Description: Climate sensitivity is defined as either the temperature change resulting from a doubling of atmospheric carbon dioxide concentration or the temperature change resulting from a 1W/m2 increase in radiative forcing. There are several different climate sensitivities that take into account different feedbacks in the climate system. The simplest climate sensitivity is black body sensitivity, which does not account for any feedbacks but gives the temperature change resulting just from a change in radiative forcing. The calculated climate sensitivity based only on the Stefan-Boltzmann Law is lower than the climate sensitivity calculated using both temperature data over the last 100 years and ice age data over the last ~200,000 years, indicating that feedbacks have played a role in climate sensitivity. World population is also discussed, with population trends outlined for various countries as well as trends associated with developing areas versus developed areas. The issue of sustainable population is introduced.