One thing is very clear – the magnitude of the problem we face with climate change is such that there is no single answer – no silver bullet – but rather a wide range of actions that must be pursued with urgency and by all peoples of the world at roughly the same time and in roughly the same way. This demands an unprecedented level of co-operation across nations and interest groups on both strategy and tactics.
The climate on our planet, over its billions of years of existence, has varied a lot – from times when the entire planet may have been enveloped by snow and ice (“snowball earth”), to times when tropical animals inhabited the polar regions. Even over the hundred thousand years or so of Homo sapiens’ tenancy, ice ages have come and gone. The most recent 8,000 years or so, since the beginnings of agriculture and the first cities, however, have been unusually steady. Over this time, ice-core records show clearly that levels of carbon dioxide (CO2) in the atmosphere have been around 280 parts per million (ppm), give or take 10ppm. CO2 is, of course, the principal “greenhouse gas” in the atmosphere, and the density of this “blanket” plays a crucial, if complex, role in determining earth’s climate. Some have indeed argued that the beginnings of agriculture, and the subsequent development of cities and civilizations, is not a coincidence but is a consequence of this unusual steadiness over many millennia.
The Industrial Revolution
Be this as it may, things began to change with the advent of the Industrial Revolution which may be said to have begun with James Watts’ development of the steam engine around 1780. As industrialization began to drive up the burning of fossil fuels in the developed world, CO2 levels rose. At first the rise was slow. It took about a century and a half to reach 315ppm, moving outside the multi-millennial envelope. Accelerating during the twentieth century, levels reached 330ppm by the mid-1970s, 360ppm by the 1990s, around 400ppm today. This change of magnitude by 20ppm over only a decade has not been seen since the most recent ice age ended around 10,000 years ago. And if current trends continue, by about 2050 atmospheric CO2 levels will have reached more than 500ppm, roughly double pre-industrial levels.
There are long time lags involved here which are not easily appreciated by those unfamiliar with physical systems. Once in the atmosphere, the characteristic “residence” time of a CO2 molecule is a century. And the time taken for the oceans’ expansion to come to equilibrium with a given level of greenhouse warming is several centuries; it takes a very long time for water-expanding heat to reach the deepest areas of the oceans. It is worth noting that the last time our planet settled to greenhouse gas levels as high as 500ppm was some 20–40 million years ago, when sea levels were around 300ft higher than today. The Dutch Nobelist, Paul Crutzen, has suggested that we should recognize that we are now in a new geological epoch, the “Anthropocene”, which he dates from 1780 when industrialization began to change the geochemical history of our planet. Crutzen points out that the earth is no longer entirely “natural” thanks to the effects of human civilization.
Such increases in the concentrations of the greenhouse gases which blanket our planet will cause global warming, albeit with the time lags just noted. In their most recent report in May 2007, the Intergovernmental Panel on Climate Change (IPCC), which brings together the world’s top climate scientists from 169 countries, estimates that this warming will be in the range of 1.1 to 6.4ºC by 2100, with the likelihood of settling at 2.0 to 2.8ºC. This assumes that we will manage to stabilize greenhouse gas concentrations at around 440–540ppm by that date (which could be optimistic); things get very much worse at higher concentrations. This would be the warmest period on earth for at least the last 100,000 years. Many people find it hard to grasp the significance of such a seemingly small change, given that temperatures change daily by 10ºC. However, there is a huge difference between daily fluctuations and global averages sustained year on year. The difference in average global temperature between today and the depth of the last ice age is only around 5ºC.
The impacts of a rise of around 2–3ºC in global average temperatures are many and serious. And they fall disproportionately on the inhabitants, human and non-human, of developing countries. Sea-level rise derives both from warmer water expanding and also from ice melting at the poles. This will threaten not only low-lying islands and countries (such as Bangladesh), but also – at the higher levels of estimated temperature increase – major cities such as London, Shanghai, New York, Tokyo.
