Avoiding Catastrophe

Only recently have scientists understood that changes in the concentration of carbon dioxide, methane, and other less common gases could trigger an ecological catastrophe of staggering proportions. The climate, it turns out, is not the vast, implacable system it appears to be.

Past climate changes have been caused by tiny alterations in Earth's orbit and orientation to the sun—providing, for example, just

Building a Low-Carbon Economy

Figure 6-1. Atmospheric Concentration of Carbon Dioxide, 1744-2004

o 330 Q

Source: NOAA, ORNL

Atmospheric measurements J

Ice core measurements

1740 1770 1800 1830 1860 1890 1920 1950 1980 2010

enough added energy to warm the planet over thousands of years, increasing the concentration of carbon dioxide in the atmosphere, and in turn triggering even larger changes in the temperature, which scientists call a positive feedback. Today's massive release of CO2 and other greenhouse gases is leading to far greater changes to the atmosphere in a period of decades.3

Scientists now project that within the decades immediately ahead, the capacity of the earth and ocean to absorb carbon emissions will decline, while vast changes in the Arctic may further accelerate warming. Melting tundra will release millions of tons of methane, a greenhouse gas more powerful than CO2. And as the Arctic ice pack disappears in summer—nearly half is already gone—it will be like removing a large air conditioner from Earth's northern hemisphere. This will further warm the climate and could mean the end of the million-year-old Greenland ice sheet—which by itself contains enough water to raise worldwide sea levels by more than seven meters.4

When the world will reach such a tipping point—or whether it already has—is not known. But it is already clear that ecological change of this magnitude would lead to unprecedented disruptions to the world's economies. A groundbreaking 2006 study led by former World Bank chief economist Nicholas Stern concluded that climate change could cut global economic output by between 5 and 20 percent. In his 2007 book, The Age of Turbulence, Alan Greenspan, the leading freemarket economist of the day, included climate change as one of five forces that could derail the U.S. economy in the twenty-first century. The uneven and disruptive nature of these changes could set off an even more serious crisis as conflict within and between societies undermines their stability.5

In 2006 the combustion of fossil fuels released 8 billion tons of carbon to the atmos-phere—nearly a million tons every hour— with coal and oil contributing roughly 40 percent each and natural gas accounting for the rest. (The manufacture of cement released nearly another 350 million tons, while deforestation and agriculture contributed roughly 1.6 billion tons.) Global fossil fuel carbon emissions have increased fivefold since 1950 and are up 30 percent just since 1990. Today, fossil fuels provide four fifths of the energy that powers the global economy.6

Burning fossil fuels on this scale is a vast and risky experiment with Earth's biosphere; scientists are still not sure when the world will cross an invisible but catastrophic threshold

Building a Low-Carbon Economy

Table 6-1. Global Energy Use and Carbon Emissions in 2006 and in 2050 Under Two Scenarios




Business as Usual

Stabilization Scenario

CO2 concentration (parts per million)



< 450

Energy (billion tons oil equivalent)




Energy-related carbon emissions (billion tons)




Source: See endnote 9.

of no return. But growing evidence suggests that it may be close. James Hansen, Director of the NASA Goddard Institute of Space Studies, is among a growing group of climate scientists who believe that the world should make every effort to avoid pushing the atmospheric concentration of CO2 beyond 450 parts per million and the effective concentration (including methane and trace gases) beyond 500 parts per million. This would limit the increase in the average global temperature to 2.4-2.8 degrees Celsius above pre-industrial levels. The increase so far is just under 0.8 degrees Celsius.7

To keep the world's climate within the range it has occupied for at least a million years, current emission trends will need to be quickly reversed, according to the complex models used by scientists and included in the report of the Intergovernmental Panel on Climate Change (IPCC) released in early 2007. The IPCC scenario that most closely matches likely ecological limits suggests that global carbon emissions will need to peak before 2020 and be reduced by 40-70 percent from the current emissions rate by 2050, eventually falling to zero.8

The magnitude of the challenge is clear when the emissions path needed to stay below an atmospheric CO2 concentration of 450 parts per million is compared with the current path. (See Table 6-1.) The U.S. Department of Energy forecasts that both world energy use and carbon emissions will grow nearly 60 percent by 2030—an average rate of 1.8 percent per year. This would take emissions to nearly 12 billion tons in 2030 and, assuming continued growth at that rate, to almost 16 billion tons in 2050—nearly four times the annual emissions of 4 billion tons that would be needed to keep the CO2 concentration below 450 parts per million.9

Complicating the challenge is the fact that the energy needs of poor countries such as India and China have accelerated in recent years as they entered the most energy-intensive stages of their development—building industries and infrastructure at an astonishing pace. In 2006, industrial countries, with less than 20 percent of the world's population, contributed roughly 40 percent of global carbon emissions, and they are responsible for more than 60 percent of the total carbon dioxide that fossil fuel combustion has added to the atmosphere since the Industrial Revolution began. But this picture is now changing rapidly, particularly in China, where emissions are now rising at 10 percent a year—10 times the average rate in industrial nations. By 2006, China's fossil fuel emissions were only 12 percent below the United States—and gaining rapidly. (See Table 6-2.) Emissions are also growing quickly in the Middle East, where rapid population growth, rising oil wealth, and low, subsidized energy prices have led to skyrocketing energy demand.10

At the G-8 Economic Summit in Ger

Building a Low-Carbon Economy

Table 6-2. Energy-Related Carbon Emissions, Selected Countries, 2006

Country Carbon or Region Emissions*

Carbon Emissions, Per Capita

Carbon Emissions, Per $ GDP



(kilograms per


$1,000 GDP (PPP))

United States








Western Europe




















*Does not include emissions resulting from gas flaring, cement making, or land use change. Source: See endnote 10.

