The world is at heightened risk of triggering multiple climate ‘tipping points’, causing cascading effects that could lead to irreversible and uncontrollable impacts on Earth, according to an assessment by leading climate scientists.
There is an increased likelihood that tipping points will be crossed if the average global temperature exceeds 1.5 degrees, concludes the analysis published by the research journal Science. Limiting the rise in temperatures to 1.5 degrees is the most demanding of the objectives of the Paris Agreement.
The most immediate tipping points scientists have identified are: the collapse of the Greenland and West Antarctic ice sheets; an abrupt and widespread thaw of the permafrost releasing large quantities of methane; weakening convection in the Labrador Sea and mass mortality of tropical coral reefs around the equator. Permafrost is most concentrated in the Arctic beneath large parts of Alaska, Canada, and Siberia.
The planet may have already left a ‘safe’ climate state when temperatures exceeded 1 degree of warming, he finds – current global average temperatures are 1.1 to 1.2 degrees above levels preindustrial.
Human-caused carbon emissions have raised Earth’s temperature through the greenhouse effect, and much greater warming is expected in the coming decades if carbon levels in the atmosphere are not reduced.
Warming may not always be constant – passing a ‘tipping point’ can cause a sudden or irreversible change, warns the group led by Dr David Armstrong McKay from the Stockholm Resilience Centre.
Scientists now fear that Earth is approaching certain climate tipping points sooner than expected, beyond which rapid and difficult-to-reverse climate change could occur – a scenario confirmed in the most comprehensive assessment of tipping points published. Thursday.
Co-author Johan Rockström, co-chair of the Earth Commission and director of the Potsdam Institute for Climate Impact Research, said: “The world is heading towards 2-3 degrees of global warming. This puts Earth on track to cross several dangerous tipping points that will be disastrous for people around the world.
“To maintain livable conditions on Earth, protect people from rising extremes, and enable stable societies, we must do all we can to avoid crossing tipping points. Every tenth of a degree counts,” he added.
Co-author Professor Tim Lenton, director of the Global Systems Institute at the University of Exeter, said their new work “provides compelling evidence that the world needs to radically accelerate the decarbonisation of the economy to limit the risk to overcome climatic tipping points”. To achieve this, we must now trigger positive social tipping points that accelerate the transformation to a clean energy future.”
“We may also need to adapt to deal with climate tipping points that we fail to avoid and support those who may suffer uninsurable loss and damage,” Professor Lenton added.
By sifting through paleoclimate data, current observations and climate model results, the international team concluded that 16 major biophysical systems involved in regulating the Earth’s climate – called “tipping elements” – have the potential to cross tipping points where change becomes self-sustaining.
This means that even if global temperatures stop rising, once the ice sheet, ocean or rainforest have passed a tipping point, they will continue to shift to a new state, Professor Lenton explained. The duration of the transition varies from several decades to thousands of years depending on the system.
Professors Rockström and Lenton are co-hosting a global conference at the University of Exeter on September 15 to look at how to improve warnings of impending risks of catastrophic climate tipping points and accelerate positive tipping points to avert the climate crisis.
Climate risks hitting critical ‘tipping points’ sooner than expected – study