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Author: Robert M. White
Forestalling the projected adverse effects of climate change presents an immense and complex challenge to the engineering profession.
Humans have been engineering Earth systems for thousands of years. Primitive engineering was aimed at local or regional issues and tended to focus on such basics as shelter, water resources, and transportation. Little thought was given to the ancillary and frequently deleterious consequences of the products of human innovation. The need to address these consequences has penetrated our consciousness relatively recently and with it the concept of Earth systems engineering.
Climate systems engineering (CSE), a subset of Earth systems engineering, is a multipurpose, multidisciplinary approach for monitoring, adapting to, and even mitigating the consequences of climate change. Climate change is, of course, a topic of intense national and international interest because of its environmental, economic, and social consequences. For much of history, climate change has been regarded as an act of God over which humans had no control. Recently, however, climate change, and global warming in particular, has come to be seen as at least in part the result of human activities.
Engineering and technology now represent the underpinnings of modern weather and climate science. Scientific weather forecasting became possible 150 years ago with the introduction of the telegraph of Samuel B. Morse, which permitted weather conditions to be transmitted from remote to central locations where they could be analyzed. Since World War II, a host of other technologies has opened our eyes to some of the mysteries of climate. Radiosondes provide a view of the upper atmosphere; radar has transformed our understanding of the dynamics of precipitation and cloud systems; computers have enabled the mathematical modeling of weather and climate, transforming prediction from art to science; and space technology has permitted the imaging, sounding, and location capabilities to provide global monitoring of weather and climate.
It is not my purpose to discuss climate science in any depth. But without some background, the concept of CSE is meaningless. Briefly, the increasing global use of fossil fuels, deforestation, and emissions from other sources have increased dramatically the atmospheric concentration of greenhouse gases since the beginning of the Industrial Age. For example, from barely detectable amounts 140 years ago, annual emissions of carbon dioxide (CO2) have risen to over 6 billion metric tons per year today. This increase has been essentially monotonic except for seasonal fluctuations, as indicated by the observations at Mauna Loa in Hawaii and other observatories. This level of CO2 emissions has increased the atmospheric concentration of CO2 by 25 percent, from approximately 290 parts per million by volume (ppmv) in 1860 to its present level of about 360 ppmv. The result has been a rise in global mean surface temperature. This temperature change is a matter of observational fact about which there is little dispute.
Mathematical climate models indicate that global surface temperatures will increase significantly by 2100, according to the Intergovernmental Panel on Climate Change (IPCC; 2001). Most models project an increase in the range of 1.5 to 4.5?C. The latest IPCC assessment estimates a temperature rise of between 1.5 and 5.8?C, with the most likely rise estimated to be 2.5?C. There is also general agreement that global precipitation will increase. Sea level is rising largely due to thermal expansion of seawater, with the most likely rise predicted to be 0.5 meters. Considerable uncertainty exists about the regional distribution of climate change and its impact on agriculture, ecosystems, and water resource availability, as well as its contribution to severe weather events, such as hurricanes.
A recently published report by the National Assessment Synthesis Team (2000) estimates the impact of climate change on the United States. The analysis considers the consequences through 2100 for 5 sectors of the economy and 16 geographical regions. It uses as a basis for its analysis two different climate models, one developed by scientists in Canada and the other by scientists in the United Kingdom. These models yield consistent climate warming projections for the United States as a whole but differ significantly in their regional projections.
Our ability to anticipate future climate change, with all its uncertainties, presents a dilemma. How do we balance the costs of the economic and social impacts of climate change with the costs of the engineering and technology needed to prevent those consequences? When and at what costs do we decide to build dams and seawalls and strengthen bridges? When do we invoke biotechnology to develop drought- and heat-resistant strains of grain?
Almost 10 years ago, in the Framework Convention on Climate Change (FCCC), the international community agreed to try to “achieve stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” (United Nations, 1992). In addition to CO2, the greenhouse gases addressed by the convention are methane, ozone, and nitrous oxide. (Because CO2 so dominates the greenhouse gas mixtures, what follows focuses on CO2.)
The convention leaves the term “dangerous” undefined, but it must include the familiar, if sometimes devastating, phenomena indicated in Box 1 . Ameliorating global warming is arguably one the most difficult and complex challenges facing engineering and technology. The prime causes of elevated global CO2 concentrations are shown in Table 1 . Humanity’s addiction to fossil fuels (coal, gas, and oil) as a source of energy underlies much of this rise in greenhouse gases. The root solution is to decarbonize the global energy supply. Decarbonization has been proceeding for over a century.
Since the initialing of the climate convention in 1992, governments around the world have been grappling with ways to control atmospheric greenhouse emissions without setting targets for the desired atmospheric concentrations. The Conference of the Parties (COP), the group established to negotiate the details of the FCCC, has met six times to try to seek agreement on international action. The most recent meeting of the group, at The Hague in late 2000, ended in disagreement.
A protocol initialed by the COP in Kyoto, Japan, in 1997 limits the emissions of carbon dioxide and other greenhouse gases and assigns emission targets to industrialized countries. Developing countries unwilling to commit to the protocol were given a pass (United Nations, 1997). The Kyoto agreement requires the United States to reduce greenhouse gas emissions to a level 7 percent below 1990 levels by 2010. Achieving such a reduction would require a lowering of U.S. fossil fuel consumption by some 35 percent below what would be expected in 2010. It could not be accomplished without dramatic changes in the manner of energy production and use in this country.
The Kyoto signatories agreed that sequestration of carbon in the biosphere, principally by trees, could be an ancillary approach for reducing greenhouse gas concentrations in the atmosphere. The United States has proposed that it be permitted to use carbon sequestration by forest and agricultural lands, and emissions trading with other countries, to account for about 50 percent of the required emissions reduction. This proposal was rejected by the European members of COP and was in large part responsible for the collapse of the Hague conference. Alternative scenarios for meeting the Kyoto targets that focus more on non-CO2 gases have been proposed by Hansen et al. (2000).
