The response by NOAA’s Martin Hoerling to James Hansen’s recent op-ed does not reflect the scientific literature.
I’m traveling, so let me focus first on Hoerling’s incorrect statements — posted on this blog and Dot Earth — about drought. As readers know, the journal Nature asked me to write a Comment piece on the threat posed by drought after they read one of my posts examining the latest science on prolonged drought and “Dust-Bowlification.”
The research I did for that article — along with the comments of the expert reviewers I sent it to — is why I know Hoerling is quite wrong. Hoerling begins by quoting Hansen’s recent New York Times Op-Ed piece:
“Over the next several decades, the Western United States and the semi-arid region from North Dakota to Texas will develop semi-permanent drought, with rain, when it does come, occurring in extreme events with heavy flooding. Economic losses would be incalculable. More and more of the Midwest would be a dust bowl. California’s Central Valley could no longer be irrigated. Food prices would rise to unprecedented levels.”
Hoerling then asserts:
He doesn’t define “several decades,” but a reasonable assumption is that he refers to a period from today through mid-century. I am unaware of any projection for “semi-permanent” drought in this time frame over the expansive region of the Central Great Plains. He implies the drought will be due to a lack of rain (except for the brief, and ineffective downpours)….
But facts should, and do, matter to some. The vision of a Midwest Dustbowl is a scary one, and the author appears intent to instill fear rather than reason.
That’s a very serious attack on Hansen — if it were true. But it isn’t, and it should be retracted.
The fact is that the recent literature examining warming-driven drought in America could not be clearer in warning about a “semi-permanent” (or worse) drought in both the South West and the Central Great Plains and “More and more of the Midwest.” Here are two studies that lay things out starkly:
Aiguo Dai of the National Center for Atmospheric Research, “Drought under global warming: a review” (2010)
Michael Wehner et al., “Projections of Future Drought in the Continental United States and Mexico” (2011)
I would also add the 2010, Environmental Research Letters article “Characterizing changes in drought risk for the United States from climate change.”
And that’s not even counting the Journal of Geophysical Research study that Hansen himself co-authored in 1990, “Potential evapo transpiration and the likelihood of future drought,” which 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.
As an important aside, contrary to what Hoerling states, Hansen was not implying the drought will be due to lack of rain (by itself). Everyone seriously writing about warming-driven drought knows we are talking about a combination of factors, ones that I laid out in my Nature article:
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 temperature. 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.
Obviously, since Hansen coauthored an article titled, “Potential evapotranspiration and the likelihood of future drought,” we know he understands the drought conditions are driven by more than precipitation changes. The whole point of that 1990 paper was to examine the impact of warming-driven evaporation on soil moisture and drought.
It is quite surprising that Hoerling doesn’t appear to know the drought literature given that, as Revkin notes, he “runs an effort by the National Oceanic and Atmospheric Administration to assess the forces contributing to extreme weather events!”
Hoerling says it is reasonable to assume Hansen means “a period from today through mid-century.” Hansen says the “semi-permanent drought” will develop “over the next several decades.” That would clearly seem to mean that these conditions will evolve by just after mid-century, the 2050s and 2060s. This is also the first period of time where aggressive action to reduce emissions today could substantially change the projected climate.
Dai’s analysis does indeed project drought conditions over the Great Plains and Midwest. He is in the process of revising his analysis, but the figure below (which had been his 2030s projection in his original version) is a rough representation of where his analysis projects things will be in Hansen’s time frame for the U.S.
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
Of course, just because several models project this future doesn’t make it a certainty. As I note in the article, “drought models need to be improved. They successfully chart the hydrological changes seen in the US Southwest and the drying seen at the global level7, but regional predictions can be disturbingly variable.”
On the other hand, these models most certainly are not the worst-case scenario. Dai is modeling A1B (720 ppm), whereas we are on track for worse than that. A plausible worst-case scenario is here (and below): Royal Society Special Issue on Global Warming Details ‘Hellish Vision’ of 7°F (4°C) World — Which We May Face in the 2060s!
