There's an ongoing debate in the scientific community regarding the threshold value, tipping point, for frozen grounds in the Arctic, permafrost, to start thawing irreversibly. And whether released methane from the permafrost will occur gradually over time or more abruptly. There is more stored carbon in frozens soils than we currently have in the atmosphere.

There are basically two camps, some believe the permafrost to be stable with a threshold value around <3°C while others claim 1,5°C is enough to start thawing large parts of the frozen grounds and lakes in the Arctic. 

For a lay person this is quite confusing, but it simply means that there isn't enough data to know for sure and so some scientists are more or less conservative in their estimates. Then there is the question of using climate models to try and predict potential threshold values or doing actual fieldwork and extrapolating conclusions from that. To my knowledge, climate models have a pretty bad track record of capturing highly non-linear dynamics in the climate system. For example, Arctic sea ice passed a tipping point in 2007 and is now in a death spiral but models had predicted sea ice to remain until the end of this century. Pretty high margin of error if you ask me. Also, we are learning that there seems to be differences in how permafrost soils and lakes thaw. 

According to a recent field research study funded by NASA of thermokarst lakes, formed by thaw of permafrost below the soil, in Alaska and Siberia the potential for abrupt thaw (decades) is now likely and irreversible. As the Arctic warms more of these lakes are appearing and growing in size which expands the thaw below. It has been estimated that they now cover about 20% of northern permafrost regions. This could double the release from terrestrial landscapes by the 2050s. A carbon cycle feedback that is not yet included into climate models.

This is bad news for climate change mitigation efforts. This feedback is significant because methane is about 30 times more potent than carbon dioxide as a heat-trapping gas. And the lakes are expected to thaw even under the lowest IPCC emissions scenario, adding further warming. Since we most likely are already committed, warming yet to come from current emissions, to 1,5-2°C this extra warming from the permafrost reinforcing feedback could take us above the 2C threshold for potentially catastrophic warming. Unless we rapidly decarbonize our economy and try to take out carbon from the atmosphere by for example large-scale reforestation efforts. Time is not on our side. We need a climate emergency plan.

We know that there are tipping points in many different complex systems. Although they may be hard to study and exactly define. For example in large systems such as the global economy or climate system. A recent study shows beautifully, in simpler ways, how social animals that lives in communities also have tipping points, before the function of the system changes fundamentally.

In this case the research focused on the communal spider which lay their eggs, spin webs and share their prey in cooperatives colonies, from Massachusetts to Argentina, in relatively cool temperatures. However, only until 31 degrees C, after which they start to attack each other. Suggesting a tipping point where some small perturbation can cause an abrupt and dramatic shift in the behavior of the system.

Reversal is difficult

We need to increase society’s general resilience to shocks and disturbances. With that I mean that we need to increase communities capacity to adapt or transform in response to unfamiliar, unexpected and extreme shocks.

Extreme events have long lasting effects on society and need to be managed properly or major losses will be inevitable. Megadroughts in Syria and California, the rapid spread of wildfires in Indonesia and Canada or massive flooding in the UK and Denmark are just some examples of extreme events that we will have to get used to due to climate change and resource depletion. Other shocks may come from a fragile financial system in form of massive unemployment, from a dysfunctional political system that leads to a revolution or from mass migrations due to failed states. 

Extreme events are notoriously difficult to predict because probabilities are hard to measure and uncertainties are high. That's why it's so important to take proactive measures to strengthen a society's general resilience to such events. This requires a complex systems perspective and understanding of human-nature interactions. Strengthening general resilience includes:

The important thing with diversity is that it can offer both functional diversity and response diversity. In other words, a diverse system can offer many different functions but also a diversity of responses to disturbances so that critical functions are maintained even if some parts of the system fail. For example, in a marine ecosystem some fish may carry out similar functions (e.g. grazing on corals) so that if one species disappears there is another that can keep on carry out the critical function for the benefit of the overall ecosystem. Similarly if a bridge or air plane has many backup safety mechanisms that all perform the same function (i.e.redundancy) the risk of a collapse or crash is much lower. This is also applicable to the economy where a diversity of many small companies with similar functions contributes to stability in case some should default. That's why it’s very unhealthy to have a few but major banks that can crash the entire system. It is also a reason why societies with high income inequality do poorly, because all the wealth has been concentrated at the top which creates instability and risk of revolution. Heterogeneous landscapes with high biodiversity have higher resilience to extreme events and so monocultures is a really bad idea since it increases vulnerability to massive crop failure, loss of pollinators, and spread of pests.

