Climate change ‘tipping points’ too close for comfort

Published November 29, 2019, 12:11 PM

by AJ Siytangco

By Agence France-Presse

PARIS – Loading the atmo­sphere with five million tons of CO2 every hour has pushed Earth danger­ously close to a no-return threshold, beyond which lies an unlivable hot­house world, top climate scientists have warned.

There are 15 known tipping points in the planet's complex and joined-up climate system, and nine of them are alarmingly "on the move", scientists say (AFP/File / Agustin PAULLIER / MANILA BULLETIN)
There are 15 known tipping points in the planet’s complex and joined-up climate system, and nine of them are alarmingly “on the move”, scientists say (AFP / File Photo / Agustin PAULLIER / MANILA BULLETIN)

There are 15 known tipping points in the planet’s complex climate sys­tem, and nine of them – including permafrost, the Amazon rainforest, the Greenland icesheet, Arctic sea ice, and the Atlantic Ocean’s circulation – are alarmingly “on the move,” they reported in the journal Nature.

Locked inside the tundra of Rus­sia, Alaska and Canada, for example, is twice as much CO2 and methane as there is already in the atmosphere. If humanity cannot manage its own carbon pollution, what will we do if Earth turns from sink to source, adding even more?

AFP spoke to two of the authors – Tim Lenton, director of the Global Systems Institute at the University of Exeter, and Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research.

Losing control

Q: How has scientific understand­ing of tipping points changed over the last decade or two?

ROCKSTROM: Today, we are reaching a point of unequivocal sci­entific evidence that these tipping elements are real. The Earth system is an interconnected, self-regulating bio-geophysical system that can exist in different stable states. You can have rainforests, such as in the Amazon, that can tip over and become savan­nah. You can have stable icesheets, or ice-free conditions.

We have come to realise that two degrees Celsius (35.6 degrees Fahr­enheit) is not just a political tempera­ture target, it is actually a planetary boundary. Go beyond that and we are at risk of unleashing self-reinforced warming – this is what Earth system scientists fear most.

The moment that the Earth system flips over from being self-cooling – which it still is – to self-warming, that is the moment when we lose control.

In 2001, the threshold was seen to be around 5C or 6C of warming. Today, the IPCC estimate is between 2C and 3C. Coral reefs, Arctic sea ice and the West Antarctic icesheet have either crossed the tipping point already or are very close. You could call them the first planetary victims of Anthropo­genic climate change.

‘Toppling dominoes’

Q: Does that mean we need to shift our focus to preparing for the inevi­table impacts that will follow?

LENTON: We will have to adapt to some changes that may now be un­avoidable. The Amundsen Sea Embay­ment of West Antarctica might have passed a tipping point – the “ground­ing line” where ice, ocean and bedrock meet is retreating irreversibly.

When this sector collapses, it could destabilize the rest of the West Antarctic icesheet like toppling domi­noes, leading to about three meters of sea-level rise on a timescale of centuries to millennia. Models sug­gest that the Greenland icesheet could be doomed at 1.5C of warming, which could happen as soon as 2030.

For long-term sea level rise, then, we should be looking seriously at relocation.

But what we know about tipping points should strengthen the argu­ment for reducing greenhouse gas emissions. The fact that we start to see some unexpected shifts in the system should give an extra impetus to meet the Paris goals of limiting the warm­ing as close to 1.5 as we can.

We’ve got a short-term challenge which is to try and get to net-zero greenhouse gas emissions in the next 30 years. That should be the focus of the most urgent attention. We need a joined-up strategy – it has to be a two-pronged approach.

‘Cascading impacts’

Q: You highlight the ways in which different facets of Earth’s climate system interact, and how that may amplify the risk of dire impacts.

ROCKSTROM: The cascading com­binations are critically important, and pose a challenge to the scientific commu­nity. We see three in evidence today.

There is a connection, for example, between the Arctic and Antarctica via the ocean circulation system in the Atlantic. The slowdown in the so-called Atlantic overturning leads to more warm surface water in the Southern Ocean, which in turn leads to faster melting of the West Antarctic icesheet.

Changes in the Arctic and Greenland, meanwhile, can also help explain the more intense droughts in the Amazon basin, which result in more forest fires and pulses of CO2 into the atmosphere.

About 17 percent of the Amazon has been lost since 1970. Estimates of where an Amazon tipping point could lie range from 40 percent to just 20 percent of forest-cover loss. Finding the tipping point will require models that include the interaction of deforestation and climate change.

