Cascading & domino effects
In my master thesis (2010) started exploring the ideas of domino effects across regime shifts. Although the idea is cool, attractive and hard to avoid, it’s hard to break down to formal theory and even worst to test empirically. This post from Scientific American (March 15, 2013) best summarises the state of the art in the debate. It only focus on climate tipping points, but the reader can easily extend it to non-climatic ones, such as the global collapse scenario proposed by the HANDY model recently developed with NASA support (news from the Guardian), where the tipping points rest on inequality.
From here down is copied from Scientific American website, I just find it inspiring:
Quick-Change Planet: Do Global Climate Tipping Points Exist?
Is there a chance that human intervention—rising temperatures, massive land-use changes, biodiversity loss and so on—could “tip” the entire world into a new climatic state? And if so, does that change what we should do about it?
As far back as 2008 NASA’s James Hansen argued that we had crossed a “tipping point” in the Arctic with regard to summer sea ice. The diminishing ice cover had moved past a critical threshold, and from then on levels would drop precipitously toward zero, with little hope of recovery. Other experts now say that recent years have confirmed that particular cliff-fall, and the September 2012 record minimum—an astonishing 18 percent lower than 2007’s previous record—was likely no fluke.
Sea ice represents a big system, but it is generally thought to be self-contained enough to follow such a tipping-point pattern. The question that has started to pop up increasingly in the last year, however, is whether that sort of phase transition, where a system shifts rapidly—in nonlinear fashion, as scientists say—from one state to another without recovery in a timescale meaningful to humanity, is possible on a truly global scale.
“You’re pushing an egg toward the end of the table,” says Tony Barnosky, a professor at the University of California, Berkeley. At first, he says, “not much happens. Then it goes off the edge and it breaks. That egg is now in a fundamentally different state, you can’t get it back to what it was.” Barnosky was the lead author on a much-discussed paper in Nature[DL1] last summer that suggested the world’s biosphere was nearing a “state shift”—a planetary-scale tipping point where seemingly disconnected systems all shifted simultaneously into a “new normal.” (Scientific American is part of Nature Publishing Group.)
Claims of catastrophic temperature shifts are unlikely to go down without an argument. A new paper published recently in Trends in Ecology & Evolution by Barry Brook of the University of Adelaide in Australia and colleagues argues that there is no real grounding to the idea that the world could display true tipping-point characteristics. The only way such a massive shift could occur, Brook says, is if ecosystems around the world respond to human forcings in essentially identical ways. Generally, there would need to be “strong connections between continents that allow for rapid diffusion of impacts across the planet.”
This sort of connection is unlikely to exist, he says. Oceans and mountain ranges cut off different ecosystems from each other, and the response of a given region is likely to be strongly influenced by local circumstances. For example, burning trees in the Amazon can increase CO2 in the atmosphere and help raise temperatures worldwide, but the fate of similar rainforests in Malaysia probably depend more on what’s happening locally than by those global effects of Amazonian deforestation. Brook and colleagues looked at four major drivers of terrestrial ecosystem change: climate change, land-use change, habitat fragmentation and biodiversity loss; they found that truly global nonlinear responses basically won’t happen. Instead, global-scale transitions are likely to be smooth.
“To be honest, when others have said that a planetary critical transition is possible [or] likely, they’ve done so without any underlying model,” Brook says. “It’s just speculation…. No one has found the opposite of what we suggested—they’ve just proposed it.” In their analysis Brook’s group concluded that the diversity of local responses to global forcings like increasing temperature means we cannot identify any particular point of no return.
Tim Lenton, an expert on tipping points at the University of Exeter in England, says there is no convincing evidence of global shift yet, but he doesn’t rule out the possibility. “It’s not obvious how you can get a change in Siberia then causing a synchronized change in Canada or Alaska,” he says, referring to a commonly cited climate feedback loop of permafrost melting at northern latitudes. “That doesn’t seem likely. It’s more that different parts of the Arctic are going to reach the thawing threshold at the same time just because they’re getting to the same kind of temperature.” This is a fine distinction: Are we looking at multiple systems tipping as one, or just a coincidental amalgam of unconnected systems falling off a ledge at similar time points?
