A serious ecological consequence of global warming

Ocean acidification as a result of increasing CO2 doesn't get mentioned often lately, although it presumably continues to increase.   (There was, no doubt, some sloppily done lab based experimentation on this with fish and other creatures which I think has perhaps harmed its reputation amongst science journalists.  But the problem is still real.)  

The other big problem in the oceans from global warming is the increase in lack of oxygen as the water warms, and I have mention it from time to time over the years.  (You can search "ocean oxygen" in the search bar at the side, if you like.)

There was an article about it in Science recently, and yeah, maybe it will be a race between it and acidification as to which will cause the most serious ecological collapse within the next few decades.  Some extracts:

Climate change is leaching oxygen from the ocean by warming surface waters. Two other climate-related threats to the seas—ocean acidification and marine heat waves—get more attention from scientists and the public. But some researchers believe deoxygenation could ultimately pose a more significant threat, making vast swaths of ocean less hospitable to sea life, altering ecosystems, and pushing valuable fisheries into unfamiliar waters. As global warming continues, the problem is sure to get worse, with disturbing forecasts that by 2100 ocean oxygen could decline by as much as 20%. Sharks—fast-moving fish that burn lots of oxygen, sit at the top of food chains and crisscross huge ocean expanses—should be sensitive indicators of the effects....

SCIENTISTS FOR YEARS have documented oxygen-starved dead zones in places like the Gulf of Mexico and the Baltic Sea. There, pollution from nutrients running off the land, such as synthetic fertilizer, sparks algae blooms. Microbes feast on the rotting vegetation, consuming oxygen. A surge of low-oxygen water can flood an area so quickly that crabs, sea stars, and even fish suffocate before they escape. Low-oxygen zones also form naturally along the western edges of the Americas and Africa, where oxygen-depleted water that hasn’t seen daylight for decades wells up.

In the open ocean, currents and storms churn the water, keeping oxygen levels higher. Yet since the 1990s climate models have foretold that a warming climate would deplete oxygen there, too. Surface water warmed by rising air temperatures holds less oxygen, and the growing temperature contrast between surface layers and colder, deeper water slows the mixing that transports oxygen into the depths. At higher latitudes, melting ice can flood surface layers with fresh, low-density meltwater, strengthening the layering and reducing mixing.

In 2008, a paper in Science sounded the alarm. German and U.S. scientists found that the low-oxygen zones off Africa and the Americas were growing deeper and losing still more oxygen. Since the 1960s these areas had expanded by about 4.5 million square kilometers, close to the area of the European Union. In the waters frequented by Sims’s sharks off Africa’s northwest coast, the low-oxygen layer had nearly doubled in thickness over 5 decades, from 370 meters to 690 meters. By 2008 its top had risen to less than 150 meters below the surface. The global trend, the scientists warned, “may have dramatic consequences for ecosystems and coastal economies.”

In 2017, scientists delivered more troubling news in Nature. Overall, the world’s oceans had already lost some 2% of their oxygen since 1960, roughly double what climate models predicted.

For Andreas Oschlies, a biogeochemist at the GEOMAR Helmholtz Centre for Ocean Research Kiel and a leading expert on modeling oxygen in the ocean, the implications were staggering. If the trend continues, it could mean a potential loss of 20% by 2100, he says. That’s equal to going from sea level to more than 2000 meters elevation on land. “I thought ‘Wow!’” Oschlies recalls. “That’s the biggest change and maybe the most worrying change that we see in the ocean. Immediately I thought of (past) major extinction events.” For example, at the end of the Permian period 256 million years ago, rising ocean temperatures and an 80% plunge in oxygen levels helped drive the largest extinction in Earth’s history. Up to 96% of all marine species disappeared.

By comparison, the 2% drop in oxygen levels seen so far might not sound like much. But global averages can be misleading, warns Lisa Levin, a biological oceanographer at the Scripps Institution of Oceanography who has studied the effects of low oxygen on ocean ecosystems for more than 30 years. “There are places in the ocean where there’s been much bigger declines,” Levin says. “These changes are probably very important.”

