Global Warming: East-West Connections

Air pollutants that damage human health and agricultural productivity, such as tropospheric ozone and black soot, also affect global climate. Multiple benefits of reducing these pollutants become more compelling as concern about global warming increases. Air pollution is especially harmful in developing countries that are now large emitters of carbon dioxide, providing incentive for developed and developing countries to cooperate in reducing both global air pollution and climate change. The Earth’s history provides a sobering perspective on prospects for climate change. The Earth’s climate is sensitive to changes in climate forcings, human-made forcings now overwhelm natural climate forcings, and the climate system is dangerously close to tipping points that could have disastrous consequences. Atmospheric composition is now near the limits that must not be exceeded if we wish to maintain a planet resembling the one on which civilization developed, with the equable climate of the Holocene. Yet quantitative examination of climate forcings reveals a potential path to climate stability with a bright future for life on the planet. Except for carbon dioxide, human-made forcings are increasing more slowly than in the scenarios of the Intergovernmental Panel on Climate Change (IPCC). A focused effort to achieve absolute reductions in non-CO2 forcings, combined with a slowdown of CO2 emissions and phase-out of coal use except at power plants that capture and store the gas, could keep additional global warming well below 1°C. Attainment of this ‘alternative scenario’ for future climate requires overturning the common presumption of energy departments that all fossil fuels, including those that are remote or difficult to extract, must be exploited before the world turns to energy sources ‘beyond fossil fuels’ and begins placing much greater emphasis on energy efficiency and renewable energies. Cooperation between developed and developing countries is essential. Recognition of responsibilities for the present situation and the numerous mutual benefits of required actions make such cooperation plausible.