There will also be significant changes in the availability of fresh water, in a world where human numbers already press hard on available supplies in many countries (conversely, some countries will be winners here, although often offset by floods, as we have already witnessed). More generally, we will see increasing incidence of “extreme events”– droughts, floods, hurricanes, heat waves – the serious consequences of which are rising to levels which nowadays invite comparison with our purposefully manufactured “weapons of mass destruction”. Studies made before Hurricane Katrina indicated that increasing ocean surface temperatures (the primary source of a hurricane’s energy) would have little effect on the frequency of hurricanes but strong effects on their severity. We now know that the damage inflicted by Katrina was equivalent to 1.7% of US GDP for 2005. Based on simple projections of trends, estimates of the increasing annual costs of damage from such extreme weather amount to 0.5–1% of global GDP by 2050, and these costs will keep rising as the world continues to warm (see The Stern Review below).
The timescales and magnitudes of other important and nonlinear processes associated with climate change are less certain. “Nonlinear” means, roughly, that doubling the cause does not simply double the effect – huge, and often irreversible, “tipping points” can easily occur. For example, as the polar ice caps melt, the surface reflectivity is altered: dazzling white ice or snow will give way to dark oceans which in turn will cause more warming and faster melting.
The timescale for the ice caps to disappear entirely is still unclear. We simply do not know whether it will take a few decades, a century or longer. We do know, however, that melting on this scale, along with the collapse of ice sheets, would eventually threaten land which today is home to 1 in every 20 people. As the northern permafrost thaws, large amounts of methane gas will be released, further increasing global warming because methane is a more efficient greenhouse gas than CO2.
Increased precipitation in the North Atlantic region, and the consequent increase in fresh water run-off, will reduce the salinity of surface water. This means that surface water will become less dense and so will not sink so readily. Such changes in marine salt balance have occurred before. The result has been that the fluid dynamic processes which ultimately drive the Gulf Stream are turned off, and turned off fast. Although current thinking sees this as unlikely within the next century or so, it is worth reflecting that the Gulf Stream, in effect, transports “free” heat towards the British Isles alone amounting to roughly 30,000 times the total power generation capacity of the UK. These and other nonlinear and potentially catastrophic events are less well understood than is the direct warming caused by increased greenhouse gases. However, their potential impacts are great and should be given high priority in any risk assessment.
A recent Royal Society report* addresses the interplay between climate change and crop production, unhappily emphasizing that “Africa is consistently predicted to be among the worst hit areas across a range of future climate change scenarios”. This echoes the disconnect between two central themes in global politics. On the one hand, solemn promises have been made to increase aid and support development in Africa. On the other, the lack of agreement on measures to curb greenhouse gas emissions means that increasing amounts of aid will be spent tackling the consequences of climate change.
Other living things
Moving beyond ourselves, how about concern for the other living things – plants and non-human animals – that share the planet with us? Seen through a wider-angle lens, the impending diminution of the planet’s diversity of plant and animal species – which derives from human impacts and pre-dates the effects of climate change – could be an even greater threat than climate change itself.
We have named and recorded around 1.5 to 1.6 million distinct species of plants and multi-cellular animals. However, we do not know how many species actually do exist on earth today. Plausible estimates range between 5–10 million, which means that the number remaining to be discovered greatly exceeds the total number so far identified by us. Given this lamentable ignorance, we clearly cannot say much about the number of species that are likely to become extinct this century. We can note, however, that the IUCN Red List of 2006 estimates that 20% of recorded mammal species are threatened with extinction, and likewise 12% of all birds, and 4% of all reptiles and fish. But this is not the best way to express these figures. If re-expressed in terms of the number of species whose status has been properly evaluated, the numbers for mammals and birds are more or less consistent, at 23% and 12% respectively, but for reptiles and fish the numbers leap to 61% and 26% – demonstrating just how little attention has been paid to reptiles and fish. The corresponding figures for threatened plant species are equally dramatic, but most dramatic are the two numbers for the most numerous group of species, insects: 0.06% of all known species are threatened, versus 73% of those actually evaluated. The same pattern holds true for other invertebrate groups. Of these small things, which arguably run the world, we know too little to make even a rough estimate of the percentages that have either become extinct or are imminently threatened.
