Exceeding 1.5°C global warming could trigger multiple climate tipping points

Abstract

Climate tipping points occur when change in a part of the climate system becomes self-perpetuating beyond a warming threshold, leading to substantial Earth system impacts. Synthesizing paleoclimate, observational, and model-based studies, we provide a revised shortlist of global “core” tipping elements and regional “impact” tipping elements and their temperature thresholds. Current global warming of ~1.1°C above preindustrial temperatures already lies within the lower end of some tipping point uncertainty ranges. Several tipping points may be triggered in the Paris Agreement range of 1.5 to <2°C global warming, with many more likely at the 2 to 3°C of warming expected on current policy trajectories. This strengthens the evidence base for urgent action to mitigate climate change and to develop improved tipping point risk assessment, early warning capability, and adaptation strategies.

Network motifs shape distinct functioning of Earth’s moisture recycling hubs

“…S 1 ) to focus on the regions of strongest moisture flows, our results are robust to substantial changes of ρ (see sensitivity analyses in the Methods). By making this choice, we find the main moisture recycling hubs, which are relevant on an Earth system scale, and are of at least a sub-continental scale (similar to what has been used to define climate tipping elements 24 ). As an initial step, we study the in-degree and out-degree of the moisture recycling network 25 (Fig.…”

“…Considering that particularly FFLs have been shown to increase the possibility of cascading tipping in networks of tipping elements 19 , we here present an additional argument for assessing the robustness of Earth’s major moisture recycling hubs. It is feared that parts of the Amazon rainforest may tip as a result of deforestation and climate change 24 , 41 , 42 . The weakening of links in the network may heavily affect moisture flows down the network.…”

Climate tipping points and expert judgment

“…Providing a precise general definition of the notion of tipping point in the climate system (or, more globally, in the Earth system) is a rather subtle question, in particular if nonequilibrium properties are considered 10 . For the purpose of this review, we do not need to enter into any technicalities and we pragmatically adopt a standard characterization in terms of a threshold (or critical parameter value) in an Earth system component (called tipping element) beyond which a small perturbation leads to some qualitative change in a crucial system feature within some time frame (Lenton et al, 2008; see also the very recent reassessment in Armstrong McKay et al, 2022). 11 Tipping points are naturally related to abruptness and irreversibility (or hysteresis), but they do not necessarily imply these notions in this general understanding.…”

“…So, expert judgment needs regular updating. This is explicitly acknowledged in Kriegler et al (2009, 5045), which is unsurprising given the Bayesian framework they assume (see Section 2.2): “It should be noted that expert beliefs are tied to the time of elicitation, and may be updated in light of new information.” However, as recently noted in Wunderling et al (2021), an updated expert elicitation has not been carried out more than 10 years later, despite the new knowledge about climate and Earth system tipping points that has emerged since then (similarly, Armstrong McKay et al, 2022 write that “an updated expert elicitation [building on Kriegler et al, 2009] is overdue”) 20…”

An architecture for a net zero world: Global climate governance beyond the epoch of failure

“…As if to underscore such warnings, recent research raises concerns that the Eastern Amazon is now a net emitter (rather than a globally crucial sink) for carbon dioxide and is already undergoing 'savannaisation' (Gatti et al, 2021). Scientists warn that the collapse of the Greenland and West Antarctic ice sheets is possible at 1.5°C, and other tipping points well before 2°C of global heating (Armstrong-McKay et al, 2022).Just in the few years, vast areas of Australia, the US, Canada and Russia have burned; heatwaves have killed thousands in India and Europe; drought has crippled China, Africa and Europe; more intense and frequent cyclones have destroyed Tacloban, Fiji, the…”