EPIBuilding a Sustainable Future
Lester R. Brown

Chapter 3. Rising Temperatures and Rising Seas: Cutting Carbon 80 Percent by 2020

In 2004, Stephen Pacala and Robert Socolow at Princeton University published an article in Science that showed how annual carbon emissions from fossil fuels could be held at 7 billion tons instead of rising to 14 billion tons over the next 50 years, as would occur with business as usual. The goal of Pacala, an ecologist, and Socolow, an engineer, was to prevent atmospheric CO2 concentrations, then near 375 ppm, from rising above 500 ppm. 71

They described 15 ways, all using proven technologies, that by 2054 could each cut carbon emissions by 1 billion tons per year. Any seven of these options could be used together to prevent an increase in carbon emissions through 2054. Pacala and Socolow further theorize that advancing technology would allow for annual carbon emissions to be cut to 2 billion tons by 2104, a level that can be absorbed by natural carbon sinks in land and oceans. 72

The Pacala/Socolow conceptualization has been extraordinarily useful in helping to think about how to cut carbon emissions. During the three years since the article was written, the urgency of acting quickly and on a much larger scale has become obvious. We also need now to go beyond the conceptual approach that treats all potential methods of reducing carbon emissions equally and concentrate on those that are most promising.

Researchers such as James Hansen, a leading climate scientist at NASA, believe that global warming is accelerating and may be approaching a tipping point, a point at which climate change acquires a momentum that makes it irreversible. They think we may have a decade to turn the situation around before this threshold is crossed. I agree. 73

We often hear descriptions of what we need to do in the decades ahead or by 2050 to avoid “dangerous climate change,” but we are already facing this. Two thirds of the glaciers that feed the Yellow and Yangtze rivers of China will disappear by 2060 if even the current 7 percent annual rate of melting continues. Glaciologists report that the Gangotri glacier, which supplies 70 percent of the ice melt that feeds the Ganges River during the dry season, could disappear entirely in a matter of decades. 74

What could threaten world food security more than the melting of the glaciers that feed the major rivers of Asia during the dry season, the rivers that irrigate the region’s rice and wheat fields? In a region with half the world’s people, this potential loss of water during the dry season could lead not just to hunger but to starvation on an unimaginable scale.

Asian food security would take a second hit because its rice-growing river deltas and floodplains would be under water. The World Bank tells us that a sea level rise of only 1 meter would inundate half of the riceland in Bangladesh. While a 1-meter rise in sea level will not happen overnight, what is worrisome is that if ice melting continues at today’s rates, at some point such a rise in sea level will no longer be preventable. The melting that would cause this is not just what may happen if the earth’s temperature rises further; this is something that is starting to happen right now with the current temperature. 75

As summer neared an end in 2007, reports from Greenland indicated that the flow of glaciers into the sea had accelerated beyond anything glaciologists had thought possible. Huge chunks of ice weighing several billion tons each were breaking off and sliding into the sea, causing minor earthquakes as they did so. 76

With melt-water lubricating the surface between the glaciers and the rocks on which they rested, ice flows were accelerating, flowing into the ocean at a pace of 2 meters an hour. This accelerated flow, along with the earthquakes, shows the potential for the entire ice sheet to break up and collapse. 77

Beyond what is already happening, the world faces a risk that some of the feedback mechanisms will begin to kick in, further accelerating the warming process. Scientists who once thought that the Arctic Ocean could be free of ice during the summer by 2100 now see it occurring by 2030. Even this could turn out to be a conservative estimate. 78

This is of particular concern to scientists because of the albedo effect, where the replacement of highly reflective sea ice with darker open water greatly increases heat absorbed from sunlight. This, of course, has the potential to further accelerate the melting of the Greenland ice sheet.

A second feedback loop of concern is the melting of permafrost. This would release billions of tons of carbon, some as methane, a potent greenhouse gas with a global warming effect per ton 25 times that of carbon dioxide. 79

The risk facing humanity is that climate change could spiral out of control and it will no longer be possible to arrest trends such as ice melting and rising sea level. At this point, the future of civilization would be at risk.

This combination of melting glaciers, rising seas, and their effects on food security and low-lying coastal cities could overwhelm the capacity of governments to cope. Today it is largely weak states that begin to deteriorate under the pressures of mounting environmental stresses. But the changes just described could overwhelm even the strongest of states. Civilization itself could begin to unravel under these extreme stresses.

In contrast to Pacala and Socolow’s goal of holding carbon emissions constant until 2054, in Plan B we propose an all-out effort to cut net carbon dioxide emissions 80 percent by 2020. Our goal is to prevent the atmospheric CO2 concentration from exceeding 400 ppm, thus limiting the future rise in temperature. 80

This is an extraordinarily ambitious undertaking. It means, for example, phasing out all coal-fired power plants by 2020 while greatly reducing the use of oil. This is not a simple matter.

We can, however, make this shift using currently available technologies. The three components of this carbon-cutting effort are halting deforestation while planting trees to sequester carbon (see Chapter 8), raising energy efficiency worldwide (see Chapter 11), and harnessing the earth’s renewable sources of energy (see Chapter 12). Plan B calls for using the most energy-efficient technologies available for lighting, for heating and cooling buildings, and for transportation. It calls for an ambitious exploitation of the earth’s solar, wind, and geothermal energy sources. It means, for example, a wholesale shift to plug-in hybrid cars, running them largely on wind-generated electricity.

Plan B includes a wholesale restructuring of the world energy economy with a wartime sense of urgency, much as the U.S. restructured its industrial economy in a matter of months at the beginning of World War II. (See Chapter 13.) The stakes in World War II were high, but they are far higher today. What is at issue now is whether we can mobilize fast enough to save our global civilization.

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71. S. Pacala and R. Socolow, “Stabilization Wedges: Solving the Climate Problem for the Next 50 Years with Current Technologies,” Science, vol. 305 (13 August 2004), pp. 968–72.

72. Ibid.

73. “Earth’s Climate Approaches Dangerous Tipping Point,” Environment News Service, 1 June 2007; James Hansen et al., “Climate Change and Trace Gases,” Philosophical Transactions of the Royal Society A, vol. 365 (2007), pp. 1925–54.

74. Wax, op. cit. note 22; Coonan, op. cit. note 23; Watts, op. cit. note 24; “Glacier Study Reveals Chilling Prediction,” op. cit. note 24.

75. World Bank, World Development Report 1999/2000 (New York: Oxford University Press, September 1999).

76. Brown, op. cit. note 35.

77. Ibid.

78. Adam, op. cit. note 41.

79. IPCC, Summary for Policymakers, op. cit. note 9, p. 33; Sergey A. Zimov et al., “Permafrost and the Global Carbon Budget,” Science, vol. 312, no. 3780 (16 June 2006), pp. 1612–13.

80. Figure of 400 ppm calculated using fossil fuel emissions from G. Marland et al., “Global, Regional, and National CO2 Emissions,” in Trends: A Compendium of Data on Global Change (Oak Ridge, TN: Carbon Dioxide Information and Analysis Center, Oak Ridge National Laboratory, 2007), and land use change emissions from R. A. Houghton and J. L. Hackler, “Carbon Flux to the Atmosphere from Land-Use Changes,” in Trends: A Compendium of Data on Global Change (Oak Ridge, TN: Carbon Dioxide Information and Analysis Center, Oak Ridge National Laboratory, 2002), with decay curve cited in J. Hansen et al., “Dangerous Human-Made Interference with Climate: A GISS ModelE Study,” Atmospheric Chemistry and Physics, vol. 7 (2007), pp. 2287–312.


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