<!DOCTYPE html>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<font size="+2" face="Calibri"><i><b>February</b></i></font><font
size="+2" face="Calibri"><i><b> 11, 2024</b></i></font><i><font
face="Calibri"><br>
</font></i> <br>
<i>[ RealClimate.org is the renowned, long-lasting climate science
site - this entry is more straight-talking than usual ]</i><br>
<b>New study suggests the Atlantic overturning circulation AMOC “is
on tipping course”</b><br>
9 FEB 2024 BY STEFAN <br>
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.<br>
<br>
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.)<br>
<br>
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.<br>
<br>
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.<br>
<br>
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.
<a class="moz-txt-link-freetext"
href="https://www.realclimate.org/index.php/archives/2023/07/what-is-happening-in-the-atlantic-ocean-to-the-amoc/"
moz-do-not-send="true">https://www.realclimate.org/index.php/archives/2023/07/what-is-happening-in-the-atlantic-ocean-to-the-amoc/</a><br>
-- <a class="moz-txt-link-freetext"
href="https://www.nature.com/articles/s41586-018-0006-5"
moz-do-not-send="true">https://www.nature.com/articles/s41586-018-0006-5</a><br>
<br>
But now, let’s get straight to the main findings of the new paper:<br>
<br>
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.)<br>
<br>
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?<br>
<br>
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.”<br>
<br>
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.<br>
<br>
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.<br>
- - <a class="moz-txt-link-freetext"
href="https://www.realclimate.org/images/van-westen-2024-1536x509.png"
moz-do-not-send="true">https://www.realclimate.org/images/van-westen-2024-1536x509.png</a><br>
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.<br>
<br>
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.<br>
<br>
<b>Update 10. February:</b> 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.<br>
<br>
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.<br>
<br>
<a class="moz-txt-link-freetext"
href="https://www.realclimate.org/index.php/archives/2024/02/new-study-suggests-the-atlantic-overturning-circulation-amoc-is-on-tipping-course/"
moz-do-not-send="true">https://www.realclimate.org/index.php/archives/2024/02/new-study-suggests-the-atlantic-overturning-circulation-amoc-is-on-tipping-course/</a><br>
<p><br>
</p>
<br>
<i>[ (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."
<a class="moz-txt-link-freetext"
href="https://www.statista.com/statistics/373814/cable-news-network-viewership-usa/"
moz-do-not-send="true">https://www.statista.com/statistics/373814/cable-news-network-viewership-usa/</a>
]</i><br>
Wide Awake Media @wideawake_media<br>
<b>Fox News guest PERFECTLY summarises the World Economic Forum's
'Great Reset' agenda, in just one minute:</b><br>
<blockquote>"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."<br>
</blockquote>
<p>"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."</p>
<p><a class="moz-txt-link-freetext"
href="https://x.com/wideawake_media/status/1756285711282573723?s=20"
moz-do-not-send="true">https://x.com/wideawake_media/status/1756285711282573723?s=20</a><br>
</p>
<a class="moz-txt-link-freetext"
href="https://twitter.com/wideawake_media/status/1756285711282573723"
moz-do-not-send="true">https://twitter.com/wideawake_media/status/1756285711282573723</a><br>
<br>
<p><br>
</p>
<font face="Calibri"><i>[The news archive - not prepared ]</i></font><br>
<font face="Calibri"> <font size="+2"><i><b>February 11, 2013 </b></i></font>
</font><br>
<font face="Calibri"> </font> 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.'"<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.upi.com/Science_News/2013/02/11/Climate-change-risks-to-US-security-seen/UPI-54781360632325/#ixzz2m3sx4HrC">http://www.upi.com/Science_News/2013/02/11/Climate-change-risks-to-US-security-seen/UPI-54781360632325/#ixzz2m3sx4HrC</a>
<br>
<br>
<br>
<p><font face="Calibri"> <br>
</font><font face="Calibri"><br>
=== Other climate news sources
===========================================<br>
</font> <font face="Calibri"><b>*Inside Climate News</b><br>
Newsletters<br>
We deliver climate news to your inbox like nobody else. Every
day or once a week, our original stories and digest of the web’s
