1.2.1 Introduction

The Earth’s cryosphere, encompassing large expanses of frozen landscapes, is critical to its climate system (Fox-Kemper et al., 2021). From the vast ice sheets on Greenland and Antarctica to mountain glaciers, sea ice and the permanently frozen soils of the Arctic, the cryosphere plays a crucial role in storing freshwater and carbon, regulating global climate patterns and influencing major ecosystems (Figure 1.2.1). However, it is also one of the parts of the Earth system most vulnerable to climate change. As our climate undergoes unprecedented shifts due to human-induced global warming, the cryosphere is at risk of crossing potential tipping points (Lenton et al., 2012; Armstrong McKay et al., 2022; Wang et al., 2023).

Cryospheric tipping dynamics are triggered when changes in part of a system become self-perpetuating beyond some threshold, leading to substantial, widespread, often abrupt and often irreversible impacts (see Section 1 Introduction). This definition highlights different characteristics of tipping systems that have been discussed previously – namely the existence of critical thresholds and the potential for abrupt and possibly irreversible change, all of which we assess here for ice sheets, sea ice, glaciers and permafrost.

The consequences of crossing cryospheric tipping points amplify the effects of climate change and have widespread impacts, affecting sea level, ecosystems, wildlife habitats, coastal infrastructure, human livelihoods and regional climate patterns (Fox-Kemper et al., 2021). They could further lead to cascading effects to other climate tipping systems, which would result in far-reaching consequences for the entire Earth system (Steffen et al., 2018; Wunderling et al., 2021; Wunderling and von der Heydt et al., preprint).