Summary
- Earth systems are complex, dynamic and interdependent. While they can absorb small shocks, large changes and feedback effects can push them to critical thresholds beyond which a tiny change will ‘tip’ them into very different states. Their interactions with one another mean that a change in one will affect others like falling dominoes.
- Tipping points are often referred to as ‘non-linear’ events because they happen in abrupt jumps rather than gradually, they are irreversible in human time-frames, and they trigger natural additional greenhouse gas emissions (for example permafrost and methane clathrates) over which we have no control.
- Anthropogenic greenhouse gas emissions—over which we do have control—are reaching critical thresholds that are tipping the climate into a state that humans have never before experienced.
- In 2015, most governments agreed that to ‘avoid a critical threshold above which the planet could experience irreversible catastrophic impacts‘, global temperatures must not exceed 1.5°C above pre-Industrial levels.
- In 2015, most governments agreed that to ‘avoid a critical threshold above which the planet could experience irreversible catastrophic impacts‘, global temperatures must not exceed 1.5°C above pre-Industrial levels.
- However, calculations how to achieve this did not consider the feedback effects if tipping points were exceeded.
- IPCC reports in 2018 and 2019 indicated that major tipping points could be reached between 1° and 2°C.
- We have now passed 1°C and there is strong evidence that key tipping points are being breached. Even if countries act on their Paris climate agreement pledges to reduce emissions, the most recent UN Report states that we are on track for warming of more than 3°C.
Overview
“It’s a nasty shock that tipping points we thought might happen well into the future are already underway.” – Professor Timothy Lenton interview in Phys.org following his co-authored paper in Nature, 2019.
The implications for tipping points are so complex and widespread that only two intertwined tipping points with the most obvious physical impacts on New Zealand are currently outlined on this website:
- The melting cryosphere: Arctic sea ice, Greenland, permafrost, (eg Fig. 2) and Antarctica: leading to accelerated rising sea levels, more extreme weather events, loss of critical ecosystem services (biodiversity), social and economic impacts
- Changes in ocean currents: leading to extreme weather events, loss of critical ecosystem services (biodiversity), social, and economic impacts
“In New Zealand, 72,000 people are currently exposed to present-day extreme coastal flooding, along with about 50,000 buildings worth $12.5 billion. The risk exposure increases markedly with sea-level rise, particularly during the first metre of rise…. There is near certainty that the sea will rise 20-30cm by 2040.” – NIWA, 2019
The other tipping points in Fig. 1 will also have some physical impacts as well as global economic and social impacts outside the scope of this website. For further information about these tipping points, see Carbon Brief’s website (Fig. 1) and the free to access paper in Nature (published Nov. 2019; updated April 2020).
Video 1: Professor Timothy Lenton, Director Global Systems Institute, briefly explains climate tipping points
Video 1: Steffen M. Olsen, Danish Meteorological Institute. The ice sheet near Qaanaaq Greenland that they would normally sled across is covered in vast meltwater lakes due to extreme surface warming (17°C) in June 2019. Meltwater eventually drains into the ocean, contributing to rising sea levels and disrupting oceanic currents.
References and further reading
- 2020 Carbon Brief Explainer: Nine ‘tipping points’ that could be triggered by climate change
- 2020: Turetsky et al; Carbon release through abrupt permafrost thaw, Nature Geoscience 13, pp138–143
- 2020: Keuper et al; Carbon loss from northern circumpolar permafrost soils amplified by rhizosphere priming Nature Geoscience 13, pp560-565
- 2020: Thomas et al; Tipping elements and amplified polar warming during the Last Interglacial, Quaternary Science Reviews 233 / 106222
- 2019: Lade et al; Human impacts on planetary boundaries amplified by Earth system interactions, Nature Sustainability 3, pp 119–128
- 2019 NIWA: New Zealand Fluvial and Pluvial Flood Exposure; prepared for Deep South Challenge
- 2019 NIWA: Coastal Flooding Exposure Under Future Sea-level Rise for New Zealand; prepared for Deep South Challenge
- 2019: Lenton et al; Climate tipping points — too risky to bet against, Nature article (free to access)
- 2019 IPCC: Special Report on the Ocean and Cryosphere in a Changing Climate
- 2018 IPCC: Summary for Policymakers of IPCC Special Report on Global Warming of 1.5°C approved by governments
- 2018: Carbon Brief Analysis; Why the IPCC 1.5C report expanded the carbon budget
- 2017: Jones; How the World Passed a Carbon Threshold and Why It Matters, Yale Environment 360 – Yale School of Forestry & Environmental Studies
- 2015: United Nations Climate Change: The Paris Agreement
- 2015 Carbon Brief interactive: The Paris Agreement
- 2010: Ditlevsen: Tipping points: Early warning and wishful thinking, Geophysical Research Letters 37/19
- 2009: Schneider: Science as a Contact Sport, National Geographic Books NY