Claim: 60% of Fish Can’t Cope with Worst Case Global Warming

Guest essay by Eric Worrall

Scientists claim that a 5C warming will kill off 60% of the world’s fish. But such claims ignore major abrupt temperature excursions which occurred in the not too distant past.

Climate change will make world too hot for 60 per cent of fish species


By  Adam Vaughan

Fish are at a far greater risk from climate change than previously thought, as researchers have shown that embryos and spawning adults are more susceptible to warming oceans.

In a worst-case scenario of 5°C of  global warming, up to 60 per cent of fish species around the world would be unable to cope with temperatures in their geographical range by 2100, when different stages of their lives are taken into consideration. Even if humanity meets the Paris deal’s tough goal of holding warming to 1.5°C, it would be too hot for 10 per cent of fish.

Previously, we thought that just 5 per cent of fish species would struggle to cope with 5°C of global warming, but that was based on analysis of adult fish alone.

“We can say 1.5°C is not paradise, there will be changes. But we can limit those changes if we manage to stop climate change. Fish are so important for human nutrition, so this study makes a strong case for protecting our ecosystems and natural environments,” says Hans-Otto Pörtner at the Alfred Wegener Institute in Bremerhaven, Germany, part of the team behind the research.

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The abstract of the study;

Thermal bottlenecks in the life cycle define climate vulnerability of fish

Flemming T. Dahlke1,*, Sylke Wohlrab1,2, Martin Butzin1, Hans-Otto Pörtner1,3,*

 See all authors and affiliationsScience  03 Jul 2020:
Vol. 369, Issue 6499, pp. 65-70
DOI: 10.1126/science.aaz3658 

Species’ vulnerability to climate change depends on the most temperature-sensitive life stages, but for major animal groups such as fish, life cycle bottlenecks are often not clearly defined. We used observational, experimental, and phylogenetic data to assess stage-specific thermal tolerance metrics for 694 marine and freshwater fish species from all climate zones. Our analysis shows that spawning adults and embryos consistently have narrower tolerance ranges than larvae and nonreproductive adults and are most vulnerable to climate warming. The sequence of stage-specific thermal tolerance corresponds with the oxygen-limitation hypothesis, suggesting a mechanistic link between ontogenetic changes in cardiorespiratory (aerobic) capacity and tolerance to temperature extremes. A logarithmic inverse correlation between the temperature dependence of physiological rates (development and oxygen consumption) and thermal tolerance range is proposed to reflect a fundamental, energetic trade-off in thermal adaptation. Scenario-based climate projections considering the most critical life stages (spawners and embryos) clearly identify the temperature requirements for reproduction as a critical bottleneck in the life cycle of fish. By 2100, depending on the Shared Socioeconomic Pathway (SSP) scenario followed, the percentages of species potentially affected by water temperatures exceeding their tolerance limit for reproduction range from ~10% (SSP 1–1.9) to ~60% (SSP 5–8.5). Efforts to meet ambitious climate targets (SSP 1–1.9) could therefore benefit many fish species and people who depend on healthy fish stocks.

Read more (paywalled):

The temperature excursion I was thinking of is the Younger Dryas, an abrupt return to ice age conditions just under 13,000 years ago, which lasted around 1200 years. The temperature shift was extreme (4-10C in Greenland), and occurred very rapidly, much faster than today’s mild global warming. The recovery was slower – but there were rapid periods of both warming and cooling.

Big freeze plunged Europe into ice age in months

… Carbon isotopes in each slice reveal how productive the lake was, while oxygen isotopes give a picture of temperature and rainfall. At the start of the ‘Big Freeze’ their new record shows that temperatures plummeted and lake productivity stopped over the course of just a few years. “It would be like taking Ireland today and moving it up to Svalbard, creating icy conditions in a very short period of time,” says Patterson, who presented the findings at the European Science Foundation BOREAS conference on humans in the Arctic, in Rovaniemi, Finland. …

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One thing which did not happen during this period of wild temperature swings was the extinction of a large number of fish species.

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Mike McHenry
July 4, 2020 10:07 am

Do they say how much they think the water is going to warm? Even 5C of air temperature I wouldn’t think it to much of an effect on SST

Reply to  Mike McHenry
July 4, 2020 1:21 pm

The sun warms the water. How fast that heat is transferred to the atmosphere is in part regulated by the temperature of the air.

