Emergent patterns in nature and society

Posts tagged “disturbance frequency

Climate change and conflict – violence

It’s becoming a trendy topic, the connection between future climate scenarios and conflict, violence and terrorism. Some quotes from The Guardian – Climate change will increase threat of war, Chris Huhne [UK climate secretary] to warn:

“Climate change is a threat multiplier. It will make unstable states more unstable, poor nations poorer, inequality more pronounced, and conflict more likely,” Huhne is expected to say in a speech to defence experts. “And the areas of most geopolitical risk are also most at risk of climate change.”


His comparison of climate change and terrorism echoes Sir David King, the former chief scientific adviser to the government who warned in 2004 that global warning posed “a bigger threat than terrorism”. The warning so incensed the then US president George W Bush that he phoned Tony Blair to ask him to gag the scientist.


Climate change intensifies security threats in three ways: increasing competition for resources; more natural and humanitarian disasters, such as the droughts now causing famine in Africa, which will also lead to mass migration and the conflicts that ensue; and threats to the security of energy supplies.

The recently published book Tropic of Chaos: Climate change and the New Geography of Violence by Christian Parenti seems to be on the same line of thought. Although disentangling causality from a bunch of case studies is a delicate issue, by looking at the TOC’s one get some curiosity on his arguments on the links between e.g. monsoons, droughts, CPR dilemmas -cattle, water management- and particular syndromes of violence in different places of the planet. The interested reader may have a look at his interview on Grist: Packing heat: Why violence boils over on a warming planet. He for example picked up on the link between food crises and the Arab spring also reported by Bar-Yam and Homer-Dixon on a previous post here. Such linkages reinforces my idea that the frequency of disturbance is a key component on a regime shift archetype that operationalize the link between social and ecological processes. Let’s see how the idea evolves. In the meanwhile, I’ll need an extra summer to catch up my readings list.


Wet and dry monsoon in South America

Researchers have found evidence of the two-mode South American monsoon by studying lake sediments from Laguna Pumacocha in Peru. They discovered that the monsoon can have dry and wet regimes. In addition, their data suggest that the monsoon is shifting towards its dry mode given the fact that precipitation has sharply drop during the last century. I quote from EurekAlert:

A 2,300-year climate record University of Pittsburgh researchers recovered from an Andes Mountains lake reveals that as temperatures in the Northern Hemisphere rise, the planet’s densely populated tropical regions will most likely experience severe water shortages as the crucial summer monsoons become drier. The Pitt team found that equatorial regions of South America already are receiving less rainfall than at any point in the past millennium.


the sediment record illustrated that rainfall during the South American summer monsoon has dropped sharply since 1900—exhibiting the greatest shift in precipitation since around 300 BCE—while the Northern Hemisphere has experienced warmer temperatures.

“This model suggests that tropical regions are dry to a point we would not have predicted,” Abbott said. “If the monsoons that are so critical to the water supply in tropical areas continue to diminish at this pace, it will have devastating implications for the water resources of a huge swath of the planet.”

The sediment core shows regular fluctuations in rainfall from 300 BCE to 900 CE, with notably heavy precipitation around 550. Beginning in 900, however, a severe drought set in for the next three centuries, with the driest period falling between 1000 and 1040. This period correlates with the well-known demise of regional Native American populations, Abbott explained, including the Tiwanaku and Wari that inhabited present-day Boliva, Chile, and Peru.

After 1300, monsoons increasingly drenched the South American tropics. The wettest period of the past 2,300 years lasted from roughly 1500 to the 1750s during the time span known as the Little Ice Age, a period of cooler global temperatures. Around 1820, a dry cycle crept in briefly, but quickly gave way to a wet phase before the rain began waning again in 1900. By July 2007, when the sediment core was collected, there had been a steep, steady increase in dry conditions to a high point not surpassed since 1000.

If you want to follow up the paper, it was recently published in PNAS: A 2,300-year-long annually resolved record of the South American Summer monsoon from the Peruvian Andes by Bird and colleagues.

Early warnings: Floods prediction with climate models

The Columbia Water Center is developing an initiative to predict floods events around the world by using climate models to perform seasonal predictions.

The Columbia Global Flood Initiative, a new joint initiative of Columbia Water Center, the International Research Institute for Climate & Society (IRI), CICAR (the Cooperative Institute for Climate Applications and Research) and the Center for Climate Systems Research, seeks to better understand, predict and plan for extreme floods. The project is based on the conviction that while human beings may not have direct control of where and how much rain falls (the long-term effects of human-caused global warming notwithstanding) there is a great deal more that can be done to manage the risk of extreme flooding around the world. […]

Today, scientists have a much better understanding of how the global climate works than they did even a few years ago. As a result, phenomena such as flooding—once thought of as essentially random events–are increasingly understood as the result of predicable (if complex) climate patterns.

What this means is for any given part of the world it may be possible to forecast when and where the next extreme flood will occur, anywhere from a season to a year ahead of time. Global climate patterns that can affect where and when extreme floods will occur include El Nino/La Nina-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO) and other “climate precursors” such as ocean temperatures, or the amount of regional snowpack. […]

The implications are vast. Understanding when and where an extreme flood is likely to occur a season or even a year ahead of time could allow everyone from policymakers to reservoir managers to emergency responders better plan for what is coming.

