Gulf stream could collapse, but no idea when

[Brightonian]

What do you reckon? Next year? Ten years? Fifty? Never?
https://www.theguardian.com/environment ... m-collapse

[dyqik]

The "must not be allowed to happen" thing is a bit difficult, given the lag time in the response of ocean temperatures to carbon emissions, and the fact this would likely be a hysteretic change, so getting the temperatures down again probably wouldn't restore it.

There's a pretty high chance that it's already been allowed to happen, we just haven't realized that yet.

[Grumble]

The "must not be allowed to happen" thing is a bit difficult, given the lag time in the response of ocean temperatures to carbon emissions, and the fact this would likely be a hysteretic change, so getting the temperatures down again probably wouldn't restore it.

There's a pretty high chance that it's already been allowed to happen, we just haven't realized that yet.

I thought that was a funny phrase too, but I guess they’re just trying to push politicians into action.

[Bird on a Fire]

The "must not be allowed to happen" thing is a bit difficult, given the lag time in the response of ocean temperatures to carbon emissions, and the fact this would likely be a hysteretic change, so getting the temperatures down again probably wouldn't restore it.

There's a pretty high chance that it's already been allowed to happen, we just haven't realized that yet.

This is a super important point. The longer emissions keep rising, or stay high, the likelier it is we'll discover a tipping point in some system.

The 1.5°C threshold was chosen for the Paris agreement because it was deemed pretty likely to avoid most of them, whereas 2°C could be very bad (remembering that these are global averages, and that polar regions especially are heating much faster).

Unfortunately, it turns out that our current 1.2°C is worse than generally expected, and current commitments under Paris put us in the 3-4°C range. We'll see if anything cha6nges at the COP this year. I really f.cking hope so.

I thought that was a funny phrase too, but I guess they’re just trying to push politicians into action.

Unfortunately, politicians respond to crises by doing whatever seems immediately expedient. I don't know how we make it immediately expedient for them to listen to scientists, but we haven't worked it out during the pandemic.

[hakwright]

An important point of clarification (which I caught from Radio 4 this morning):

This research does NOT suggest the Gulf Stream is at risk of collapse. It suggests that "currents that researchers call the Atlantic meridional overturning circulation (AMOC)" are unstable and at risk of collapse. If the AMOC collapsed, it would have an effect on the Gulf Stream (pushing it south from what I caught on the Radio), but there is no suggestion or risk that the Gulf Stream itself would stop.

[Grumble]

An important point of clarification (which I caught from Radio 4 this morning):

This research does NOT suggest the Gulf Stream is at risk of collapse. It suggests that "currents that researchers call the Atlantic meridional overturning circulation (AMOC)" are unstable and at risk of collapse. If the AMOC collapsed, it would have an effect on the Gulf Stream (pushing it south from what I caught on the Radio), but there is no suggestion or risk that the Gulf Stream itself would stop.

So if the Gulf Stream moved south presumably Britain’s climate could become more like coastal Alaska.

[IvanV]

So if the Gulf Stream moved south presumably Britain’s climate could become more like coastal Alaska.

If Britain got a climate more like the west coast of North America, on a latitude for latitude basis, that would actually mean it got warmer on average. Winters would be rather colder. But both seasonal variation and day-night temperature differences would be larger.

The Kuroshio Current plays the same role in the north Pacific as the Gulf Stream in the north Atlantic. That is, the Kuroshio is a warm current, originating near Japan, that travels broadly west to east across the Pacific, and taking its warm waters to higher latitudes. But the Gulf Stream is tilted somewhat more anti-clockwise in comparison to the Kuroshio. The Gulf stream takes warm water from a bit further south to a bit further north than the Kuroshio. So, very broadly speaking, sending the Gulf Stream south ought to make the north Atlantic a bit more like the north Pacific, in terms of latitudes of interest below 60N, where the British Isles (Lerwick is about 60N), British Columbia, and the very far south-eastern corner of Alaska lie.

