This chapter frames the problem of climate change. It opens with a brief overview of Earth’s energy balance and the greenhouse effect and then outlines the root causes of the problem along with key controls in the climate system that determine its responses. This is followed by an introduction of spatial variability and fluctuations through time in the expressions of climate change, which are key to understanding regional impacts. Such geographic and temporal variations do not invalidate the existence of the global average temperature increase, but merely cause fluctuations around the global average. Finally, the chapter shows that achieving the Paris Agreement’s 1.5°C warming limit will require the removal of 260–1030 billion tons of atmospheric carbon dioxide. The low-end estimate applies to best-case scenarios and the high-end estimate to scenarios where business-as-usual (as in the past two decades) emissions are allowed until 2030 or beyond.
Regional impacts of COVID-19 on carbon dioxide detected worldwide from space