 

 

 

Global warming and everyone's favourite fish

It's been a long time since I posted about ocean warming (and acidification) and it's very uncertain effects on the food chain.

This Washington Post article talks about the worrying effect on salmon fisheries.

When the oceans died

There's a good article at The Atlantic talking about the end-Permian great extinction, and the implications for the future planet under climate change.   Long story short: 

“This study suggests we should be worrying much more about hypoxia than about ocean acidification,” Deutsch says. “There’s vastly more resources being put into [studying] organisms’ responses to pH in seawater than there is into understanding temperature-dependent hypoxia. I think that the field has basically allocated those resources in exactly the wrong way.”

The modern oceans have already lost 2 percent of their oxygen since 1960, a remarkable loss driven mostly by coastal nutrient pollution and global warming. It’s an environmental problem that promises to worsen in the warmer world of the coming centuries, just like it did in the end-Permian. And if Earth’s past is any indication of its future, this asphyxiation could be truly world changing. The prospect has led dozens of paleoclimatologists, geochemists, and oceanographers to sign the Kiel Declaration on Ocean Deoxygenation, developed this September to raise global awareness of a problem with increasingly worrying geological precedent.

“This study shows that we’re on that same road toward extinction, and the question is how far down it we go,” Penn says.

Read the whole thing.

Save the oyster

I don't eat that many oysters anymore - the general cost of most wild caught seafood has escalated so much that the good quality fish shops where I used to buy them have closed in the shopping malls of my part of Brisbane, and the supermarket fish counters don't routinely have them.   But I do prefer the Sydney rock oyster over the Pacific if I have a choice.

Anyway, some bad news in The Guardian about how ocean acidification (both from soil run off and the ocean's general increasing acidification) is apparently making Sydney Rock oysters smaller (they were already small enough) and fewer. 

I have posted before about oysters being affected by ocean acidification, including in 2014 in which I noted that research that indicated that the variety could adapt to increasing acidification.   I expressed a bit of skepticism about that at the time, and it looks like that may have been well justified.

Ocean acidification is not going away

Ocean acidification only pops its head up occasionally in the media now as a dire threat from increasing CO2 in the atmosphere:  probably because it is such an incremental change that it doesn't have the ring of immediate alarm about climate change as do heat waves, floods or fires. 

But it's not going away, even if it is pretty difficult to study.    (Replicating the effect in laboratory settings turned out to be a lot trickier than initially realised.)

There's a new study out on how it affects ocean areas with naturally venting CO2.  I'm sure we've seen similar studies in other places, but it confirms that the future of the coastal areas under high CO2 is more likely green and slimy with less biodiversity:

To assess the likely ecological effects of ocean acidification we compared intertidal and subtidal marine communities at increasing levels of pCO₂ at recently discovered volcanic seeps off the Pacific coast of Japan (34° N). This study region is of particular interest for ocean acidification research as it has naturally low levels of surface seawater pCO₂ (280–320 µatm) and is located at a transition zone between temperate and sub-tropical communities. We provide the first assessment of ocean acidification effects at a biogeographic boundary. Marine communities exposed to mean levels of pCO₂ predicted by 2050 experienced periods of low aragonite saturation and high dissolved inorganic carbon. These two factors combined to cause marked community shifts and a major decline in biodiversity, including the loss of key habitat-forming species, with even more extreme community changes expected by 2100. Our results provide empirical evidence that near-future levels of pCO₂ shift sub-tropical ecosystems from carbonate to fleshy algal dominated systems, accompanied by biodiversity loss and major simplification of the ecosystem.

 A report on the study explains:

They found that while a few plant species benefitted from the changing conditions, they tended to be smaller weeds and algae that blanket the seabed, choking corals and lowering overall marine diversity.

These species, and some smaller marine animals, are thriving because they are more tolerant to the stress posed by rising levels of CO₂.