 
CLICK HERE TO SIGN-UP
 

YOU MAY ALSO LIKE

["news"]
[2191986,2814292,2534630,2485825,2408462,2358243,2358052,2344118,2339143,2047660,1998697,996820,995332,995948,995006,994327,994303,993947,993860,993770,993529,993383,993285,798318,2874419,2874416,2874410,2874413,2874398,2874404]

Climate change ‘tipping points’ too close for comfort

Published November 29, 2019, 12:00 AM

by manilabulletin_admin

By Agence France-Presse

PARIS – Loading the atmo­sphere with five million tons of CO2 every hour has pushed Earth danger­ously close to a no-return threshold, beyond which lies an unlivable hot­house world, top climate scientists have warned.

There are 15 known tipping points in the planet's complex and joined-up climate system, and nine of them are alarmingly "on the move", scientists say (AFP/File / Agustin PAULLIER / MANILA BULLETIN)
There are 15 known tipping points in the planet’s complex and joined-up climate system, and nine of them are alarmingly “on the move”, scientists say (AFP / File Photo / Agustin PAULLIER / MANILA BULLETIN)

There are 15 known tipping points in the planet’s complex climate sys­tem, and nine of them – including permafrost, the Amazon rainforest, the Greenland icesheet, Arctic sea ice, and the Atlantic Ocean’s circulation – are alarmingly “on the move,” they reported in the journal Nature.

Locked inside the tundra of Rus­sia, Alaska and Canada, for example, is twice as much CO2 and methane as there is already in the atmosphere. If humanity cannot manage its own carbon pollution, what will we do if Earth turns from sink to source, adding even more?

AFP spoke to two of the authors – Tim Lenton, director of the Global Systems Institute at the University of Exeter, and Johan Rockstrom, director of the Potsdam Institute for Climate Impact Research.

Losing control

Q: How has scientific understand­ing of tipping points changed over the last decade or two?

ROCKSTROM: Today, we are reaching a point of unequivocal sci­entific evidence that these tipping elements are real. The Earth system is an interconnected, self-regulating bio-geophysical system that can exist in different stable states. You can have rainforests, such as in the Amazon, that can tip over and become savan­nah. You can have stable icesheets, or ice-free conditions.

We have come to realise that two degrees Celsius (35.6 degrees Fahr­enheit) is not just a political tempera­ture target, it is actually a planetary boundary. Go beyond that and we are at risk of unleashing self-reinforced warming – this is what Earth system scientists fear most.

The moment that the Earth system flips over from being self-cooling – which it still is – to self-warming, that is the moment when we lose control.

In 2001, the threshold was seen to be around 5C or 6C of warming. Today, the IPCC estimate is between 2C and 3C. Coral reefs, Arctic sea ice and the West Antarctic icesheet have either crossed the tipping point already or are very close. You could call them the first planetary victims of Anthropo­genic climate change.

‘Toppling dominoes’

Q: Does that mean we need to shift our focus to preparing for the inevi­table impacts that will follow?

LENTON: We will have to adapt to some changes that may now be un­avoidable. The Amundsen Sea Embay­ment of West Antarctica might have passed a tipping point – the “ground­ing line” where ice, ocean and bedrock meet is retreating irreversibly.

When this sector collapses, it could destabilize the rest of the West Antarctic icesheet like toppling domi­noes, leading to about three meters of sea-level rise on a timescale of centuries to millennia. Models sug­gest that the Greenland icesheet could be doomed at 1.5C of warming, which could happen as soon as 2030.

For long-term sea level rise, then, we should be looking seriously at relocation.

But what we know about tipping points should strengthen the argu­ment for reducing greenhouse gas emissions. The fact that we start to see some unexpected shifts in the system should give an extra impetus to meet the Paris goals of limiting the warm­ing as close to 1.5 as we can.

We’ve got a short-term challenge which is to try and get to net-zero greenhouse gas emissions in the next 30 years. That should be the focus of the most urgent attention. We need a joined-up strategy – it has to be a two-pronged approach.

‘Cascading impacts’

Q: You highlight the ways in which different facets of Earth’s climate system interact, and how that may amplify the risk of dire impacts.

ROCKSTROM: The cascading com­binations are critically important, and pose a challenge to the scientific commu­nity. We see three in evidence today.

There is a connection, for example, between the Arctic and Antarctica via the ocean circulation system in the Atlantic. The slowdown in the so-called Atlantic overturning leads to more warm surface water in the Southern Ocean, which in turn leads to faster melting of the West Antarctic icesheet.

Changes in the Arctic and Greenland, meanwhile, can also help explain the more intense droughts in the Amazon basin, which result in more forest fires and pulses of CO2 into the atmosphere.

About 17 percent of the Amazon has been lost since 1970. Estimates of where an Amazon tipping point could lie range from 40 percent to just 20 percent of forest-cover loss. Finding the tipping point will require models that include the interaction of deforestation and climate change.

 
CLICK HERE TO SIGN-UP
 

YOU MAY ALSO LIKE

["news","news"]
[2078117,2874404,2874392,2874382,2874378,2874373,2874369]