#vanwesten — Public Fediverse posts

New AMOC paper by vanWesten's team in Utrecht
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JC022651

This study isn't about collapse impacts, but they do add some information.
2 other also published papers concern impacts and are cited in the conclusion at the end of the paper.

What this study wanted to determine: where is the early warning signal location so we can monitor and estimate the time of arrival?
Earlier studies by the team also searched for it. And one pointed to Southern Atlantic at 34°S. I recall hearing vanWesten say on a podcast (ClimateChat maybe?), that the Cold Blob in the North Atlantic Subpolar Gyre is not a good location.
But: that one at 34°S was found during the experiment of a pre-industrial hosing experiment without climate change.

Now they looked again and specifically under climate change and specifically at the Cold Blob.
Turns out, in some conditions, it is a very good early warning location, in others not so much, namely with big freshwater pulses.
Or at least, that's how I understand the Conclusion part of the paper.

That 34°S turns out to be not a good location in real world climate change (IUUC) is quite good. Because high-resolution proxies about past behaviour have not been studied from there, and monitoring by ships is too scarce, making reanalyses like EN4 by UKMetOffice for example, unreliable in that area in the South Atlantic.
We'd be flying blind if 34°S were the canary in the coal mine. 🖖🏽
#AMOC
#ClimateChange
#Tipping
#Collapse
#Europe
#vanWesten

@AlexanderVI @EarthOrgUK @JeffC1956 @Sustainable2050

The paper is open access.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JC022651
And while the study wasn't about impacts,
they did add 4 maps of Europe for temperature after the 2 emission scenarios and 2 hosing speeds,
along with line charts of annual temperature average for Iceland, Bergen, Vienna, Madrid and London until year 2400 under these scenarios/speeds.

From my memory (so you best verify):
Temperature evolution doesn't become at all worrisome in 2 emission scenarios/speeds, and very worrisome in the other 2 scenarios/speeds from some time in the next(!) century for Bergen and Iceland.

In words, they add the information that winter storms and winter precipitation change in all 4 scenarios/speeds, as does the tropical rain belt.
I add: annual average temperature says nothing about temperature extremes. Which will be the stuff of future studies, I expect. 🖖🏽

#AMOC #ClimateChange #Tipping #Collapse #Europe #vanWesten

The promised plots.
I'll show data since 2003 only because only then did real measurements really kick off. Before that, measurements were so spotty with 1 in January in one year, then 3 years nothing, then 5 measurements in for example August and so on.
Data source for measurements is #NOAA https://www.ncei.noaa.gov/access/world-ocean-database-select/dbsearch.html

The other plot is from a #ReAnalysis called EN4.2 https://www.metoffice.gov.uk/hadobs/en4/download-en4-2-2.html#c14_analyses
It is based on the same NOAA data, and goes back to 1900. EN4.2 has better quality assurance than my download. And EN4.2 is able to calculate the likely values in adjacent coordinates and adjacent months.

Among other Reanalyses, EN4.2 has also been used in the newest preprint by the Dutch team around #vanWesten. It sees AMOC tip in 2065 in RCP8.5 and in 2085 in RCP4.5. But it is based on biased Reanalyses and known-to-be too stable #CMIP6: https://arxiv.org/pdf/2407.19909

Whereas the first new preprint by van Westen's team, which tips AMOC 2037-2064, uses only real measurements of the 3 dedicated monitoring arrays in the North, tropical and South #Atlantic. https://arxiv.org/pdf/2406.11738
Here, the caveat is: very short data series.

With measurements being so spotty, I only show monthly salinity 2003ff in down to 10m depth. And only from the area in the South Atlantic. Averaged on a 2 by 2 degree grid from Argentina's coast to longitude -48, and latitudes 40-48 South.

Sorry, not sorry: neither dataset shows a smoking gun. 😁
#FridaysForFuture #ChartsForFuture