Global Warming
I
INTRODUCTION
Global Warming, term denoting the accelerated warming of the Earth’s surface due to anthropogenic (human activity-related) releases of greenhouse gases due to industrial activity and deforestation.
II
EARTH’S ENERGY BALANCE
But for the greenhouse effect, life on Earth would not exist. The Sun emits radiation to the Earth. If we could imagine a flat surface at the top of the atmosphere, that radiation is about 340 watts per square metre (340 W/m-2). Just over 100 W/m-2 is reflected out again by atmospheric aerosols and clouds, and the Earth’s surface, leaving some 240 W/m-2 that heats up the surface of the Earth. The system must be in balance—energy “in” must equal energy “out”—so the Earth needs to re-radiate this amount back into the atmosphere. But the amount actually re-radiated depends on the Earth’s surface temperature: the hotter the surface is the more it will emit radiation. The outgoing radiation takes the form of “long wave” infrared thermal radiation. If the system balanced “naturally”, then the Earth’s surface would have a temperature of about –19° C (-66° F) since at this temperature 240 W/m-2 would be emitted. Obviously, something else must be happening because at such low average temperatures life would not exist. The Earth’s surface is very much warmer than this “natural” level (around 15° C/59° F) and hence far more radiation is emitted than the 240 W/m-2. What happens is that a lot of the Earth’s re-radiation bounces back to the Earth’s surface because it gets absorbed mainly by water vapour and carbon dioxide (CO2) in the atmosphere. Water vapour, CO2, and a few other minor gases act like a “blanket”. The balance is secured as follows: Incoming solar radiation: + 340 W m-2 Reflected from clouds, the Earth’s surface, etc.: - 100 W m-2 Net incoming radiation absorbed by the Earth = + 240 W m-2 Outgoing radiation: - 420 W m-2 Greenhouse effect: + 180 W m-2 Net outgoing (thermal) radiation = - 240 W m-2
The way the system balances, then, is that the Earth’s surface warms up compared to what would happen if the Earth was not surrounded by a blanket of greenhouse gases.
III
ANTHROPOGENIC GREENHOUSE GASES
So far nothing is amiss. Indeed, the greenhouse effect is a good thing for life on Earth. The problem arises because humankind is adding to the effect by increasing the amounts of CO2 and a few other gases in the atmosphere, notably methane (CH4) and nitrous oxide (N2O). This results in the enhanced greenhouse effect, or “global warming”. Since the concentration of water vapour tends to be fixed (it is determined by the oceans) imagine what would happen if the atmospheric concentrations of CO2 were increased. The effect would be to increase the radiation bouncing back to the Earth and reducing the radiation leaving the top of the atmosphere. For a doubling in CO2 concentrations, the reducing atmospheric radiation would be about 4 W/m-2. But the system is now out of balance: 240 W/m-2 is coming in but 236 W/m-2 (240 W/m-2 minus 4 W/m-2) is going out. In order to balance, something must change, and what changes is the temperature of the Earth’s surface. Recall that if it increases, outward radiation will increase. This will happen until the 240:240 balance is restored. But while the balance is restored, the Earth has basically got hotter. For each doubling of CO2 concentration, the temperature increase is expected to be about 1.2° C. Various complicating factors intervene to enhance or reduce this figure. Water vapour might increase and this would make the enhanced greenhouse effect stronger still. Other factors of relevance are changes in cloud formation, changes in surface vegetation, the melting of the tundra (which would release methane), changes in ocean circulation, the cooling effects of sulphur aerosols, and so on. The end result is some uncertainty about projected climate change but an average temperature change of about 2° C by 2100 might be expected.
Where do the greenhouse gases come from? The fact that they come from economic activities that are so pervasive to human society largely explains why global warming control is so complicated and so controversial. CO2 is emitted from the burning of fossil fuels, so that most electricity production and most industrial activity contribute to global warming. Since gasoline, kerosene, and diesel are fossil fuels, they too contribute, which means that the entire transport sector is implicated. Methane is also emitted from fossil fuel burning, but also from gas pipeline leaks and from decomposing vegetation. Methane emissions are therefore associated with livestock and with rice growing. Nitrous oxide comes from fossil burning and fertilizers. The burning of forests also contributes significantly to CO2 emissions.