Alaska stretches from just south of 55N to just north of 71N, a very similar range of latitudes to the Scandinavian Peninsular. But the great bulk of continental Alaska likes north of 60N, ie north of the British Isles. There is just this very thin panhandle stretching down to the SE, separating northern British Columbia from the sea, that has latitudes similar to Scotland and the Northern Isles. Most of England and Wales have latitudes similar to coastal British Columbia, and the far north of Washington State in the USA.

The southernmost point of coastal Alaska has about the same latitude as Carlisle or Malmö. The climate in Ketchican, the southernmost town in Alaska, is more like Malmö than Carlisle, in having a wider range of temperatures both seasonally and day-night than Carlisle. But its summers are distinctly warmer than either, so overall is warmer than both of those, especially Carlisle, which is on average is rather cooler than Malmö.

[dyqik]

An important point of clarification (which I caught from Radio 4 this morning):

This research does NOT suggest the Gulf Stream is at risk of collapse. It suggests that "currents that researchers call the Atlantic meridional overturning circulation (AMOC)" are unstable and at risk of collapse. If the AMOC collapsed, it would have an effect on the Gulf Stream (pushing it south from what I caught on the Radio), but there is no suggestion or risk that the Gulf Stream itself would stop.

So if the Gulf Stream moved south presumably Britain’s climate could become more like coastal Alaska.

Alaska has a big mountain range just to the east, and whole continent backing that up though. I'd suggest Labrador and Newfoundland as maybe closer parallels, particularly as they get many of the east coast US storm systems that travel across the Atlantic to the UK.

Although for political punning purposes, maybe that should be Prince Edward Island (after a series of unfortunate accidents in the Royal Family) and Nova Scotia...

[monkey]

What about Japan? Hot summers, cold winters, occasional storms and Godzillas.

[basementer]

What about Japan? Hot summers, cold winters, occasional storms and Godzillas.

It's about 15 degrees closer to the Equator than are the British Isles.

[discovolante]

Uncertainty aside (it's not hugely reassuring...) this is keep me awake at night and wonder why anyone has kids stuff. Is there any reason at all to be hopeful about COP26?

[monkey]

What about Japan? Hot summers, cold winters, occasional storms and Godzillas.

It's about 15 degrees closer to the Equator than are the British Isles.

I just wanted to do the joke about Godzillas. I nearly added earthquakes too.

All I know is that it will annoy the farmers.

[IvanV]

Alaska has a big mountain range just to the east, and whole continent backing that up though. I'd suggest Labrador and Newfoundland as maybe closer parallels, particularly as they get many of the east coast US storm systems that travel across the Atlantic to the UK.

Although for political punning purposes, maybe that should be Prince Edward Island (after a series of unfortunate accidents in the Royal Family) and Nova Scotia...

The most important factor for climate, if you live where an ocean meets a continent at temperate latitudes where the prevailing winds are from the west, is which side of the ocean you live on. This is more important than whether there is some warm ocean current.

Thus the western edge of Europe has a climate about 6 to 9C warmer than places at the same latitude on the eastern edge of the Americas. A similar difference exists in the north Pacific at similar latitudes. Most of that difference is simply due to which side of the ocean you are on. Only a little bit due to to the warm current you benefit from if you are on the eastern side. For example, simply being on the eastern side of the Atlantic is worth about 6C to Britain's climate, and the gulf stream only about 1.5C. Though as you go further north, the relative influence of the gulf stream is larger, hence the astonishingly mild climate of the northern half of Norway, which gains about 3C from the gulf stream.

The reason is simply that the wind travels a long distance over an ocean to come to you of you are the eastern side of the ocean, whereas it travels a long distance over land if you are on the western side.

[plodder]

Uncertainty aside (it's not hugely reassuring...) this is keep me awake at night and wonder why anyone has kids stuff. Is there any reason at all to be hopeful about COP26?

yes, I think there is. Low carbon technology is being developed and implemented at an amazing rate and although our policy makers are useless the US is back on board with the Paris agreement and the direction of travel is definitely to reduce carbon. There will always be plenty of room for concern but things are starting to gradually move in the right direction and I think change could be really rapid once it finally beds in. I am hopelessly over optimistic.

