Part 4 (2/2)
Speed of transition: The speed of our transition to a safe-climate zone is also a critical issue. The risks posed by allowing the world to stay outside the safe-climate zone need to be a.s.sessed, along with the impacts that would be generated, ecologically and socially, by speeding up the transition. We know, for example, that species losses increase the faster that temperatures change, and we need to weigh up those sorts of impacts alongside the risks a.s.sociated with a slower transition.
Dangerous climate change versus the safe-climate zone: How does the achievement of a safe climate relate to the more widely held goal of avoiding dangerous climate change?
The core objective of the UN Framework Convention on Climate Change, which also governs the Kyoto Protocol, is to achieve: stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system. Such a level should be achieved within a time-frame sufficient to allow ecosystems to adapt naturally to climate change, to ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner.
It is self-evident that the world should act to avoid 'dangerous anthropogenic [human] interference with the climate system', but making that our primary goal has created problems.
The theory of the greenhouse effect was developed more than a hundred years ago by the Swedish chemist Svante Arrhenius. In the 1960s, scientific interest in the theory began to intensify when the American scientist Charles Keeling published his findings, which showed that carbon dioxide levels in the atmosphere were systematically rising from the 315 parts per million that he had first observed in 1958. Thirty years later, scientific knowledge was strong enough to lead to the formation of the IPCC, by which time the atmospheric carbon dioxide level was 350 parts per million.
Although concern about global warming was now growing strongly, it was also clear that changing human behaviour enough to stop, or slow, greenhouse-gas emissions would require very significant changes to the economy, and that these changes would be resisted strongly. So, scientists focused their message on the need to avoid dangerous climate change - a message that proffered threats big enough to grab the attention of the political elite and, perhaps, convince them that matters other than short-term economic gain should be considered. Corporate elites, however, maintained widespread resistance to their message, so scientists opted to focus on only the strongest concerns about climate change: how could we avoid the loss of the Greenland and the West Antarctic ice sheets and the metres of sea-level rise that would occur as a result? How could widespread ecosystem collapse be avoided?
The result of this tactic was that scientists began to focus on action to avoid outright climate catastrophe. In response, the politicalcorporate elite set targets for change just a fraction under the levels that the scientists identified as having catastrophic consequences. Once these targets were articulated - for example, an upper-warming limit of 2 degrees, or 550 parts per million atmospheric carbon dioxide - policy inertia tended to lock them in, regardless of later changes in scientific knowledge. Scientists' concerns about identifying dangerous climate change, and about the measures necessary to avert it, were transformed into a process for avoiding catastrophe, or apocalypse, in some far-distant future. As a result, unrealistic targets have been set that, even if achieved, would see civilisation-destroying climate change.
An alternative approach would identify climate conditions that are known to be safe, and then make it the goal of public policy to get back into this safe-climate zone and avoid leaving it again. Instead of scientists being asked to identify what elevated greenhouse-gas levels might be bearable (should we stabilise at 450, 550, or 650 parts per million?), the safe-climate approach would be to ask what actions are necessary to get back to the zone in which greenhouse-gas levels are known to be safe.
The danger of tipping points: a major concern is the possibility that key elements of the Earth system could go through critical thresholds or tipping points (as discussed in Chapter 10) that lead to a significant increase in warming processes, such as a big jump in greenhouse-gas emissions, or to a major change that severely harms other species or human societies.
The evidence is clear that the Earth's biosphere is already in a state of dangerous climate change. Current impacts - including desertification and water shortages, extreme weather events, severe and frequent bushfires, ecological breakdown, difficulties with food production, and changes to major geophysical systems such as the Arctic - are already causing problems in many parts of the world. Pressures are building in the Earth system that will give way to even bigger changes in temperature and the environment, which means that the problems already causing concern are a relatively mild foretaste of what will come if the economy and the climate system are left to follow current trends.
While climate danger is generally cast as occurring at some time in the future, climate change is already dangerous for some people: the populations of the small nations of the Pacific, who are already abandoning their low-lying island atolls because rising sea levels and storm surges make life there impossible; people in sub-Saharan Africa badly affected by extended drought; and the Inuit people of the Canadian Arctic who can no longer move safely across the sea-ice to hunt, and whose homes are cracking and tipping as the permafrost melts.