This group of researches have been using a top-down approach to floods frequency, where they are mainly determined by climate. And of course they are. It would be interesting, however, to check how the ability of the ecosystem to deal with high precipitation discharges has been reduced by deforestation, or more precisely, by land use and land cover change. If such relation is strong, then it would offer a way to increase insurance to flood events.

Here you can read the complete note on the State of the Planet blog:

Before the Flood—Predicting the Deluge – Water Matters – State of the Planet.

and here you can find an interesting video of a successful application of the early warning system to flooding events in Western Africa in 2008. If you feel like diving into the literature in your Easter holidays, there is a couple of interesting papers:

Magnitude and timing of annual maximum floods: Trends and large-scale climatic associations for the Blacksmith Fork River, Utah

River Flood Forecasting Using Complementary Muskingum Rating Equations

Floods frequency: New regime shift coming soon

Floods frequency is tricky example of a regime shift. I have not idea yet whether it can be considered one. However, it seems so; and it seems to be driven by deforestation. The more deforested and fragmented a landscape is, the less likely it is to retain water coming from strong rainfall events. Vegetation speed down water drops, and root-rich soils with high porosity retain more humidity. When soils are clean or barely vegetated, one would expect water to run down faster.

On the top of this idea, it seems that climate change and green house gas emissions are playing an important role.  NewScientist recently reports a study by Pal and colleagues titled “Anthropogenic greenhouse gas contribution to flood risk in England and Wales in autumn 2000“. They comment:

This week, a study has shown that the devastating floods which damaged nearly 10,000 properties in England and Wales in 2000, and cost £1.3 billion in insurance losses, were made significantly more likely by climate change caused by humans.

It is the first study to quantitatively link a severe rainfall event and climate change. The team that carried out the work, led by Myles Allen of the University of Oxford, had earlier linked the 2003 European heatwave to climate change.

The bottom line of all this? Allen and his team found that human greenhouse gas emissions “significantly increased” the likelihood of the 2000 floods. They can say, with a 66 per cent confidence level, that emissions nearly doubled the risk of the 2000 floods.

Conversely, says Allen, there is only a 10 per cent chance that the increase in flood risk rose by just 20 per cent as a result of human contributions to climate.

Here some more comments from NatureNews:

The research directly links rising greenhouse-gas levels with the growing intensity of rain and snow in the Northern Hemisphere, and the increased risk of flooding in the United Kingdom […]

“We can now say with some confidence that the increased rainfall intensity in the latter half of the twentieth century cannot be explained by our estimates of internal climate variability,” she says.

The findings mean that Northern Hemisphere countries need to prepare for more of these events in the future. “What has been considered a 1-in-100-years event in a stationary climate may actually occur twice as often in the future,” says Allen.

“Governments plan to spend some US$100 billion on climate adaptation by 2020, although presently no one has an idea of what is an impact of climate change and what is just bad weather,” says Allen […]  “If rich countries are to financially compensate the losers of climate change, as some poorer countries would expect, you’d like to have an objective scientific basis for it.”

For the interested reader:

Nature 470, 382–385 (17 February 2011) doi:10.1038/nature09762
Nature 470,378–381 (17 February 2011) doi:10.1038/nature09763

Hawaii will face more frequent cyclones – New Scientist

NewScientist reports:

Tim Li of the University of Hawaii in Honolulu used two climate models to forecast cyclone formation. When he factored in the impact of global warming, he found that by the end of this century, the frequency of tropical cyclones will have fallen by 31 per cent over south-east Asia and grown by 65 per cent over the north central Pacific Geophysical Research Letters, DOI: 10.1029/2010GL045124.

via Hawaii will face more frequent cyclones – environment – 01 October 2010 – New Scientist.

Extreme cold event collapse fishery and induce hypoxia in Bolivia rivers

Last week, the World Water Week was held in Stockholm. According with Swedish newspapers, one of the issues more debated was increasing variability of rainfall in the northern hemisphere summer, which lead to sounded headlines related to fires in Russia and floods in Pakistan.

However, the southern hemisphere was no the exception, in such case suffering of extreme events presumably due to climate change. NatureNews reports that the unprecedented wave of cold in Bolivia killed at least 6 million fish and thousands of other animals related with riverine ecosystems. They add the following on the ecosystem services affected:

The extraordinary quantity of decomposing fish flesh has polluted the waters of the Grande, Pirai and Ichilo rivers to the extent that local authorities have had to provide alternative sources of drinking water for towns along the rivers’ banks. Many fishermen have lost their main source of income, having been banned from removing any more fish from populations that will probably struggle to recover.

The blame lies, at least indirectly, with a mass of Antarctic air that settled over the Southern Cone of South America for most of July. The prolonged cold snap has also been linked to the deaths of at least 550 penguins along the coasts of Brazil and thousands of cattle in Paraguay and Brazil, as well as hundreds of people in the region.

Water temperatures in Bolivian rivers that normally register about 15 ˚C during the day fell to as low as 4 ˚C.

The causes, however, remain unknown and open an active front for South America research. Interestingly, among the causes proposed there is a feedback mechanism related with hypoxia; given that the cold temperature can reduce water mixing, causing in turn lower oxygen levels. Other interactive drivers proposed are disease outbreaks and pollution.

via: Cold empties Bolivian rivers of fish : Nature News.