*Does not include emissions resulting from gas flaring, cement making, or land use change. Source: See endnote 10.

many in June 2007, Canada, France, Germany, Italy, and Japan called for a 50-percent cut in global emissions by 2050—consistent with the trajectory needed to keep atmospheric concentrations below 450 parts per million. Although Russia and the United States abstained from that portion of the final statement, it is clear that the need for drastic cuts in emissions is increasingly accepted by political leaders as well as scientists. This is an ambitious goal, and achieving it will mean reversing an upward trend in carbon dioxide emissions that has been under way for a century and a half.11

Providing energy services for the much larger global economy of 2050 while reducing emissions to 4 billion tons of carbon will require an energy system that is very different from today's. For the world as a whole to cut emissions in half by 2050, today's industrial countries will need to cut theirs by more than 80 percent. Getting there depends on three elements in a climate strategy: capturing and storing the carbon contained in fos sil fuels, reducing energy consumption through new technologies and lifestyles, and shifting to carbon-free energy technologies.12 A variety of combinations of these three strategies can in theory do the job. Princeton scientists Robert Socolow and Stephen Pacala have broken the task down into 15 1-billion-ton "wedges" of reductions—including such options as improved fuel economy or massive construction of wind farms—that policymakers can choose from. The key question is which combination of strategies will minimize the substantial investment cost but also provide a healthy and secure energy system that will last.13 Phasing out oil, the most important fossil fuel today, may turn out to be the easiest part of the problem. Production of conventional crude oil is expected to peak and begin declining within the next decade or two. By 2050, output could be a third or more below the current level. Reliance on natural gas, which has not been as heavily exploited as oil and which releases half as much carbon per unit of energy as coal, is meanwhile likely to grow.14

But the slowdown in the rate of discovery of oil and gas is pushing world energy markets toward dirtier, more carbon-intensive fossil fuels. The greatest problem for the world's climate is coal, which is both more abundant and more carbon-intensive than oil, and the "unconventional" energy sources such as tar sands and oil shale, which at current oil prices have become economically accessible.

The central role of coal in the world's climate dilemma has led policymakers and industrialists to focus on so-called carbon capture

Building a Low-Carbon Economy and storage (CCS). Although it is only likely to be feasible for large, centralized uses of fossil fuels, many energy planners are counting on it. They hope to build a new generation of power plants equipped with devices that capture carbon either before or after the combustion of fossil fuels and then pipe the CO2 into underground geological reservoirs or into the deep ocean, where it could in principle remain for millions of years.

Coal can either be gasified (as it already is in some advanced power plants), with the CO2 then separated from the other gases, or it can be directly burned in a super-critical pulverized plant that also allows the capture of carbon dioxide. Three significant CCS projects are in operation in Algeria, Canada, and Norway. The facilities in Algeria and Norway simply capture CO2 that is extracted together with natural gas, which is much easier than capturing CO2 from coal combustion. A better demonstration of technical feasibility is offered by the sequestration project in Weyburn, Canada, which captures CO2 from a coal gasification plant. However, even these advanced facilities lack the modeling, monitoring, and verification that are needed to resolve the many outstanding technical issues.15

The United States, the European Union, Japan, and China have all launched government-funded CCS programs in the last few years, but the pace of the programs is surprisingly lethargic, given the urgency of the climate problem and the fact that much of the power industry expects CCS to allow continued reliance on the hundreds of coal-fired power plants that today provide over 40 percent of the world's electricity. A 2007 study by the Massachusetts Institute of Technology (MIT) concluded that the U.S. Department of Energy's main program to demonstrate large-scale CCS is not on track to achieve rapid commercialization of key technologies.

Locating, testing, and licensing large-scale reservoirs where carbon dioxide can be stored is a particularly urgent task.16

In light of the lead times required for technology development and demonstration, it will be 2020 at the earliest before significant numbers of carbon-neutral coal plants come online. Nor is it guaranteed that CCS plants will be competitive with other carbon-free generators that are likely to be in the market by that date. But the bigger question is whether that would not be too late, considering the hundreds of new coal-fired power plants that are currently being considered in China, the United States, and other nations. To have any hope of halving carbon emissions by 2050, it is hard to avoid the conclusion that the uncontrolled burning of coal will need to be eliminated—and soon. In the meantime, a growing number of climate experts are calling for a moratorium on building new coal-fired power plants unless or until CCS becomes available.

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