Connectivity can both be a good and a bad thing depending on degree. In today’s society we most often have a high degree of connectivity, international interdependence, that makes us vulnerable to the rapid spread of extreme events or cascading effects. Modularity helps contain disturbances to specific regions/sectors and lowers the risk of contagion. The more self-sufficient communities can be the better. Especially for the provision of essential goods and services such as water, food, energy and health care. Decentralised systems of decision making are also more flexible and can respond more rapidly to a crisis than any central control system ever can.

As was common sense only two generations ago having reserves, no matter if it’s food or skills, contribute to a faster recovery after a disturbance. Just-in-time logistics make communities vulnerable to sudden shocks or major disturbances. So does a reliance on finite resources like oil. Keeping strategic reserves while improving local supply or transitioning to renewables is increasingly important. We know that plants and animals that survive a disturbance are critical to ecological recovery from e.g. extraordinary fires or volcanic eruptions. Keeping seed banks is also increasingly important as ever more species are lost. Social memory is another important aspect that can help push for a faster recovery.

Transparency and up to date information about status and trends of ecosystem and social health is essential to maintain resilience over the long-term. Complex systems are not static but ever changing and so to provide adaptive management one needs to constantly be learning and collecting information to ensure stability of the system. Citizen science and decentralised monitoring is much more effective and low cost than large-scale operations by central authorities. Traditional knowledge about changes over time is invaluable. Indicators can also help provide early warnings of potential tipping points.

Trust is the basic glue that holds society together and it’s fundamental to everyday social and economic interactions. It is easier to maintain trust when groups are small and people know each other but harder in large communities and cities. When trust is high people are more willing to cooperate and transaction costs are low. This is yet another reason why decentralisation of decision-making is important. Today we live in a society where basic trust between actors has been replaced with money, but that monetary system is inherently unstable and increasingly untrustworthy. Trust takes a long time to build up but can be erased rapidly. When trust in a society is low transaction costs increase as fewer people are willing to cooperate or trade. The erosion of social trust is very damaging to a society that in the end may lead to bank runs, social unrest or even conflict.

The risk of abrupt and/or irreversible climate change is determined by a crossing of tipping elements in the Earth system. One such tipping element is the North-South ocean current circulation in the Atlantic Ocean, also known as the Gulf Stream system. The Gulf Stream system is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. It is responsible for the mild climate in northwestern Europe and the most important source of heat transport to Scandinavia.

A potential abrupt change, or slowing down of the Gulf Stream circulation could lead to a weakening of heat transportation towards the Arctic which in turn would result in a cooling effect of high northern latitudes (including Scandinavia). 

Scientists at Potsdam University have now found evidence for a slowdown of the Gulf Stream (published in Nature). Multiple lines of observation suggest that in recent decades the current system has been weaker than ever before in the last 1000 years. The gradual but accelerating melting of the Greenland ice-sheet, caused by man-made global warming, is a possible major contributor to the slowdown.

The blue cooling spot south of Greenland: NASA GISS warming map 1901-2013. Source: PIK-Potsdam

“Now freshwater coming off the melting Greenland ice sheet is likely disturbing the circulation”, says Jason Box of the Geological Survey of Denmark and Greenland. The melting glaciers are diluting the North Atlantic ocean salty water. Less salty water is less dense and doesn’t sink to the ocean deep as easy. 

The observed cooling in the North Atlantic, just south of Greenland, is stronger than what most climate models have predicted so far. One reason for this is that most computer simulations underestimate the stability of the Gulf Stream or don’t account properly for the Greenland ice sheet melt. This is yet another example where observations suggest that climate models are too conservative when it comes to the pace at which certain aspects of climate change are proceeding.

A slowing down of the Gulf Stream will not lead to a new ice age but it could have major negative effects on ocean ecosystems and thereby fisheries and coastal livelihoods. A slowdown also adds to the regional sea-level rise affecting cities like New York and Boston. Further weakening of the current could also result in temperature changes in the northern latitudes, influencing weather systems on both sides of the Atlantic, in North America as well as Europe.

Rising temperatures in the Arctic are contributing to melting sea ice, thawing permafrost, and destabilization of a system also known as “Earth’s Air Conditioner”. The Arctic regulates ocean and atmospheric circulation and keeps the the planet cool. Climate change is impacting weather patterns, natural systems, and human life around the world. The Arctic, however, is central to these impacts as it is warming more rapidly relative to lower latitudes, about twice as fast as the rest of the globe, making it “the canary in the coal mine”. What happens in the Arctic is of utmost importance to us humans if we want to know how climate change will impact our only home, planet Earth.

