Paul Crutzen

Lecture & Discussion: Atmospheric Chemistry and Climate in the Anthropocene


Abstract

Despite their relatively small mass, 10-5 of the earth biosphere as a whole, generations of ambitious ‘homo sapiens’ have already played a major and increasing role in changing basic properties of the atmosphere and the earth’s surface. Human activities accelerated in particular over the past few hundred years, creating a new geological era, the ‘Anthropocene’, as already foreseen by Vernadsky in 1928: “…the direction in which the processes of evolution must proceed, namely towards increasing consciousness and thought, and forms having greater influence on their surroundings.”

Vernadsky’s predictions were more than fulfilled. Human activities are affecting, and in many cases out-competing, natural processes, for instance causing the ‘ozone hole’, the rise of greenhouse gases with their impact on climate, urban and regional air pollution, ‘acid rain’, with all their consequences for human and ecosystem health. These problems are also increasingly affecting the developing nations of the world. Despite the tremendous progress that has been made, major questions remain and much research needs to be done.

There are major uncertainties regarding future human activities and their impact on climate and environmental chemistry. Some examples are given. Because major impacts, for instance global warming beyond the ‘tolerable window’, > 2°C or 0.2°C/decade, cannot be excluded, it is proposed that research on climate engineering should not be tabooed anymore, for instance through enhancing earth’s albedo by injection of H2S and SO2 in the stratosphere, where it is oxidized to sulphate particles, which reflect solar radiation and thus cool earth. An alternative is injection of soot particles. The albedo enhancement should only be conducted if research shows that it leads to positive results.


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