Climate change 'tipping points' an ill omen, scientists say

Scientists are warning that "irreversible climate tipping points" are now more numerous and closer to being triggered than previously thought, as shown by frequent disastrous droughts and floods, hurricanes and typhoons.

As the United Nations pushes for a reduction in carbon emissions in order to scale down global warming, many researchers now say climate change has already reached the point of no return.

Tipping points are when key factors in Earth's climate, such as the Amazon rainforest or the Greenland ice sheet, start to irreversibly break down.

When a tipping point has been reached, it will experience runaway effects that essentially make it irreversible, even if global temperatures become cooler, scientists say.

In a research report published on Sept 9 in the journal Science, a team of scientists, using data compiled since 2008, found that there are now 16 major tipping points, almost all of which could reach a point of no return if global warming continues beyond 1.5 C above preindustrial levels.

The scientists concluded that there is "strong scientific evidence "pointing to the need for "urgent action to mitigate climate change".

They said that even the Paris Agreement goal of limiting warming to below 2 C and preferably 1.5 C is not safe, "as 1.5 C and above risks crossing multiple tipping points".

"Crossing these climate tipping points, or CTPs, can generate positive feedbacks that increase the likelihood of crossing other CTPs. Currently, the world is heading toward 2 to 3 C of global warming; at best, if all net-zero pledges and nationally determined contributions are implemented it could reach just below 2 C," the report concluded.

"This would lower tipping point risks somewhat but would still be dangerous, as it could trigger multiple climate tipping points," it said.

Study co-author Johan Rockstroem, director of the Potsdam Institute for Climate Impact Research in Germany, said, "This sets Earth on course to cross multiple dangerous tipping points that will be disastrous for people across the world."

Co-author Tim Lenton, director of the Global Systems Institute at the University of Exeter in the United Kingdom, said, "Since I first assessed climate tipping points in 2008, the list has grown, and our assessment of the risk they pose has increased dramatically."

The scientists have isolated key tipping points: the ice sheets of Greenland and the West Antarctic; Arctic permafrost; tropical coral reefs; and a key ocean current in the Labrador Sea.

They also isolated another 11"likely" or "possible" tipping points if warming continues past 2 C.

"To maintain livable conditions on Earth, protect people from rising extremes, and enable stable societies, we must do everything possible to prevent crossing tipping points," Rockstroem said.

Another report by a new multi-agency coordinated by the World Meteorological Organization said, "Climate science is clear: We are heading in the wrong direction."

"Without much more ambitious action, the physical and socioeconomic impacts of climate change will be increasingly devastating," the "United in Science" report said.

It said that greenhouse gas concentrations are continuing to rise to record highs.

The ambition of emissions reduction pledges for 2030 needs to be seven times higher to meet the Paris Agreement's goal of global warming to at least 1.5 C, it said.

According to the World Meteorological Organization, the past seven years were the warmest on record.

In a video message reacting to the report, United Nations Secretary-General Antonio Guterres said, "Floods, droughts, heat waves, extreme storms and wildfires are going from bad to worse, breaking records with alarming frequency.

"Heat waves in Europe. Colossal floods in Pakistan. Prolonged and severe droughts in China, the Horn of Africa and the United States. There is nothing natural about the new scale of these disasters. They are the price of humanity's fossil fuel addiction.

"This year's 'United in Science' report shows climate impacts heading into uncharted territory of destruction. Yet each year we double down on this fossil fuel addiction, even as the symptoms get rapidly worse," Guterres said.

Emeritus Professor Neville Nicholls, from the School of Earth, Atmosphere and Environment at Monash University, said the reports show that "our slow progress in restraining the growth of greenhouse gases means that the world will not be able to restrain global warming sufficiently to avoid at least some deleterious impacts."