks to the synergistic effects of drying, warming and the melting of snow and ice.

Precipitation patterns are expected to shift, expanding the dry subtropics. What precipitation there is will probably come in extreme deluges, resulting in runoff rather than drought alleviation. Warming causes greater evaporation and, once the ground is dry, the Sun’s energy goes into baking the soil, leading to a further increase in air temp- erature. That is why, for instance, so many temperature records were set for the United States in the 1930s Dust Bowl; and why, in 2011, drought-stricken Texas saw the hottest summer ever recorded for a US state. Finally, many regions are expected to see earlier snowmelt, so less water will be stored on mountain tops for the summer dry season. Added to natural climatic variation, such as the El Niño–La Niña cycle, these factors will intensify seasonal or decade-long droughts. Although the models don’t all agree on the specifics, the overall drying trends are clear.

I used to call the confluence of these processes ‘desertification’ on my blog, ClimateProgress.org, until some readers pointed out that many deserts are high in biodiversity, which isn’t where we’re heading. ‘Dust- bowlification’ is perhaps a more accurate and vivid term, particularly for Americans — many of whom still believe that climate change will only affect far-away places in far-distant times.

Prolonged drought will strike around the globe, but it is surprising to many that it would hit the US heartland so strongly and so soon.

The coming droughts ought to be a major driver — if not the major driver — of climate policies. Yet few policy-makers and journalists seem to be aware of dust-bowlification and its potentially devastating impact on food security. That’s partly understandable, because much of the key research cited in this article post-dates the 2007 Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Raising public awareness of, and scientific focus on, the likelihood of severe effects of drought is the first step in prompting action.

I first heard of the risks in a 2005 talk by climatologist Jonathan Overpeck of the Uni- versity of Arizona in Tucson. He pointed to emerging evidence that temperature and annual precipitation were heading in oppo- site directions over many regions and raised the question of whether we are at the “dawn of the super-interglacial drought”.

The idea wasn’t new. As far back as 1990, scientists at NASA’s Goddard Institute for Space Studies in New York projected that severe to extreme drought in the United States, then occurring every 20 years or so, could become an every-other-year phenom- enon by mid-century.

Events are starting to bear out these worrying predictions. Snowpack reduction, early snowmelt and a decrease in dry-season river flow in the American West, forecast more than two decades ago, have now been measured. In much of the northern Rockies, the peak of the annual stream runoff is up to three or four weeks earlier than it was half a century ago.  Heat and drought — coupled with the greater impact of destruc- tive species, such as bark beetles, aided by warming — have increased forest die-off and the risk of wildfire.

The palaeoclimate record dating back to the medieval period reveals droughts lasting many decades. But the extreme droughts that the United States faces this century will be far hotter than the worst of those: recent decades have been warmer than the driest decade of the worst drought in the past 1,200 years.

And much warmer conditions are pro- jected. According to a 2009 report of the US Global Change Research Program, warming over mid-latitude land masses, such as the continental United States, is predicted to be higher than the forecast average global warming: much of the inland United States faces a rise of between 5 °C and 6 °C on the current emissions path (that is, ‘business as usual’) by the century’s end, with a substantial fraction of that warming occurring by mid-century.

A 2007 analysis of 19 climate projections estimated that levels of aridity comparable to those in the Dust Bowl could stretch from Kansas to California by mid-century. To make matters worse, the regions at risk of reduced water supply, such as Nevada, have seen a massive population boom in the past decade. Overuse of water in these areas has long been rife, depleting groundwater stores.

Of course, the United States is not alone in facing such problems. Since 1950, the global percentage of dry areas has increased by about 1.74% of global land area per decade. Recent studies have projected ‘extreme drought’ conditions by mid-century over some of the most populated areas on Earth—southern Europe, south-east Asia, Brazil, the US Southwest, and large parts of Australia and Africa. These dust-bowl conditions are projected to worsen for many decades and be “largely irreversible for 1,000 years after emissions stopped”….

In the past six years, the Amazon has seen two droughts of the sort expected once in 100 years, each of which may have released as much carbon dioxide from vegetation die-off as the United States emits from fossil-fuel combustion in a year. More frequent wildfires also threaten to increase carbon emissions.

The key worry, as Climate Progress has spelled out this year, is food insecurity — how will we feed the world and where will people live if their land turns to dust:

Most pressingly, what will happen to global food security if dust-bowl conditions become the norm for both food-importing and food- exporting countries? Extreme, widespread droughts will be happening at the same time as sea level rise and salt-water intrusion threaten some of the richest agricultural deltas in the world, such as those of the Nile and the Ganges. Meanwhile, ocean acidification, warming and overfishing may severely deplete the food available from the sea….

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. We need to plan how the world will deal with drought-spurred migrations (see page 447) and steadily growing areas of non- arable land in the heart of densely populated countries and global bread-baskets. 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.

These predictions are not worst-case scenarios: they assume business-as-usual greenhouse-gas emissions. We can hope that the models are too pessimistic, but some changes, such as the expansion of the subtrop- ics, already seem to be occurring faster than models have projected10. We clearly need to pursue the most aggressive greenhouse-gas mitigation policies promptly, and put dust-bowlification atop the world agenda.

That’s how the piece ended.

What does the future look like?  Dai laid it out in a 2010 study from the National Center for Atmospheric Research, “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”):

drought map 3 2060-2069

The PDSI [Palmer Drought Severity Index] in the Great Plains during the Dust Bowl apparently spiked very briefly to -6, but otherwise rarely exceeded -3 for the decade (see here).

The large-scale pattern shown in Figure 11 [of which the figure above is 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 National Center for Atmospheric Research 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 A1F1 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.

The time to act is now.



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