Gary Pearse
Reply to  MarkW
July 4, 2020 1:40 pm

Max open ocean SST 31°C. Evap cooling in equilib with Sst at 31. More heating, just more eapud evap, cloud formation and cooling thunder storms.

Reply to  Gary Pearse
July 4, 2020 3:33 pm

Not all of the oceans can be found in the tropics.

Bryan A
Reply to  MarkW
July 4, 2020 4:49 pm

97% of Climate Scientists can’t cope with a few degrees of warming
100% of Klimate Hactivists can’t pass up the opportunity to incite violence to overthrow government

Rich Davis
Reply to  MarkW
July 4, 2020 5:03 pm

I think Gary’s point is that sea surface temperature is limited to about 31C by evaporative cooling. Which means that tropical fish won’t need to adapt to anything warmer than that. Everywhere else, it should just mean that species might shift their range pole-ward to cooler waters.

Why would we assume that they will stay put until they die? Also why assume that the rate of warming could possibly be so fast that the fish could not easily adjust their range gradually?

I suppose that there may be situations where the food chain needed to support a species might not be present in the cooler regions adjacent to their old range. Also fish changing their range could have a serious impact on fishing communities. But assuming that most of the fish will die just doesn’t make sense.

Reply to  Mike McHenry
July 4, 2020 1:24 pm

Not if they are predicting that 5C by 2100. The Great Lakes would be hard pressed to show that much warming over such a short period, much less the Oceans.

Less then half of all fish are freshwater fish. Ocean fish aren’t going to be in much danger from this, at least in the next century, even IF their worst case happens.

Mike McHenry
Reply to  Schitzree
July 4, 2020 2:37 pm

I wrote this to another post: Pure water has more than 3000 X the heat in dry air at equal volume, temperature and pressure.

Reply to  Mike McHenry
July 4, 2020 3:34 pm

True, but hardly relevant.

Mike McHenry
Reply to  MarkW
July 4, 2020 5:15 pm

Why isn’t it relevant?

Bryan A
Reply to  Mike McHenry
July 4, 2020 4:54 pm

Their is very little “Pure Water” existing in the natural environment
Most of it is contaminated with Salt
Only 0.5% is considered “Fresh Water” but Fresh doesn’t equal Pure

Mike McHenry
Reply to  Bryan A
July 4, 2020 5:38 pm

Salt water etc has still 1000’s of times more heat than air. Very simply put air can only have a minute effect on water temperatures. That’s the laws of thermodynamics. Sea Temperature records of the last 60 years bears this out

Mike McHenry
Reply to  Bryan A
July 4, 2020 6:01 pm

Salt water has 1000 of times the heat of air. If you have a liter of salt water its 1000 grams of mass or 2.2 lbs on the other hand a liter of air is between 1 and 2 grams. Water molecules are polar unlike air think sticky. It takes a lot more heat to get water moving aka heat/temperature. That’s thermodynamics as learned by chemists like me. So air can’t heat up water that’s the laws of thermodynamics

John Dowser
Reply to  Bryan A
July 4, 2020 11:16 pm

Mike, not sure if your point is relevant. The article is about the idea of 5C of total, globally averaged warming of the temperature, be it lower troposphere or at surface level.

How water surfaces warm and currents move the heat content, would be yet another story. You seem to oppose the idea of thermal conduction in this context but there’s also still direct absorption of energy from the sun. Also keep in mind a dynamic model of both massive water and air currents when compared to a static conduction test.

Mike McHenry
Reply to  Bryan A
July 5, 2020 3:26 pm

John Dowser fish live in the water not in the air. Air temperatures are irrelevant water temperatures are relevant. A 5C rise in air temperatures would have little effect on water temperatures. Ergo fish would be unaffected. I posted this here because there was no option to reply to his reply

Reply to  Schitzree
July 5, 2020 11:12 pm

Zebra muscles may die, which would be good, yes? Isn’t there something else that’s affecting fish populations?

Bruce Cobb
July 4, 2020 10:19 am

What if the sky really did fall, and it was our fault? Then we’d be sorry!

