Category Archives: Regime Shifts

Regime Shifts

Abrupt Climate Change: an oceanic heat transport regime shift

Leave a comment

On Real Climate, Stefan Rahmstorf writes of new evidence for regime shifts in global ocean circulation:

The latest results of the EPICA team (the European Project for Ice Coring in Antarctica) are published in Nature today (see also the News & Views by RealClimate member Eric Steig). Their data from the other pole, from the Antarctic ice sheet, bring us an important step closer to nailing down the mechanism of the mysterious abrupt climate jumps in Greenland and their reverberations around the world, which can be identified in places as diverse as Chinese caves, Caribbean seafloor sediments and many others. So what are the new data telling us?

These data connect the Antarctic ups and downs of climate to the much greater ones of Greenland. This is hard, as dating an ice core is a difficult art (no pun intended). If one makes an error of only 5% in determining the age of an ice layer, for 40,000-year-old ice that’s an error of 2,000 years. But to understand the mechanisms of climatic changes, one needs to know the sequence of events – for example, one needs to know whether a particular warming in Antarctica happens before, after, or at the same time as a warming in Greenland.

… Antarctica gradually warms while Greenland is cold. But as soon as Greenland temperatures jump up in a DO event, Antarctic temperatures start to fall. …

It is (at least in the model) a result of a big change in northward heat transport in the Atlantic. If the heat transport by the Atlantic thermohaline circulation suddenly increases for some reason (we’ll come to that), Greenland suddenly gets warm (an effect amplified by receding sea ice cover of the seas near Greenland) and Antarctica starts to cool. Changes in Antarctica are much smaller and more gradual, as it is far from the centre of action and the vast reservoir of ocean around it acts as a heat store. The basic physics is illustrated very nicely in a simple “toy model” developed by Thomas Stocker and Sigfus Johnsen.

There is still debate over what kind of ocean circulation change causes the change in heat transport. Some argue that the Atlantic thermohaline circulation switches on and off over the cycle of DO events, or that it oscillates in strength. Personally, I am rather fond of another idea: a latitude shift of oceanic convection. This is what happens in our model events pictured above: during cold phases in Greenland, oceanic convection only occurs in latitudes well south of Greenland, but during a DO event convection shifts into the Greenland-Norwegian seas and warm and saline Atlantic waters push northward. But I am biased, of course: my very first Nature paper (1994) as a young postdoc demonstrated in an idealised model the latitude-shift mechanism. Other oceanic mechanisms may also agree with the phasing found in the data. In any case, these data provide a good and hard constraint to test models of abrupt climate events.

But irrespective of the details: the new data from Antarctica clearly point to ocean heat transport changes as the explanation for the abrupt climate changes found in Greenland. We are thus not talking about changes primarily in global mean temperature (these are small in the model results shown above). We are talking about what I call a climate change of the second kind: a change in how heat is moved around the climate system.

There are very few possibilities to change the global mean temperature, a climate change of the first kind: you have to change the global heat budget, i.e. either the incoming solar radiation, the portion that is reflected (the Earth’s albedo), or the outgoing long-wave radiation (through the greenhouse effect). Temporarily, you can also store heat in the ocean or release it, but the scope for changes in global mean temperature through this mechanism is quite limited.

Changes of the second kind are due to changes in heat transport in the atmosphere or ocean, and these can occur very fast and cause large regional change. …

The two kinds of climate change are sometimes confounded by non-experts – e.g., when it is claimed that DO events represent a much larger and more rapid climate change than anthropogenic global warming. This forgets that our best understanding of DO events suggests they are changes of the second kind. The same error is made by those who claim that the 1470-year cycle associated with the DO events could lead to an “unstoppable global warming”. A global warming of 3 or 5 ºC within a century, as we are likely causing in this century unless we change our ways, has so far not been documented in climate history.