IV
THE IMPACT OF GLOBAL WARMING
The next issue is to predict what would happen if these temperature changes were allowed to happen. The science of climate change impact assessment is very uncertain, not least because humans have the capacity to adapt to some of the expected changes. There are two stages to impact assessment: predicting what the consequences will be for ecosystem change and human health, and assessing how important those changes will be. The context to all this assessment is uncertainty, not least because the rate of change of temperature and the levels of temperature change together place some of the change outside human experience. That is, we have little idea how environments and humans will respond if the worst-case scenarios occur. An additional complication is that impacts will vary region by region, not just because of different susceptibilities but because there will be regional variations in temperature change, in precipitation, and in extreme events such as hurricanes. Summer monsoons in Asia could become heavier, but summer rains in southern Europe could become less.
The kinds of impacts that would seem to be important are as follows. Sea levels will rise due to the thermal expansion of the oceans. Low-lying areas, such as the coastal regions of Bangladesh, and many small islands, could be seriously affected unless adequate sea defences are built and maintained. Fresh water resources could be affected by saline intrusion as sea levels change. Existing dry land regions may become drier still, resulting in a greater likelihood of desertification. Agricultural output may change adversely in some regions, due to reduced rainfall, but may increase in other areas because CO2 also has a “fertilizing” effect on crops. While most of the work on impacts has been carried out on the agricultural sector, it is not clear that world food supply will be significantly affected: some regions will lose and some will gain. But the regions suffering losses may be some of the poorest in the world. In terms of human health there are similar ambivalent effects: if winter temperatures rise there may be fewer premature deaths due to winter cold. But if summer temperatures also rise there may be added deaths from heat stress. The pattern of the world’s diseases may also change—diseases such as malaria, eradicated from Europe, could return to some areas. Perhaps the most important effects are the ones we know least about. Ecosystems change in response to climate change but, in general, past changes have occurred slowly as temperatures varied over long periods. A rise of 1 or 2° C in just a century is a very fast rate of temperature change, and some ecosystems may not be able to adjust. Even more speculative are the effects of extreme events: for example, the worsening of El Niño, and the potential effects on ocean currents and hence marine productivity.
V
MEASURING THE ECONOMIC IMPORTANCE OF GLOBAL WARMING
How much does it all matter? Listing possible impacts is one thing; saying how important they are is another. Yet some idea of the collective magnitude of the impacts is essential because the measures needed to reduce rates of warming will not be cheap. Economic studies suggest a fairly uniform measure of damage of about 1 to 2 per cent of the world’s entire economic output. But this is a figure relating to “2 x CO2”, that is, for a doubling of CO2 concentrations in the atmosphere. It is a benchmark widely used for economic and scientific analysis, but global warming will not stop there if unchecked, so the damages in the very far future could be very much higher. Another way of thinking about the economic scale of the damage is to translate it back into the economic damage done by the release of one additional tonne of carbon-equivalent now. This figure is probably around US$30 per tonne, but with a fairly wide range of uncertainty surrounding it. Since this is the extra damage incurred for the world as a whole from releasing one extra tonne of carbon-equivalent, it can be compared directly with the costs of reducing that tonne of carbon emission. As long as the cost of control is less than the damage done, it will pay the world as a whole to take action. This is the essence of the cost-benefit analysis approach to global warming policy.
As with virtually all aspects of the global warming debate, there are many complications. First, it seems likely that the costs of controlling carbon emissions now is fairly low for the first tranche of emissions, but as more and more reduction occurs it will become increasingly expensive to reduce emissions. Many of the economic models used to simulate policies estimate control costs of over US$100 per tonne of carbon, well above the damage figure and suggesting that it may not be economically justified to take drastic action to control global warming. Second, recent economic analyses have suggested that the incorporation of human adaptation into the calculations of damage would greatly reduce the damage figures, although there appears to be limited adaptation possibilities to some of the major ecosystem impacts. Third, and offsetting the argument about reduced damage, the control of CO2 emissions brings with it many other benefits. For example, CO2 emissions from the transport sector might be controlled by having more fuel-efficient cars and by traffic restraint programmes. This will bring with it benefits in the form of reduced conventional pollutants that harm human health, such as particulate matter, and traffic restraint will reduce congestion, noise, and perhaps accidents. Estimates of these ancillary benefits are very uncertain but may actually double the US$30 figure, so that it will pay to spend up to US$60 to reduce a tonne of carbon emissions in order to save US$30 of avoided global warming damage and to gain another US$30 of ancillary benefits. Fourth, failure to control global warming now simply shifts the problem forward on to future generations who are likely to face larger damage costs still. It can be argued that the current generation should incur costs now that are greater than the US$60 per tonne benefit figure in order to be fair to future generations. Others disagree: why use valuable resources now to protect future generations who are likely to be richer anyway when the same resources could be used to reduce poverty now?
