ABSTRACT
This chapter describes the other world-wide atmospheric problem and the processes by which human activities are bringing it about: human-induced global climate change. The problem of climate change arises because the concentration of most of the gases is steadily increasing, raising the prospect of a warming and changing climate. The most important gas in concentration and contribution to the normal climate heating is water vapor. Climate models are very elaborate, but even with this complexity it is possible that modelers have failed to consider properly some climate feature of major importance. The verification techniques actually employed involve comparisons of climate model calculations with observations of present and past climates and climate changes. One method of estimating the total societal impact of an average warming of one-third degree per decade is to examine climate changes in the past and see what impact they had.