Lenton says that there is a chance that ice-free Arctic summers could start a cascade effect—for example, elevated temperatures on nearby land that eventually find their way down into the permafrost and cause rapid melting. The carbon released by the permafrost could in turn initiate further warming, and maybe tip another disconnected system and so forth. “It’s a bit like having some dominos lined up,” he says. “I’m not sure yet whether we have a scenario like that for future climate change, but it’s worth consideration.”
Such a domino effect could end up looking more like a “smooth” response than a nonlinear one, but NASA’s Hansen says this doesn’t suggest we should ignore it. “Most tipping points are ‘smoothed out,’ but that does not decrease their importance,” he says. Even Arctic sea ice shows a smoothed response as it rolls past the point of no return. “Once you have passed a certain point, it takes only little additional forcing to lose all the sea ice.” And he echoes Lenton on the idea of dominos and hugely important sub-global systems: “[It’s] hard to see how the Greenland ice sheet would survive if we have sea ice-free summers.” In other words, melted sea ice could beget massive sea level rise, thanks to a supposedly unconnected system.
And further, that non-connectivity is not necessarily a given. Barnosky argues that the fundamental assumption that systems around the world are not strongly connected is no longer true. “What used to be isolated parts of the Earth really are very connected now, and we’re the connectors,” he says. Further, his group’s paper based the possibility of a global tipping point largely on comparisons to planetary history: Earth has exhibited rapid phase shifts in the past, and we are blowing those types of changes out of the water now. For example, the shift from the last glacial period into the current interglacial, which took only a few millennia ending around 11,000 years ago, featured abrupt land-use change: about 30 percent of the land surface went from ice-covered to ice-free over those few thousand years. In just a few hundred years, humans have converted about 43 percent of the world’s land to agricultural or urban landscapes.
Whether such rapid changes portend a new global shift is, to some extent, an esoteric, academic question. The answer depends on whether the world can really follow the classic mathematical definition of tipping points that relies on “bifurcation theory.” That theory holds that a system follows a smooth curve until a certain threshold—the egg rolls at similar speed until it hits the edge of the table—when it jumps to a new state with no obvious change in external pressures. And importantly, once that jump is made there is essentially no going back; you can’t “unbreak” the egg.
And at the bottom of the mathematical debate is a question of utility: Would the existence of a real planetary-scale tipping point change how we should confront our environmental challenges, from energy sources to land use?
A more accurate picture would not just let us prepare for rapid climate change, but might help us predict it as well. Marten Scheffer, of Wageningen University in the Netherlands, has done extensive work on ways we can see tipping points coming. On smaller scales, he says, a system can exhibit “critical slowing down”—a slowed ability to recover from perturbations—before jumping to the irreversible new state. Scheffer says, arguing for tipping points, that past global-scale, quick changes in climate appear to have exhibited a similar effect.
And if we agree a tipping point can exist, maybe we can even try and stave it off. As the world seems to be inching closer to addressing climate change, identifying specific targets for the most effective mitigation grows ever more important. In his recent State of the Union speech, Pres. Barack Obama called for unilateral action to address global warming–related emissions; if we can find a tipping point threshold, is that reason to adjust such action to reflect the possibility of rapid global-scale change?
“If there is plausibility to one of these tipping points, which I think there is, then it’s an even more urgent matter to act to slow all of these individual stressors down,” U.C. Berkeley’s Barnosky says, “because the outcomes could be more surprising and more disruptive to society, and happen faster than we have time to react…. I’d much rather err on the side of precaution then ignore the possibility of tipping points and then be unpleasantly surprised when they happen.”
