The ratio of CO2 emissions from power plants to natural emissions is a measure of the environmental impact associated with geothermal power production. Emissions from Icelandic geothermal power plants amounted to 1.6 × 108 kg year−1 in 2002. Two independent estimates of natural CO2 emissions range between 1 × 108 and 2 × 109 kg year−1. Thus, power plant emissions are significant compared…