The task, now, is to establish the boundaries of the safe-climate zone. Policy and action should be framed: * to protect all people, all species, and all generations; * to accept an even smaller risk of failure than the best-practice safety standards for the protection of people in civil engineering (the one-in-a-million principle) in avoiding dangerous changes to the Earth caused by climate change; and * to keep the Earth in the safe-climate zone, rather than to simply avoid dangerous climate change.
CHAPTER 13.
The Safe-Climate Zone.
For the past 100,000 years, humans and their predecessors have survived and adapted as the Earth's temperature has fluctuated by up to 7 degrees. The current global average temperature is within 1 degree of the maximum temperature known to have occurred during the past million years, but conditions 6 degrees colder were experienced during the depths of the recurring ice ages. At a cold point 20,000 years ago, so much ice was stacked on the land that sea levels were 120 metres lower than they are now. On the other hand, 125,000 years ago, when temperatures were similar to today, the sea level was 56 metres higher.
The past 11,500 years since the last ice age is known as the Holocene - a period that coincides with the establishment of human civilisation. During the Holocene, temperatures have varied within a 1-degree band, although the variation has, for the most part, been considerably less. Sea levels have been almost constant over the last few thousand years of human civilisation and, more significantly, over recent centuries, when most climate-sensitive infrastructure has been built. Coastal cities, including the special case of Venice, s.h.i.+pping facilities, the permanent settlement of river deltas, and other low-lying areas have survived because sea levels have moved very little.
Increasingly, however, human activity is changing the surface of the planet and also, consequently, the climate. Today we see that impact around the globe. Large parts of the land have been taken over by humans for grazing and cropping, and for cities. Wetlands have been drained on a huge scale; rivers have been regulated with dams; and forests have either been cleared, or cut into small patches by roads and clearings. As we've extracted and processed resources, and thrown away our wastes, our natural world has become very fragile, fragmented, and impacted by chemical and physical a.s.saults.
The nation-states and the vast, fixed physical infrastructure of cities and roads that human civilisation has built will make it very hard to adapt and move across the continents if the climate were to become more changeable - if, for example, it began to swing between warm periods and glacial periods, such as those that left much of North America and northern Europe under metres, and sometimes kilometres, of ice, 20,000 years ago. While we might adapt to lower sea levels, higher seas would be catastrophic for whole cities, farming communities, nations, and coastal-wetland species.
Given our sedentary pattern of living, how can we identify a band of environmental conditions that defines a contemporary safe-climate zone? Would the relatively stable climate pattern of the Holocene and its development of agriculture and civilisations be appropriate? Can we tolerate today's temperature, which is at the top end of the Holocene range? Should we accept a summer-ice-free state in the Arctic as a normal part of the range of conditions to be included in the safe-climate zone? To maintain the Earth system's resilience, is it ecologically necessary to cycle through a summer-ice-free state periodically?
Avoiding a summer-ice-free Arctic.
During the past million years, the Arctic has been partially free of summer sea-ice for short periods, but today's circ.u.mstances are very different. In the past, this event represented the gently sloping top of the warming hill; now, however, the level of greenhouse gases, and the upward pressure on temperatures, is substantially higher. What is more, the temperature is charging through this barrier with the human foot still pressing on the emissions accelerator. The real risk is that, rather than mark the natural peak of the temperature cycle between periods of ice ages, a summer-ice-free state in the Arctic will kick the climate system into run-on warming and create an aberrant new climate state many, many degrees hotter. The last time such a warming occurred - many tens of millions of years ago - many plants and animals became extinct around the world.
An Arctic free of summer sea-ice cannot, then, be considered part of the safe-climate zone, and urgently restoring its full extent is necessary to avoid significant ecological damage and, possibly, catastrophic greenhouse heating.
In defining the safe-climate zone, it is more important to identify tangible elements of the environment that need to be restored and maintained, rather than just to focus on temperature and carbon dioxide levels.