Jason Hall-Spencer, Professor of Marine Biology at the University of Plymouth, said: "Our research site is like a time machine. In areas with pre-Industrial levels of CO₂ the coast has an impressive amount of calcified organisms such as corals and oysters. But in areas with present-day average levels of surface seawater CO₂ we found far fewer corals and other calcified life, and so there was less biodiversity. It shows the extensive damage caused by humans due to CO₂ emissions over the past 300 years and unless we can get a grip on reducing CO₂ emissions we will undoubtedly see major degradation of coastal systems worldwide."

Time for more climate change whiplash

This article in Nature News:  Can the world kick its fossil fuel addiction fast enough is another in the long line of "climate change whiplash" reporting we've been seeing for a few years.  On the one hand, emissions are clearly still going up when the economy picks up; on the other, past estimates of the decreasing cost and increasing deployment of renewable energy were clearly underestimates, and a lot of renewable energy deployment is in the pipeline.

As to whether market based policy is going to work fast enough, there seems to be increasing doubt:

But politics can also help to bring about rapid change. While Trump is fighting on behalf of the fossil-fuel industry, leaders of other countries are moving in the opposite direction. The United Kingdom and France have both announced plans to ban the sale of petrol- and diesel-powered vehicles by 2040. And more than two dozen countries have committed to phasing out coal by as early as 2030.

These types of mandate are a sign that energy politics might be shifting towards more brute-force methods, says Michael Mehling, an energy and environmental-policy researcher at the Massachusetts Institute of Technology in Cambridge. Economists tend to favour market-based programmes, such as the EU’s Emissions Trading System, but Mehling says there is little evidence that such arrangements will drive the kind of rapid transformational change needed to meet global climate goals. Old-school government mandates might be the last resort, Mehling says. “If the decisions are made at a sufficiently high level,” he says, “they can change the landscape pretty much overnight”.

In any case, as I've been posting for some time, it's not as if those who are supposed to be the Right wing proponents of small government and free market solutions (libertarians and so called "classical liberals") are actually interested in addressing climate change at all:  they are more interested in corporations making money now, and a gormless in principle belief that governments never doing anything is better than governments doing something, such that they will clasp any reason (ranging from entertaining outright denialists to a "it's too late now anyway" defeatism) so as to justify not endorsing any policy action.   They are worse than useless, and just need to be bypassed.  

And to be fair, the Left of politics needs to be criticised for a certain gullibility in the policies and advice they have promoted, too.   At least they are interested in solutions, which is the first step in the process.

But look at the revision now going on regarding the estimates of the social cost of climate change, just in the matter of agriculture.  From this paper's abstract:

Despite substantial advances in climate change impact research in recent years, the scientific basis for damage functions in economic models used to calculate the social cost of carbon (SCC) is either undocumented, difficult to trace, or based on a small number of dated studies. Here we present new damage functions based on the current scientific literature and introduce these into an integrated assessment model (IAM) in order to estimate a new SCC. We focus on the agricultural sector, use two methods for determining the yield impacts of warming, and the GTAP CGE model to calculate the economic consequences of yield shocks. These new damage functions reveal far more adverse agricultural impacts than currently represented in IAMs. Impacts in the agriculture increase from net benefits of $2.7 ton⁻¹ CO₂ to net costs of $8.5 ton⁻¹, leading the total SCC to more than double.

That's some massive change to an input into an IAM, isn't it?

And further to my skepticism that IAMs could have adequately worked out the cost of intense rainfall and sea level rise, I note from a review of a new book on the latter (my bold):

Projections diverge on how fast the inundation will proceed if nations stay on a “business as usual” path in their greenhouse gas emissions. The most recent report from the Intergovernmental Panel on Climate Change projects a maximum of about three feet by the year 2100; James Hansen and colleagues project several times that much over the same time frame; a recent research paper that recalculates the dissolution of Antarctic ice warns of five feet as a median estimate. Sea level rise on such a scale would submerge an area inhabited, just now, by 153 million people. For an indefinite number of decades or centuries after that, the rise would continue.

