Risk of rapid North Atlantic cooling in 21st century greater than previously estimated

This paper in Nature would not have have had any chance of being published a few years ago. But times are changing.

CNRS: “The possibility of major climate change in the Atlantic region has long been recognized and has even been the subject of a Hollywood movie: The Day After Tomorrow. To evaluate the risk of such climate change, researchers from the Environnements et Paléoenvironnements Océaniques et Continentaux laboratory (CNRS/University of Bordeaux) and the University of Southampton developed a new algorithm to analyze the 40 climate models considered by the latest report from the Intergovernmental Panel on Climate Change (IPCC). Their findings raise the probability of rapid North Atlantic cooling during this century to nearly 50%. Nature Communications publishes their work on February 15, 2017”.

My own view is that man-made global warming is insignificant and virtually impossible to measure. The apparent climate turbulence we may currently be experiencing is probably the exhibition of instabilities as climate shifts from an interglacial paradigm to the, more normal, glacial conditions. The transition will probably be “rapid” in geologic terms which probably means a thousand years or so. Major volcanic eruptions (VEI>6) are overdue. This interglacial has lasted some 13,000 years and is also, relatively, long. I think it feasible that 2 or 3 major volcanic eruptions in relatively quick succession could provide the conditions to trigger a full transition. Once glacial conditions are established they will last for about 100,000 years. And we will then be very thankful for all the fossil or nuclear energy we can have available to us.

Giovanni Sgubin, Didier Swingedouw, Sybren Drijfhout, Yannick Mary, Amine Bennabi. Abrupt cooling over the North Atlantic in modern climate models. Nature Communications, 2017; 8 DOI: 10.1038/ncomms14375

Abstract: Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models’ varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy.

Even The Guardian (a high priest of the man-made global warming religious fantasy) is compelled to report!!


CNRS Press Release:

Current climate models all foresee a slowing of the meridional overturning circulation (MOC)2—the phenomenon behind the familiar Gulf Stream, which carries warmth from Florida to European shores—that could lead to a dramatic, unprecedented disruption of the climate system. In 2013, drawing on 40 climate change projections, the IPCC judged that this slowdown would occur gradually over a long period of time. The panel’s findings suggested that fast cooling of the North Atlantic during this century was unlikely.

Oceanographers from the EU EMBRACE project team reexamined the 40 projections by focusing on a critical spot in the northwest North Atlantic: the Labrador Sea. The Labrador Sea is host to a convection system ultimately feeding into the ocean-wide MOC. The temperatures of its surface waters plummet in the winter, increasing their density and causing them to sink. This displaces deep waters, which bring their heat with them as they rise to the surface, preventing the formation of ice caps. To investigate this phenomenon in greater detail, the researchers developed an algorithm able to detect quick sea surface temperature variations. Their number crunching revealed that 7 of the 40 climate models they were studying predicted total shutdown of convection, leading to abrupt cooling of the Labrador Sea: by 2–3 °C over less than 10 years. This in turn would drastically lower North Atlantic coastal temperatures.

But is such rapid cooling a real possibility? (After all, only a handful of the models supported this projection.) To answer this question, the researchers honed in on the critical parameter triggering winter convection: ocean stratification. Indeed, 11 of the 40 models incorporated vertical variation in the density of oceanic water masses. And of these 11 models, which we may furthermore consider to be the most reliable, 5 (i.e., 45% of the models) predicted a rapid drop in North Atlantic temperatures.  



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