3 - Climate Sensitivity, Climate Feedbacks and Policy Implications

Summary

Editor's Introduction

The study of climatic problems includes much more than the atmosphere. In this chapter, Martin Hoffert looks back over the Earth's history to explore the natural archives of paleoclimate data, using modern techniques of isotopic and oceanographic analysis. He combines these analyses with computer modelling studies, which were designed to estimate the sensitivity of global climate to changes in atmospheric composition, the position of the Earth's orbit, and circulation of the world ocean. In the process, as one of the paper's reviewers (geophysicistTyler Volk) observes, Hoffert spins a complex web, providing us a rapid and enthralling tour of Ice Ages, the planetary evolution of Earth, Mars, and Venus, atmospheric physics, soil chemistry, and ocean circulation. And he explains the strengths, weaknesses, and fundamental limits of climate models in terms that are readily penetrable by the lay reader.

Because its range is the widest, this chapter is the longest in the book. But it also expands directly on the discussion of linkages in the previous chapter, to show the interconnections among the major components of our planetary system — air, ocean, land, and biota. Hoffert notes that everything on the surface of the planet — from the smallest dust particle to the largest iceberg — absorbs and re-emits the radiation that comes to us from the sun. And he explains how each of these components interacts with Earth's lifeforms to affect the overall radiative balance of the planet with its surroundings.

Woven throughout this chapter, you will find a thread of respect for the fundamental uncertainties in our understanding of natural processes, and the intellectual challenge facing geophysicists, geochemists, and other scientists who try to model future effects of human activities on climate.