Introduction
This chapter outlines the challenge facing us. The Paris Agreement sets a target maximum of 2°C global warming and a preferred limit of 1.5°C. Yet, the subsequent combined national pledges for emission reduction suffice only for limiting warming to roughly 3°C. And because most nations are falling considerably short of meeting their pledges, even greater warming may become locked in. Something more drastic and wide-ranging is needed: a multi-pronged strategy. These different prongs to the climate-change solution are introduced in this chapter and explored one by one in the following chapters. First is rapid, massive reduction of greenhouse gas emissions. Second is implementation of ways to remove greenhouse gases from the atmosphere. Third may be increasing the reflectivity of Earth to incoming sunlight, to cool certain places down more rapidly. In addition, we need to protect ourselves from climate-change impacts that have already become inevitable.