The Arctic is very sensitive to global heat forcing, and any small warming there could rapidly trigger a number of feedbacks that generate more warming for the Arctic and the globe. These feedbacks include but are not limited to: A) snow and ice melting; B) changes in ocean and atmospheric circulation; C) thawing permafrost and methane release. The concept of a “tipping point” - a threshold beyond which a system shifts to an alternate state - has become familiar to most people concerned with the climate debate. If tipping point means crossing a critical threshold in which a system enters substantial, potentially irreversible, change that causes it to move into an entirely new state, there may be precursors or early warning signals of such change. Such warnings are exactly what climate researchers and ecologists are looking for and trying to map out. The graphic below shows potential tipping elements in the Arctic region.

Map show potential tipping points in the Arctic region: ice melting (white); ocean and atmospheric circulation (aqua green); and biome changes (dark green). Source: Lenton (2012)

Snow & Ice melt

Source: meltfactor.org

As snow and sea ice retreat, exposing land and sea with lower albedo (i.e. less reflectiveness), more solar energy is absorbed, thus leading to further melting and retreat in a vicious cycle. The present thinning and retreat of Arctic sea ice is one of the most serious geophysical consequences of global warming and the rate of ice melting have greatly exceeded the predictions of most models (Wadhams, 2012). Experts suggest that we may have, in 2007, passed a tipping point towards having sea-ice free summers in the Arctic (Livina and Lenton, 2013). Some studies suggest that the Arctic could have sea-ice free summers in only a couple of years, 2016-2020 (Maslowski et al. 2012; Wadhams 2014) while others predict it to occur later, around 2041-2050 (Cawley 2014; Liu et al. 2012) given continued warming. Eighty-one percent of Greenland, which is located mostly inside the Arctic Circle and is the world’s largest island, is covered by ice. The Greenland ice sheet is currently losing mass at a rate that has been accelerating (Lenton, 2012). And in July of 2012 Greenland ice sheet reflectivity at 2000m-2500m collapsed during the summer (figure 1). In a study published in Nature Reyes et al. (2014) argued that between 4.5 and 6.0 meters of sea level rise 400,000 years ago could be attributed to a collapse of Greenland's southern ice sheet. Data from marine records in the North Atlantic show that the average temperatures in Greenland during that period were only about 1°C warmer than today’s temperatures. The similarity in climate between then and now “suggests the threshold for ice sheet collapse is pretty low”, according to one of the co-authors, “We could be nearing the tipping point” (Oregon Live, 25th June 2014).

Changes in ocean and atmospheric circulation

Permafrost—the ground that stays frozen for two or more consecutive years—is a ticking time bomb of climate change. Some 24 percent of Northern Hemisphere land is permafrost. That's 23 million square kilometers found mostly in Siberia, the Tibetan Plateau, Alaska, the Canadian Arctic, and other higher mountain regions. When the Arctic warms, permafrost can start thawing and releasing carbon and methane into the atmosphere (figure 2). In a controversial paper in Nature, Comment, Whiteman et a. (2013) posited a scenario whereby a 50 Gigatonne (Gt) methane pulse would occur over a decade time period and calculated its potential economic costs. To put this in context, the total amount of methane in the world’s air now is about 5 Gt, and the annual input is about 0.5 Gt, so this would double the methane in the air within the first year. Newspapers such as the Guardian and popular blogs were quick to pick up the story and claimed that there was a possibility of an Arctic “methane bomb”. Following articles have, however, shown little evidence pointing to the likelihood of such a scenario. A group of international scientists wrote in Nature Geoscience in 2014 that “significant quantities of methane are escaping the East Siberian Shelf as a result of the degradation of submarine permafrost over thousands of years” (Shakova et al. 2014). The authors claim that a sudden release of methane, in a “pulse”, seems unlikely and that methane will probably continue to bubble up slowly, contributing to greenhouse gases in the atmosphere. But they do caution that its possible that global warming could cause more storms in the Arctic Ocean, releasing methane on a bigger scale. There is no established tipping point for methane release, but some studies suggest that a tipping point for continuous Siberian permafrost thaw could be as low as 1.5°C warmer than the pre-industrial period (Oxford University). 

Sea levels are rising due to thermal expansion from warmer oceans and melting of land-based ice. Satellite measures since 1993 show global sea level rise of around 3.2 mm/year (CSIRO). The potential for increases in sea level rise is enormous because the ice caps of Greenland and Antarctic contain over 99% of all the freshwater on Earth (NSIDC). Estimates suggest that if Greenland ice sheets would melt completely it could raise sea level 6 meters. In other words, a one per cent loss of the Greenland ice cap would result in a sea level rise of 6cm (NSIDC). In a process that is accelerating, ice caps are losing mass. In past periods of Earth’s history, levels of atmospheric greenhouse gasses and sea levels have followed one another closely, allowing an inference about where sea level is headed. Sea levels may rise by more than 2 meters for each degree Celsius of warming the planet experiences over the next 2000 years (see figure), according to one study (Levermann et al. 2013). But even a one meter sea level rise could cause major problems for low-lying countries such as the Maldives and Bangladesh, forcing inhabitants to migrate. Around 150 million people live within 1 metre of high tide level (CSIRO). Coastal cities, ports and airports could be flooded, as could cities sited near tidal estuaries, like London. And many nuclear installations are built by the sea which is of great concern knowing what happened in Fukushima.

