Archives par mot-clé : AMOC

climate-debate, Cooling

Study: Greenland’s Melting Ice Unlikely To Trigger Atlantic Current’s Collapse

P. Gosselin, Apr, 10, 2025 in ClimateChangeDispatch 

Day after Tomorrow
We hear it again and again: the melting ice in Greenland due to global warming will soon lead to a collapse of the Gulf Stream system, with the result that it would be difficult to restart. [emphasis, links added]

Then we would see great disasters like those depicted in Roland Emmerich’s dramatic climate movie “The Day after Tomorrow”.

The seawater salinity in the north is critical because the salt-rich tropical water cools and sinks due to the higher salt content.

This acts as the pump that makes circulation possible in the first place. It serves to transport very large amounts of heat into the North Atlantic, keeping Europe on the mild side in the wintertime.

Scenarios have been published recently that calculate a drastic cooling of the large area (especially Europe) around it if the Gulf Stream system got “switched off”.

But those scenarios are proving to be overdramatic and alarmist.

Yuxin Zhou, a postdoctoral researcher in UC Santa Barbara’s Department of Earth Science, recently went back in history to study when the AMOC was severely weakened, from 68,000 to 16,000 years ago, when the Laurentide Ice Sheet existed and thick ice covered northern North America and even New York City.

Today, that massive ice shelf no longer exists and thus there is no longer the potential of an ice melt and iceberg release of that scale.

Very different, less dramatic circumstances today

By analyzing sea sediment deposited by floating icebergs in the North Atlantic, Zhou found that the AMOC heat-transferring oceanic current had already been moderately weakened before all the icebergs floated over the North Atlantic.

Comparing the situation to today, Zhou says, “In contrast, the circulation is very vigorous right now,” which suggests the melting of Greenland is not likely to plunge the North Atlantic into another deep freeze of the sort the alarmists fret about all the time.

Moreover, Technology Networks here adds (emphasis added):

Not all melting has the same effect on the Atlantic circulation. Freshwater released as icebergs has a much larger impact on the AMOC than runoff, which is released after melting on land. Icebergs can cool the surrounding seawater, causing it to freeze into sea ice. Ironically, this ice layer acts as a blanket, keeping the ocean surface warm and preventing it from plunging down to the depths and driving the Atlantic circulation. What’s more, icebergs travel much farther out to sea than runoff, delivering freshwater to the regions where this deepwater formation occurs.”

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climate-debate

The “Collapsing Gulf Stream” Scare is Back—Again

by C. Rotter, Feb 5, 2025 in WUWT

Ah, the Atlantic Meridional Overturning Circulation (AMOC) collapse—our old friend. Like a horror movie franchise that refuses to die, the idea that the Gulf Stream is about to shut down and plunge Europe into an icy apocalypse has returned. This time, the BBC is breathlessly warning that “the chance of it happening is growing”​. But before you start knitting survivalist-grade wool socks, let’s take a moment to review how many times we’ve heard this story before—and why it never seems to pan out.

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A Climate Catastrophe… Someday, Maybe, Possibly

According to the BBC, AMOC is supposedly “getting weaker,” but they immediately admit that direct measurements have only been taken since 2004—meaning we have barely two decades of actual data​. Now, call me old-fashioned, but when you’re talking about an ocean system that has been operating for millions of years, 20 years of data is like trying to predict a person’s entire life based on a single Tuesday morning.

And what’s their big evidence? Ocean floor sediments and a “cold blob” in the Atlantic. That’s right, they’re looking at dirt samples and a patch of water that isn’t warming like the rest of the ocean, and somehow, this is supposed to spell doom for civilization​.

This wouldn’t be so bad if they admitted the uncertainty. Instead, the article plays a game of “it’s probably not happening, but it totally could!” For instance, the IPCC says they have “medium confidence” that AMOC will notcollapse this century. But some other scientists say, well, maybe it could! As one of them warns, we “maybe need to be worried”​.

What kind of science is this? It sounds more like a horoscope than a serious climate analysis.

Fear-Mongering 101: Every Climate Scare is the Last One

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climate-debate

Climate Alarmist Stefan Rahmstorf Struggles With The Reality Of Uncertainty

by P. Gosselin, Feb 2, 2025 in NoTricksZone

By Frank Bosse

(Translated from the original at Klimanachrichten)

We have kept you, dear readers, very promptly informed about AMOC conjectures.

Recently, we also informed you about a new study that found a stable Atlantic overturning circulation since the 1960s. It is not the only one in the recent past.

However, Prof. Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research (PIK) is a great advocate of the “The Day after Tomorrow” scenario of a collapsing oceanic current. As recently as June, 2024, he noted on X (formerly Twitter) that the AMOC mitigation saga “is even more dramatic than it ever was”.

He himself had been responsible for a whole series of papers as author or co-author, which also contributed to the scenario, and he initiated an “open letter” in the fall of 2024 that dramatically addressed politicians. We also reported on this.

Of course, the new findings could not couldn’t pass him by without comment. Under the headline “The AMOC is slowing down, is stable, yes, no, no, yes…” he commented on it on the blog “Real Climate”, which is run by scientists, including himself, Gavin Schmidt from NASA, and others.