As former presidential science advisor John Holdren once pointed out, human beings have three options: reduce the amount of climate disruption they are causing, adapt as intelligently as possible to the change they can’t avoid, and suffer. “The question – the issue that’s up for grabs – is what the mix going forward is going to be,” Holdren has said.

Under a “work and hope” scenario – one in which the world cuts emissions with extreme speed and hopes that the more optimistic climate change projections are the accurate ones – sea level rise might be limited to something like two feet. But even that more modest figure would imply worldwide consequences exceeding our ability to comprehend them. “Staggering,” “catastrophic,” and other alarm words have lost much of their voltage. In these busy times, “trillions” are the new “millions” – and thus rather negligible. But two feet of sea level rise is, beyond question, coming.

So, have IAMs been worked out on the "best case" scenario of 2 feet by 2100, when it may be 2 1/2 times  that, and causing the re-location of 153 million people? 

But, again, why should this be taken as a licence to do nothing in terms of CO2 reduction?   Even if it takes 200 to 300 years (instead of 100 years) of increase to reach a 3 metre sea level rise, slowing down the rate surely buys time for (some) cities to respond.  

It's about time I revisited the matter of ocean acidification too.  That is a key area that, I believe, is not realistically amenable to to geoengineering, regardless of what techno-optimists may think can be done temperature wise.  

The problem with geo-intervention

Victor Venema, who does work on climate change, has a post up in which he explains that he thinks taking climate geo-intervention seriously is probably unavoidable, and we may as well start investigating it now.

But he does explain a key practical problem with the concept, as follows:

We would have to keep on managing the insolation for millennia or until someone finds a cheap way to remove carbon dioxide from the air. The largest danger is thus that humanity gets into trouble over these millennia and would no longer be able to keep the program up, the temperature would jump up quickly and make the trouble even worse. Looking back at our history since Christ was born and especially the last century, it seems likely that we will be in trouble once in a while over such a long period.

This danger could also be an advantage, just as the mutual assured destruction (MAD) with nuclear arms brought us a period of relative peace, the automatic triggering of Mad Max would force humanity to behave somewhat sensibly and make people who love war less influential.

My impression is that the main objection from scientists against geo-interventions is their worry about creating such an automatically triggered doomsday machine. Those people seem to think of a scenario without mitigation, where we would have to do more and more Solar Radiation Management. While carbon dioxide accumulates in the atmosphere over millennia, the stratospheric particles (after a volcanoes) are removed after a few years. So we would need to keep adding them to the stratosphere and if we do not reduce greenhouse gas emissions increasingly many particles. 

 I am surprised that he does not also consider that natural disasters effectively beyond human control might put a serious hole in maintaining the necessary work - a seriously large asteroid strike, for example, would have economic and society disrupting consequences that I doubt anyone can forecast.  While it won't likely be the end of humanity (it's a big planet), and the dust it throws up would initially cool the place, perhaps to crop destroying and famine inducing levels, when the sky clears enough again the world economy may take a long time to recover before large scale geo-intervention can resume.   This scenario would involve initial disaster from sudden darkness and lingering cold weather, to a reversal where the temperature climbs rapidly to dangerously high levels.

I would much prefer to not have the dangerously high temperatures a possibility.

And besides, at an ecological level, no one knows how ocean acidification is going to pan out.  Lots more algae, sometimes of the poisonous variety;  key crustaceans in the ocean food chain (pteropods) dying out;  oxygen low areas of the ocean that can support little sea life of any variety - these are all realistic predictions of increased CO2 in the atmosphere and oceans, and keeping the temperature down alone won't solve them.

So, I will remain a skeptic of this band-aid approach to dealing with climate change and CO2 emissions.

Just use your common sense...

Curious as to what permanent Trump sycophant and excuse maker Scott Adams had said about the decision to pull out of the Paris Accord, I visited his blog and found that (of course!) he wasn't concerned, and had put up this short explanation of his take on climate change:

Disclosure: My current view on climate science is that the climate scientists are probably right on the basic science, and their climate models are probably directionally right too. But no one has created a credible economic model around climate change. Until you have a long-term economic model that you can trust, you have no way to know what to do about climate change or when to do it. The climate science models don’t tell you any of that. They aren’t designed for that. If you want to make rational decisions about climate change economic risks, you need credible long-term economic models, not climate models.
On a related note, there’s no such thing as a credible long-term economic model. It isn’t a thing.

