Category Archives: Environment

Southwest U.S. megadroughts loom as earth warns

Maps of megadrought risk for the American Southwest under different levels of warming, and the required increase in precipitation to compensate for that warming. From the study [see below].

Maps of megadrought risk for the American Southwest under different levels of warming, and the required increase in precipitation to compensate for that warming. From the study [see below].

It’s the nightmare everyone should fear, and it’s almost inevitable.

From Cornell University:

As a consequence of a warming Earth, the risk of a megadrought – one that lasts more than 35 years – in the American Southwest likely will rise from a low chance over the past thousand years to a 20 to 50 percent chance in this century. However, by slashing greenhouse gas emissions, these risks are nearly cut in half, according to a Cornell-led study in Science Advances, Oct. 5.

“Megadroughts are rare events, occurring only once or twice each millennium. In earlier work, we showed that climate change boosts the chances of a megadrought, but in this paper we investigated how cutting fossil fuel emissions reduces this risk,” said lead author Toby Ault, Cornell professor of earth and atmospheric science.

If climate change goes unabated – and causes more than a 2 degree Celsius increase in atmospheric temperature – megadroughts will become very probable, Ault said.

“The increase in risk is not due to any particular change in the dynamic circulation of the atmosphere,” Ault said. “It’s because the projected increase in atmospheric demand for moisture from the land surface will shift the soil moisture balance. If this happens, megadroughts will be far more likely for next millennium.”

Ault explained a natural “tug-of-war” governing the surface moisture balance between the precipitation supply (rain) and evaporation (transpiration). But he cautions that increases in average regional temperatures could be so dramatic – more than 4 degrees Celsius (7.2 degrees Fahrenheit) – that evaporation wins out. This, in turn, dries out the land surface and makes megadroughts 70 to 99 percent likely.

“We found that megadrought risk depends strongly on temperature, which is somewhat good news,” Ault said. “This means that an aggressive strategy for cutting greenhouse gas emissions could keep regional temperature changes from going beyond about 2 degrees Celsius (3.6 degrees Fahrenheit).”

This lower average warming figure cuts the megadrought risk almost in half, he said.

These tug-of-war scenarios could very well play out in the American Southwest, according to tree ring and geologic records. During sequences of exceptionally dry years, those rings tend to be relatively narrower than in wet years, he said.

“Tree rings from the American Southwest provides evidence of megadroughts, as there are multiple decades when growth is suppressed by dry conditions,” Ault said, pointing to several megadroughts that occurred in North America between 1300 and 1100 B.C.

“We also know they have occurred in other parts of the world, and they have been linked to the demise of several pre-industrial civilizations,” he said.

The tug-of-war between moisture supply and demand might play out differently in other parts of the world, Ault said.

“Nonetheless, even in the Southwest we found examples of plausible 21st-century climates where precipitation increases, but megadroughts still become more likely,” said Ault, who noted the normally verdant Northeast is in the middle of drought. “This should serve as a cautionary note for areas like the Northeast expecting to see a more-average moisture supply.

“Megadrought risks are still likely to be higher in the future than they were in the past,” he said. “Hence, efficient use of water resources in the drought-stricken American Southwest are likely to help that region thrive during a changing climate.”

On the paper, “Relative Impacts of Mitigation, Temperature, and Precipitation on 21st-Century Megadrought Risk in the American Southwest [open access],” Ault is joined by Justin S. Mankin and Benjamin Cook, both of the NASA Goddard Institute for Space Studies, and Jason E. Smerdon of Columbia University. The National Science Foundation supported this research.

Big Agra African land grabs raise risk of violence

Regions of Africa where the relative availability of fresh water, as calculated by the Blue Water Index [BWI] threatens violence as the competition got fresh water between smallholders and giant foreign-owned farms intensifies.

Regions of Africa where the relative availability of fresh water, as calculated by the Blue Water Index [BWI] threatens violence as the competition got fresh water between smallholders and giant foreign-owned farms intensifies.

We’ve long been concerned about the increasing share of African farmlands, once owned in common by the people who farm them, being sold to foreign agricultural giants by cash-strapped African governments.

One of our deepest concerns has been the power of those corporations, largely own by Chinese and European multinationals, to gain control over the continent’s water supplies, raising the risk of starvation and violence for the planet’s poorest continent.

