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Figure 5.5 Greenhouse gas emissions have long-term effects Magnitude of response Time to reach equilibrium Sea-level rise due to ice melting: several millennia
CO2 emissions peak 0–100 years
Sea-level rise due to thermal expansion: centuries to millennia Temperature stabilization: a few centuries CO2 stabilization: 100–300 years CO2 emissions Today ⫹100 years
Source: IPCC 2001.
Box 5.2 Can efficiency and renewables be the answer?
ignificant reductions in GHG emissions can be achieved through improvements in energy efficiency and increased use of renewable energy sources. Nevertheless, the share of renewables in energy use is not expected to increase much within the forecast period, and the demand for hydrocarbons is set to rise by more than 50 percent (IEA 2004, 2005). This underlines the need for policies to encourage energy savings and improve the profitability of alternative energy sources. Developing countries have much greater potential than industrial countries for reducing emissions, in great part because they are moving toward the technological frontier in existing industry and infrastructure. For example, China could use some 20 percent less coal if its plants were as efficient as the average plant in Japan, and the potential for adopting proven energy savings in cement and pulp and paper is significant. Moreover, rapidly growing developing economies can invest directly in energyefficient technologies, thereby leapfrogging earlier, inferior processes. For example, expansion of low-power, white-light-emitting diodes that run on batteries charged by solar panels could enable the rural poor in some countries to bypass the need for centralized electrical grids. Developing countries
have the opportunity now to adopt more efficient choices for infrastructure and technology that could drastically reduce GHG emissions for decades to come. Energy efficiency is often the most cost-effective and low-risk approach to reducing the need for energy, and can also generate significant environmental benefits. Considerable potential exists for adopting more efficient technologies in transport, industry, buildings, and power generation. • In transport, new materials, compact engines, and advanced fuel systems can lead to lighter and more fuel-efficient vehicles, while hybrid vehicles can provide substantial fuel savings. If all technical means were implemented, the International Energy Agency estimates that a 40 percent improvement in fuel economy of gasoline engines is achievable in the coming decades. The prospects for hydrogen and fuel cell vehicles are less promising over the forecast period because they require significant cost reductions, performance improvements, and development of fuel cell vehicle markets and hydrogen infrastructure. • Many new buildings could be 70 percent more energy efficient than the existing stock through the use of new technologies in windows,
Managing the Next Wave of Globalization