Hansen’s use of the term “Dust Bowl” is justified since that is the term widely used in the drought literature (see below). We are talking conditions that become as bad as the original Dust Bowl by mid-century and then get much, much worse for a long, long time. The Nature editors made repeated use of the term “Dust-Bowlification,” and I was particularly delighted that one of the leading experts in the field that I sent the piece to, Jonathan Overpeck, also liked the term.
Indeed, Hoerling’s critique is really only about whether the semi-permanent drought conditions will extend outside the U.S. SW to include most of Northern U.S. Great Plains. The literature is very clear that the Southwest is very likely headed for Dust Bowl conditions:
In 2007, Science(subs. req’d)published research that “predicted a permanent drought by 2050 throughout the Southwest” — levels of aridity comparable to the 1930s Dust Bowl would stretch from Kansas to California. And they were also only looking at a 720 ppm case.
In December 2008, the Bush Administration quietly released a US Geological Survey stunner: SW faces “permanent drying” by 2050, which 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.
NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe. This January 2009 PNAS paper finds
… the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop…. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450-600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the “dust bowl” era
So again, the ‘debate’ such as it is, is how far into the northern US Great Plains and Midwest these Dust Bowl conditions will extend — and that’s without even considering the impact of the increasingly early loss of the winter snowpack, which most of these studies don’t even model. Since the recent literature suggests the droughts will extend that far, Hansen’s warning is justified by the literature.
And Hansen’s use of the phrase “semi-permanent” is fully warranted. Given that the drought conditions just keep getting worse and worse as long as we keep warming – and are “largely irreversible for 1000 years” (according to a NOAA-led paper), “semi-permanent” seems like a rather mild word.
Bottom Line: Given how catastrophic it would be to the nation and the world if our breadbasket were indeed hit by these conditions, Hansen’s warning seems fully justified and Hoerling’s response does not.
Finally, it’s always worth repeating that much of human behavior and government policy is driven by the desire to avoid it worst-case scenarios, which is why we have fire insurance and catastrophic health insurance — and a military budget equal to that of the next 16 countries combined.
If we look at the plausible worst case for climate, we get both continuing high levels of emissions and high carbon-cycle feedbacks. That possibility was discussed in a Royal Society Special Issue on a 7°F (4°C) World, which notes “In such a 4°C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world.”
This would be the worst-case for the 2060s, but is in any case, close to business as usual for 2090s:
This is 13-18°F over most of U.S. and 27°F in the Arctic. The drought conditions that would be created by such warming over most of the central and western U.S. are beyond imagining.
And there is every reason to believe that the earth would just keep getting hotter and hotter:
Science stunner — On our current emissions path, CO2 levels in 2100 will hit levels last seen when the Earth was 29°F (16°C) hotter: Paleoclimate data suggests CO2 “may have at least twice the effect on global temperatures than currently projected by computer models”
Indeed, Steve Easterbrook’s post “A first glimpse at model results for the next IPCC assessment” shows that for the scenario where there is 9°F warming by 2100, you get another 7°F warming by 2300. Of course, folks that aren’t motivated to avoid the civilization-destroying 9°F by 2100 won’t be moved by whatever happens after that.
So if folks want to quibble about whether the semi-permanent Dust Bowl that the U.S. Southwest is headed to by mid-century might not spread to the northern U.S. Great Plains for, say, another few decades after that, well, I must say they are rearranging deck chairs on the Titanic.
Extreme Weather and Climate Change Understanding the Link, Managing the Risk
By Daniel G. Huber and Jay Gulledge, Ph.D.
Dated December 2011
Thousands of record-breaking weather events worldwide bolster long-term trends of increasing heat waves, heavy precipitation, droughts and wildfires. A combination of observed trends, theoretical understanding of the climate system, and numerical modeling demonstrates that global warming is increasing the risk of these types of events today. Debates about whether single events are “caused” by climate change are illogical, but individual events offer important lessons about society’s vulnerabilities to climate change. Reducing the future risk of extreme weather requires reducing greenhouse gas emissions and adapting to changes that are already unavoidable.
Box 1. Why can’t scientists say whether climate change “caused” a given weather event?