Good news about climate change?: South winds can counteract sea level rise
Nature News recently reported that changing winds dampen Antarctic sea-level rise. In a nutshell, driven by the ozone hole and continued by climate change, southern circumpolar winds might increase in force reducing somehow the exchange of heat between atmosphere and ocean. As a result this will counter act sea level rise by dampening feedbacks related with gravitational effects of the heavy ice sheets that would displace water towards the tropics. I quote:
The work, published online this month in Geophysical Research Letters1, also finds that the southern shift of the wind by up to 4 degrees latitude over the next 70 years could significantly decrease the transfer of heat from the air to the sea. Because the Southern Ocean has a key role in global ocean circulation, this would lower the heat content of the entire ocean. In the absence of global warming, this chain of events could cause global sea levels to drop by about 5 centimetres. “Our model really does show how fundamental the Southern Ocean is,” says Frankcombe. “It can affect global sea levels.”
Shifting winds are not the only reason why local sea levels will be kept in check. Slangen has shown that as the massive ice sheets in Antarctica and Greenland lose weight by melting, the poles lose some of their gravitational pull. As a result, water slopes away from the poles and towards the equator. This means that the net sea-level rise around the Antarctic Peninsula is expected to be about zero by 2100, she says
The big question, however, is whether these effects will have a stabilizing effect on the ice sheets.
In theory, sea-level rise would help to cause the collapse of the West Antarctic Ice Sheet. The base of this ice sheet is underwater; the weight of the continent’s ice presses it down onto bedrock, preventing it from floating like an iceberg. Thinning of the ice-sheet edges or rising sea levels would lever more of the ice up off bedrock, pushing the ‘grounding line’ ever farther inland. Slowing sea-level rise should hinder this, says Slangen. By contrast, a drop in sea level might cause some ice to flow more steeply and quickly into the sea. “There’s a lot of complicated processes happening there,” she says.
Sridhar Anandakrishnan, a glaciologist at Pennsylvania State University in Philadelphia, notes that the biggest factor affecting the stability of the western ice sheet is not sea level but water temperature. Warm waters can melt floating ice shelves from the bottom up at rates of metres per year, allowing continental ice to flow outwards to replace it. “Relative sea-level rise is not what makes the ice shelves go away in the 200-year timescale,” says Anandakrishnan. Although a decline in heat exchange in the Southern Ocean might help, he adds, it depends on exactly where those cooler waters hit the ice. “I’m not convinced that’s going to help us a lot,” he says.
Although the note mention that wind circulation can counteract half of the expected sea level rise from Antarctica over the next 100 years, it is still uncertain if this new feedback will be enough to avoid the West Antarctica Ice Sheet collapse.
1. Frankcombe, L. M., Spence, P., Hogg, A. M. , England, M. H., & Griffies, S. M. Geophys. Res. Lett. http://dx.doi.org/10.1002/2013GL058104 (2013).
On climate change responsibility
Today NewScientist reports “The seven deadly sinners of global warming“. What captured my attention was the visualization map telling us that US, China, Russia, Brazil, India, Germany and the UK are responsible for more than 60% of the global warming between 1906 and 2005. Their source is the paper “National contributions to observed global warming” by Matthews, Graham and Keverian (freely available Environmental Research Letters, DOI: 10.1088/1748-9326/9/1/014010).
The top countries change depending how you make the accounting but they can group in two: industrialized countries and deforestation countries. The review from NewScientist put Matthews on my to-read list.
Cascading effects of permafrost melting
EurekAlert reports today the latest findings of Michael Gooseff presented in the annual meeting of the Ecological Society of America. It’s a suggested reading if you are into the impacts of climate change on polar areas. I’ll only highlight some of the links between drivers of regime shifts that potentially cause cascading effects among them.
The increasing melting of polar ice is driven by climate change. Ice is melting faster and it’s expected to “change flow patterns, expand the stream networks, and change both the location of habitats and timing of life cycles” . For example, Gooseff reports “temperatures and snow and rain across the tundra shifts annually and seasonally. We know that fall is beginning later than it once did”.
