[✔️] Feb 11 2024 Global Warming News | RealClimate AMOC Tipping Point, Fox denialism, 2013 not prepared

[R.Pauli]

/*February*//*11, 2024*//
/
/[ RealClimate.org is the renowned, long-lasting climate science site - 
this entry is more straight-talking than usual ]/
*New study suggests the Atlantic overturning circulation AMOC “is on 
tipping course”*
9 FEB 2024 BY STEFAN
A new paper was published in Science Advances today. Its title says what 
it is about: “Physics-based early warning signal shows that AMOC is on 
tipping course.” The study follows one by Danish colleagues which made 
headlines last July, likewise looking for early warning signals for 
approaching an AMOC tipping point (we discussed it here), but using 
rather different data and methods.

The new study by van Westen et al. is a major advance in AMOC stability 
science, coming from what I consider the world’s leading research hub 
for AMOC stability studies, in Utrecht/Holland. (Some of their 
contributions spanning the past 20 years are in the paper’s reference 
list, with authors Henk Dijkstra, René van Westen, Nanne Weber, Sybren 
Drijfhout and more.)

The paper results from a major computational effort, based on running a 
state-of-the-art climate model (the CESM model with horizontal 
resolution 1° for the ocean/sea ice and 2° for the atmosphere/land 
component) for 4,400 model years. This took 6 months to run on 1,024 
cores at the Dutch national supercomputing facility, the largest system 
in the Netherlands in terms of high-performance computing.

It is the first systematic attempt to find the AMOC tipping point in a 
coupled global ocean-atmosphere climate model of good spatial 
resolution, using the quasi-equilibrium approach which I pioneered in 
1995 with an ocean-only model of relatively low resolution, given the 
limited computer power available 30 years ago.

If you’re not familiar with the issues surrounding the risk of abrupt 
ocean circulation changes, I briefly summarized ten key facts on this 
topic last year in this blog post. 
https://www.realclimate.org/index.php/archives/2023/07/what-is-happening-in-the-atlantic-ocean-to-the-amoc/
   -- https://www.nature.com/articles/s41586-018-0006-5

But now, let’s get straight to the main findings of the new paper:

1. It confirms that the AMOC has a tipping point beyond which it breaks 
down if the northern Atlantic Ocean is diluted with freshwater (by 
increasing rainfall, river runoff and meltwater), thus reducing its 
salinity and density. This has been suggested by simple conceptual 
models since Stommel 1961, confirmed for a 3D ocean circulation model in 
my 1995 Nature article, and later in a first model intercomparison 
project in 2005, among other studies. Now this tipping point has been 
demonstrated for the first time in a state-of-the-art global coupled 
climate model, crushing the hope that with more model detail and 
resolution some feedback might prevent an AMOC collapse. (This hope was 
never very convincing, as paleoclimate records clearly show abrupt AMOC 
shifts in Earth history, including full AMOC breakdowns triggered by 
meltwater input (Heinrich events). The last AMOC breakdown occurred 
about 12,000 years ago and triggered the Younger Dryas cold event around 
the northern Atlantic.)

2. It confirms by using observational data that the Atlantic is “on 
tipping course”, i.e. moving towards this tipping point. The 
billion-dollar question is: how far away is this tipping point?

3. Three recent studies (for more on these see this blog post), using 
different data and methods, have argued that we are approaching the 
tipping point and that it might be too close for comfort, even posing a 
risk of crossing it in the next decades. However, the reliability of the 
methods used has been questioned (as discussed here at RealClimate). 
Based on their epic computer simulation, the Dutch group proposed a new, 
physics-based  and observable type of early warning signal. It uses a 
diagnostic – the freshwater transport by the AMOC at the entrance of the 
South Atlantic, across the latitude of the southern tip of Africa – 
which I proposed in a 1996 study. They do not present a particular time 
period estimate for reaching the tipping point, as more observations of 
the ocean circulation at this latitude will be needed for that, but they 
note about last year’s Ditlevsen study that “their estimate of the 
tipping point (2025 to 2095, 95% confidence level) could be accurate.”