top headlines deliver the full story, for free.<br>
</font> <font face="Calibri"><a class="moz-txt-link-freetext"
href="https://insideclimatenews.org/" moz-do-not-send="true">https://insideclimatenews.org/</a><br>
--------------------------------------- <br>
*<b>Climate Nexus</b> <a class="moz-txt-link-freetext"
href="https://climatenexus.org/hot-news/*"
moz-do-not-send="true">https://climatenexus.org/hot-news/*</a>
<br>
Delivered straight to your inbox every morning, Hot News
summarizes the most important climate and energy news of the
day, delivering an unmatched aggregation of timely, relevant
reporting. It also provides original reporting and commentary on
climate denial and pro-polluter activity that would otherwise
remain largely unexposed. 5 weekday <br>
================================= <br>
</font> <font face="Calibri"><b class="moz-txt-star"><span
class="moz-txt-tag">*</span>Carbon Brief Daily </b><span
class="moz-txt-star"><a class="moz-txt-link-freetext"
href="https://www.carbonbrief.org/newsletter-sign-up"
moz-do-not-send="true">https://www.carbonbrief.org/newsletter-sign-up</a></span><b
class="moz-txt-star"><span class="moz-txt-tag">*</span></b> <br>
Every weekday morning, in time for your morning coffee, Carbon
Brief sends out a free email known as the “Daily Briefing” to
thousands of subscribers around the world. The email is a digest
of the past 24 hours of media coverage related to climate change
and energy, as well as our pick of the key studies published in
the peer-reviewed journals. <br>
more at <a class="moz-txt-link-freetext"
href="https://www.getrevue.co/publisher/carbon-brief"
moz-do-not-send="true">https://www.getrevue.co/publisher/carbon-brief</a>
<br>
================================== <br>
*T<b>he Daily Climate </b>Subscribe <a
class="moz-txt-link-freetext"
href="https://ehsciences.activehosted.com/f/61*"
moz-do-not-send="true">https://ehsciences.activehosted.com/f/61*</a>
<br>
Get The Daily Climate in your inbox - FREE! Top news on climate
impacts, solutions, politics, drivers. Delivered week days.
Better than coffee. <br>
Other newsletters at <a class="moz-txt-link-freetext"
href="https://www.dailyclimate.org/originals/"
moz-do-not-send="true">https://www.dailyclimate.org/originals/</a>
<br>
<br>
</font> </p>
<font face="Calibri">
/-----------------------------------------------------------------------------------/
<br>
/Archive of Daily Global Warming News <a
class="moz-txt-link-freetext"
href="https://pairlist10.pair.net/pipermail/theclimate.vote/"
moz-do-not-send="true">https://pairlist10.pair.net/pipermail/theclimate.vote/</a><br>
<br>
<br>
/To receive daily mailings - click to Subscribe <a
class="moz-txt-link-rfc2396E"
href="mailto:subscribe@theClimate.Vote?subject=Click%20SEND%20to%20process%20your%20request"
moz-do-not-send="true"><mailto:subscribe@theClimate.Vote?subject=Click%20SEND%20to%20process%20your%20request></a>
to news digest./<br>
<br>
Privacy and Security:*This mailing is text-only -- and carries no
images or attachments which may originate from remote servers.
Text-only messages provide greater privacy to the receiver and
sender. This is a personal hobby production curated by Richard
Pauli<br>
By regulation, the .VOTE top-level domain cannot be used for
commercial purposes. Messages have no tracking software.<br>
To subscribe, email: <a
class="moz-txt-link-abbreviated moz-txt-link-freetext"
href="mailto:contact@theclimate.vote" moz-do-not-send="true">contact@theclimate.vote</a>
<a class="moz-txt-link-rfc2396E"
href="mailto:contact@theclimate.vote" moz-do-not-send="true"><mailto:contact@theclimate.vote></a>
with subject subscribe, To Unsubscribe, subject: unsubscribe<br>
Also you may subscribe/unsubscribe at <a
class="moz-txt-link-freetext"
href="https://pairlist10.pair.net/mailman/listinfo/theclimate.vote"
moz-do-not-send="true">https://pairlist10.pair.net/mailman/listinfo/theclimate.vote</a><br>
Links and headlines assembled and curated by Richard Pauli for <a
class="moz-txt-link-freetext" href="http://TheClimate.Vote"
moz-do-not-send="true">http://TheClimate.Vote</a> <a
class="moz-txt-link-rfc2396E" href="http://TheClimate.Vote/"
moz-do-not-send="true"><http://TheClimate.Vote/></a>
delivering succinct information for citizens and responsible
governments of all levels. List membership is confidential and
records are scrupulously restricted to this mailing list. </font><font
face="Calibri"><br>
</font>
</body>
</html>