[discovolante]

Uncertainty aside (it's not hugely reassuring...) this is keep me awake at night and wonder why anyone has kids stuff. Is there any reason at all to be hopeful about COP26?

yes, I think there is. Low carbon technology is being developed and implemented at an amazing rate and although our policy makers are useless the US is back on board with the Paris agreement and the direction of travel is definitely to reduce carbon. There will always be plenty of room for concern but things are starting to gradually move in the right direction and I think change could be really rapid once it finally beds in. I am hopelessly over optimistic.

I'm definitely feeling more optimistic about the low carbon/renewable tech side of things these days but the politics, domestic and international, seems...trickier? Unsurprisingly. US aside.

[Bird on a Fire]

Low carbon tech is great. High carbon tech is still being subsidised by governments, as is deforestation, drainage of wetlands, etc etc. Politics is the obstacle, not tech (and not economics).

I'm optimistic that some progress will be made. But we need to halve global emissions by 2030 to meet the Paris target (chosen by scientists to give us a decent chance of avoiding disaster - although recent events have been worse than those scientists' predictions). I'm not that optimistic.

The EU's new CAP and forestry proposals are still supporting, rather than restricting, obvious idiocy like beef production and logging. Biden did a good job of lifting much of Sanders's climate policy to try and get some youth vote, but I'm not convinced he actually gives enough of a sh.t to force things through. He's spent his whole career as a quisling to the forces of darkness, and old habits die hard. China is total garbage, environmentally. Some developing countries are trying their best to develop along low-carbon pathways, but the rich countries are withholding the money they promised in Paris. It's only $100b a year - you can't even build a train line from London to Birmingham for that. Peanuts.

So yeah, no kids for me either. I don't have a pension either. I'll be retirement age in 2060, and everything will be on fire by then, so I might as well just spaff all my money in the here and now before killing myself as an auld c.nt by spending an hour outdoors on a summer afternoon.

[Bird on a Fire]

I reckon eco terrorists freedom fighters will probably start blowing stuff up soon, which will be fun. The first(?) grassroots bombing campaigns backed by scientific consensus, intergovernmental agreements and majority public opinion (though you know they'll stick some hapless saps in Guantanamo forever pour encourager les autres, like that kid who nicked a bottle of water during a riot).

[Bird on a Fire]

An important point of clarification (which I caught from Radio 4 this morning):

This research does NOT suggest the Gulf Stream is at risk of collapse. It suggests that "currents that researchers call the Atlantic meridional overturning circulation (AMOC)" are unstable and at risk of collapse. If the AMOC collapsed, it would have an effect on the Gulf Stream (pushing it south from what I caught on the Radio), but there is no suggestion or risk that the Gulf Stream itself would stop.

AMOC seems to be collapsing already. It's at its lowest level in 1600 years, so including during the "Little Ice Age" that climate deniers were so fond of.

The link with the Gulf Stream isn't straightforward. The Gulf Stream is a surface current, whereas AMOC is a system of surface and subsurface currents. There are media articles calling the Gulf Stream a component of AMOC, calling AMOC a component of the Gulf Stream, or saying that the two terms are synonymous. Similarly, there are scientific studies treating AMOC as a driver of the Gulf Stream, and others treating the Gulf Stream as a driver of AMOC. One goes along the top, the other goes round and round underneath.

I'm no oceanographer, but the two seem to be strongly correlated, and AFAICT a continued decline in AMOC is indeed reason to worry (a) anyway and (b) about the Gulf Stream specifically.

I'm hoping for some good sci comm to clarify this in the next week or so, because the Gulf main stream media stuff I'm finding at the moment is pretty contradictory.