There is general recognition that even if successful, the Kyoto protocol is only the first step in the process and by itself will have only a minimal effect on projected global warming. Emissions targets spelled out by the protocol will reduce global average temperatures by an insignificant amount, according to the IPCC. Emissions reductions of 60 to 80 percent would be needed to stabilize atmospheric CO2 concentrations at their present levels. The fact that China, India, and other developing countries remain unwilling to restrict their emissions has created considerable political controversy.
The U.S. Senate, anticipating the wrenching changes that will be required and aware that not all nations are required to reduce emissions, has voted unanimously against actions by our government to implement the Kyoto protocol. Recently, the Bush Administration announced it will not regulate CO2 emissions from power plants (Associated Press, 2001), and it has indicated it will withdraw from the Kyoto protocol (Drozdiak and Pianin, 2001).
Target Concentrations Undefined
Forestalling the projected adverse effects of climate change is an example of Earth systems engineering at its most complex. As engineers, we would want to know the target levels of global greenhouse gas concentrations proposed by the FCCC, because it is the concentrations that determine climate change, not emissions. At the present time, however, such targets are undefined.
Setting such target levels is fraught with uncertainty and controversy. It requires knowledge of the consequences of specific limits, a knowledge that we presently do not possess. A commonly accepted target, aiming for greenhouse gas concentrations roughly double those predating the Industrial Revolution, would yield a concentration of about 550 ppmv. This is a number that many believe would avoid dangerous interference with the climate system. Doubling present levels of emissions would yield gas concentration of about 750 ppmv. If the target concentration of 550 ppmv is to be achieved through emission reductions, the trajectory of the emission reductions can vary. Economists refer to this as “when flexibility.” A trajectory that permits delays in controlling emissions can have the same effect on CO2 concentration as one that does not permit delays.
With this kind of framework, engineers and technologists can begin to consider a mind-boggling array of options for achieving specific target concentrations of greenhouse gas. These include those that reduce emissions of CO2 from fixed and mobile sources, sequester carbon dioxide, reduce the emissions of other greenhouse gases, and employ geoengineering on a global scale ( Box 2 ). Geoengineering is the use of technology to affect the radiation balance of the atmosphere, for example by injecting dust or other particulate matter into the stratosphere to reduce the amount of solar radiation reaching Earth.
CSE Success Depends on Collaboration
However effective the development of a new, low-carbon energy system, the sequestration of carbon, and attempts at reducing other greenhouse gases, if we are to reduce atmospheric concentrations of greenhouse gases, CSE will need to do much more. It must anticipate the consequences of climate change for ecosystems, water resources, agriculture, health, and other concerns of importance to humanity. This must not be a mere afterthought; it must be an integral part of the requirements. Will new technologies have adverse health effects? Will they result in unwanted effects on ecosystems? Will they be culturally acceptable? There are many questions, and collaboration between scientists and engineers from many fields will be required to address them meaningfully.
Because of its global nature, climate change has both political and international engineering dimensions. Not only are international consultations and negotiations about approaches for achieving agreed-upon atmospheric CO2 concentrations important, but there is also a need to reach out to engineering communities in other countries to enlist their help. The task before us is formidable. The wisest course may be to take actions that contribute to emissions reduction and carbon sequestration at low economic cost now and make the investment in research and engineering to generate the new and advanced technologies that can meet CO2 concentration targets in the future.
Possible “Dangerous” Consequences of Climate Change
• Endangered food supply and water resources
• Rising sea level leading to island and coastal inundations
• Increase in severe weather events such as hurricanes, floods, and droughts
• Changes in natural ecosystems
• Health effects such as pulmonary and cardiovascular disease
Principal Causes of Anthropogenic CO2 Emissions (Gt C/yr)
Fossil fuel combustion 5.5 ? 0.5
Deforestation 1.6 ? 1.0
Total Anthropogenic Emissions 7.1 ? 1.1
Gt = gigatons. C = carbon.
Options for Reducing Concentrations of Atmospheric Greenhouse Gases
CO2 Emissions Reduction
• Increase efficiency of both mobile and fixed sources of CO2, for example as in the program for the Partnership for a New Generation of Vehicles (PNGV).
• Increase efficiency of electric power generation by changing power-station fuel sources from coal and oil to gas, and by introducing turbines and distributed energy sources.
• Increase use of renewable energy sources such as wind power, photovoltaics, biomass, and hydropower. (These can produce significant amounts of energy but are not candidates for satisfying base power loads.)
• Increase use of already-proven nuclear energy, a CO2-emission-free energy source that occupies a central role in power production in France and other countries.
• Continue development of new types of energy systems such as fuel cells for use in automobiles and in fixed locations operating on hydrogen stripped from fossil hydrocarbons.
• Increase sequestration by growing trees and other plants, which consume carbon dioxide
in photosynthesis. This approach can be enhanced through biotechnology by producing fast-growing trees. Sequestration of carbon in soil also merits consideration.
• Sequester carbon stripped from hydrocarbons by pumping it into deep geological structures and use the hydrogen to power fuel cells.
• Inject CO2 into oceans at depths that allow the formation of CO2 hydrates.
• Fertilize the oceans by adding iron or phosphorous to increase the production of algae, which then would sequester more carbon in the oceans.
Non-CO2 Emissions Reductions
• Reduce emissions of non-CO2 greenhouse gases such as methane, ozone, and nitrous oxide.
• Disperse dust or inject SO2 into the stratosphere to reduce sunlight and thereby lower global temperatures. (This proposal is totally speculative.)