Below some excerpts from
Why ‘Carbon-Cycle Feedbacks’ Could Drive Temperatures Even Higher. It is a nice summary so do read it.
https://e360.yale.edu/features/why-carbon-cycle-feedbacks-could-drive-temperatures-even-higher1
last September at the National Institute for Space Research in the Brazilian research city of Sao Jose dos Campos. Atmospheric chemist Luciana Gatti was rushing to tell her colleagues the result of her latest analysis of carbon dioxide emissions from the Amazon rainforest, which she had completed that morning.
For a decade, her team had been sampling the air from sensors on aircraft flying over the world’s largest rainforest. Their collating of recent results showed that, perhaps for the first time in thousands of years, a large part of the Amazon had switched from absorbing CO2 from the air, damping down global warming, to being a “source” of the greenhouse gas and thus speeding up warming.
“We have hit a tipping point,” Gatti almost shouted, caught between elation at her discovery and anguish at the consequences. ... But now it no longer mattered if it was a wet or a dry year, or how many fires there were, the sink had become a source.
...
The scientists are warning that past climate models used by the UN’s Intergovernmental Panel on Climate Change (IPCC) have not fully reflected the scale of the warming that lies ahead as carbon sinks die. These revelations are coming from three areas of research:
1 Studies such as Gatti’s in the Amazon, showing forests turning from sinks to sources of CO2;
2 A new generation of climate models that incorporate these findings into future projections of climate change, and whose early outputs are just emerging;
3 Recent revelations that ecosystems are releasing rising volumes of methane, the second most important greenhouse gas and of vital importance for temperatures in the next couple of decades.
The extra emissions, known as carbon-cycle feedbacks, could already be making the prospect of keeping warming below 2 degrees Celsius — the target agreed to in the Paris climate accord in 2015 — all but impossible....
Non-tropical forests remain largely in carbon “sink” mode. But other tropical rainforests appear to be following the Amazon in moving toward becoming carbon sources. Wannes Hubau, now at the Royal Museum of Central Africa in Belgium, reported recently that “overall, the uptake of carbon into Earth’s intact tropical forests peaked in the 1990s” and has been declining since. The jungles of tropical Africa began showing increased carbon losses around 2010, he found.
Another big concern is the impact of thawing permafrost. ... One recent study in northern Canada found thawing had reached depths “already exceeding those projected to occur by 2090.”
2
The risks of such rapid runaway carbon releases to the atmosphere have been worrying ecologists for a while. That worry is now being reinforced by the projections of a new generation of climate models designed to factor in how ecosystems respond to climate change.
Until now, most climate models have largely confined themselves to assessing how our CO2 emissions warm the air, and how that warming interacts with physical feedbacks such as reduced ice cover, elevated atmospheric water vapor, and changes to clouds. This remains a work in progress. I wrote here on Yale Environment 360 in February how new field research suggests that the ability of clouds to keep us cool could be drastically reduced as the world warms, pushing global heating into overdrive.
When ecological feedbacks have been included in the models, it has mostly been in a very simplistic way. But new models being developed for the next IPCC assessment of climate science are changing that.
...
Even a scenario that is “reasonably consistent with currently enacted climate policies” could deliver up to 5 degrees C of warming rather than the current estimate of 3 degrees. This, Betts says, is “because the upper end of possible feedbacks results in 40 percent more CO2 in the air than previously supposed: 936 parts per million [ppm] by 2100, compared to a prediction without the carbon-cycle feedbacks of 670 ppm.” (Current levels are 415 ppm, and pre-industrial levels were around 280 ppm.)
3
The growing concern about CO2 feedbacks comes on top of alarm about trends in atmospheric levels of the second most important greenhouse gas, methane. These are more than twice pre-industrial levels, and after a decade of stability until 2007 they have been rising again sharply. The National Oceanic and Space Administration (NOAA) estimated this month that methane levels in the atmosphere reached a record 1,875 parts per billion in 2019, after the second largest year-on-year leap ever recorded.
How come? Euan Nisbet of Royal Holloway, University of London, says isotopic analysis shows industrial emissions such as those from fracking remain important sources of methane.
But the major reason for the recent upsurge is microbial emissions, mostly from the tropics....
None of this methane increase is built into even the new climate models with carbon-cycle feedbacks. These models mostly assume that methane levels in the air will remain stable. But the concern is growing that, even if technology can reduce industrial emissions, a warmer world will drive a continuing surge in methane levels — and more warming as a consequence.
Methane typically lasts in the atmosphere for only a decade – much less than CO2. But while it is there, it packs a big warming punch. Measured over 20 years, each molecule of methane emitted has 84 times more warming effect than each molecule of CO2.
Climate models conventionally assess the warming impacts of greenhouse gases over a century. This effectively tunes them to emphasize the importance of C02, and relegates methane to an also-ran.
But if they were tuned to the shorter timeframe, methane would appear almost three times more important.
It seems odd that this shorter timeframe is rarely adopted, given that the world risks exceeding its two-degree warming limit by 2050. As Nisbet puts it, if natural ecosystems keep pumping out more methane as the world warms, “it may become very difficult to meet the Paris goals.”
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Bottom line: we need lots of real carbon and methane reductions this decade.
In fact you can already argue that we have passed the tipping points. If we stopped emitting today we would still be in a world that keeps warming thus pushing up the methane emissions from the tropics and northern sources.
We would still have the amazon and northern permafrost as carbon sources.
We would still have ocean acidification get worse for decades etc.
So we cannot rely on markets to fix it, or technology to fix it.
We need real action which also includes sacrifices. Especially the historical big emitters (see vid above) should invest in going zero first and export those technologies but most won´t because they are captured by the carbon economy.
Hope is important but we have only 1 planet so we are going to have to live here anyway.
So we can´t give up hope anyway...but we need real action and then we have to hope for the best effects from that.
We already gave the younger generation a huge set of problems to solve and i hope we make the AGW problem as small as we can this decade.
(Just imagine being born now or say 2010 and at age 20 figuring out how we got in this mess. It would piss me off.)