These are just a few of the philosophical and economic issues that continue to be aired in the global warming debate. Not surprisingly, views about the right course of action vary radically from those who see the damage to the future well-being of humankind as being little short of catastrophic, to those who believe that technology and adaptation will come to the rescue, and that delaying serious action is the best policy.
VI
THE INTERNATIONAL RESPONSE
These widely varying views also explain the differences of opinion about the adequacy of the actions already taken. It does not benefit any single nation to take action unless it can be assured others will act likewise. The disadvantages of being a “first mover” explain why the subject has to be dealt with at the international level, initially through the Framework Convention on Climate Change (FCCC) in 1992 in Rio de Janeiro, and subsequently at the Conference of Parties in Kyoto in 1997. The Kyoto Protocol, which emerged from the 1997 conference, is the first agreement under the FCCC with greenhouse gas emission reduction targets that will be binding in international law. The FCCC itself set voluntary targets for industrialized nations such that their CO2 emissions should be no higher in 2000 than they were in 1990. Developing countries argued that they had no responsibilities to cut emissions because the industrialized countries were the main emitters of greenhouse gases. Unsurprisingly, not many nations met their voluntary targets. The Kyoto Protocol sought a 5.2 per cent reduction in overall (carbon-equivalent) greenhouse gas emissions by about 2010 relative to 1990. This target applies collectively to industrialized economies only. Once again, developing countries have no mandatory targets. The target is differentiated between industrialized countries. The European Union (EU) as a whole must achieve an 8 per cent reduction, the United States 7 per cent, and Japan 6 per cent. Within the EU a separate agreement allocates the 8 per cent cut between member states.
How much of a breakthrough is the Kyoto Protocol? That there was any agreement at all is an achievement. After all, reducing greenhouse gases affects virtually all aspects of economic activity from electricity generation, industrial activity, agriculture, forestry, and transport. By calling for a change to a less carbon-intensive world, Kyoto signals the need for fundamental change in the way economic activity is organized. A second positive feature is that the agreement enables carbon trading to take place in order to help secure emission reduction targets. Carbon trading involves one country cutting emissions of CO2 (or another greenhouse gas) in another country. This has no deleterious environmental effect overall because a tonne of CO2 does the same amount of damage wherever it is emitted. But it is known that it is much cheaper to reduce emissions in, say, Eastern Europe than in the United States, so securing the reductions in Eastern Europe could save substantial sums of money for the US. Keeping these compliance costs down is crucial since the cost of meeting the Protocol targets are the biggest obstacle to further international agreement. Under carbon trading, the United States would pay for the reductions but would secure the paper credit for the CO2 reductions, which it can then set against its target. More sophisticated forms of trading are enabled under the Protocol as well.
Critics of the Kyoto Protocol point to the very slow pace of ratification and to the fact that even if the 2010 targets are met, very little happens to projected rates of global warming. The reason is that developing countries’ growth rates of emissions are very much higher than in the developed world. So far, developing countries have refused to adopt emission reduction targets. If they continue to refuse to do so, little will happen to change the rate of global warming. However, a more serious threat to the success of international climate cooperation came in early 2001 when President George W. Bush announced that the US would not implement the Kyoto Protocol. That the world’s greatest producer of greenhouse gases should review its climate change policy in this way was greeted with anger and frustration by governments and environmentalists worldwide, and meant that not enough big producers of greenhouse gases had signed up to bring the treaty into effect. This disappointment has been further exacerbated by the continuing refusal of Russia to ratify Kyoto, despite an initial enthusiasm to do so at the World Summit in Johannesburg in September 2002.
Despite the setback of at least one developed nation refusing to adhere to the Kyoto Protocol, having some form of international agreement has produced some new initiatives in environmental policy elsewhere. A number of European countries have taxes on the carbon content of fuels—so-called carbon taxes—and there is a rapid growth in the various forms of carbon trading. There is a renewed focus on renewable energy because it is generally carbon-free, and on fuel-efficient transport. In the longer term, the agreements could still spur the technological changes needed to bring about economies based more on hydrogen than carbon, and a generally more energy-efficient world. But it could go wrong. Reflecting on the human race, James Lovelock, author of Gaia: the Practical Science of Planetary Medicine (1991), remarks: “Intelligent we may be, but as social collectives we behave churlishly and with ignorance.” Overcoming this human trait is fundamental to global warming control.
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