SOMETHING SURPRISING happened to Greenland’s massive ice sheet in July 2012. One glaciologist described it as the “nightmare” they’d been dreading: For the first time in observed history, the entire ice sheet was melting.
Ice always melts along Greenland’s coast during the summer. To witness the Ilulissat Icefjord breaking off massive chunks of ice into the sea at this time of year is truly overwhelming. As pieces calve off the ice sheet, they form a seemingly endless archipelago of icebergs floating down the west coast.
But over the course of four days in July 2012, a persistent high-pressure system locked warm air over this vast ice sheet mass, turning a thin layer into slush across almost the entire ice sheet (97 percent) for the first time in observed history. As a result, its surface shifted from white to a darker color, with dramatic consequences for the atmosphere.
Ordinarily during the summer, the ice sheet’s bright surface reflects 85 percent of incoming heat from sunlight back to space. But during this short period of unprecedented surface melting, the ice sheet’s darker surface absorbed more than 50 percent of that heat. That tipped Greenland from a net “cooler” of Earth’s atmosphere to a net “heater.”
In fact, Jason Box and his team at the Byrd Polar Research Center at Ohio State University, estimated that during this extraordinary two-week period Greenland injected an estimated 300 exajoules (EJ) (10 followed by 18 zeros) of energy into the atmosphere. To put this into perspective, the annual energy use of the entire world is approximately 600 exajoules. (The USA, the largest energy-using nation, consumes some 200 exajoules.) This means that, for a short time that summer, Denmark surpassed China and the USA as the country having the greatest impact on Earth’s climate—not because the Danish people were dumping more greenhouse gases into the atmosphere, but because the ice sheet on Greenland stopped reflecting all that energy back into space.
When lakes and rivers are overloaded with nutrients and chemicals from urban and agricultural runoff, algae blooms can choke the ecosystem by consuming all the oxygen when they decay.
Figure 3.1 Rising Global Risks. The more we learn about how the Earth system works, the larger our reasons for concern. As climate science advances, the level of risk has risen, here shown as “red embers” of risk from the past three assessments of the Intergovernmental Panel on Climate Change (IPCC), the third assessment (TAR) in 2001 at top, the 2007 fourth assessment (AR4) in the middle, and the latest fifth assessment (AR5) from 2013 at bottom. As seen from the graph, the risk for climate-induced disasters (the last category in each assessment) was estimated at 4–5°C in 2001, but as low as 2–3°C in 2013. The 2°C (3.6°F) target for global warming is shown by the dashed line, including past (1900–2000) warming and future warming.
* Majority of people adversely affected
This was just an early warning. We don’t know yet if Greenland has actually passed a tipping point, beyond which the island will enter a phase of permanent self-reinforced warming. The ice sheet hasn’t shown the same dramatic melting since 2012. The tricky thing is that if Greenland does this a few times, it could induce a self-reinforced warming that will be impossible for us to stop. As Box told one reporter, “the sleeping giant is awakening.”
The Greenland ice sheet contains enough water that, if all the ice were to melt, it would raise global sea levels by about 7 m (23 ft), with catastrophic impacts on coastal cities and regions. But as the 2012 “flash” melting demonstrated, the biggest danger of transgressing planetary boundaries isn’t so much that such an event will cause an immediate crash. It could take hundreds or even thousands of years to melt Greenland’s entire ice sheet. Rather, it’s that such a disturbance could light the fuse on a planetary “time bomb” by triggering changes in feedback processes (from “negative,” dampening processes to “positive,” self-reinforcing processes) in which Earth takes over, transforming the initial event into a self-accelerating, irreversible engine of change so strong it pushes the planet into another state.
Should that happen, as mentioned in Chapter 1, Earth could turn from friend to foe. Instead of counteracting human pressures through negative feedbacks, Earth could launch runaway positive feedbacks with enormous consequences. And there’d be nothing we could do about it.