One crucial point has been left unanswered thus far. If DO events are due to ocean circulation changes, what triggers these ocean circulation changes? Some have argued the ocean circulation may oscillate internally, needing no trigger to change. I am not convinced – the regularity of the underlying 1470-year cycle speaks against this, and especially the fact that sometimes no events occur for several cycles, but then the sequence is resumed with the same phase as if nothing happened. I’d put my money on some regularly varying external factor (perhaps the weak solar cycles, which by themselves cause only minor climate variations), which causes a critical oceanic threshold to be crossed and triggers events. Sometimes it doesn’t quite make the threshold (the system is noisy, after all), and that’s why some events are “missed” and it takes not 1,500, but 3,000 or 4,500 years for the next one to strike. But the field is wide open for other ideas – the cause of the 1470-year regularity is one mystery waiting to be solved.

Ideas, Regime Shifts, Vulnerability

Levin Asks What are the Fundamental Questions in Biology?

Leave a comment
In PLoS Biology ecologist Simon Levin asks what are the Fundamental Questions in Biology. His essay introduces a new series of essays in PLoS Biology that are meant to pose questions that span biology. He argues that robustness, which to me seems pretty much the same as resilience, is at the heart of these questions. He writes:

At the core of this potential future shift in biological sciences is the recognition that all biological systems are what have come to be known as complex adaptive systems, in which macroscopic patterns reflect the collective dynamics of individual units at lower levels of organization and feed back to affect those more microscopic dynamics. Evolutionary changes operate on multiple levels and multiple scales: from cells, to organisms, to populations, to communities and the biosphere. As my Princeton colleague, Philip Anderson, wrote years ago, “more is different.” Although the details at lower levels govern the behavior at higher levels, understanding those details is not sufficient for understanding how macroscopic patterns emerge or how natural selection operates at lower levels to lead to those patterns. Where those patterns refer to properties of the organism, natural selection operates to modify the details, such as the rules that govern organismal development due to feedbacks from fitness differences among organisms. On the other hand, where those properties refer to those of the biosphere, there is no comparable process of natural selection choosing among competing biospheres. What properties arise are hence largely emergent, reflecting selective events at much lower levels of organization. This is the principal reason that our biosphere is in trouble. It also emphasizes the importance of understanding at what levels selection operates most strongly.The questions that biologists from diverse subdisciplines are asking have commonalities that make clear the continued existence of fundamental challenges that unify biology and that should form the core of much research in the decades to come. Some of these questions are as follows: What features convey robustness to systems? How different should we expect the robustness of different systems to be, depending on whether selection is operating primarily on the whole system or on its parts? How does robustness trade off against adaptability? How does natural selection deal with environmental noise and the consequent uncertainty at diverse scales? When does synchrony emerge, and what are its implications for robustness? When and how does cooperative behavior emerge, and can we derive lessons from evolutionary history to foster cooperation in a global commons?

These are among what we identify as fundamental questions in biology, cutting across subdisciplines and with the potential to reunify the subject. To encourage recognition of these challenges, PLoS Biology is publishing a series of brief discussion papers raising core issues and designed to be provocative (the first in the series is published today [DOI: 10.1371/journal.pbio.0040299]). Contributions to the Challenges Series are encouraged; ideas should be sent to biology_editors@plosbiology.org.

Greenlash, Ideas, Regime Shifts

Pollution risks Yangtze’s ‘death’

2 Comments

From BBC news, Pollution risks Yangtze’s ‘death’, briefly describes China’s fears that how large scale eutrophication and pollution is impacting human wellbeing and economic growth prospects along the Yangze.

YangtzeThe Yangtze, China’s longest river, is “cancerous” with pollution, reports in the country’s state media have said.Environmental experts fear pollution from untreated agricultural and industrial waste could turn the Yangtze into a “dead river” within five years.

That would make it unable to sustain marine life or provide drinking water to the booming cities along its banks.

The Yangtze rises in China’s western mountains and passes through some of its most densely populated areas.

The government has promised to clean up the Yangtze, which supplies water to almost 200 cities along its banks.

But experts speaking in China’s state media say that unless action is taken quickly, billions of tonnes of untreated industrial and agricultural waste and sewage are likely to kill what remains of the river’s plant and wildlife species within five years.

China’s rapid economic development means that many of the nation’s waterways are facing similar problems.

Last year the authorities announced that the country’s second-longest river, the Yellow River, was so polluted that it was not safe for drinking.