Perhaps surprisingly, we can nevertheless say some relatively precise things about current and likely future “rates of extinction” when we look at the average rate observed over the 550 million year sweep of the fossil record. As the figures above prove, humans have much greater emotional resonance with the furry and feathery creatures – mammals and birds – than with other species and so they have been relatively well studied. Over the last 100 years, documented extinctions of mammals and birds have been at a rate roughly 1,000 times greater than that seen in the whole fossil record. And four different lines of argument suggest a further upswing of extinction rates, by a factor of around 10, over the coming centuries.
So, if mammals and birds are typical (and there is no reason to suppose they are not), we are looking at an acceleration in extinction rates of the magnitude which characterized the Big Five mass extinction events in the fossil record, one of which “did in” the dinosaurs. There is, however, a crucial difference between the Sixth Wave of mass extinction, upon whose breaking tip we stand, and the previous Big Five: all the earlier extinctions stem from entirely external environmental events. The Sixth, set to unfold over the next several centuries (seemingly long to us, but a blink of the eye in geological terms), derives directly and indisputedly from “human impacts”. In other words, from us.
The main causes of extinction so far have been habitat loss, over-exploitation and the introduction of alien species. Often two, or all three, combine to escalate the impact. Recent studies show clearly that the effects of climate change are now already compounding the effects of these strictly human activities.
The Stern Review
The UK Treasury’s Stern Review on the Economics of Climate Change, led by Sir Nicholas Stern, notes that “Ecosystems will be particularly vulnerable to climate change, with around 15–40% of species potentially facing extinction after only 2ºC of warming. And ocean acidification, a direct result of rising carbon dioxide levels, will have major effects on marine ecosystems, with possible adverse consequences on fish stocks.”
The UN-sponsored Millennium Ecosystem Assessment (MEA), published in 2005, integrated ecological studies with economic and social considerations and concluded that approximately 60% of the ecosystem services that support life on earth – such as fresh water, fisheries, air and water regulation, pollinators for crops, along with the regulation of regional climate, pests, and certain kinds of natural hazards – are being degraded and/or used unsustainably. These ecosystem services are not counted in conventional economic measures of global GDP but the necessarily rough estimates of their monetary value come to between £20–30 trillion (where 1996 is the baseline) which is about equal to the conventional economists’ calculations for total global GDP.
Despite the growing weight of evidence of climate change and the loss of biological diversity, along with growing awareness of the adverse consequences, there remains an active and well-funded “denial lobby”. It shares many features with the lobby that for so long denied that smoking is the major cause of lung cancer. For climate change, the plain fact is that, of the 1,000 or so papers on the subject published in peer-reviewed scientific journals in recent years, not one denies that climate change is real and that it is caused primarily by us. The loss of biodiversity is also clearly evident, although its long-term consequences are far less well understood.
In order to emphasize the scientific consensus on climate change, in the summer of 2005 The Royal Society took the unprecedented step of producing a brief statement on the science of climate change. This was signed by the Science Academies of all the G8 countries – USA, Japan, Germany, France, UK, Italy, Canada, Russia – along with China, India and Brazil. The statement makes it very clear that climate change is real, that it is caused by human activities and that it has very serious consequences. All eleven of these prestigious academies call upon the G8 nations, in particular, to “Identify cost-effective steps that can be taken now to contribute to substantial and long-term reduction in net global greenhouse gas emission [and to] recognize that delayed action will increase the risk of adverse environmental effects and will likely incur a greater cost”.
The Stern Review – the most detailed and authoritative review of its kind to date – underlines these concerns. It elaborates the likely economic impacts and the cost of the actions required to ameliorate them. Under the “Business As Usual” scenario for greenhouse gas emissions and using the most recent scientific evidence on global warming and its consequences, the Stern Review estimates that the economic impact over the next two centuries will cause between 5–7% reduction in global GDP or “personal consumption”. If the impact of global warming on the environment and on human health are included, these figures increase to a massive 11–14% or more. Environmental and health impacts are sometimes called “non-market” impacts and are not usually included in such calculations, despite their obvious relevance.
