Cool patch below Greenland is bad news

Two years ago this month I posted Global temperature, the North Atlantic cool patch and the Gulf Stream. The cool patch was still there, lasting throughout the 2018 northern summer:

This now needs to be recognised as an enduring feature associated with the slowdown of the overturning ocean circulation AMOC (Atlantic Meridional Overturning Circulation) which James Hansen and Makiko Sato say is having an effect on the east coast hurricanes which have been so prominent during this summer.

The cool patch is thought to be due to a combination of sea ice export from the Arctic, the Greenland melt, and increased precipitation and river runoff.

Normally the Gulf Stream current becomes increasingly salty as the prevailing winds evaporate the sea water travelling across the North Atlantic. Near the north-east the heavier saltwater sinks, driving the thermohaline current:

Now the just-melted freshwater is diluting the salty water, inhibiting the sinking. Indeed the whole circulation system is slowing down. The system of currents bringing warm water to the North Atlantic has been in operation at least since the closing of the Panama Isthmus 2.8 million years ago. This closure has been called the most important geological event in the past 60 million years, because it makes northwestern Europe as much as 10 degrees C warmer than it otherwise would be.

How this may play out over the next century was addressed in 2016 in a 52-page paper by James Hansen and others – Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming could be dangerous. The paper is complex, and impossible to do justice in a blog piece, but I had a go in Hansen worries that all hell will break loose. The focus there was on the possibility that giant storms could occur in line with evidence of what may have happened during the last interglacial, the Eemian, roughly 115 to 130 thousand years ago.

Hansen and Sato now say that the slowdown of AMOC is currently contributing to storminess in three ways.

First, sea level rise (SLR) is enhanced along the north American coast by the AMOC slowdown:

    The slowdown reduces the west-to-east upward slope of the ocean surface across the Gulf Stream, causing piling up of water on the East Coast. The combined sea level rise from these effects, which is also responsible for “sunny day flooding” on the Eastern Seaboard, makes hurricane storm surges greater.

Combining their second and third effects, there is a warm band south of the cool patch, where the warmer ocean makes for larger storms in physical size and slower tracking, which then delivers huge amounts of precipitation.

All this makes for a greater impact on humans, their environment and the structures they have built.

Tamino at Open Mind, who has been talking to hurricane experts, identifies the rapid intensification of hurricanes as a key factor.

Hansen and Sato say that the tracking patterns may be different, but that has not yet been studied and it is probably too early to say. They do say that the numbers of hurricanes making landfall in the US may not have increased, and looks to be down in the current decade:

Please note, the number hurricanes in the North Atlantic basin is an entirely different number.

At this point I don’t want to repeat the ground I covered in Hansen worries that all hell will break loose. Hansen et al have used direct observations, paleoclimate information and a climate model incorporating ice sheet decay in both hemispheres. They are aware that there is insufficient information to be certain about anything, but warn that during the Eemian there was SLR of 2-3 metres within several decades at one point, that ice sheet melting may on average double every 10, 20 or 40 years, (they think closer to 10) and that if AMOC shuts down it could take centuries to restart.

The IPCC Special Report on 1.5°C has SLR at 26 to 77 cm by 2100 for 1.5°C global warming, 10 cm more for 2°C. The Hansen paper contemplates the possibility of 1 metre by 2060, whereupon the surface temperature map might look like this:

mid century temperatures_cropped

If ice sheet melt keeps doubling we could have five metres of SLR by 2096, whereupon with all that cold water spread around surface temperature may look like this:

The cooler surface in those circumstances does not stop ice sheet decay, because warmer water still has access to ice shelves. The paper suggests that:

    global surface air temperature, although an important diagnostic, is a flawed metric of planetary “health”, because faster ice melt has a cooling effect for a substantial period.

They suggest Earth’s energy imbalance as a more fundamental climate diagnostic. The control knob for energy imbalance is CO2 and other GHGs which should be reduced to 350ppm as soon as possible.

Their warning is not about linear gradients of temperature, rather an earth system which could become quite chaotic to human perception and may become beyond control.

We should recognise that we have a tiger by the tail.

Earlier post – Trouble at the top of the world.

6 thoughts on “Cool patch below Greenland is bad news”

  1. Indeed Brian the cold patch is bad news, but it is complicated. You were one of the first people recently to comment on this developing situation, but it was predicted in the 90’s as paleo climatologists have demonstrated that this has happened in the past before dramatic climate shifts.