Correspondents say that 300 million people in China do not have access to safe drinking water.

They say that government efforts to clean up the country’s polluted lakes and waterways are being thwarted by lax enforcement standards.

Ecological Management, Regime Shifts, Vulnerability

Does Rainfall Increase in the Sahel Mask a Degradation Trend?

1 Comment

There have been heated debates about the dynamics of land degradation and climate change in the Sahel region in West Africa. The region has suffered a number of extreme droughts since the 1960’s causing famine, loss of livestock and reduced vegetation. However, a ‘greening trend’ trend has recently been detected. To a large extent this trend appears to be driven by increased rainfall (although some scientists argue that this alone can not explain the full extent of the greening trend).

Several studies, based on remote sensing, have now analyzed the reduced vegetation during the drought years and compared it to current land cover. Interestingly, they have not detected any land degradation that can be attributed to land management, which is in contrast with earlier studies suggesting that livestock management in the region is reducing productivity and increasing the systems vulnerability to drought.

A recent paper ‘Desertification in the Sahel: a reinterpretation’ by Hein and De Ridder published in Global Change Biology, suggests that the analyses based on remote sensing may be flawed and that land degradation may have been masked by rainfall.

Hein and De Ridder’s reasoning builds on the way that previous studies linked net primary production (NPP) (or actually a vegetation index – NDVI) to rainfall. These previous studies assumed that for a given site with no land degradation a linear relationship exists between NPP and rainfall (i.e. the Rain Use Efficiency (RUE) is constant). When they did not see any change in RUE over time they assumed that there has not been any land degradation.

Hein and De Ridder studied RUE in six field sites and found that in the absence of land degradation the relationship between NPP and rainfall was non-linear (followed a quadratic curve). When they looked at expected RUE values based on their quadratic estimates they found that the RUE from satellite estimates were lower than the expected ones, and thus land degradation may have occurred. They conclude:

If anthropogenic degradation of the Sahel is demonstrated, this would have repercussions for the debate on the causes of climate change in the Sahel. Currently, a weakness in the argumentations … that anthropogenic land cover changes have contributed to the occurrence of the extreme Sahelian droughts of the last decades of the 20th century is a lack of evidence of degradation from remote sensing data. Hence, if new remote sensing analyses confirm anthropogenic degradation, this would support the hypothesis that degradation of the vegetation layer, in particular through sustained high grazing pressures, has contributed to the occurrence of the 20th century droughts in the Sahel. Furthermore, if degradation of the Sahelian vegetation cover is confirmed, this would indicate that Sahelian pastoralists may be more vulnerable for future droughts than currently assumed. Because degradation of the Sahel in the 1980s and 1990s has been masked by an upward trend in annual rainfall, the consequences of a future drought for the local population could be unexpectedly severe.

Ideas, Regime Shifts, Reorganization

Punctuated Equilibrium in Environmental Policy

Leave a comment

Readers familiar with panarchy theory will find a rich set of relevant examples in a new book edited by Robert Repetto, Punctuated Equilibrium and the Dynamics of U.S. Environmental Policy.

In Chapter 2, Frank Baumgartner explains how U.S. environmental policy shows is static for long periods of time, reflecting stable institutional structures, shared understanding of goals, and balance of power among competing interests. Occasionally, however, there are bursts of innovation as public policies are radically restructured. These rare but crucially important bursts of innovation occur across a range of scales, from local to national. Baumgartner makes his case using statistical case histories of policy dynamics.

William Brock, in Chapter 3, explains social and economic mechanisms that cause long periods of stasis interrupted by bursts of enormous change in environmental policy. Brock uses minimal models grounded in well-established social and economic phenomena. The remainder of the book develops case studies in depth.

Some cases have undergone radical change: management of water in California, certain marine fisheries, and timber in the Pacific Northwest. Other systems seem locked in traps: greenhouse gas and climate policy, vehicular fuel economy standards, and livestock grazing on public lands. History suggests that these traps will eventually be broken.