Reply to  Bruce Cobb
July 5, 2020 5:20 am

So if you are that convinced that means you need to overthrow every government now … like today. Wish you luck 🙂

July 4, 2020 10:32 am

So 60% of the fish died during the Holocene Optimum?

Reply to  rah
July 4, 2020 12:49 pm

No , they migrated. Like they will migrate this time if it get too warm where they are.

How far would shoal of fish have to migrate to find 1.5 deg C cooler? That is not even year to year variability. This is just more alarmist horseshit.

unable to cope with temperatures in their geographical

They drop this little get out clause in but then ignore for the rest of the paper like it is obvious that 60% of all fish species would stay in the same place where they cannot reproduce rather than move and then we’d all starve to death ourselves …. UNLESS we do as we are told !!

Reply to  Greg
July 4, 2020 3:45 pm

They don’t have to migrate, they just have to swim a few feet deeper.

Rich Davis
Reply to  accordionsrule
July 4, 2020 5:27 pm

That’s true if they still have a food supply at that depth. And if not they “migrate”. It’s more like diffusion. Fish that randomly swim into inhospitable waters are going to tend to swim back toward their preferred conditions. That will happen at all edges of their current range.

If that range of hospitable conditions slowly shifts toward the pole, the fish don’t hold a convention to decide on whether to set up a migration committee. They don’t all need to apply for visas to enter a new territory. Each fish acts autonomously to stay in hospitable waters, in realtime.

Good God, isn’t this obvious?

Reply to  accordionsrule
July 5, 2020 5:22 am

We have the correct answer .. they can also undergo behavioural adaption.
There is a large group of animals (poikilotherms) that already do it.

Reply to  Greg
July 4, 2020 4:47 pm

Yes… they migrate. To suitable T waters. Kinda like people to suitable T air.

BUT Worrrall’s research centered about the super-cute fishy in their picture. He is so adorable and delicate that he can’t survive anywhere except a temp-controlled fish tank set at 76°F ± 0.4°. This is why the authors are so paranoid.

July 4, 2020 10:42 am

So even under water it’s a jungle out there where survival of the fittest reigns.

Ron Long
July 4, 2020 10:46 am

I wonder what 5 deg C increase in atmospheric temperature translates to in ocean, or big lake, water temperature? Maybe 1 deg C change in the water? Ocean currents swirl around and change the ocean water temperature far more than that, and no pasa nada. Still freezing my patootie off here in Argentina, waiting for that global warming deal to kick in.

Mike McHenry
Reply to  Ron Long
July 4, 2020 11:11 am

Not even. Pure water has more than 3000 X the heat in dry air at equal volume, temperature and pressure

July 4, 2020 10:47 am

No worries. At least warmth-loving large-mouth bass will survive. Yum!

Tom in Florida
July 4, 2020 10:57 am

That number sounds fishy to me.

Climate believer
Reply to  Tom in Florida
July 4, 2020 12:20 pm

Oh my cod it’s worse than we thought.

Reply to  Climate believer
July 4, 2020 3:52 pm

Better ask the Codfather to intercede.

July 4, 2020 11:10 am

“ Previously, we thought…”

AKA: Science is Settled unless we can find/invent stuff that shows we are worse off.

Michael Jankowski
July 4, 2020 11:14 am

“…Previously, we thought that just 5 per cent of fish species would struggle to cope with 5°C of global warming, but that was based on analysis of adult fish alone…”

Really? They didn’t know that “embryos and spawning adults are more susceptible to warming oceans” and just started studying them?

Nick Werner
Reply to  Michael Jankowski
July 4, 2020 12:23 pm

The factor has gone from 5% to 60%… twelve times… more than an order of magnitude.
In other words, from (yawn + risk of being defunded) to (OMG + need more funding).

On a related note, the quality control and attention to detail on display suggests the “climate science is settled consensus factor” could be anywhere between 8.1% and 1164%.

July 4, 2020 11:18 am

We have a commet and a koi in a cut-off 45g drum outside with temp ranging from 25 to 0 over the year, with day to day variability of several degrees in less than 24h. Plants also doing fine. I do make sure the tank is not heated by direct sun on the side. They are now in their 3rd year with no problems now they have a steel grid to keep out racoons.