One of the most common link reported in the literature is that as polar areas warm up, permafrost begins to melt and liberate huge amounts of carbon dioxide and methane that has been stored for centuries. As carbon is released to the atmosphere, climate change is reinforced by the permafrost melting feedback loop.
However, something I haven’t seen is the link between permafrost melting and nutrients runoff. The latest is an important driver of regime shifts like eutrophication, hypoxia and transitions in food webs. Here are some notes:
Extended frost-free time causes soils that do thaw annually to have longer active periods when microbes can mineralize nutrients. While the soils remain frost free longer, plants continue their normal cycle dictated by the length and intensity of daylight, which has not changed. Microbes may continue to create nutrients, but the plants no longer use them, so that when rain or meltwater comes the nutrients leach into the rivers and streams.
“That is exactly what we are seeing,” said Gooseff. “In September and October, we see a substantial increase in nutrients in the water. Concentrations increase many times for nutrients such as nitrate and ammonium.”
I wonder how such linkages will change the map of dead zones, or areas under hypoxia regime around the world. Do you think it will be strong enough to create new dots in polar coasts?
The Dead Zones map was created by EarthObservatory | NASA based on the following paper:
Diaz, R. J., & Rosenberg, R. (2008). Spreading Dead Zones and Consequences for Marine Ecosystems. Science, 321(5891), 926-929.
via: Polar climate change may lead to ecological change. | EurekAlert
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:
Colombia: Climate Change impacts for farmers
The CGIAR program on Climate Change, Agriculture and Food Security recently post a couple of video photoessays on ‘Two Degrees Up’- What a two degree cange in temperature looks like for farmers in Colombia and Ghana.
You can find more info and the second video of Ghana on CCAFS website or via @faonews here: http://ht.ly/3oKDN
NASA Study Finds Earth’s Lakes are Warming
NASA finds lakes are warming up. This brings unexpected consequences to eutrophic lakes which now have to handle another driver: global warming. NASA reports:
Researchers Philipp Schneider and Simon Hook of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide.
They reported an average warming rate of 0.45 degrees Celsius (0.81 degrees Fahrenheit) per decade, with some lakes warming as much as 1 degree Celsius (1.8 degrees Fahrenheit) per decade. The warming trend was global, and the greatest increases were in the mid- to high-latitudes of the Northern Hemisphere.
Small changes in water temperature can result in algal blooms that can make a lake toxic to fish or result in the introduction of non-native species that change the lake’s natural ecosystem.
Hawaii will face more frequent cyclones – New Scientist
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.
Rob Dunbar: Discovering ancient climates in oceans and ice | Video on TED.com
Rob Dunbar: Discovering ancient climates in oceans and ice | Video on TED.com.
Oceans are often forgotten in climate negotiations. Ron Dunbar point out why we should be worried about abrupt transitions in the ocean. Acidification, despite to be one of the latest concerns, seems to be our first global regime shift. The reason proposed by Dunbar is that oceanic fauna probably wont have enough time to adapt to the proposed 450 ppm on the global climate agenda.
Climate change and conflict: arguments about causality.
Mark Levy, deputy director of the Center for International Earth Science Information Network (Columbia University), explain the controversy risen by recent studies on the linkages of climate change and conflict. He summarizes challenges for future research:
Here’s how I would characterize what we know and we are trying to learn:
1) Economic deprivation almost certainly heightens the risk of internal war.
2) Economic shocks, as a form of deprivation, almost certainly heighten the risk of internal war.
3) Sharp declines in rainfall, compared to average, almost certainly generate economic shocks and deprivation.
4) Therefore, we are almost certain that sharp declines in rainfall raise the risk of internal war.
To understand how climate change might affect future conflict, we need to know much more. We need to understand how changing climate patterns interact with year-to-year variability to affect deprivation and shocks. We need to construct plausible socioeconomic scenarios of change to enable us to explore how the dynamics of climate, economics, demography, and politics will interact and unfold to shape conflict risk.
via Climate-Security Linkages Lost in Translation – State of the Planet.
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.