    I have commented on the prospect of this shutting down the thermo haline circulation, and that this has the up tick of starving the Arctic Ocean of the warming that would release the immense amount of Methane stored there. what wasn’t predicted was the timing of the shutdown and the source of the fresh water. I thought that this would come from the Arctic fringe, I didn’t appreciate that the bulk of the cold fresh water would come from Greenland. For the time being this water does not appear to be fully blocking the warm water entering the Arctic Ocean as it seems the warm water flows underneath the cool lighter pool of water. But there is is another surprise and that is that the Arctic is generating its own warm water as the ice sheet thins towards near future “blue water” events. This has the effect of stirring up an ocean water body that has largely been slow moving. New currents are forming in the Arctic waters to circulate the warming waters, and that spells disaster for the whole world. These new currents will deliver warm water to the Clathrate reserves on the Arctic ocean shelves and more rapidly warm the submerged permafrost.

    This is all game over. Any thing we do from here is “fiddling as Home (Earth) burns”. These nut jobs who think that “we can adapt” really have no idea. To begin with they have demonstrated an incapacity to understand the science of Global Warming, so they equally do not have the capacity to understand the science of cooking human bodies due to,…not specifically hot air,.. but high energy air in the form of humidity. Our bodies rely on evaporation to cool when our body temperatures increase, but if the air is saturated with moisture then this impossible and people die from heat stress, in the tens of thousands as we have seen now a number of times in Europe.

    This is NOW becoming impossible to deny any more,……………………………….BUT…………………………the problem is that the time for slowing global warming has passed us by.

    We are now in the escalating consequences phase.

    Who is the key Climate Criminal in Australia? John Howard, whose most damaging act was harbouring Tony Abbott who he kept around because his narcissistic disconnection with truth and reality were useful for stomping on opposition, and that gave rise to the extended Climate Denialism which still persists as Abbott attempts to drive the political agenda from the back benches with his “back bench climate committee”.

    A warning we need globally to understand…Narcissists never give up…they will scorch the earth to win. They have no interest in other people’s need, only their own self engrandisement and winning. These people must never be in government, particularly where they can affect the future of everyone’s lives as they have with their Global Warming Denialism.

  2. I’m sorry for being so extreme, Brian, but this is no longer an issue for intellectual or casual discussion, particularly when this far down the path we have a Prime Minister who has said publicly “there is no need to pull out of the Paris Agreement as it will achieve nothing (and unstated we have minimised to cost of climate action to an insignificant level)”.

    In Australia Climate action is in reverse, and the likes of Abbott would like to wipe it out altogether with his “back bench climate committee” attempting to steer the government with demands such as his recent “urging” to the front bench for the end to all renewable energy subsidies.

  3. Wishing everybody a

    Happy Wentworth By-election Day!

    It would seem that, this time at least, action-on-global-warming has been an important matter in the electorate.

  4. Brian: I might be missing something but my take is that parts of the world will be able to produce more food than they do now, parts of the world will be able to produce less food than they do now and the same is true for livability.
    To make matters worse the livable, food producing zones may move around so that some places may become and then unbecome food bowls at various stages in the future. Large countries may have relatively stable food producing capacity even though the food producing zones move around over time. They may also have the capacity to defend themselves from the starving hordes across the border. Tough luck in the future for the land of Brexit?
    We also live in a world where the population has more than quadrupled since 1920.
    We need to talk about rapidly reducing population as well as reducing greenhouse emissions.

  5. JohnD,

    The future food picture is further complicated by extreme weather, shifting seasons, and insect evolution.

    In the past we have looked at growing conditions by averages. Average rainfall which arrives in stages for instance. In the future Average rainfall will tend to arrive on the same day in a deluge. Deluges destroy crops so while the average is perhaps better, the delivery is out of seasonal timing (as the season has shifted due to average temperature) and in the wrong way.

    I was listening to some scientists with an interest in the insect “field” who were saying that a warmer wetter climate accelerates insect evolution greatly, ie the ability for crop protection technology to keep up will be overwhelmed.

    Global Warming is all bad news for food production, and ocean acidification is going to diminish the “harvest from the sea” even more so than overfishing has.

    Yes, population reduction will be a pressure, though I can’t see it having an impact in time to be a solution, rather it will be a consequence. I am going to make a prediction here: In order to have reasonably traditional lives in the future environment, there will be a greater trend for families to group together. ie multiple couples sharing the same living space to better manage costs, resources, and to share the children so that a family of four parents can enjoy the experience of two children rather than one child for two parents.

  6. Bilb: Developed countries like Australia, the US, most of Europe and Japan would all have declining populations if they had no net immigration.
    Factors that help drive population growth include:
    Need to have a lot of kids to be sure of having descendants. (Or the numbers in inter-family fights.)
    A lack of welfare (kids will look after you and siblings when you are old.)
    Better health systems = more survivors.
    Kids become net contributors at young age. (Think kids on farms.)
    Compulsory education and the normal education leaving age getting older and older. (Father in law went down pit before he finished first year high school because his father became too sick to work. Mother in law did 3 years primary school before helping her mother look after the mega family. (Birth certificate signed by her fathers mark.) Their daughter and all their grandchildren have degrees with all except one having post graduate degrees.
    Catholic church opposition to contraception.

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