July 4, 2020 11:25 am

Are they having a hard time coming up with new things to fear? Is that why they have to recycle the oldies?

Reply to  Chaamjamal
July 4, 2020 12:31 pm

Chaamjamal – This latest generation seems to feed on fear. So would anyone raised by the current crop of teachers, parents, politicians, the press, etc. Their generation will someday be known as the ‘frightened’ generation.

July 4, 2020 11:30 am

they just said 60% of fish made a bad evolutionary choice…’s darwin

damn planet has been too stable….that’s the whole problem

Reply to  Latitude
July 4, 2020 6:56 pm

Good, I hope they all die. I don’t want to eat unlucky fish. You don’t know where they might have been.

Curious George
July 4, 2020 11:53 am

They severely underestimate the worst case. Nothing and nobody can survive the worst case 🙂

Reply to  Curious George
July 4, 2020 1:23 pm

Apparently the worst case is worser than we thunk.

Loren C. Wilson
July 4, 2020 11:58 am

This does not pass the smell test. Prior to the current ice age, the oceans were significantly warmer. The fish that need cooler water just go to where the water is cooler. The rest adapt. The ocean temperatures change by more than 1.5°C seasonally, and due to El Niño, etc. This does not cause extinctions. The fish relocate if they need to. The major cause of relocation of fish off of South America during an El Niño event is the nutrient-rich upwelling water is replaced by warmer but less rich water flowing east along the surface. It is not the temperature that bothers the fish, it is the lack of food down the food chain due to less nutrients in the water.

Smart Rock
July 4, 2020 12:02 pm

It does my heart good to see that the Bad News Industry™ is still busily churning out foregone conclusions. Those selfless, brave souls just keep on modelling away, even in the middle of the covid pandemic, ensuring that no one gets complacent about the future of the planet.

“We are the Bad News Industry™. We adhere to the scientific method: – if it ain’t worse than we thought, we go back and model it again!”

Tim Gorman
July 4, 2020 12:07 pm

I’m not sure I agree with this, at least for ponds, rivers, and lakes. Crappie spawn in the spring when the water temperatures reach around 60degF (or perhaps one to two degF hotter). It’s highly doubtful that river and lake water won’t get below 60degF in the winder so the spawn should happen just as it always has. The timing might change slightly but that won’t affect the actual spawn. The eggs will hatch in about a week and the fry will emerge. From then on it is predators that affect the future population, not temperature. The temperature won’t matter unless it gets hot enough to fry the fry so to speak.

It’s the same for all kinds of freshwater fish.

I’m not well versed on seawater fish but I am aware that bluefin tuna spawning is related to water temperature and they like to spawn in warmer water – which also helps the survival of the offspring. If the oceans warm 5degC I would expect this to do nothing more than change the timing of the spawn but not the survival of the offspring. I just highly doubt the oceans are going to get so warm in the winter that it will never get cold enough for the bluefin to ever span. Again, the biggest killer of the offspring will be predators and not the water temp.

This study abstract says it was based on ” observational, experimental, and phylogenetic data” but it’s not obvious that the study was empirical. Instead it sounds as if it is hypothesis based. I.e. “If it gets too hot the spawns won’t happen”. Does the study actually include sea temperature trends that show the oceans, rivers, and lakes are going to get too hot for the fish to spawn?

July 4, 2020 12:13 pm

Wow, great analysis!
We’re home-free only 40% of fish die off, right?
kool; sign me up for a coal-powered pickup truck

Reply to  chris
July 4, 2020 6:57 pm

I don’t think Tesla are making pickup trucks yet.

Coeur de Lion
July 4, 2020 12:26 pm

How can they call themselves scientists? See Donna Laframboise on the corruption of the IPCC

Moderately Cross of East Anglia
July 4, 2020 12:38 pm

Did 97 per cent of the fish they surveyed agree this consensus position or did they lose the majority of ballot papers again?

My three pond fish say they never got their ballot vote.

Gordon A. Dressler
July 4, 2020 12:42 pm

Anybody have information on how much warming has occurred over, say, the last 100 years for ocean waters below the thermocline as compared to the ocean layer above the thermocline?

