3.3.2.5 Irreversibility and permanence of change

A tipping point involves a shift between two alternative stable states of a system, which implies not only a fundamental (identity) change of the system in question (phase 2), but often also the stability – permanence – of the altered conditions (phase 3). For many tipping points, there would be no way back to the initial (current) conditions, at least on timescales that are relevant for decision makers today. For example, if the Amazon rainforest shifts to a savannah-like state, there would be no viable return path to a rainforest state over multiple centuries, even if temperatures were reduced back to current levels. Tipping elements such as ice sheets and related sea level rise are technically reversible, but the deposition of new glacial mass operates through a very different mechanism than those that produce ice melting. Re-establishing lost glacial mass in Greenland, for example, would thus take place on much longer timescales than the time over which current losses are occurring, and would require a decrease of the global temperature to below pre-industrial levels. The IPCC’s 6th assessment report recognises the risk of irreversible climate impacts in case of temperature overshoot (IPCC, 2022b), but not in a more systematic way linked to Earth system tipping processes.

The irreversibility of tipping processes is the characteristic that creates most concern among decision makers (Milkoreit, 2019), likely because it has important implications for impact governance.

First, the irreversible, structural changes associated with the crossing of ESTPs imply that loss and damage provisions will play a much greater role than currently recognised. Environmental conditions for human existence will be permanently altered at large scales, and current conditions – ecosystems, landscapes, natural resources, and the associated human uses and experiences of nature – will be lost. In extreme cases, these losses will be observable, like species extinctions, or the loss of a glacier or river. In other cases, the reorganisation will be more creeping, such as loss of habitable coastline, the changes to a landscape or disappearance of industries that are not sustainable in the post-tipping state. There will be a greater need for loss and damage institutions, including financing, which is already sorely lacking, to compensate for impacts that cannot be avoided by mitigation and adaptation efforts. Furthermore, as more wealthy countries grow increasingly aware of the impacts they face from the crossing of ESTPs, they may also grow wary of contributing to loss and damage funds aimed at compensating communities and countries with lower adaptive capacity.

Second, current climate change adaptation approaches might not be adequate to deal with the effects of ESTPs. Current climate adaptation frameworks focus on “reducing climate risks and vulnerability mostly via adjustment of existing systems” (IPCC, 2022b). The IPCC also noted that, while there has been progress in adaptation efforts around the world, “Many initiatives prioritise immediate and near-term climate risk reduction, which reduces the opportunity for transformational adaptation.” Adjustments of the current system and short-term risk-reduction measures would likely be insufficient in communities affected by profound and lasting disruptions associated with ESTPs.

The existence of ESTPs also creates risks for maladaptation, which refers to adaptation measures with adverse outcomes that reinforce, redistribute or create new sources of vulnerability now or in the future (Juhola et al., 2016; Schipper, 2020; Eriksen et al., 2021). Maladaptation can range from simply inefficient measures to those with wide-reaching negative externalities (Brink et al., 2023), including increased GHG emissions from air-conditioning in response to increasing heat, more inequitable welfare distribution or increasing social conflict (Nadiruzzaman et al., 2022).