What he has to say there can be stated in a nutshell: He defends his approaches and lists the problems of the more recent studies. That was to be expected. For example, he emphasizes that the new climate models (CMIP 6) hardly show any connection between “his fingerprint”, the sea surface temperatures of the “warming hole” in the North Atlantic (see the article here from 17 January 2025) and the actual current, but that the approximately 4 years older ones called CMIP5 do. He also questions whether the new ones are really more reliable in this respect than the older ones. However, the effort for the former was considerable.

He summarized:

I don’t believe that the newer methods are more reliable than the old ones (his, the author). … However, since we don’t have measurements going back far enough, there is still some uncertainty in this respect…“

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unclassified

Climate Alarmists Push AMOC Collapse AND Greenland Ice Collapse

by E. Worrall, Dec 28, 2024 in WUWT

Two for the price of one? The weather will be record cold with melting ice.

Climate change is the worst. Here’s just how bad it got this year.

By Hannah Osborne

The big news in Earth science this year was all about climate change, with extreme weather, flooding and drought attributed to warming. Scientists also warned about much worse to come if we don’t rein in carbon emissions.

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Climate change devastation edging closer

But some of the scariest news about the planet isn’t what happened this year but rather what could occur if we don’t stop spewing carbon into the atmosphere. A study published in June suggested ecological tipping points — such as the collapse of the Greenland Ice Sheet and the transformation of the Amazon rainforest into savanna — could be reached in just 15 years if climate change isn’t controlled.

In October, scientists penned an open letter warning about the risk posed by the collapse of a key Atlantic current. In it, researchers urged policymakers to address the threat posed by the weakening Atlantic Meridional Overturning Circulation (AMOC) — a giant ocean conveyor belt that transports heat to the Northern Hemisphere, and the breakdown of which could cause temperatures across Europe to plummet.

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Read more: https://www.livescience.com/planet-earth/climate-change-is-the-worst-heres-just-how-bad-it-got-this-year

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unclassified

Can we trust projections of AMOC weakening based on climate models that cannot reproduce the past?

by G.D. McCarthy & L. Caesar, Nov 2023 in PhilosophicalTransactions

The Atlantic Meridional Overturning Circulation (AMOC), a crucial element of the Earth’s climate system, is projected to weaken over the course of the twenty-first century which could have far reaching consequences for the occurrence of extreme weather events, regional sea level rise, monsoon regions and the marine ecosystem. The latest IPCC report puts the likelihood of such a weakening as ‘very likely’. As our confidence in future climate projections depends largely on the ability to model the past climate, we take an in-depth look at the difference in the twentieth century evolution of the AMOC based on observational data (including direct observations and various proxy data) and model data from climate model ensembles. We show that both the magnitude of the trend in the AMOC over different time periods and often even the sign of the trend differs between observations and climate model ensemble mean, with the magnitude of the trend difference becoming even greater when looking at the CMIP6 ensemble compared to CMIP5. We discuss possible reasons for this observation-model discrepancy and question what it means to have higher confidence in future projections than historical reproductions.

This article is part of a discussion meeting issue ’Atlantic overturning: new observations and challenges’.

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unclassified

Understanding Abrupt Climate Change in the Late Quaternary

by R.S. Bradley & H.F. Diaz, Nov18,  2021 in Eos

Between about 75,000 and 10,000 years ago, there was a series of sudden and dramatic changes in rainfall patterns in tropical regions likely triggered by changes in ocean water circulation. A recent article in Reviews of Geophysics examines the evidence of these “Tropical Hydroclimatic Events” and explores the potential causes. Here, one of the authors explains more about these abrupt climate change events of the past and suggests how it can inform our understanding of potential future climate change.

What are “Tropical Hydroclimatic Events” (THEs)? When and where did they occur?

When we look back at past climate variations in continental regions of the Tropics and sub-Tropics (~30ºN-30ºS), it is abundantly clear that there were times when climate abruptly changed, causing some areas that were formerly wet to become quite dry, and areas that were formerly dry to become much wetter, disrupting plant and animal communities, as well as people living in the region. We call those changes “Tropical Hydroclimatic Events (THEs).” The changes affected vast areas (and lasted for centuries in some cases_ before the climate shifted back to the former conditions. There were at least half a dozen of these THEs between about 10,000 and 75,000 years ago.

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climate-debate

Yet Another Model-Based Claim Of Anthropogenic Climate Forcing Collapses

by K. Richard, Feb 25 2021 in NoTricksZone

High-resolution climate models have projected a “decline of the Atlantic Meridional Overturning Circulation (AMOC) under the influence of anthropogenic warming” for decades (Lobelle et al., 2020). New research that assesses changes in the deeper layers of the ocean (instead of “ignoring” these layers like past models have) shows instead that the AMOC hasn’t declined for over 30 years.

The North Atlantic has been rapidly cooling in recent decades (Bryden et al., 2020, Fröb et al., 2019). A cooling of “more than 2°C” in just 8 years (2008-2016) and a cooling rate of -0.78°C per decade between 2004 and 2017 has been reported for nearly the entire ocean region just south of Iceland. The cooling persists year-round and extends from the “surface down to 800 m depth”

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