In his introductory chapter, Repetto summarizes the positive and negative feedback mechanisms that underlie punctuated equilibrium. He writes:

Though they [the feedback mechanisms] are fully capable of explaining the observed patterns of stability and abrupt change, their workings are difficult to predict in particular policy struggles because of their complex interactions. The infrequency of policy breakthroughs suggests that most efforts to bring them about will fail. Entrenched interests and ideology will retain their dominance; challengers will be unable to gather sufficient resources, attention, and momentum. Nonetheless, such failed efforts may build a foundation for later success when conditions are more favorable by undermining the prevailing policy image, by mobilizing new interests, and by forming new coalitions. Even knowing that the odds are long, effective policymakers continue to work on their issues in order to be ready and primed when opportunities arise. Timing is crucial . . . . Across the broad range of resource and environmental policy issues, only a few, if any, are likely to have potential for significant change at any particular time. The ability to discern which ones these are is a vital strategic skill.

This pattern is well known to researchers familiar with adaptive cycles and panarchy. Surprisingly, this scholarly and well-documented volume has almost no references to research on adaptive cycles, resilience and panarchy. The lone exception is a citation to the 2002 Panarchy book edited by Gunderson and Holling. I hope that there is more exchange of ideas on punctuated policy dynamics and panarchy in the future.

Ideas, Regime Shifts, Reorganization, Vulnerability

Exploring Resilience in Social-Ecological Systems – E&S special feature

Leave a comment

Ecology & Society has just published a special feature Exploring Resilience in Social-Ecological Systems: Comparative Studies and Theory Development based upon the comparisons of 15 Resilience Alliance case studies.

The current table of contents of the issue is:

Exploring Resilience in Social-Ecological Systems Through Comparative Studies and Theory Development: Introduction to the Special Issue
by Brian H. Walker, John M. Anderies, Ann P. Kinzig, and Paul Ryan

A Handful of Heuristics and Some Propositions for Understanding Resilience in Social-Ecological Systems
by Brian Walker, Lance Gunderson, Ann Kinzig, Carl Folke, Steve Carpenter, and Lisen Schultz

Scale Mismatches in Social-Ecological Systems: Causes, Consequences, and Solutions
by Graeme S. Cumming, David H. M. Cumming, and Charles L. Redman

Resilience and Regime Shifts: Assessing Cascading Effects
by Ann P. Kinzig, Paul Ryan, Michel Etienne, Helen Allyson, Thomas Elmqvist, and Brian H. Walker

Fifteen Weddings and a Funeral: Case Studies and Resilience-based Management
by John M. Anderies, Brian H. Walker, and Ann P. Kinzig

Toward a Network Perspective of the Study of Resilience in Social-Ecological Systems
by Marco A. Janssen, Örjan Bodin, John M. Anderies, Thomas Elmqvist, Henrik Ernstson, Ryan R. J. McAllister, Per Olsson, and Paul Ryan

Collapse and Reorganization in Social-Ecological Systems: Questions, Some Ideas, and Policy Implications
by Nick Abel, David H. M. Cumming, and John M. Anderies

Governance and the Capacity to Manage Resilience in Regional Social-Ecological Systems
by Louis Lebel, John M. Anderies, Bruce Campbell, Carl Folke, Steve Hatfield-Dodds, Terry P. Hughes, and James Wilson

Water RATs (Resilience, Adaptability, and Transformability) in Lake and Wetland Social-Ecological Systems
by Lance H. Gunderson, Steve R. Carpenter, Carl Folke, Per Olsson, and Garry Peterson

Shooting the Rapids: Navigating Transitions to Adaptive Governance of Social-Ecological Systems
by Per Olsson, Lance H. Gunderson, Steve R. Carpenter, Paul Ryan, Louis Lebel, Carl Folke, and C. S. Holling

Greenlash, Ideas, Regime Shifts, Visualization

Mapping anoxic zones – pt 2

1 Comment

Global International Waters Assessment is a systematic assessment of the environmental conditions and problems in large transboundary waters, comprising marine, coastal and freshwater areas, and surface waters as well as ground waters. Involving over 1,500 expert it has assessed 66 of the world’s major river basins and recently published a synthesis report. These publications are freely available online. The synthesis report‘s section on pollution provides a map of eutrophication impact.