And now comes a study confirming our suspicions and revealing just where the risks of conflict are greatest.

From Sweden’s Lund University:

For the first time, researchers point to areas in Africa where foreign agricultural companies’ choice of crops and management of fresh water are partly responsible for the increased water shortages and greater competition for water. This in turn increases the risk of outright conflicts between all those who need water – plants, animals and humans.

During the 21st century, foreign companies have leased large tracts of land in Africa – more so than in other parts of the world – in order to produce cheap food, cheap timber and cheap raw material for biofuels. An interdisciplinary study from Lund University in Sweden shows that about three per cent of the land leased in Africa by foreign companies has been registered as currently in production, for the purpose of growing crops. For various reasons, the companies have either pulled out or not started producing on other leased land.

The study also shows that the crops that foreign investors decide to grow often require more water than the traditionally grown crops. Furthermore, it shows that the same crop can have very different needs for water, depending on the climate where it is grown and which irrigation systems the companies use.

The researchers in Lund, together with a colleague in France, have developed a model that shows how much water is needed for different production systems, in different types of climates, in different parts of the continent. The model takes into account both the size of the land and the type of irrigation system.

This model has enabled researchers to distinguish between areas where rainwater accounts for the largest share of irrigation water, and areas where large foreign agricultural companies satisfy more than half of their water needs by using fresh water sources, such as groundwater, rivers and ponds. This has allowed the researchers to highlight the areas around the continent where increased competition for water escalates the risk of water-related conflicts between different sectors and ecosystems.

“These hotspots have not been identified in this way before. Previous studies have often focused on the size of the area and not on how much fresh water is used to grow the demanding crops that foreign companies are interested in”, says physical geographer Emma Li Johansson, who was in charge of the study.

The leases are often written for periods of 33 to 99 years. The contracts rarely include any rules or limits concerning the use of water.

“Our research can perhaps lead to foreign investors showing greater consideration for how much water is necessary, in relation to how much water is actually available. Hopefully, the results can serve as a basis for documents that regulate the water consumption of large-scale farming companies”, says Emma Li Johansson.

The results are published in an article in the scientific journal PNAS.

Download article: Johansson E L et al (2016) Green and blue water demand from large-scale land acquisitions in Africa. PNAS (open access).

Massive ecosystem collapse hits San Francisco Bay

And the cause is the human hunger for water.

From an ominous report in the San Francisco Chronicle:

Evidence of what scientists are calling the planet’s Sixth Mass Extinction is appearing in San Francisco Bay and its estuary, the largest on the Pacific Coast of North and South America, according to a major new study.

So little water is flowing from the rivers that feed the estuary, which includes the Sacramento-San Joaquin River Delta, Suisun Marsh and the bay, that its ecosystem is collapsing, scientists who conducted the study say.

Human extraction of water from the rivers is not only pushing the delta smelt toward extinction, they say, but also threatening dozens more fish species and many birds and marine mammals, including orca whales, that depend on the estuary’s complex food web.

The findings by scientists at the Bay Institute, an environmental group, underline conclusions already reached by state regulators and are intended to buttress the environmental case for potentially drastic water restrictions in San Francisco and other parts of the Bay Area, and among farmers in the northern San Joaquin Valley.

From the report itself, a graphic revelation [the white line is a reproduction artifact — esnl]:


Key findings summarized

From the Bay Institute website, a summary of significant findings:

The report’s major findings include:

  • On average, since 1975 more than half (53%) of runoff from the Central Valley watershed has been diverted, stored, or exported before it can reach the Bay – and in many years two-thirds or more of the Bay’s inflow is captured;
  • As a result of intensive water diversions, the Bay experiences catastrophically dry years almost half the time (only one “supercritically dry” year occurred naturally between 1975-2014, but the Bay experienced nineteen supercritical years during that period);
  • Numerous unrelated fish species – from sharks to salmon, from sturgeon to smelt – show strong positive correlations with Bay Inflow; many of these species are now endangered, and even commercially viable fisheries are in decline;
  • Predators that feed on flow-dependent fish and shrimp are feeling the pinch – for example, dwindling supplies of Central Valley Chinook salmon may restrict the recovery of the local Orca whale population;
  • Blooms of toxic “algae” (cyanobacteria) are becoming more frequent, and other pollutants are becoming more concentrated, as a result of reductions in freshwater flows from the Bay’s watershed;
  • Bay Area beaches and tidal wetlands are deprived of sediment that was once transported by high river flows.

