The observed climate of the past

Question 1

Overview

Answer 1

 Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750.

 They now far exceed pre-industrial values determined from ice cores (see Fig. 9.4).

 The global increases in C02 are due primarily to fossil fuel use and land use change, while those of methane and nitrous oxide are primarily due to agriculture.

 Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level (see Fig. 9.5).