[Trinucleus]

Alaska has a big mountain range just to the east, and whole continent backing that up though. I'd suggest Labrador and Newfoundland as maybe closer parallels, particularly as they get many of the east coast US storm systems that travel across the Atlantic to the UK.

Although for political punning purposes, maybe that should be Prince Edward Island (after a series of unfortunate accidents in the Royal Family) and Nova Scotia...

The most important factor for climate, if you live where an ocean meets a continent at temperate latitudes where the prevailing winds are from the west, is which side of the ocean you live on. This is more important than whether there is some warm ocean current.

Thus the western edge of Europe has a climate about 6 to 9C warmer than places at the same latitude on the eastern edge of the Americas. A similar difference exists in the north Pacific at similar latitudes. Most of that difference is simply due to which side of the ocean you are on. Only a little bit due to to the warm current you benefit from if you are on the eastern side. For example, simply being on the eastern side of the Atlantic is worth about 6C to Britain's climate, and the gulf stream only about 1.5C. Though as you go further north, the relative influence of the gulf stream is larger, hence the astonishingly mild climate of the northern half of Norway, which gains about 3C from the gulf stream.

The reason is simply that the wind travels a long distance over an ocean to come to you of you are the eastern side of the ocean, whereas it travels a long distance over land if you are on the western side.

That's really interesting.

Would the lack of a gulf stream not reduce the temperature of the wind if the water is cooler?

[IvanV]

Would the lack of a gulf stream not reduce the temperature of the wind if the water is cooler?

Clearly. But that's a small difference in comparison to temperature variations of continental land.

[Gfamily]

Would the lack of a gulf stream not reduce the temperature of the wind if the water is cooler?

Clearly. But that's a small difference in comparison to temperature variations of continental land.

What will make a difference is the amount of water absorbed into the westerlies as they cross the Atlantic. I have a working assumption that this explains to some extent the more severe rainstorms that we* seem to have been getting over the last decade or so**.

*here in UK at least

** I don't know if there has been a change to the frequency or intensity of severe rainfall events, but it feels as though there has been.

[monkey]

** I don't know if there has been a change to the frequency or intensity of severe rainfall events, but it feels as though there has been.

Met Office say "Several indicators in the latest UK State of the Climate report show that the UK’s climate is becoming wetter. For example the highest rainfall totals over a five day period are 4% higher during the most recent decade (2008-2017) compared to 1961-1990. Furthermore, the amount of rain from extremely wet days has increased by 17% when comparing the same time periods. In addition, there is a slight increase in the longest sequence of consecutive wet days for the UK."

clicky

They do not say if that's due to the Gulf Stream slowing, but they say extreme events are more likely due to climate change and is likely to get worse in the summer (they did cites, if you want more detail). But overall, the summer will be drier.


ETA: The main citation is the UK State of the Climate Report from 2018, more recent reports are available - clicky

[Bird on a Fire]

Yes, increased concentration of rainfall into fewer, more extreme events is a pretty well-known consequence of climate change in the UK and other temperate regions.

The Met Office said as much at least 7 years ago https://www.carbonbrief.org/met-office- ... d-flooding and there have been more such warnings constantly, including last year and last month.

It's bizarre that this isn't common knowledge. Not having a go at you, Gfamily, but "we are sleepwalking into a regime of increasing devastating losses to people's homes and livelihoods" seems like it ought to be making regular front page headlines.

Homeowners should already be demanding a two-pronged response from the government, to minimise carbon emissions and ramp up catchment-scale flood defences. Apparently little-Englanders' nimbyism can't cope with large-scale problems.

(Because a lower percentage of rainfall gets absorbed into saturated soils, this increasingly peaky distribution of rainfall is also partly why wildfire risk is shooting up, combined with the additional drying from a generally warmer climate.)

[IvanV]

Yes, increased concentration of rainfall into fewer, more extreme events is a pretty well-known consequence of climate change in the UK and other temperate regions.

** I don't know if there has been a change to the frequency or intensity of severe rainfall events, but it feels as though there has been.