Well, oddly enough, over the years, I have run some posts expressing similar-ish doubts about economic modelling related to climate change:  you can read some here, here, here, here, here and here.

But the problem with the economic uncertainty and difficulty in modelling it is that the increasingly held  view is that the models may have underestimated the cost of climate change, not over estimated it. 

He seems incapable of understanding the argument that uncertainty is not your friend - it doesn't mean "do nothing", at least when it's on a matter where the parameters of possible change are known.  He seems to accept the broad parameters (or so he says), but then uses the technicality of the uncertainty as to when economic benefits of some global warming will be overcome by the economic negatives to say we can never decide to do anything!

It is clearly a nonsense position to take, and exhibits no common sense.   Does he really think it's a good idea to set in place sea level rises of several metres over the next hundred to two hundred years?  Does he think the idea of New York as New Venice is cool?   Does he think that vastly changed rain patterns and heat waves making current large population areas very difficult to live in may not be a costly and unfortunate result?   Does he have a clue about the uncertain ecological consequences of ocean acidification, more algal blooms and low oxygen in the oceans?   And no, you can't use the notion of "wait and see, and then we'll decide if we have to take action".   It's not that kind of problem - you can't reverse it with a wave of the wand, and geo-engineering is likely to invite its own problems.

Yeah, just shrug you ignorant shoulders, Scott; but you make no common sense.

Ocean acidification continues apace, with hardly anyone noticing

From Nature Climate Change:

The uptake of anthropogenic CO₂ by the ocean decreases seawater pH and carbonate mineral aragonite saturation state (Ω_arag), a process known as Ocean Acidification (OA). This can be detrimental to marine organisms and ecosystems^{1, 2}. The Arctic Ocean is particularly sensitive to climate change³ and aragonite is expected to become undersaturated (Ω_arag < 1) there sooner than in other oceans⁴. However, the extent and expansion rate of OA in this region are still unknown. Here we show that, between the 1990s and 2010, low Ω_arag waters have expanded northwards at least 5°, to 85° N, and deepened 100 m, to 250 m depth. Data from trans-western Arctic Ocean cruises show that Ω_arag < 1 water has increased in the upper 250 m from 5% to 31% of the total area north of 70° N. Tracer data and model simulations suggest that increased Pacific Winter Water transport, driven by an anomalous circulation pattern and sea-ice retreat, is primarily responsible for the expansion, although local carbon recycling and anthropogenic CO₂ uptake have also contributed. These results indicate more rapid acidification is occurring in the Arctic Ocean than the Pacific and Atlantic oceans^{5, 6, 7, 8}, with the western Arctic Ocean the first open-ocean region with large-scale expansion of ‘acidified’ water directly observed in the upper water column.

Evidence for harmful reef effects already taking place

Landmark experiment confirms ocean acidification’s toll on Great Barrier Reef : Nature News & Comment

Given the complexity of this type of experiment, I would still be a little cautious about its conclusions.

But it's still not good news for the long term prospects for the GBR.

Some plankton doing well, for now...

Published Thursday in the journal Science, the study details a tenfold increase in the abundance of single-cell coccolithophores between 1965 and 2010, and a particularly sharp spike since the late 1990s in the population of these pale-shelled floating phytoplankton.

"Something strange is happening here, and it's happening much more quickly than we thought it should," said Anand Gnanadesikan, associate professor in the Morton K. Blaustein Department of Earth and Planetary Sciences at Johns Hopkins and one of the study's five authors.

Gnanadesikan said the Science report certainly is good news for creatures that eat coccolithophores, but it's not clear what those are. "What is worrisome," he said, "is that our result points out how little we know about how complex ecosystems function." The result highlights the possibility of rapid ecosystem change, suggesting that prevalent models of how these systems respond to climate change may be too conservative, he said.

