Part 5 (1/2)
How long will it take the Earth to cool sufficiently if we achieve zero greenhouse-gas emissions and start reducing atmospheric carbon dioxide? This will depend, in part, on how long it takes us to make the major economic change necessary to achieve zero emissions and to put in place a system to capture and sequester excess carbon dioxide from the atmosphere. Historical precedents for rapid industrial change, such as the Asian 'tiger economies' and the information-technology revolution, suggest that it could be achieved in two to three decades. The economic restructuring achieved during World War II shows that a fast economic transition like this is possible.
However, even after major economic changes were made, drawing down excess carbon dioxide from the air could take 50 to 100 years (even at a high depletion-rate of 6 billion tonnes a year), because of the carbon still being emitted, and the time necessary to develop, build, and maintain such large-scale processes.
While Arctic cooling would start before all the excess carbon dioxide was taken out of the air, it could still be a century before it returned to a safe-climate condition. Over that lengthy amount of time, the Earth would still be subject to rising temperatures. A 1-to-2-degree rise above the present temperature is not out of the question, even if we established a zero-emissions economy in two to three decades - especially when the aerosol dilemma is taken into account.
The risk is real that during the early decades of the transition, major damage could be done to Earth's ecosystems, such as tropical rainforests. It is also possible that the permafrost, and other sources of natural carbon, could be so strongly mobilised, and the natural carbon sinks so damaged, that the process of taking carbon dioxide out of the air would be overwhelmed. In one century, enough ice could be lost from the Greenland and West Antarctic ice-sheets to raise sea levels by several metres. If most of the ice in the Himalayas were lost, food production in nations from the Indian sub-continent to China would be drastically reduced. These would be civilisation-disrupting changes, even if run-on heating was avoided.
The grim reality is that the Earth is too hot right now. Even a zero-emissions strategy and a monumental effort to pull excess carbon dioxide out of the atmosphere will not achieve the necessary cooling soon enough. We must consider the third strategy - cooling the Earth directly.
Natural ecosystems play a role in moderating the Earth's temperature. Marine plankton releases a gas, dimethyl sulphide, that disperses into the air and helps to form dense, sunlight-reflecting cloud; there is also some evidence that water evaporating from forests carries bacteria into the atmosphere to aid the formation of light-reflecting clouds. So boosting the health of marine plankton could help, as could re-establis.h.i.+ng forests on a large scale; however, as global warming grips the planet, it is becoming more difficult to maintain biological systems, let alone to re-establish large areas of forest. If they are to cool the atmosphere, the Earth's ecosystems may need even more help.
In 1992, a US National Academy of Science report on greenhouse warming discussed climate geo-engineering, including very large-scale projects that would deflect a small proportion of the solar radiation striking the upper atmosphere, in order to produce a small cooling. The possibilities considered ranged from the science-fiction-like placement of reflectors in s.p.a.ce, to copying the cooling effect of volcanic eruptions by pumping sulphates, or other particles, into the upper atmosphere, where they would last for a year or two.
More recently, scientists such as Ken Caldeira and n.o.bel-laureate Paul Crutzen have studied proposals to pump sulphate aerosols into the stratosphere, and it seems that this measure could fully cancel the warming caused by greenhouse gases and other warming agents, such as black soot. The sulphate program could be implemented within a few years and have an immediate cooling effect. However, it is not a subst.i.tute for a zero-emissions program, or an excuse to continue emitting greenhouse gas. Nor is it a safe solution in the long-term, since any premature end, or interruption, to such a program - through war or economic recession, for example - would subject the globe to a major heating-pulse within two years.
The greatest value from a sulphate geo-engineering program, with the least ecological risk, would be to carry it out as soon as possible, for as short a time as possible. Every effort should be made to reduce the necessary intensity of any geo-engineering program - for example, by bringing down methane and black-soot pollution as fast as possible.
Humans have been unintentionally geo-engineering the Earth for a long time. The first major intervention was the use of fire to reshape ecosystems over large areas; the second was the introduction of large-scale land clearing for farming and other purposes; and the most recent has been industrialisation, which moved ma.s.sive amounts of materials into the air, the waters, and the land. The warming effects of this pollution are now, belatedly, recognised as very dangerous; but it looks as though simply stopping this geo-engineering, without first returning the Earth to a viable state, is not a workable option.
It is critical that temporary atmospheric geo-engineering should complement, rather than replace, a zero-emissions industrial structure that would remove the full excess carbon dioxide from the air as fast as possible. If it is not part of such a package, atmospheric geo-engineering should be rejected outright.