Fig 14 GIWA

As mentioned in a earlier post on mapping dead zones, eutrophication can produce large coastal hypoxic zones. The GIWA regional assessments reported that dead zones:

… have become increasingly common in the world’s lakes, estuaries and coastal zones, with serious impacts on local fisheries, biodiversity and ecosystem functions. Extensive dead zones have been observed for many years in the Baltic Sea, Black Sea and Gulf of Mexico. The GIWA assessment has compiled information on dead zones in the Southern Hemisphere, including several lagoons in the Brazil Current region, coastal locations in the Humboldt Current region, and in the Yangtze River estuary located in the East China Sea region.

Greenlash, Ideas, Regime Shifts, Visualization, Vulnerability

Anthropogenic Modification of Vapours Flows and Tipping Points in the Earth System

Leave a comment

Compare the map of soil moisture – atmosphere couplings against Gordon et al’s 2005 map of changes in vapour flows in the Human modification of global water vapor flows from the land surface.

PNAS Vapour Flows

Figure shows spatial distribution of net changes in vapor flows between potential vegetation and actual deforested and irrigated vegetation in mm/yr. The aggregated global change as compared with the potential vegetation is small (400 km3/yr), but the map illustrates the large spatial redistribution of water vapor flows from the land surface at the global scale.

Note that the location of increases in vapor flows in irrigation matches up with several of the hotspots identified in the map of soil moisture – atmosphere couplings – central Great Plains of North America, and India. Change occurs also in less intense hot spots appear in South America and China. Consquently, the combination of these two papers predicts that irrigation should have altered the local climate in these regions more than in other regions.

General, Regime Shifts, Visualization, Vulnerability

Leverage Points in the Earth System: Soil Moisture

Leave a comment

The 2004 Science paper – Regions of Strong Coupling Between Soil Moisture and Precipitation – by Koster et al. used a dozen independent climate models to estimate ‘hot spots’ on Earth’s surface where precipitation is affected by soil moisture anomalies during Northern Hemisphere summer. They propose that these hot spots are, in a sense, land-surface analogs to the ocean’s “El Niño hot spot” in the eastern tropical Pacific.

Soil moisture is a slowly vary aspect of the Earth system (relative to weather). Soil moisture can persist for months. Soil moisture, influences evaporation and other surface energy fluxes can influence weather.

Soil moisture atmospheric coupling

Figure: Hot spots of soil moisture – local precipitation coupling appear in the central Great Plains of North America, the Sahel, equatorial Africa, and India. Less intense hot spots appear in South America, central Asia, and China.

The hot spots are located in regions that in areas that are at intermediate moisture levels. The authors argue that this is because in wet climates, soil water is plentiful and evaporation is controlled not by soil moisture but by net radiative energy. In dry climates evaporation rates are sensitive to soil moisture but they are small. Consquently the biggest impact of soil moisture on evaporation is in the transition areas between dry and wet climates.

What this analysis suggests is that these hotspots are areas in which changes in land use – especially those that alter soil moisture – such as irrigation or land clearing, will have a larger impact of regional climate.

Greenlash, Regime Shifts, Visualization

Anoxic zones – mapping ecosystem tradeoffs (a start)

1 Comment

Current industrial agricultural practices, particularly the overuse of fertilizer and its sloppy management, frequently create a tradeoff between agricultural production and coastal eutrophication. That is increases in agricultural yields have produced low oxygen zones around the world. The UNEP Global Environmental Outlook 2003 maps the location of coastal anoxic zones world wide (somewhat confusingly the worst cases – the persistent ones are coloured yellow, next worst red and orange, and least worst blue).
Global distribution of oxygen-depleted coastal zones.

Global distribution of oxygen-depleted coastal zones. The 146 zones shown are associated with either majorpopulation concentrations or with watersheds that deliver large quantities of nutrients to coastal waters.

Legend:

  • Annual – yearly events related to summer or autumnal stratification
  • Episodic – events occurring at irregularintervals greater than one year
  • Periodic – events occurring at regular intervals shorter than one year
  • Persistent –all-year-round hypoxia

Continue reading →