The team's analysis of Continuous Plankton Recorder survey data from the North Atlantic Ocean and North Sea since the mid-1960s suggests rising carbon dioxide in the ocean is causing the coccolithophore population spike, said Sara Rivero-Calle, a Johns Hopkins doctoral student and lead author of the study.

Link to the story here.

This is interesting, given that coccolithophores have been the subject of some intensive study to work out whether they are very sensitive to ocean acidification, or not.  (The results of lab tests have been contradictory and it's been difficult to work out why.)    The concern is (I expect) that at a certain threshold of CO2, this type of plankton suddenly goes into reverse because of the acidification effect. 

Let's play "climate change whiplash"!

Only In It For The Gold: Have We Missed the 2C Target Already?

As I have noted before, there's a real "whiplash" problem going on in the lead up to Paris, with some apparent experts pointing out things like how much could be achieved in CO2 reductions even with current technology; how coal may have already peaked in China; how batteries could revolutionise the use of clean energy, etc.

On the other hand, you have posts like the one linked above complaining that by pretending that the 2C limit is achievable when it most likely isn't, scientists are giving false optimism to nations, which leads to them not committing to the degree of effort that really would be needed. 

On the third hand, surely it has to be realised that the long standing enemies of effective policy towards reducing CO2 (the small government/anti regulation/anti tax conservative/libertarians of America) can seize on discussion that 2C is effectively inachievable to argue that there is no point in seeking to limit CO2, and promote instead a foolhardy "aircondition the planet" strategy (that is, the idea to push economic growth as the priority, including by burning more fossil fuels, because it is only by getting richer that the planet can be airconditioned - or geoengineered - fast enough to survive any temperature rise.)

It is a very tricky business, but I would have thought the appropriate response just has to include the following:

a. likely overshooting of 2C doesn't mean you don't seek to limit it as low as possible above 2C;

b. no one has any clear idea how well geoengineering may work and how it may hurt some countries for the benefit of others.  It will only be worth trying once things really are dire, and cannot address ocean acidification in any realistic scenario;

c. don't let pessimism become self fulfilling defeatism.   When strong commitment to environmental action is made, the results are often faster and better than expected. 

About Kiribati

Before we drown we may die of thirst

I see that a couple of weeks back, Nature had a balanced article about climate change and its effects on the small Pacific Island nations.

Long time readers may recall that I have always backed away* from relying on the celebrity victim status (as it were) of these islands for communicating the seriousness of climate change, because it seemed to me that their continued existence, being barely above sea level anyway, was always in doubt.

I think, on the whole, this article vindicates that position.  The islands have several problems and indeed climate change will exacerbate them, but in the big picture, the seriousness of a metre or two of sea level increase on the vastly populated and developed regions of other countries is really the much more profound problem.  (As well as the regional effects on food production, handling more frequent flooding, and the possible vast changes in the ocean food chain.)

* Yes, that linked post was written back in 2006 when I was taking a "sitting on the fence" approach to climate change, before I became convinced that it (and ocean acidification) were indeed serious issues.

Pteropods in the news, again

Abrupt onset and prolongation of aragonite undersaturation events in the Southern Ocean : Nature Climate Change : Nature Publishing Group: Ocean acidification may lead to seasonal aragonite undersaturation in surface waters of the Southern Ocean as early as 2030 (ref. 1). These conditions are harmful to key organisms such as pteropods, which contribute significantly to the pelagic foodweb and carbon export fluxes in this region. Although the severity of ocean acidification impacts is mainly determined by the duration, intensity and spatial extent of aragonite undersaturation events, little is known about the nature of these events, their evolving attributes and the timing of their onset in the Southern Ocean. Using an ensemble of ten Earth system models, we show that starting around 2030, aragonite undersaturation events will spread rapidly, affecting ~30% of Southern Ocean surface waters by 2060 and & greater than 70% by 2100, including the Patagonian Shelf. On their onset, the duration of these events will increase abruptly from 1 month to 6 months per year in less than 20 years in & greater than 75% of the area affected by end-of-century aragonite undersaturation. This is likely to decrease the ability of organisms to adapt to a quickly evolving environment. The rapid equatorward progression of surface aragonite undersaturation can be explained by the uptake of anthropogenic CO2, whereas climate-driven physical or biological changes will play a minor role.