If this kind of program seems desperate, it is only an indication of the desperate straits our planet is now in. We must consider the least-worst options to save the Earth. These are absolutely necessary to stop the climate becoming so warm that a return to the safe zone is beyond reach.
CHAPTER 14.
Putting the Plan Together.
This book started in the Arctic, because shrinking sea-ice is one of the triggers which shows us that climate change is already dangerous. To recover the Arctic's climate, the goal developed in Chapter 13 is to replace global warming with global cooling sufficient to drop the temperature enough to allow the full return of the summer sea-ice. This is the only way we can avoid the domino effect of sea-ice loss, the albedo flip, a warmer Arctic, a disintegrating Greenland ice sheet, more melting permafrost, and the whole catastrophe.
If we fail to stop global warming, life in the future will be h.e.l.lish - not because of what we will do from now on, but because of we have already done. Based on a conservative view of climate sensitivity: * Human emissions, so far, have produced a global warming of 0.8 degrees.
* Our non-carbon dioxide greenhouse-gas emissions are adding about another 0.7 degrees to potential global warming. This amount of heating is offset by aerosols, which have a temporary cooling effect of approximately 0.51 degree, although this figure may well be too low.
* There is more warming to come as a result of 'thermal inertia', which refers to the delayed temperature effects produced by rising carbon dioxide levels. Only about half of the temperature increases will appear within 25 years, another quarter will take 150 years, and the last quarter may take many centuries to show up. This is because the oceans are continuing to absorb much of the heat acc.u.mulated as a result of rising carbon dioxide levels. Once the oceans cannot absorb any more, the heat will build up in the atmosphere. Thermal inertia and other lags in the system will take the total long-term global warming induced by human emissions, so far, to 1.4 degrees (although some warming will take a very long time to manifest, and will be affected by the extent to which the carbon cycle, over time, draws down the atmospheric concentration).
* The loss of the Arctic ice would also produce an increase of approximately 0.3 degrees, due to the albedo flip, although it will take time for this to happen.
* If total human emissions continue at their present level for two more decades, this is likely to add at least 0.5 degrees to the system by 2030; however, on current trends, emissions are projected to increase 60 per cent above present levels by 2030.
If we keep acting as we have, the Earth's atmospheric temperature will very likely be at least 2 degrees warmer by mid-century, with more warming to come.
A world free of the imminent threat of climate catastrophe would be one in which the Arctic basin again gleams white with sea-ice, and in which human ingenuity and determination is sufficient to cool the Earth back to the safe-climate zone. Although some people are incredulous when they first hear this proposition, we are yet to see a reputable climate researcher state that the Arctic could remain free of sea-ice long term without dangerous climate change occurring.
We can cool the planet, get back the Arctic sea-ice, and preserve the great polar and high-mountain ice-sheets - or watch the system spin out of control. There is no middle way between these stark options. It is not a matter of how much more greenhouse gas we can add to the atmosphere; it is a matter of what means we must use, what speed we must attain, and what extent we must reach, as we take action to draw down the current levels of greenhouse gases to a safe level, in time to avoid catastrophic climate change.
Any proposal for a goal of higher than 0.5 degrees warming would be foolhardy. The only alternative conclusion (which we do not support) is that it is safe to leave the Arctic sea-ice melted, and to plan for a long-term target much higher than the current warming of 0.8 degrees, on the a.s.sumption that such a course of action would not involve the planet crossing dangerous climate tipping points.
This second approach is, implicitly, the view of all the major nations and players involved in setting climate policy. Their challenge is to provide a reasoned argument explaining why it is a safe course of action to leave the Arctic Ocean free of ice in summer. We are not aware of any evidence that would support such a proposition.
NASA's James Hansen told scientists and others at the American Geophysical Union conference in San Francisco in December 2007 that we, as a species, pa.s.sed climate tipping points for major ice-sheet and species loss when we exceeded 300350 parts per million carbon dioxide in the atmosphere. He said that this point was pa.s.sed decades ago, and that climate zones such as the tropics, and temperate regions, will continue to s.h.i.+ft, and the oceans will become more acidic, endangering much marine life. He added: 'We either begin to roll back not only the emissions [of carbon dioxide] but also the absolute amount in the atmosphere, or else we're going to get big impacts ... We should set a target of carbon dioxide that's low enough to avoid the point of no return [our emphasis].' Hansen estimated that target to be 300350 parts per million carbon dioxide, concluding: 'We have to figure out how to live without fossil fuels someday. Why not sooner?'
