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:
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”):
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.