We are halfway to a tipping point that would trigger a 6 foot sea level rise from the melting of the Greenland Ice Sheet

New research, published this week in the journal Geophysical Research Letters, found carbon emissions are halfway to a tipping point after which a 6-foot rise in sea levels would be unstoppable as the Greenland ice sheet melts.

“Once we emit more than ~1,000 gigatons of carbon in total, we will not be able to prevent the southern part of the Greenland ice sheet from melting completely in the long term, even if we then stop emitting carbon altogether. This melting would cause sea level rise of ~1.8m” Dennis honeya climate scientist at the Potsdam Institute for Climate Impact Research who is the lead author of the study, CNBC said. (1.8 meters is 5.9 feet.)

“Although this melting would take hundreds of years, future generations will not be able to stop it,” Höning said.

The further the Earth passes the first tipping point of 1,000 gigatonnes of carbon emissions, the faster the Greenland ice sheet will melt.

And now, now we’re at about 500 gigatons of released carbon emissions.

“Certainly, the coastal regions would be hit the hardest, especially in underdeveloped countries without modern coastal management,” Höning told CNBC.

Höning said scientists found in it previous studies that the Greenland ice sheet could melt completely with global warming between 1 and 3 degrees Celsius (1.8 degrees to 5.4 degrees Fahrenheit).

But the methods used in previous studies were less accurate because the assumptions made in those models were oversimplified and therefore unrealistic, Höning told CNBC.

“While studying temperature-related tipping points is useful for understanding the stability of the system, in the real world it is the accumulated carbon emission that determines whether or not a tipping point is actually crossed,” Höning told CNBC. “Therefore, for the first time, we investigated the relationships between cumulative carbon emissions and the tipping of the Greenland ice sheet using a fully coupled Earth system model that includes all relevant feedback processes.”

Höning uses the CLIMBER-X computer system who models the evolution of the earth over long periods of time and measures everything in his paper entitled: Multistability and transient response of the Greenland ice sheet to anthropogenic CO2 emissions.

Measuring the melting of the Greenland ice sheet is challenging because it takes a long time to melt and it doesn’t happen at a constant rate.

“As soon as a critical threshold is exceeded, the behavior of the system changes qualitatively and approaches a completely new equilibrium. That’s because of self-reinforcing feedback mechanisms: as the ice sheet melts, its surface is exposed to warmer air temperatures at lower altitudes and inevitably continues to melt,” Höning told CNBC.

Höning said it is more accurate to measure total, cumulative carbon emissions released since 1850.

If total carbon emissions stay below the 1,000 gigatonnes of carbon emissions threshold, then the melting Greenland ice sheet would add “only” ten centimeters to total sea level rise, he added.

The second tipping point identified by the research would occur once 2,500 gigatons of carbon emissions were released into the atmosphere, at which point the entire Greenland ice sheet would melt and sea level rise would increase by 6.9 meters or 22.6 feet.

“Full melting will take some time, hundreds or even thousands of years, especially if we exceed the threshold by just a tiny bit,” Höning said. “Even if the atmospheric CO2 concentration will decrease on these long timescales, it will not decrease fast enough to stop the melting of the ice sheet.”

In theory, artificial carbon dioxide removal technology could pull carbon out of the atmosphere quickly enough after hitting one of those tipping points to recoup the inevitable melting. But it’s not a case study worth pursuing because the technology to remove that amount of emissions from the atmosphere doesn’t currently exist.

“We’re nowhere near the point where carbon removal is efficient. In any case, avoiding carbon emissions is much cheaper than the energy required to recapture that carbon,” Höning told CNBC.

Source : www.cnbc.com

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