Some features of a safe-climate policy would include: * retaining the full summer Arctic sea-ice cover, the full extent of the Greenland and Antarctic ice sheets, and the full extent of the mountain glacier systems, including the Himalayas and the Andes; * maintaining the ecological health and resilience of the tropical rainforests and coral reefs, with no loss of area or species; * maintaining the health and effectiveness of the natural carbon sinks, at least, to their level of 50 years ago; and * capping ocean acidity at a level that prevents any risk to organisms.
The appropriate temperature range and climate-system settings compatible with the maintenance of these environmental features can then be determined using the best available climate science, with a risk of loss of less than one in a million. Here are three ways of thinking about this range: The Hansen Arctic threshold: In the draft paper released in April 2008, James Hansen and seven co-authors say that a carbon dioxide level of '300325 parts per million may be needed to restore [Arctic] sea ice to its area of 25 years ago'. In other words, the amount of carbon dioxide in the atmosphere would need to be significantly reduced from the current level of 387 parts per million.
Maintaining Arctic sea-ice thickness: The Arctic sea-ice thinned substantially from about 3.5 metres in the 1960s to about 2.5 metres by the end of the 1980s, which was well before the beginning of the dramatic decline in ice-surface area that became apparent from the mid-1990s onwards. In the late 1980s and early 1990s, s.h.i.+fting wind patterns flushed much of the thick, older sea-ice out of the Arctic Ocean and into the North Atlantic, where it eventually disintegrated, replaced by a thinner layer of young ice that melted more readily in the succeeding summer. Mark Serreze from the University of Colorado says that 'this ice-flus.h.i.+ng event could be a small-scale a.n.a.logue of the sort of kick that could invoke rapid collapse, or it could have been the kick itself '. Pulses of warmer water that began entering the Arctic Ocean in the mid-1990s, which promote ice melt and discourage ice growth along the Atlantic ice margin, are 'another one of those potential kicks to the system that could evoke rapid ice decline and send the Arctic into a new state', according to Serreze. In 1989, the global average temperature was about 0.3 degrees cooler than it is currently. To restore this temperature, it would be necessary to drop carbon dioxide levels to 315 parts per million.
An insight from the early Holocene? For part of the period from 60008500 years ago, the Arctic warmed to the point that it was largely free of sea-ice each summer. A Dutch Danish scientific team, using plant-fossil data, estimates that the carbon dioxide level during this time ranged from about 325 parts per million to a less-well-defined lower level that allowed the summer sea-ice to return.
While more research is needed before the boundaries of the safe-climate zone can be set definitively, it is reasonable and prudent to conclude from these three case studies that we should aim, initially, for at least a 0.3 degree cooling to bring the global average temperature-increase above pre-industrial levels to less than 0.5 degrees. To bring the planet within reach of this temperature, the atmospheric carbon dioxide level should be under 325 parts per million - the level that Hansen is arguing is needed to fully restore the Arctic ice.
This would also be a reasonable boundary for avoiding a range of other major climate problems, including the loss of the mountain glaciers, and the Greenland and West Antarctic ice sheets; damage to tropical rainforests; and a decline in the capacity of carbon sinks.
Hansen, discussing the impending loss of the Arctic summer sea-ice in October 2007, noted that the climate system is dominated by positive feedbacks - knock-on effects that exaggerate the current trend of the climate. These feedbacks run in both directions, so if enough of the strong, high-inertia warming feedbacks were stalled, or turned around, and the Earth was cooled for a while, the climate system would then run in the opposite direction. If humans decided to initiate a sufficient cooling, natural feedbacks would complete the job.
Cooling the Earth.
The Earth is already too hot, and there's already too much carbon dioxide and other greenhouse gases in the atmosphere. The first key step to fix this is to stop adding to the heating processes - greenhouse-gas emissions need to be cut to zero. The second step is to remove from the air the excess carbon dioxide that is keeping the planet too hot. The third step, because time is short and there is already so much heat in the system, may be for humans to cool the Earth directly.
To cut greenhouse-gas emissions, we will need to reduce those warming agents that have a short life. Methane, for example, has a relatively short life in the atmosphere of about a decade, so cutting methane emissions would have an effect relatively quickly. Measures to achieve this include stopping coal, oil, and gas mining (to stop methane leakage); re-engineering waste disposal (trapping methane as an energy source); changing irrigation methods and varieties of rice cultivation; and decreasing the commercial herding of ruminant animals, especially cattle.