 The Sydney Morning Herald report on this notes:

"What surprised us was really the abruptness at which this
under-saturation [of calcium carbonate-based aragonite] occurs in large
areas of the Southern Ocean," Axel Timmermann​, a co-author of the study
and oceanography professor at the University of Hawaii told Fairfax
Media. "It's actually quite scary."

Since the Southern Ocean is already close to the threshold for shell-formation, relatively
small changes in acidity levels will likely show up there first, Professor Timmermann said: "The background state is already very close to corrosiveness."

And of course, the "let's burn coal to make poor people rich and airconditioned into safety" crowd never address the point that their tactic will only accelerate potential food chain collapse in the oceans.

Another go at the economics of climate change

Expect to hear a lot about this study just out from some Berkeley researchers.  The headline from the Washington Post:

Sweeping study claims that rising temperatures will sharply cut economic productivity 

The claim is simple, but interesting:

Culling together economic and temperature data for over 100 wealthy
and poorer countries alike over 50 years, the researchers assert that
the optimum temperature for human productivity is seems to be around 13
degrees Celsius or roughly 55 degrees Fahrenheit, as an annual average
for a particular place. Once things get a lot hotter than that, the
researchers add, economic productivity declines “strongly.”

“The relationship is globally generalizable, unchanged since 1960, and
apparent for agricultural and non-agricultural activity in both rich and
poor countries,” write the authors, led by Marshall Burke of Stanford’s
Department of Earth System Science, who call their study “the first
evidence that economic activity in all regions is coupled to the global
climate.” Burke published the study with Solomon Hsiang and Edward
Miguel, economists at the University of California, Berkeley.

If the findings are correct, they add, that means that unmitigated
global warming could lead to a more than 20 percent decline in incomes
around the world, compared with a world that does not feature climate
change. And this would also mean growing global inequality, since poorer
countries will be hit by worse temperature increases — simply because
“hot, poor countries will probably suffer the largest reduction in
growth.” Indeed, some already wealthier countries with cold weather,
like Canada or Sweden, will benefit greatly based on the study, moving
closer to the climatic optimum.

 But things start to sound a bit more shaky here:

Assuming this relationship between temperature and productivity is
correct, that naturally leads to deep questions about its cause. The
researchers locate them in two chief places: agriculture and people. In
relation to rising temperature, Burke says, “We see that agricultural
productivity declines, labor productivity declines, kids do worse on
tests, and we see more violence.”

Yes, not sure I'd be entirely confident of the heat and violence connection, but if we go over to the university press release on this study, there is more reason to question the accuracy of the new study:

Unmitigated climate change is likely to reduce the income of an average
person on Earth by roughly 23 percent in 2100, according to estimates
contained in research published today in the journal Nature that is co-authored by two University of California, Berkeley professors.

 So far, so disastrous.  But look:

The Nature paper focuses on effects of climate change via
temperature, and does not include impacts via other consequences of
climate change such as hurricanes or sea level rise. Detailed results
and figures for each country are available for download online.

Or, I might add, rainfall pattern changes, or ocean acidification and potential large scale changes to the food cycle there.  How the heck can you be confident of projections if you cannot be certain how many poor countries may be destined to longer droughts and/or more frequent ones, followed by larger floods?    And what about poor coastal countries where local fish is an important food source?

So, I think there are grounds to argue that this study is another example that accurate predictions of the economic consequences of global warming decades into the future are pretty much guesswork. But at least it notes that the uncertainty is no grounds for complacency, as techo-optimist libertarian types seem to think.