Typically, climate change is described in terms of average changes in temperature or precipitation, but most of the social and economic costs associated with climate change will result from shifts in the frequency and severity of extreme events. This fact is illustrated by a large number of costly weather disasters in 2010, which tied 2005 as the warmest year globally since 1880. Incidentally, both years were noted for exceptionally damaging weather events, such as Hurricane Katrina in 2005 and the deadly Russian heat wave in 2010. Other remarkable events of 2010 include Pakistan’s biggest flood, Canada’s warmest year, and Southwest Australia’s driest year. 2011 continued in similar form, with “biblical” flooding in Australia, the second hottest summer in U.S. history, devastating drought and wildfires in Texas, New Mexico and Arizona as well as historic flooding in North Dakota, the Lower Mississippi and in the Northeast.
Munich Re, the world’s largest reinsurance company, has compiled global disaster for 1980-2010. In its analysis, 2010 had the second-largest (after 2007) number of recorded natural disasters and the fifth-greatest economic losses. Although there were far more deaths from geological disasters—almost entirely from the Haiti earthquake—more than 90 percent of all disasters and 65 percent of associated economic damages were weather and climate related (i.e. high winds, flooding, heavy snowfall, heat waves, droughts, wildfires). In all, 874 weather and climate-related disasters resulted in 68,000 deaths and $99 billion in damages worldwide in 2010.
The fact that 2010 was one of the warmest years on record as well as one of the most disastrous, begs the question: Is global warming causing more extreme weather? The short and simple answer is yes, at least for heat waves and heavy precipitation. But much of the public discussion of this relationship obscures the link behind a misplaced focus on causation of individual weather events. The questions we ask of science are critical: When we ask whether climate change “caused” a particular event, we pose a fundamentally unanswerable question (see Box 1). This fallacy assures that we will often fail to draw connections between individual weather events and climate change, leading us to disregard the real risks of more extreme weather due to global warming.
Climate change is defined by changes in mean climate conditions—that is, the average of hundreds or thousands events over the span of decades. Over the past 30 years, for example, any single weather event could be omitted or added to the record without altering the long-term trend in weather extremes and the statistical relationship between that trend and the rise in global temperatures. Hence, it is illogical to debate the direct climatological link between a single event and the long-term rise in the global average surface temperature.
What about climate change and tornadoes?
Scientists are unsure if tornadoes will become stronger or more frequent, but with increased temperatures changing the weather in unexpected ways, the risk is real that tornado outbreaks will become more damaging in the future. The lack of certainty in the state of the science does not equate with a lack of risk, since risk is based on possibility. The lack of scientific consensus is a risk factor itself, and we must prepare for a future that could possibly include increased tornado damage.
Nonetheless, individual weather events offer important lessons about social and economic vulnerabilities to climate change. Dismissing an individual event as happenstance because scientists did not link it individually to climate change fosters a dangerously passive attitude toward rising climate risk. The uncertainty about future weather conditions and the illogic of attributing single events to global warming need not stand in the way of action to manage the rising risks associated with extreme weather. Indeed, such uncertainty is why risk managers exist – insurance companies, for example – and risk management is the correct framework for examining the link between global climate change and extreme weather.
An effective risk management framework accommodates uncertainty, takes advantage of learning opportunities to update understanding of risk, and probes today’s rare extreme events for useful information about how we should respond to rising risk. Risk management eschews futile attempts to forecast individual chaotic events and focuses on establishing long-term risk certainty; that is, an understanding of what types of risks are increasing and what can be done to minimize future damages. An understanding of the meaning of risk and how it relates to changes in the climate system is crucial to assessing vulnerability and planning for a future characterized by rising risk.
Food riots predicted over US crop failure
By Robert Kennedy
Date: 21 Aug 2012
Analysts say crippling drought in the US likely to trigger unrest in impoverished nations dependent on food imports.
Some scientists say the use of corn for biofuels is exacerbating the food crisis [Reuters]
The world is on the brink of a food "catastrophe" caused by the worst US drought in 50 years, and misguided government biofuel policy will exacerbate the perilous situation, scientists and activists warn.
When food prices spike and people go hungry, violence soon follows, they say. Riots caused by food shortages - similar to those of 2007-08 in countries like Bangladesh, Haiti, the Philippines and Burkina Faso among others - may be on the horizon, threatening social stability in impoverished nations that rely on US corn imports.
