Global Climate Change and Economic Analysis

Although very volatile, the climate system of the earth has been varying within broad but clearly defined bounds (see the chapter by Claussen in this book). It was not until the 18th century when economic activities started to change this. By today the atmospheric concentrations of greenhouse gases, and among them carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂0) have surpassed preindustrial levels. The CO₂-concentration in the atmosphere has grown from 280 to about 360 ppbv and is approaching 400 ppbv which is far beyond the concentrations that have been observed in the last half million years. CH₄ has grown from 700 to 1720 ppbv and N₂O from 275 to 310 ppbv (IPCC 1995).