The fact that ice and snow, because of their white surfaces, reflect incoming heat from the sun back into space, is one of the most important and well-known of Earth’s negative feedbacks. By helping to cool the planet, this process also helps keep Earth in its current stable state. But as the atmosphere warms, more ice and snow vanishes—faster than predicted. Between 2004 and 2008, the Arctic Ocean lost 42 percent of its multiyear sea ice, something experts hadn’t expected until 2030 at the earliest. During the summer of 2007 alone, the Arctic Ocean lost 30 percent of its seasonal sea ice cover. While the rest of the world is still adjusting to the realities of 1°C (1.8°F) of planetary warming, the Arctic has already been experiencing a 2°C (3.6°F) world.
The question is: Has a fuse already been lit on a planetary-scale climate bomb?
ANTARCTICA: WEAK BIG BROTHER?
Earth has gone through warm periods before. About 120,000 years ago, during the so-called Eemian period, temperatures in Greenland were at least 4°C (7.2°F) higher than they are today, sometimes surging as much as 8–10°C (14.4–18°F) higher. Thanks to studies of marine fossils along coastal shore lines, we know with a high degree of certainty that global sea levels during this period were approximately 4–8 m (13–26 ft) higher than they are today. Melting ice sheets were a dominant cause, presumably with a large contribution from Greenland.
A recent analysis of Greenland ice cores, however, tells an unexpected story. When Dorthe Dahl-Jensen of the Niels Bohr Institute in Copenhagen and her colleagues on the North Greenland Eemian Ice Drilling project (NEEM) studied ice cores from 120,000 years ago, they found that the Greenland ice sheet had not melted as much as scientists would have expected. In fact, during this prolonged and great warming, the 2.5-km (1.5-mi) thick ice sheet lost only about 400 m (0.25 mi) of ice. It appears that Greenland is more resilient to a warming shock than previously suspected. At first blush this sounds like good news!
But that raised a troubling question. If Greenland had lost only 400 m of ice, an amount estimated to have contributed about 2 m (6.5 ft) to the global sea level rise, where did the rest of the water come from? Where are the 2–6 m (6.5–19.5 ft) missing from the equation? There’s really only one possible answer: Antarctica.
For researchers, it was always the Arctic, not the Antarctic, which was seen as the vulnerable pole. Antarctica has always been considered the resilient big brother. The massive amounts of water in the ice sheets there—enough to raise global sea levels by some 70 m (230 ft) if they melted—always seemed safely locked away. But perhaps we are mistaken. Maybe Antarctica isn’t as resilient as we have always thought.
Two recent reports by independent research teams appear to suggest just that. They conclude, based on observations, that the Thwaites Glacier, a keystone holding the massive West Antarctic ice sheet together, and several neighboring and interconnected glaciers, may have irreversibly started to melt. Since 2007 these glaciers have poured as much meltwater into the Amundsen Sea in West Antarctica as all of Greenland has in the north, some 280 billion tons a year. And that amount has risen rapidly since then.
For West Antarctica, this represents a worrying tipping point, as warming ocean water melts these massive ice sheets from below. This in turn lubricates the sloping bedrock on which they rest, setting them irreversibly in motion, slowly slipping into the sea. The only thing holding the entire Thwaites Glacier from collapsing into the sea, at this point, is a 600-m (0.37-mi) deep ridge on the sea floor. Researchers believe that the Thwaites Glacier functions as a massive ice plug, holding the other glaciers in West Antarctica in place. If this plug were to be pulled out, the other glaciers could also slide into the sea.
We won’t see a gigantic domino-like tumbling of glaciers all at once, of course. It’s more likely to take place over the next 200–500 years, committing the world to at least 3 m (9.8 ft) of additional sea level rise. This may seem like a slow pace and a long time period. But the fact is, the moment of truth is right now. The fate of Antarctica will be determined by whether we push the “on” or “off” button today. Once a tipping point is crossed, it will be too late. We actually write the future in the present.