To restore the Arctic sea-ice, James Hansen and his coauthors have explicitly identified the target as being in the range of 300325 parts per million carbon dioxide. This is consistent with work by Hansen, before the Arctic summer of 2007, which pointed to the need for a cap that was a safe amount less than 1.7 degrees: Earth's positive energy imbalance is now continuous, relentless and growing ... this warming has brought us to the precipice of a great 'tipping point'. If we go over the edge, it will be a transition to 'a different planet', an environment far outside the range that has been experienced by humanity. There will be no return within the lifetime of any generation that can be imagined, and the trip will exterminate a large fraction of species on the planet.
More recently, in court testimony in Iowa, Hansen reaffirmed his view: 'I am not recommending that the world should aim for additional global warming of one degree. Indeed, because of potential sea level rise, as well as the other critical metrics ... I infer that it is desirable to avoid any further global warming [our emphasis].'
Global equity.
Until recently, most players in the climate-policy arena a.s.sumed that while global-warming emissions needed to be cut substantially, they did not need to be reduced to zero, so it would be fair for all people across the globe to share a reduced annual greenhouse-gas limit. Poor people could keep increasing their fossil-fuel use until their emissions reached the limit, and people in rich countries would need to keep reducing their emissions until they reached the same per capita level (a principle known as 'contraction and convergence').
But it is now clear that greenhouse-gas emissions must be cut to zero, levels of carbon dioxide must be drawn down and, most likely for some decades, the planet must be actively cooled. What, then, is a fair way to share these global tasks?
Our proposed safe-climate strategy is based on the protection of 'all people, all species, all generations'; but people and nations have contributed very unevenly to global warming. The developed economies are responsible for most of the historic atmospheric carbon emissions (and most emissions since 1990), and they have the responsibility and the capacity to provide resources to the world's poorer nations to create a path to development that preserves a safe climate. In a September 2007 report, the global investment bank Lehman Brothers called for a 'global warming superfund', and strongly implied that nations should pay into it on the basis of their historical emissions.
More systematically, a Greenhouse Development Rights framework has been designed by the US-based climate think-tank EcoEquity to support an emergency climate-stabilisation program while, at the same time, preserving the right of all people to reach a dignified level of sustainable human development that is free of the privations of poverty. The framework quantifies national responsibility and national capacity. Its goal is to provide a coherent, principle-based way of thinking about the national obligations to pay for emissions-reduction, and to adapt to changing climates.
There is no significant benefit to any country in continuing with a high-emissions economy, and all new investments should fit the modern zero-emissions paradigm. But what about cutting emissions from existing plant and equipment? The cost of this task, and of providing an adequate and secure energy-supply for all people in all countries, should be borne on the basis of past responsibility and present capacity.
There is no country, or cla.s.s of people, rich or poor, that will benefit in any durable way from a greenhouse-devastated world. All people, in every country, face the need for change. There is no doubt, however, that the lion's share of the problem was caused by the rich countries and cla.s.ses - initially unknowingly, but for at least the last two decades, wilfully - and so ethical equity principles would lay the bulk of the cost at their feet.
The challenge.
In light of the strong goals we have proposed - the need to develop large-scale drawdowns of carbon dioxide, and the need to solve the aerosols dilemma through geo-engineering or other means - there is a legitimate concern about whether, in present social and political circ.u.mstances, such deep and rapid change is possible. Very large levels of investment would be required to solve problems, develop and implement new technologies and solutions, and restructure the economy rapidly. It is hard to imagine that the unity of purpose required for such a transition could be attained in normal political and social circ.u.mstances.
Fortunately, human societies have another mode that they turn to in times of great need: the state of emergency. The form of emergency required to tackle the climate crisis will be different, in important ways, from more familiar emergencies: it will require coordinated global actions, it will be a long emergency, and the world will be very different, in many ways, when it is over.
It is possible that governments will grasp the gravity of our situation, recognise the emergency, and create the social, administrative, and economic circ.u.mstances required to deal with the climate crisis. More likely, we will need to create a popular movement and a deliberate advocacy program to create the necessary political will. Failure to declare a state of emergency is likely to result in a profoundly ineffective response to the climate crisis.
The risk today is that we continue to treat the climate crisis as something that lies in the future, and we continue to talk about reaching climate targets only years, or even decades, hence. So far, when practical difficulties arise with targets, we have re-calibrated the future, deluding ourselves that more warming is reasonable. It is not. Will we continue to recalibrate the future as the truth of climate change becomes increasingly inconvenient? That path will condemn our descendants to accept the bitter truth that we allowed two degrees of warming to become three, and then four, as the seas engulfed their cities and farmlands.
The alternative is to move beyond politics and business as usual, and into emergency mode.