We must also stop emitting greenhouse gases, including carbon dioxide, and heating agents, such as black soot, urgently. This is essential, because carbon dioxide is acidifying the upper ocean, preventing marine organisms from forming calcified sh.e.l.ls and exoskeletons. If this continues it will lead to major marine animal and plant extinctions in the not-too-distant future. Black soot is a short-lived warming agent that is washed out of the air by rain in a matter of days; cutting its emissions would have an immediate effect. By dirtying ice, black soot also accelerates glacier and ice-sheet melting - particularly in the Himalayas, because one-third of black-carbon emissions come from India and China. Programs to cut black-soot emissions - for example, by ending the use of coal for heating, stopping diesel use, and by providing energy-efficient and smoke-free cookers to rural communities across Asia - would have an immediate and dramatic effect in reducing the heating effect.
Zero-carbon Britain: an alternative energy strategy, published in 2007, is one of many research reports that demonstrate the feasibility of building a post-carbon economy. Many of the practical technologies and solutions are also surveyed in Chapter 20 of this book.
We must also remove excess carbon from the air. We cannot return to a safe climate if we only cut emissions to zero, because carbon dioxide remains in the atmosphere for so long. Estimates by Matthews and Caldeira from Stanford University indicate that around 200 billion tonnes of excess carbon needs to be drawn out of the atmosphere to achieve the 0.3-degree decrease in the global temperature that is necessary.
Techniques for trapping carbon that is already in the atmosphere include boosting the natural terrestrial processes (re-afforestation); and producing agricultural charcoal, known as bio-char, which is sequestered in the ground.
Such large-scale, relatively low environmental-impact methods depend on growing plants that naturally absorb carbon dioxide. Growing these in the extremely large quant.i.ties necessary to draw down substantial amounts of carbon, however, may conflict with land use for nature conservation or food production. This, along with issues such as water availability and social impacts, needs to be considered in planning such schemes.
Although it is necessary to reduce human greenhouse-gas emissions to zero as quickly as possible, there is a critical side effect. Most carbon dioxide generated by human society is produced by deliberately burning fuels such as coal, oil, gas, and wood, or by unintentionally burning plant material in bushfires, but these processes also produce aerosols, including smoke, and small-particle pollution such as soot, dust, and sulphate particles.
If we were to stop burning fossil fuels tomorrow, the aerosols that cool our planet would be rained out of the air in about ten days. Without these aerosols, which mask roughly half the heating effect caused by carbon dioxide, there would be a sudden jump in temperature. Stopping all carbon dioxide emissions could produce a short-term warming of one-half to one degree. Cutting black carbon-soot emissions would offset some of this effect.
Removing aerosols causes steeper warming the more quickly that fossil-fuel combustion is cut. If fossil-fuel combustion were to be cut to zero in two decades then, a.s.suming a mid-range climate sensitivity, the loss of the related aerosols plus the warming already in the system could produce a warming of more than one degree in twenty years. This would be highly destructive to our ecosystems.
Reducing fossil-fuel combustion to zero in 50 years will also produce a rate of warming far beyond the capacity of most ecosystems to cope, because of the aerosol cooling lost. Cutting fossil-fuel combustion much more slowly, to zero in a hundred years, would have the same effect because, particularly in the latter part of the timeline, more carbon would be kicking into the atmosphere from failing natural carbon sinks, exacerbating the long-term trend.
Slowing the rate of reduction of fossil-fuel combustion may then make the warming problem from aerosol reduction less severe in the short term, but worse in the long-term.
These 'd.a.m.ned if you do, and d.a.m.ned if you don't' problems are known in the fields of science, politics, and economics as 'wicked problems', a concept first articulated by design and planning theorist Horst Rittel. A 'wicked problem' describes a complex set of interrelated and circular problems which are resistant to resolution and where any solution is not good or bad, but only better or worse. Each 'wicked problem' is unique and, effectively, offers only one chance to achieve the least-worst resolution, because poorly constructed 'solutions' can compound the problem and, in many cases, there is a limited time horizon for effective action.
Getting to the safe-climate zone will take time. But, as each year slips by, the impact of warming and the problem of positive feedbacks takes us further away from that zone.
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