Even if we take actions immediately to slow the pace of melting in Antarctica, however, we may already be committed to an additional 1 m (3.3 ft) of global sea level rise during this century. This is in addition to the 1 meter already estimated by the IPCC for this same period. The fact is, we don’t know how to adapt to such a pace. As glaciologist Richard Alley of Pennsylvania State University pointed out when these studies were released, crossing this tipping point in Antarctica means that we are now committed to a global sea level rise equivalent to a permanent Hurricane Sandy-size storm surge.
MESSAGE FROM EARTH: PAYMENT DUE
Until now, the remarkable resilience of the Earth system has given human development a “free ride.” Even during the current era of massive abuse of the planet—especially since the great acceleration of pressures that began in the mid-1950s—the planet has been remarkably forgiving, applying dampening (negative) feedbacks to absorb most human impacts. Despite our business-as-usual practices—emitting greenhouse gases, losing biodiversity, polluting air and water, over-extracting natural resources, degrading land and forests—Earth has pushed ahead without major repercussions.
In fact, the model of economic growth at the expense of the environment model has actually worked quite well! As Al Gore has pointed out, we’ve profited handsomely from using our climate as a sewer. For those nations that took part in the industrial revolution, this approach generated immense wealth extremely quickly. It worked because the growth was subsidized by Earth: More energy, more resource use, greater consumption of ecosystems, largely for free.
But the era of “massive Earth abuse” is now over. We’ve reached the end of the road with our current development paradigm. Not because we’ve run out of resources. Nor because of poor water, polluted air, or deteriorating ecosystems. But, rather, because we’re approaching a point where the pressure we put on the planet may push the wrong “on” buttons, triggering Earth to kick in with self-reinforcing “positive” feedbacks—like the rapid warming of Greenland from loss of reflective snow and ice. These are the “big whammies” we need to avoid above all else.
A farmer in India’s Madhya Pradesh state clears land by burning the forest. Slash-and-burn methods cause health problems and regional-scale air pollution that affects rainfall patterns.
Earth’s message is loud and clear: It’s time to pay up. Red warning flags are flying everywhere. Humanity has already transgressed three of the nine planetary boundaries our team of scientists identified in 2009 to keep the world in a safe operating space: climate change, rate of biodiversity loss, and the global nitrogen cycle. Other thresholds are also in danger of being crossed, such as land-use change (because of deforestation and urban expansion) and freshwater use (because of the ever-increasing demand for food, which requires huge amounts of freshwater during its production). Recent analyses by our scientific peers show that the global phosphorus cycle has also reached a global danger zone.
Consider the situation with climate change. The year 2014 will almost certainly be remembered as a milestone in global climate risk. This was the year when CO2 concentrations in the atmosphere reached the critical level of 400 ppm—450 ppm for all greenhouse gases. Political leaders have generally accepted the idea that a greenhouse gas concentration of 450 ppm will correspond, on average, with a 2°C (3.6°F) increase in global warming. As many scientists have shown (and our planetary boundaries research strongly supports), this is a very optimistic assumption. In fact, most risk analyses indicate that we must stabilize the atmosphere at a lower GHG concentration to avoid a 2°C rise in global temperature. But be that as it may, a rise of 2°C is agreed upon as the boundary beyond which we could cross catastrophic tipping points.
Now we’ve reached that ceiling. We’ve saturated the atmosphere. Yet we still haven’t changed our ways. As Corinne Le Quéré and her large international team of Future Earth scientists in the Global Carbon Project have shown, global emissions of carbon actually surged in 2014. Their estimates show that, in 2013, a staggering 36 billion tons of CO2 were emitted—the most in human history! And projections show that we will likely break through the 40-billion ton barrier by 2015. In fact, we’re following a path that, on average, takes us to 4°C of warming by the end of this century.
This is unacceptable, in our view. We believe that even 2°C of warming will lead us into very dangerous territory. The last time we had 2°C warming—120,000 years ago—the global sea level was 4–8 m (13–26 ft) higher than today. Based on everything we know about how Earth has fared in its geological past, 4°C of warming will create nothing less than a global crisis in which we have no idea how to feed humanity, much less preserve cities like New York or Sydney.
As if that weren’t enough, we must always remember that these estimates could be overly conservative, since they’re based on optimistic assumptions about Earth’s continued resilience (from large carbon sinks in the biosphere) and no tipping points. In the face of potentially catastrophic outcomes, we need to consider the probabilities of even the improbable.
Is what we have to look forward to: A gradually less beautiful world? A gradually weaker planet? A more expensive place to live, where resources such as oil and metals are harder to find, and ecosystem services such as food and drinking water are more scarce? A place where healthy conditions like air quality are more difficult to deliver? Is this the price we have to pay for using up the safe operating space on Earth?
BIODIVERSITY ON THE BRINK
The risk of triggering “big whammies”—of crossing thresholds that bring abrupt planetary-scale changes—is not unique to the climate system. We know from vast empirical evidence that many ecosystems, from local lakes to forests and coral reefs, also have tipping points. After remaining in a stable state for a long time, such ecosystems can flip abruptly into another state.
Take a rainforest, for example. Under pressure from deforestation and climate change, a rainforest can abruptly shift into a savannah, and get locked in that new stable state. To maintain a stable state, an ecosystem needs feedbacks that reinforce that state. For a rainforest, the feedback that keeps it stable is the self-generation of moisture and rainfall, thanks to its vast canopy. But when a rainforest is opened up by the cutting of trees, and the atmosphere gets warmer, the system gradually dries out. Its resilience is lost. Eventually it gets to the point where the system crosses a threshold, and the feedback changes direction, from self-generating moisture to self-generating dryness. Suddenly dry air flows through the opened canopy, evaporating moisture that was previously held within the system. Less rain is generated due to less pumping of water from tree roots. The system becomes self drying, locked in a savannah state.
Two other examples of ecosystem tipping points that we’ve tracked at the Stockholm Resilience Centre include hard coral reef systems, which can suddenly collapse under the pressure of ocean warming, nutrient overload, and overfishing, leading to the establishment of soft coral systems or reefs dominated by seaweed; and lakes, wetlands, rivers, and groundwater systems, which can suddenly explode with algae blooms and anoxic conditions when runoff from farms and urban areas overloads them with nitrogen or phosphorus.
Of all the factors contributing to the resilience of an ecosystem, and thus helping to maintain its current state, perhaps the most important is biodiversity. When top predators like sharks, wolves, lions, or cod—or critical grazers like parrot fish or surgeon fish—are removed from an ecosystem, the entire food web can be thrown out of balance, triggering tipping points that can abruptly push these ecosystems into a different state. The same thing is true of Earth. Biodiversity operates from the “bottom up” as a planetary boundary that regulates local ecosystems, becoming a global concern if enough systems topple at the same time. The stability of the whole planet relies on a myriad of stable ecosystems, which in turn depend on the richness of different functional groups of species—from bacteria in the soils to pollinators and top predators.
Figure 3.2 Atmospheric CO2. The planetary boundary for climate is set at 350 ppm CO2, based on an analysis of the sensitivity of the climate system to increased greenhouse gas concentrations in the atmosphere, on the behavior of the large polar ice sheets under conditions warmer than those of the present geological epoch, and on the observed behavior of the climate system at a current CO2 concentration very close to 400 ppm. As the chart shows, we are already beyond the climate change boundary and in the danger zone. The challenge before us, therefore, is not just to change the trajectory of our path of an ever-increasing concentration of CO2, but also to remove CO2 from the atmosphere if we are to move back into a safe operating space for the climate.
Figure 3.3 Staying with a Global Climate Boundary Means Operating Within a Finite Carbon Budget. A world transformation into the safe operating space of the climate boundary will require the decarbonization of the world economy by mid-century. The earlier we bend the global CO2 emission curve, the easier it will be to return into the safe operating space. Waiting until 2020 before bending the curve will impose an almost impossibly steep 9 percent per year rate of global reductions.
Since we published our analyses of planetary boundaries in 2009, new evidence has come to light suggesting that biodiversity can also function as a “top down” planetary-scale tipping point. A recent analysis by an international group of ecologists led by Anthony Barnosky of the University of California, Berkeley, recently presented evidence that by mid-century we could face a planetary-scale tipping point if we continue to lose biodiversity at the current pace. The combined pressures of population growth, widespread destruction of natural ecosystems, and climate change may be driving Earth’s biosphere toward an irreversible change. This could lead to a collapse of many, if not most, agricultural systems on Earth, which depend on a balanced configuration of species, including micro-biota for soil productivity, and pollinators for seed and fruit development. Without adequate preparation, such a planet-wide tipping point would have massively destructive consequences—one of them being to undermine our ability to feed ourselves.
CORAL REEFS: THE “CANARIES” IN THE CLIMATE COAL MINE
If you want to know what’s happening in the oceans, pay close attention to the world’s major coral reefs. Often described as the “rainforests of the sea,” coral reefs host a wealth of biologically rich and productive ecosystems. They could also be called the “canaries in the coal mine” of climate change, because they’re so sensitive to shifting conditions. Whenever there’s a change in the ocean, it often shows up first in coral reefs.
Lately, the coral reefs have been suffering badly. Even the richest coral reefs on Earth, such as those off the Raja Ampat Islands in Indonesia’s West Papua province, haven’t been immune to the impacts of global changes. Even here, far from pollution and overfishing, warming seas have triggered coral bleaching, which occurs when corals lose the micro-algae that live within their tissues and provide their lively colors.
It only takes a few weeks of warmer-than-usual seas—from 1–2°C (1.8–3.6°F) above normal—for widespread bleaching to occur. As we know, 95 percent of the heat increase caused by greenhouse gas emissions is trapped in the oceans, making climate change a key trigger behind the rising severity of bleaching events. Moreover, as Daniel F. Gleason and Gerard M. Wellington of the University of Houston reported two decades ago, bleaching often occurs in combination with higher levels of solar radiation. In addition to higher water temperatures, many of the reefs in the Caribbean Sea, where bleaching was observed by Gleason and Wellington, had also been exposed to higher-than-average intensities of UV-radiation. What caused the increase in UV-radiation? It was probably a thinning of the stratosphere’s protective layer of ozone, due to the presence of chlorofluorocarbons (CFCs) and other chemicals emitted by industries and communities.
More than 75 percent of Borneo’s lowland rainforests have been cleared to make way for palm oil plantations.
Another problem has emerged in the Great Barrier Reef of Australia. During the past 20 years or so, healthy calcification by coral seems to have decreased by 14 percent. Although research suggests that increasing water temperatures provided some of the stress affecting the coral, science shows that another factor is at work, making it difficult for reef corals to build their calcium carbonate skeletons. That factor is increased ocean acidification.
Almost a third of the CO2 pumped into the atmosphere by humanity dissolves in the oceans. There the CO2 forms carbonic acid, which decreases the pH of sea-water, making it more acidic. This in turn reduces the concentrations of carbonate ions in the water, which corals need to grow their skeletons. Left unchecked, ocean acidification can even cause coral skeletons and reefs to dissolve.
Research indicates that coral reefs weakened by overfishing and pollution are less likely to survive rising water temperatures and higher ocean acidity than pristine ones like those in the Raja Ampat Islands. Overfishing of reefs by nearby communities or international fleets removes key species of plant-eaters at the same time that runoff loaded with fertilizers and other pollutants stimulates the growth of soft coral and seaweed. The combination can be overwhelming for coral reefs, flipping them into a new and unproductive state. By contrast, reef ecosystems that maintain biodiversity have a much better chance of bouncing back from the impacts of climate change. Resilient and diverse communities, in the end, are the best defense against big whammies.
OUT OF THE BLUE?
In the new era we’ve created, the Anthropocene, it’s not enough to acknowledge that we’re putting enormous pressures on Earth through the nine planetary boundary processes we’ve identified. Nor is it enough to recognize that what happens at the local level directly affects what happens at the global level, and similarly that global-scale changes impact local problems. We must also accept the fact that, when tipping points are crossed, all of these cross-scale interactions can lead to unexpected outcomes.
When the EU, for example, revised fishing policies not long ago to drive high-tech fishing fleets from their “home waters,” few political leaders could have anticipated that they were launching a string of events that potentially is associated with the world’s worst outbreak of the ebola virus. In response to the EU’s tighter fish quotas, international fishing fleets moved their operations to the coast of West Africa, where they “vacuumed” up vast stocks of fish. This was the same area where climate change, pollution, and mismanagement of local fisheries had already degraded local mangrove forests, sea grass beds, and coral reefs. The combined effect was a rapid decline in catches for African fishermen, who, faced with a shortage of food, have increasingly turned to bush-meat as a substitute to feed their families. As a result, local trading patterns shifted, with hunters killing more forest animals such as chimpanzees that are key sources of zoonotic diseases such as ebola. It’s possible the current outbreak in Liberia, Sierra Leone, Senegal, Guinea, and Nigeria began in the forest when a child came into contact with the butchered meat of a wild animal infected with the virus. He may have spread the disease to others as impacts ricocheted around our interconnected world, where it is no longer possible to separate the legislative halls of the EU from the forests of West Africa.
A similarly unexpected train of events preceded the Arab Spring in 2010–2011. It began with a blistering heat wave in Russia, where massive wildfires and a prolonged drought prompted Prime Minister Vladimir Putin to restrict exports of wheat and other staple cereals. Similar actions by Prime Minister Kevin Rudd of Australia, which had suffered a dozen years’ drought, combined with major speculation on the world’s markets, helped to trigger a dramatic rise in world food prices. It didn’t help that the global price of phosphorus, the key fertilizer in agriculture, had also risen three-fold, or that oil prices had also shot up 100 percent, boosting energy costs for farmers. As a result, food riots erupted in most capital cities in North Africa and the Horn of Africa. The region was bubbling with unrest. When Tunisian street vendor Mohamed Bouazizi set fire to himself to protest mistreatment by police, he provoked an international revolution. After decades of repressive dictatorships, a generation of frustrated young activists stood up against aging tyrants in nation after nation and the regimes began to fall like dominoes. Social unrest among common urban citizens triggered by the abrupt rise in food prices, in turn caused by Earth’s invoices to the world food markets, apparently interacted with the social uprising of a young generation fed up with dictatorial suppression. What had begun as a heat wave in Russia became a perfect storm of social–ecological disruption in Africa.
Figure 3.4 Projected Coral Reef Bleaching. This map depicts the estimated frequency of coral reef bleaching events in the 2030s and 2050s. Corals become “bleached” when water temperatures rise too high and are sustained for too long. The colors represent the percentage of years in each decade in which a National Oceanic and Atmospheric Administration (NOAA) Bleaching Alert Level 2 (severe thermal stress) is predicted to occur.
These kinds of long-distance interactions are a new phenomenon of the Anthropocene. Human activities in one region (like coal-fired plants in the Ohio Valley or factories in Novosibirsk) cause global environmental change (like higher temperatures from greenhouse gases), which generates a surprisingly rapid downgrading of a large Earth-regulating system in another region (like the melting of sea ice in the Arctic Ocean). How a European, American, or Chinese worker chooses to commute to the office or factory can now affect the likelihood of rainfall that will benefit farmers in the Sahel. How Southeast Asian nations manage their rainforests can now impact the frequency of heat waves in Europe or the ability of Arctic Inuit peoples to hunt on a frozen sea. These actions, in turn, cause feedbacks that further amplify global changes, creating impacts that boomerang back on the first region, or, more likely, affect some other region that may not have contributed to the original problem at all.
Because of this global web of interconnections, humanity in the Anthropocene must now consider all biomes in the biosphere—every landscape and seascape—when considering the best strategies to secure social and economic prosperity in our local communities. In a world facing big whammies, it’s every nation’s concern, indeed every citizen’s concern, how we, as a world community, manage the entire biosphere.
This orangutan at the Nyaru Menteng Reintroduction Center in Borneo was rescued after its mother was killed by hunters.