Met Office say "Several indicators in the latest UK State of the Climate report show that the UK’s climate is becoming wetter. For example the highest rainfall totals over a five day period are 4% higher during the most recent decade (2008-2017) compared to 1961-1990. Furthermore, the amount of rain from extremely wet days has increased by 17% when comparing the same time periods. In addition, there is a slight increase in the longest sequence of consecutive wet days for the UK."

Why "five days"? What defines an "extremely wet day"? Why compare precisely 2008-17 with precisely 1961-1990?

The denialists love taking the piss out of this. It is so easy to make it look that this is all cherry-picked to get the politically correct answer. You can vary all the seemingly arbitrary assumptions and show numerous equally plausible formulations that come to the opposite conclusion.

And the Met is between a rock and a hard place here. Weather is so variable, so localised, and with long period variations resulting from the influence of multi-decadal oceanic oscillations, that it is very difficult to demonstrate clear conclusions that don't look cherry-picked. I once read a very clever studies which did show some robust conclusions on what was happening overall to the distribution of temperatures at specific locations as the world warms. It showed that the ovearll effect was not on average to move the temperature distribution curve for locations to the right, but rather on average to stretch and skew it to the right. But to achieve that demonstration it needed to use a very large dataset and clever techniques to extract a clear statistical signal from the noise that overwhelmed any clear conclusion by simple methods or analysis of local data.

The IPCC is much more careful how it presents its conclusions on weather trends than the Met. And I think the Met needs to be more careful if it isn't to lay itself open to such easy criticism, hard that that is.

Any Briton who has been to France or Italy or the like a few times know that the rain there is qualitatively different from British rain. It is much more frequently much more intense. And this is due to warmer air holding more water, and greater instabilities in the atmosphere. So change the climate in Britain in that direction, it stands to reason that you will get a higher frequency of higher intensity rainfall events. But when so far the climate has changed only a little bit, and when there are multi-decadal oceanic oscillations infecting your base data, and when heavy rainfall itself is so localised that you would need a very dense network of rain-gauges to pick it up, it is statistically sodding difficult to extract a clear trend from the noise in the data.

We see the same statistical problem in trying to come to a conclusion over what is happening to the frequency/intensity of tropical storms. In this case, the combination of circumstances required to produce an intense tropical storm requires the conjunction of so many things that it is much harder even to say what you would think the trend ought to be.

[Bird on a Fire]

Yes, increased concentration of rainfall into fewer, more extreme events is a pretty well-known consequence of climate change in the UK and other temperate regions.

** I don't know if there has been a change to the frequency or intensity of severe rainfall events, but it feels as though there has been.

Met Office say "Several indicators in the latest UK State of the Climate report show that the UK’s climate is becoming wetter. For example the highest rainfall totals over a five day period are 4% higher during the most recent decade (2008-2017) compared to 1961-1990. Furthermore, the amount of rain from extremely wet days has increased by 17% when comparing the same time periods. In addition, there is a slight increase in the longest sequence of consecutive wet days for the UK."

Why "five days"? What defines an "extremely wet day"? Why compare precisely 2008-17 with precisely 1961-1990?

The denialists love taking the piss out of this. <snip>

Well, the Met Office page is intended for a lay audience, so naturally it picks out easily-digestible snippets to illustrate the point to non-scientists rather than baffling folk with details of regression fits etc. Happily they provide references to all their sources, so you can find out the answers to your questions easily.

The Carbon Brief article I linked to also includes more of the actual graphs and stats, without scicomming them to death.

I know that denialists love doing this - taking a bit of a summary out of context and trying to pick holes in it without understanding the underlying science - but unless you are a denialist yourself I don't see much point in aping their tedious shenanigans. This forum is mercifully free of them, which means we can have more interesting high-level discussions about reality rather than trying to explain how to read a webpage to some a..hole who's only pretending not to understand it.

(Eta for clarity, the a..hole would be an actual denialist, I'm not calling Ivan one!)