In order to stabilize greenhouse gas concentrations, annual emissions have to be reduced to a level where they can be balanced by the earth’s natural capacity to remove them from the atmosphere. The longer emissions remain above this level, the higher the final stabilization level will be. The Stern Review therefore focuses on the “feasibility and costs of stabilization of greenhouse gas concentrations in the atmosphere in the range of 450–550ppm CO2”.
Exploring this in detail, the Stern Review concludes that stabilization at 550ppm requires global emissions to peak in the next 10–20 years, then fall at least 1–3% each year thereafter. By 2050, this would put global emissions around 25% below current levels. As the world’s economy may be 3–4 times larger than today, this will mean that emissions per unit of GDP will have to be one quarter of today’s emissions by 2050. In order to achieve the much more desirable stabilization of 450ppm, emissions would have to peak in the next decade, then fall 5% year on year, thereby attaining 70% of current levels by 2050. None of this will be easy. But the future looks very much worse if we “overshoot”, that is, we allow atmospheric greenhouse gas concentrations to rise above the 450–550ppm range.
What is the estimated economic cost of stabilizing at around 450–550ppm? The Stern Review surveys various such estimates, concluding that the cost of “stabilization at around of 550ppm CO2 is likely to be around 1% of GDP by 2050.”
Actions and adaptations
Finally and most importantly, what actions should we be taking now? One thing is very clear – the magnitude of the problem we face with climate change is such that there is no single answer – no silver bullet – but rather a wide range of actions that must be pursued with urgency and by all peoples of the world at roughly the same time and in roughly the same way. This demands an unprecedented level of co-operation across nations and interest groups on both strategy and tactics.
These changes in behaviour can be most usefully divided into four categories:
First, we can adapt to change. For example, we must stop building on flood plains, start thinking more deliberately about coastal defences and flood protection and recognize that some areas should, in effect, be given up to the sea.
Second, we can reduce wasteful consumption, in the home, marketplace and workplace. There are studies, for example, which demonstrate that we can design housing that consumes roughly half current energy levels without significantly reducing living standards, and that we can feed ourselves using substantially less energy than we do.
Third, while we continue to burn fossil fuels, we could capture some of the CO2 emitted at source and sequester it, in other words, bury it on land or under the sea.
Fourth, we could move much more rapidly toward renewable sources of energy which simply do not put greenhouse gases into the atmosphere. These include geothermal, wind, wave, and water energy; solar energy (from physics-based or biology-based devices); fission (currently generating 7% of all the world’s energy, and – despite its problems – surely playing a necessary role in the medium term); fusion (a realistic long-term possibility); biomass (where you are certain that the CO2 you put into the atmosphere equals the amount of CO2 you took out when you grew the fuel). Some of these renewables are already being used, others require more research.
If there were sufficient and effective actions in all four categories, they could also help humanity’s other major problem which is to reduce the rate at which biological diversity is being lost. Here we need to learn how to co-exist better with other living creatures and how to respect their right to live alongside us. To achieve this will mean curbing the growth and “industrialization” of the bush-meat trade and establishing properly protected areas for those fauna and flora we succeed in saving.
These are hard choices for governments, business and individuals. Will we do all this? The answer, ultimately, lies in the hands of each and every one of us. The problems are global but solvable, provided individuals and nations act in unison now. Moreover, such actions need to be taken in ways which are equitably proportionate, recognizing for example that most of the greenhouse gases already in the atmosphere came from the developed world. This implies obligations, both to acknowledge the aspirations of the developing world, and to transfer technology and expertise freely. Each individual must persuade their family and their friends, their communities and their governments, to address these questions and problems, thinking globally and acting locally.
Hard Rain 2nd edition, 2007
* Food Crops in a Changing Climate, The Royal Society, June 2005