Quote of the day: A rapid death spiral in the Arctic

From Peter Wadhams, Cambridge University professor emeritus of ocean physics, writing at Yale Environment 360:

The news last week that summer ice covering the Arctic Ocean was tied for the second-lowest extent on record is a sobering reminder that the planet is swiftly heading toward a largely ice-free Arctic in the warmer months, possibly as early as 2020.

After that, we can expect the ice-free period in the Arctic basin to expand to three to four months a year, and eventually to five months or more.

Since my days measuring the thickness of Arctic Ocean ice from British nuclear submarines in the early 1970s, I have witnessed a stunning decline in the sea ice covering the northern polar regions — a more than 50 percent drop in extent in summer, and an even steeper reduction in ice volume. Just a few decades ago, ice 10 to 12 feet thick covered the North Pole, with sub-surface ice ridges in some parts of the Arctic extending down to 150 feet. Now, that ice is long gone, while the total volume of Arctic sea ice in late summer has declined, according to two estimates, by 75 percent in half a century.

The great white cap that once covered the top of the world is now turning blue — a change that represents humanity’s most dramatic step in reshaping the face of our planet. And with the steady disappearance of the polar ice cover, we are losing a vast air conditioning system that has helped regulate and stabilize earth’s climate system for thousands of years.

Few people understand that the Arctic sea ice “death spiral” represents more than just a major ecological upheaval in the world’s Far North. The decline of Arctic sea ice also has profound global climatic effects, or feedbacks, that are already intensifying global warming and have the potential to destabilize the climate system. Indeed, we are not far from the moment when the feedbacks themselves will be driving the change every bit as much as our continuing emission of billions of tons of carbon dioxide annually.

New-found seismic fault raises California concerns


Just what California needs. . .another earthquake fault,, this one located parallel to the great San Andreas Fault, the sourrce of the Golden State’s most powerful shakers.

From the University of California, San Diego:

A swarm of nearly 200 small earthquakes that shook Southern California residents in the Salton Sea area last week raised concerns they might trigger a larger earthquake on the southern San Andreas Fault. At the same time, scientists from Scripps Institution of Oceanography at the University of California, San Diego and the Nevada Seismological Laboratory at the University of Nevada, Reno published their recent discovery of a potentially significant fault that lies along the eastern edge of the Salton Sea.

The presence of the newly mapped Salton Trough Fault, which runs parallel to the San Andreas Fault, could impact current seismic hazard models in the earthquake-prone region that includes the greater Los Angeles area. Mapping of earthquake faults provides important information for earthquake rupture and ground-shaking models, which helps protect lives and reduce property loss from these natural hazards.

The National Science Foundation (NSF)-funded study appears in the Oct. 2016 issue of the journal Bulletin of the Seismological Society of America [$15 for one-day access].

“To aid in accurately assessing seismic hazard and reducing risk in a tectonically active region, it is crucial to correctly identify and locate faults before earthquakes happen,” said Valerie Sahakian, a Scripps alumna, and lead author of the study.

The research team used a suite of instruments, including multi-channel seismic data, ocean-bottom seismometers, and light detection and ranging, or lidar, to precisely map the deformation within the various sediment layers in and around the sea’s bottom. They imaged the newly identified strike-slip fault within the Salton Sea, just west of the San Andreas Fault.

“The location of the fault in the eastern Salton Sea has made imaging it difficult and there is no associated small seismic events, which is why the fault was not detected earlier,” said Scripps geologist Neal Driscoll, the lead principal investigator of the NSF-funded project, and coauthor of the study. “We employed marine seismic equipment to define the deformation patterns beneath the sea that constrained the location of the fault.”

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Map of the day: Global air pollution levels

From the World Health Organization, a look at the state of Mother Earth’s air, revealing where the atmosphere has the highest concentrations of suspended particulate matter:


DroughtWatch: This is getting monotonous

Yet another week passes and still California’s drought picture doesn’t change, with all of the Golden State involved in one level or another of the dry spell that’s last for more than four years.

From the United States Drought Monitor: