Introduction: Climate Overview

Abstract

Energy exchange between Sun, Earth, and space controls the global climate. Earth is in dynamic equilibrium such that it receives the radiation from the Sun and emits the same amount of heat as infrared (IR) energy to space. Earth's energy imbalance is the difference between the incoming solar radiation absorbed by the Earth and the amount of heat the Earth radiates to the space. If positive imbalance occurs, such that the incoming radiation from the Sun is more than outgoing heat from the Earth, Earth becomes warmer. In contrast, if the imbalance is negative, such that more energy is going out than it receives, then Earth will cool. Earth's energy imbalance is the single most important measure of the status of the Earth's climate system which defines the expectations of future global climate change resulting from the anthropogenic perturbation or the greenhouse effect. The energy budget of the Earth's climate system is discussed in this chapter. The processes that Earth retains more electromagnetic radiation energy than it receives are also explained. In addition, the role of greenhouse gases (GHGs) in regulating the energy balance is discussed with the emphasis on carbon dioxide (CO2). The concentrations of GHGs have increased significantly since the Industrial Revolution {\textasciitilde} circa 1750. Most notable is the increase in concentration of CO2 which have played a significant role in the current and future global temperature increases.