This chapter describes the systems involved in regulating Earth’s temperature, its climate, geologic evidence of past climate changes, and the role humans have on today’s climate change. It is critically important to be aware of the geologic context of climate change processes if we want to understand anthropogenic (human-caused) climate change. First, this awareness increases the understanding of how and why our activities are causing present-day climate change, and second, it allows us to distinguish between natural and anthropogenic processes in the climate record in the past.
In science, a system is a group of objects and processes that interact, such as the rock cycle. Earth System Science is the study of how earth systems (geosphere, atmosphere, hydrosphere, cryosphere, and biosphere) interact and change in response to natural cycles and new human-driven forces. Changes in one earth system affect other systems. A significant part of this chapter introduces various processes from different earth systems and discusses how they influence each other and impact the global climate. For example, global temperature largely changes based on the composition of atmospheric gases (atmosphere), circulation of the ocean (hydrosphere), and characteristics of the land surface (geosphere, cryosphere, and biosphere).
In order to understand climate change, it is important to distinguish between climate and weather. Weather is the temperature and precipitation patterns occurring in the short-term such as right now or later this week. Climate is the temperature and precipitation patterns and range of variability averaged over the long-term for a particular region (Chapter 13.1). Thus, a single cold winter does not mean that the entire globe is cooling—indeed, the cold winters in the US of 2013 and 2014 took place while the rest of the Earth was experiencing record warm winter temperatures. To avoid these generalizations, many scientists use a 30-year average as a good baseline . Therefore, climate change refers to slow changes in temperature and precipitation patterns over the long-term for a particular area or the Earth as a whole.