“Thermocline, oceanic water layer in which water temperature decreases rapidly with increasing depth. A widespread permanent thermocline exists beneath the relatively warm, well-mixed surface layer, from depths of about 200 m (660 feet) to about 1,000 m (3,000 feet), in which interval temperatures diminish steadily.” —

If surface water fish feel a need to cool off from “global warming”, they just need some short periodic visits down to the thermocline. /sarc

Tiger Bee Fly
July 4, 2020 12:53 pm

“Fish are so important for human nutrition, so this study makes a strong case for protecting our ecosystems and natural environments.”

FIFY: “State repression of individual liberty is so important for long-term power, so this study makes a strong case for Stalinism v2.0.”

July 4, 2020 1:03 pm

Let me guess without reading: an RCP8.5 climate input to the ecological model?

July 4, 2020 1:12 pm

Good one!
Control freaks run out of fearful ideas.
I’m confident that they will soon run out of lies.
After all, they are already out of half-truths.

July 4, 2020 1:16 pm

It’s the Guardian. ‘Nuff said.

Bruce Cobb
July 4, 2020 1:16 pm

Amazing, innit. We humans have the power to “stop climate change”, but can’t manage to produce enough toilet paper for everyone (and their storeage closet).

July 4, 2020 1:19 pm

“unable to cope with temperatures in their geographical range”

Evidence of fish migrating because of changing water temperatures exist even today, and have been known about for thousands of years.

Yet for some reason, CO2 will make fish forget how to migrate.

Reply to  MarkW
July 4, 2020 7:03 pm

Yep, with the most prominent one being known as El Niño.

Reply to  MarkW
July 5, 2020 5:29 am

They just sit there and get cooked in the models.

son of mulder
July 4, 2020 1:23 pm

Do fish migrate?

Bruce Cobb
Reply to  son of mulder
July 4, 2020 1:35 pm

Yes, although sometimes they are just trying to find Nemo.

Jeff Alberts
Reply to  son of mulder
July 4, 2020 10:46 pm

Only if they’re carrying coconuts.

Phillip Bratby
July 4, 2020 1:30 pm

“Climate change” cannot warm the oceans. Only the sun can do that. It needs fewer clouds to do that, but we are told that global warming leads to more clouds. Something doesn’t seem quite right!

Reply to  Phillip Bratby
July 4, 2020 2:54 pm

You mean it smells fishy !!!

Reply to  saveenergy
July 4, 2020 7:05 pm

Yep, let’s not skate around the issue, it’s a load of pollocks.

Gary Pearse
July 4, 2020 1:34 pm

Recall a very senior, well respected oceanographer was reported in a WUWT article a few years ago who advised that almost all lab tank experiments being done on warming, acidification, etc in the ocean were very badly designed, citing rapid heating, overly done acidulation, etc. He gave a list of details in such design that had to be considered in order to properly investigate issues for at least qualitative results.

I’m sorry gentle Drs of the Wegener institute, but you strike out on the magnitude of your temperature change at an impossible 5°C. So, here’s how it works. The surface temperature of the tropical open ocean cannot exceed 31C. This is the point where cooling evaporation is in equilibrium with SST more heating simply increases the evaporation rate, creates more cloud shade and cooling thunderstorms. Indeed, tropical regions change little even with ice age maxima.

Most of the swing is at the poles. Tropical fish will expand to occupy a wider band and temperate region fish will swim poleward, a thing you can’t do with your few cubic meter tanks. Ergo, a warmer world will have more fish. I hope this helps.

Malthusians have a petri-dish mentality of the helplessness of humans, let alone fish, so how they design experiments gives extreme results.

July 4, 2020 2:10 pm

Most of water warming is caused by more sunshine. So in lakes you may have the problem of O2 shortage, on the one hand, because plants in water are more affected by warmer water and may die producing less O2 and on the other hand by more bluealgae, destroying plants no more able to produce O2.

HD Hoese
July 4, 2020 2:28 pm

“Our analysis shows that spawning adults and embryos consistently have narrower tolerance ranges than larvae and nonreproductive adults and are most vulnerable to climate warming……Scenario-based climate projections considering the most critical life stages (spawners and embryos) clearly identify the temperature requirements for reproduction as a critical bottleneck in the life cycle of fish.” There are probably more than 30,000 species of fishes, larvae have to deal more than eggs and adults with viscosity problems, something to do with temperature.