This summer's devastating drought has scorched much of the mid-western United States - the world's bread basket.
Crops such as corn, wheat, and soy have been decimated by high temperatures and little rain. Grain prices have skyrocketed and concerns abound the resulting higher food prices will hit the world's poor the hardest - sparking violent demonstrations.
Early dryness in Russia's wheat growing season, light monsoon rains in India, and drought in Africa's Sahel region, combined with America's lost crop, mean a perfect storm is on the horizon.
Surging food prices could kick off food riots similar to those in 2008 and 2010, Professor Yaneer Bar-Yam, president of the New England Complex Systems Institute, told Al Jazeera.
"Recent droughts in the mid-western United States threaten to cause global catastrophe," said Bar-Yam, whose institute uses computer models to identify global trends.
Hopes were high in May of a bumper corn crop this year, but sizzling temperatures in June and July scuttled those predictions. US corn yields are now expected to be the lowest in 17 years.
The United States accounted for 39 per cent of global trade in corn in 2011-12. Stockpiles are now down 48 per cent, according to the US Department of Agriculture. Corn prices have shot up 60 per cent since June 15.
Corn is a primary staple in Sub-Saharan Africa, and in much of Central and South America. In South Africa, the cost of maize has increased about 40 per cent in the last year, even before the US drought struck.
Bar-Yam highlighted the food riots of 2007-08 and 2010-11 that were fuelled by sudden and dramatic spikes in food prices. He said his institute recently entered data from the US drought into its computer model, which predicted the outbreak of food-related unrest "in a short period of time".
"When people are unable to feed themselves and their families, widespread social disruption occurs," Bar-Yam said. "We are on the verge of another crisis, the third in five years, and likely to be the worst yet, capable of causing new food riots and turmoil on a par with the Arab Spring."
Fighting for food
While Americans and other Westerners will largely escape the financial pain spawned by the drought, impoverished people around the globe won't be so fortunate.
People in wealthy industrialised countries spend between 10 to 20 per cent of their income on food. Those in the developing world pay up to 80 per cent. According to Oxfam, a one per cent jump in the price of food results in 16 million more people crashing into poverty.
More than 60 food riots occurred worldwide between 2007 and 2009, when rapidly rising commodity prices wreaked havoc on family budgets.
The world is not yet in a food crisis, said David Hallam, the UN Food and Agriculture Organisation's director of trade and markets.
"We're a long way from that … Some of the elements that we saw in 2007-08 are very much missing at the moment", Hallam told Reuters. He said wheat stocks were currently stable, and a bumper rice crop was still expected later this year.
But he added: "We are in a very vulnerable situation in markets, and any further supply-side shocks or any disruptive policy actions that individual countries might take could add further to the problems we have and create turmoil in markets."
Hallam said wheat production in Russia was a wildcard in the food-crisis equation. Russian wheat crop yields look lower than expected, but just how much lower is the major question, he explained.
Export bans and panicked-buying by governments would only compound the problem, said Hallam.
The International Food Policy Research Institute - a Washington- based organisation that monitors food prices - warned last week a global crisis could "hit us very soon".
Director-General Shenggen Fan said using corn for ethanol in automobiles needed to be halted. "That actually pushed global food prices higher and many poor people, particularly women and children, have suffered," Fan told Bloomberg.
The folly of food for fuel
The United States uses about 13 per cent of global corn production for biofuels. About 37 per cent of this year's corn crop is earmarked for ethanol production.
The biofuels industry says it has helped combat climate change and reduced American reliance on foreign oil, lowering its dependence on imported oil from 60 per cent to 45 per cent since 2007.
Industry group Growth Energy challenged those who "tie biofuel production to alleged increased food prices". CEO Tom Buis blamed high oil prices and "Mother Nature".
But many question whether using corn to fuel vehicles is justified with food prices rising. "Given the possibility of price-driven famines, burning corn for cars is unconscionable," Professor Bar-Yam said.
Robert Bryce, author of Power Hungry: The Myths of "Green" Energy and the Real Fuels of the Future, agrees, adding ethanol as a fuel is grossly inefficient.
"There should be an immediate, global, prohibition placed on the use of food crops for fuel production," said Bryce.