4. The new study confirms past concerns that climate models 
systematically overestimate the stability of the AMOC. About the crucial 
AMOC freshwater transport in models, they point out that most models 
don’t get it right: “This is not in agreement with observations, which 
is a well-known bias in CMIP phase 3 (38), phase 5 (21), and phase 6 
(37) models.” Most models even have the wrong sign of this important 
diagnostic, which determines whether the feedback on Atlantic salinity 
is stabilising or destabilising, and this model bias is a key reason why 
in my view the IPCC has so far underestimated the risk of an AMOC 
collapse by relying on these biased climate models.

5. The study also provides more detailed and higher resolution 
simulations of the impacts of an AMOC collapse on climate, albeit 
considered in isolation and not combined with the effects of CO2-induced 
global warming (Fig. 2). They show how particularly northern Europe from 
Britain to Scandinavia would suffer devastating impacts, such as a 
cooling of winter temperatures by between 10 °C and 30 °C occurring 
within a century, leading to a completely different climate within a 
decade or two, in line with paleoclimatic evidence about abrupt ocean 
circulation changes. In addition they show major shifts in tropical 
rainfall belts. These (and many more) impacts of an AMOC collapse have 
been known for a long time but thus far have not been shown in a climate 
model of such high quality.
- - https://www.realclimate.org/images/van-westen-2024-1536x509.png
Given the impacts, the risk of an AMOC collapse is something to be 
avoided at all cost. As I’ve said before: the issue is not whether we’re 
sure this is going to happen. The issue is that we need to rule this out 
at 99.9 % probability. Once we have a definite warning signal it will be 
too late to do anything about it, given the inertia in the system.

Overall the new study adds significantly to the rising concern about an 
AMOC collapse in the not too distant future. It thus adds even more 
weight to recent reports sounding strong warning sirens, such as the 
OECD Climate Tipping Points report of December 2022 and the Global 
Tipping Points report published December 2023. We will continue to 
ignore this risk at our peril.

*Update 10. February:* In the reactions to the paper, I see some 
misunderstand this as an unrealistic model scenario for the future. It 
is not. This type of experiment is not a future projection at all, but 
rather done to trace the equilibrium stability curve (that’s the 
quasi-equlibrium approach mentioned above). In order to trace the 
equlibrium response, the freshwater input must be ramped up extremely 
slowly, which is why this experiment uses so much computer time. After 
the model’s tipping point was found in this way, it was used to identify 
precursors that could warn us before reaching the tipping point, 
so-called “early warning signals”. Then, the scientists turned to 
reanalysis data (observations-based products, shown in Fig. 6 of the 
paper) to check for an early warning signal. The headline conclusion 
that the AMOC is „on tipping course“ is based on these data.

In other words: it’s observational data from the South Atlantic which 
suggest the AMOC is on tipping course. Not the model simulation, which 
is just there to get a better understanding of which early warning 
signals work, and why.

https://www.realclimate.org/index.php/archives/2024/02/new-study-suggests-the-atlantic-overturning-circulation-amoc-is-on-tipping-course/



/[ (severe denialism) "In November 2023, Fox News was the most watched 
cable news network in the United States and continues to do well in 
terms of its primetime audience, with 1.72 million primetime viewers in 
that period." 
https://www.statista.com/statistics/373814/cable-news-network-viewership-usa/ 
]/
Wide Awake Media @wideawake_media
*Fox News guest PERFECTLY summarises the World Economic Forum's 'Great 
Reset' agenda, in just one minute:*

    "The WEF is a fanatical political organisation that uses fear and
    manipulation, like Covid hysteria, like the hoax of global warming,
    to really facilitate people thinking that somehow they're the
    saviours, but really all you're doing is helping them accomplish
    their goal, which really is a global public-private fascist
    movement, and fusion of big government, big tech [and] big money, to
    create a technocratic ruling elite, which conveniently is them."

"They want to create feudalism 2.0, in which we are serfs, and they are 
the lords ruling over us… That's what they're aiming for."

https://x.com/wideawake_media/status/1756285711282573723?s=20

https://twitter.com/wideawake_media/status/1756285711282573723


/[The news archive - not prepared ]/
/*February 11, 2013 */
February 11, 2013: UPI reports on a Harvard University study that 
indicates "extreme weather and climate change present a potential threat 
to U.S. national security for which 'we are not prepared.'"

http://www.upi.com/Science_News/2013/02/11/Climate-change-risks-to-US-security-seen/UPI-54781360632325/#ixzz2m3sx4HrC 





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