Pay walled, but wonder if they know about this paper on temperature shifts in the 30s, rediscovered. Oviatt, C. A. 2004. The changing ecology of temperate coastal waters during a warming trend. Estuaries. 27(6):895-904.

“In the temperate North Atlantic Ocean the ecological changes in coastal waters associated with a warming period in the 1930s were compared with the past couple of decades when the North Atlantic Oscillation was also positive. Long-term monitoring data sets from Rhode Island and nearby coastal waters were used to identify trends in the recent warming period. During both events winter water temperatures warmed above a mean value of 2.9°C from 1°C to 3°C.”

Right-Handed Shark
July 4, 2020 2:51 pm

So much of life is on a knife edge. Makes me wonder how it ever got started.

Reply to  Right-Handed Shark
July 5, 2020 5:25 am

Or how the first drought or heat wave hasn’t killed them all off. These must be like Willis’s walking dead with covid.

Paul Johnson
July 4, 2020 3:09 pm

“In a worst-case scenario of 5°C of global warming…”
RCP8.5 strikes again! With even Hausfather disavowing this absurd scenario, when are supposedly serious journals going to stop printing, or even reviewing, papers based on this nonsense.

July 4, 2020 3:20 pm

“Even if humanity meets the Paris deal’s tough goal of holding warming to 1.5°C, it would be too hot for 10 per cent of fish. “

Paris deal was tough?
Tell that to China, India, Pakistan, etc. Countries were allowed to set their own levels of compliance to reduce the atmospheric CO2 levels. Any county (Pakistan for instance — This was Pakistan’s proposal: Pakistan’s pledge was to “Reach a peak at some point after which to begin reducing emissions.”) effectively could set a no change policy (or an increasing until whenever) and stick to it and that was fine.
( )

Only the dumb-a$$ western nations competed to outdo each other in the virtual signaling game they play, much to the cost of their citizenry.

old construction worker
July 4, 2020 3:29 pm

To think tax payers footed the bill for their “research”.

July 4, 2020 4:12 pm

Yawn. Another day, another “It’s worse than we thought!!!” claim.

It’s like they’ve never heard of Aesop’s Fable, “The Boy Who Cried Wolf”. After a while people pay little attention.

(Alarmists will point out that in the story, the wolf eventually came. But in the story, the wolf was real and it had come before.)

Geoff Sherrington
July 4, 2020 4:14 pm

So what?
Cooking oil on a stove at 250 degrees already helps kill a few % of fish each year. Geoff S

Reply to  Geoff Sherrington
July 5, 2020 5:27 am

It’s alright all the polar bears, penguins are birds are dead under the same stupid argument so there is about the same percentage for us to eat.

Alasdair Fairbairn
July 4, 2020 4:19 pm

If tens of thousands of years of solar radiation hasn’t managed to raise ocean temperatures to over around 35 C then I don’t think it likely to suddenly start raising this temperature now.
Have these scientists ever tried boiling a pan of water with a blow lamp on the surface?
Extrapolating their findings up to conjectures on the climate is highly unprofessional and damaging to the reputation of science.

July 4, 2020 4:36 pm

I guess we can all relax then, especially fish. When has a worse case climate prediction ever happened. Very few basic predictions ever happen , hence the IPCC’s perpetual revisions towards awkward reality.

July 4, 2020 4:42 pm

I predict most ‘Climate Scientists’ will have died before any of their predictions come true .

July 4, 2020 5:42 pm

Fact: 100% of fish alive today will be dead before this could possibly happen. In the mean time evolution will allow most of their species to adapt and thrive regardless of which way the trend goes. And if they can’t adapt then new species will evolve to replace them. Thus it has always been.

Joel O'Bryan
July 4, 2020 7:55 pm

The scam going on here is the climate alarmists treat CAGW as a step function. Completely unrealistic even if one believes the junk science of model projections.

Globally, sea temps will rise very slowly and unevenly, some areas warmer, some areas colder. The fish and all the species in the oceans and above it will adapt and shift and evolve just as they have for hundreds of millions of years of climate change more extreme than the junk models forecast.

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