Shifts in atmospheric circulation could influence weather patterns. Rising temperatures seems to slow down and increase the waviness of the jet stream, increasing long duration extreme weather patterns such as droughts, floods, and heatwaves (YaleEnvironment, 2012). This has significant impacts on temperature and precipitation patterns in Europe and North America. That weather patterns can "get stuck" might explain why the intensity of extreme weather events has increased. We have seen many examples of “stuck” weather patterns during the past few years. Deep southward dips in the jet stream hung over the U.S. east coast and Western Europe during the winters of 2009/2010, 2010/2011, and 2012/2013 bringing a seemingly endless string of snow storms and cold. In the early winter of 2011/2012, in contrast, these same areas were under northern peaks in the jet stream which brought unusually warm and snowless conditions (Francis, 2013). And in summer times persistent weather have been responsible for droughts and heat. The record heat waves in Europe and Russia have been linked to early snowmelt in Siberia (Jaeger and Seneviratne, 2011). These changes affects agriculture, forestry and water supplies. For example, farming becomes more precarious as weather patterns and prognosis are no longer reliable. Changes in weather patterns also impact storm surges and hurricanes. Some scientists suggest that changes to the jet stream drove hurricane Sandy west, towards the coast of northeastern United States (LiveScience, 2013). Ranking as the second costliest hurricane in United States history (Huffington Post, 2013) one can see how changes to storm patterns can have enormous costs to society and the economy.

The complete loss of Arctic summer sea ice has major knock-on effects, such as boosting phytoplankton and absorbing more heat in the oceans. Ocean warming effects marine life in temperate latitudes making species such as cod, haddock and flounder shift their geographic ranges, leaving fewer cold water species (NASA, 2013). Disease also spread faster in warmer water so parasites are having larger effects on species, especially sensitive coral reefs. Because the planet’s oceans currently absorb about a quarter of the carbon dioxide, which lowers the pH level of the water, the oceans are becoming acidic. Acidification makes shell-formation among marine organisms such as plankton and mollusks more difficult, which could have major cascading effects on marine life as these organisms make up the base of the ocean’s food chain. Coral reefs, which are marine biodiversity hotspots, are particularly sensitive to changes in temperatures and pH. Coral reef ecosystems are in global decline and this means loss of storm buffers and loss of estuaries for fish species that generate 200 million jobs and food for a billion people (NOAA).

According to most scientists, a CO2 amount of order 450 ppm or larger, if long maintained, would probably push Earth toward an ice-free state (Hansen et al. 2008, 2013). 450 ppm is considered a climate tipping point, beyond which we would have no control. We are at 400 ppm today, which constitutes high risk of transgressing the tipping point. According to science we need to get back down to 350 ppm to be considered in the safe zone. 

Some studies suggest that we may have passed a tipping point in relation to having sea-ice free summers in the Arctic already in 2007 (Livina and Lenton, 2013). The loss of reflective surfaces in the summer reinforces further warming, as dark water absorbs more heat from the sun, causing further melting. The loss of summer sea-ice cover is reversible, given that warming slows down (i.e. drastic reduction in greenhouse gas emissions). 

By looking at sediment records a team of scientists found that 1°C warmer than today's temperatures in Greenland contributed to a 4-6 meter sea level rise from the collapse of the southern part of the ice sheet (Reyes et al., 2014). 

At 1.5°C warming, from pre-industrial levels, Siberian permafrost starts thawing on a large scale (Vaks et al., 2013). Crossing this tipping point could potentially lead to runaway climate change because of the scale of carbon stores and because methane is 20 times more effective in increasing global temperatures than equal amount carbon dioxide.

What is happening in the Arctic impacts us all. Rapid climate changes are now taking place in the Arctic with impacts on a planetary scale. We do not know how to fix it except from lowering our emissions. Many experts say we need a rapid reduction in greenhouse gas emission, starting now. Global leaders have to come to an agreement that substantially reduces emissions, the rich world taking the lead. Our only home, the Earth, is changing rapidly and we are now running into dangerous risks of substantial warming and triggering climate tipping points that reinforces further warming beyond our control. The last call is coming up in November of 2015 Paris Climate Meeting. “The Arctic acts as an early warning system for the entire planet” (Dr. Chip Miller, NASA Jet Propulsion Laboratory). We should all follow what happens there closely and warn the world of the potential dangers of going on with "business as usual".