And it does support one thing that I reckon common sense suggests:     the poor nations will suffer disproportionately from climate change; and even if some pro-development-at-any-climate-cost proponents had their way and we had every poor country building coal burning power plants as fast as they could, they are not going to develop their way economically fast enough to outpace the damage from climate change.   They're not going to be able to aircondition their agricultural sectors, after all; nor are they all going to be manufacturing centres, or financial hubs making a living from mobile money.

Back to how bad some of the study's projections are (from the University link above):

They find climate change is likely to have global costs generally
2.5-100 times larger than predicted by current leading models. The
team’s best estimate is that climate change will reduce global economic
production by 23 percent in 2100.

“Historically, people have considered a 20 percent decline in global
Gross Domestic Product to be a black swan: a low-probability
catastrophe,” Hsiang warned. “We’re finding it’s more like the
middle-of-the-road forecast.”

Half of the simulation projections suggest larger losses. The hottest
countries in the world are hardest hit: in less optimistic scenarios,
the authors estimate that 43 percent of countries are likely to be
poorer in 2100 than today due to climate change, despite incorporating
standard projections of technological progress and other advances.

 Richard Tol is already bleating about this, I see.  Given that I consider him a discredited jerk, I'm not surprised, but it will still be interesting to read more coverage about this.

Update:  here's the abstract from Nature in full:

Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies^{1, 2}, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries^{3, 4}. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature⁵, while poor countries respond only linearly^{5, 6}. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human–natural systems^{7, 8} and to anticipating the global impact of climate change^{9, 10}. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change^{11, 12}, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate.

All connected

Ocean life triggers ice formation in clouds

This would suggest to me further reason to worry about the unknown, global effects of ocean acidification.

Future oceans a worry

Climate Change Plus Irreversible Evolution Will Force Key Ocean Bacteria into Overdrive – Greg Laden's Blog

Read about this paper, showing the great uncertainty (and great potential problem) that increasing ocean acidification represents to the ecology of the future oceans.

More care needed

Crucial ocean-acidification models come up short : Nature News & Comment

Interesting article here, noting that a lot of the uncertainty in working out the ecological effects of ocean acidification  comes from experimenters (especially those at the start of research into this) not being careful enough with the experimental set up. 

I had noticed myself that, over the years, after the initial flurry of reports about the dire effects on different organisms, there followed a lot of considerably more ambiguous reports from tank experiments.   And, yes, it had been noted before that how the water chemistry is altered is important.

But do the researchers writing this paper think this means there is not a serious problem for the oceans?  Nope:

Cornwall says that the “overwhelming evidence” from such studies of the
negative effects of ocean acidification still stands. For example,
more-acidic waters slow the growth and worsen the health of many species
that build structures such as shells from calcium carbonate. But the
pair’s discovery that many of the experiments are problematic makes it
difficult to assess accurately the magnitude of effects of ocean
acidification, and to combine results from individual experiments to
build overall predictions for how the ecosystem as a whole will behave,
he says.

 This article also notes that not enough experiments have looked at the combination of warming water and decreasing pH together.

Two ocean acidification papers

1.  Ocean acidification measurements across an entire ocean indicate that pH is dropping in a way consistent with modelling.

2.   If you burn fossil fuels on a "business as usual" basis for another hundred years or so, even a future (improbably efficient) means of removing CO2 from the atmosphere is not going to help the oceans much.

I think I have summarised both of these correctly.

It's coming...

New study shows Arctic Ocean rapidly becoming more corrosive to marine species | EurekAlert! Science News

New research by NOAA, University of Alaska, and Woods Hole Oceanographic Institution in the journal Oceanography shows that surface waters of the Chukchi and Beaufort seas could reach levels of acidity that threaten the ability of animals to build and maintain their shells by 2030, with the Bering Sea reaching this level of acidity by 2044.

"Our research shows that within 15 years, the chemistry of these waters may no longer be saturated with enough calcium carbonate for a number of animals from tiny sea snails to Alaska King crabs to construct and maintain their shells at certain times of the year," said Jeremy Mathis, an oceanographer at NOAA's Pacific Marine Environmental Laboratory and lead author. "This change due to ocean acidification would not only affect shell-building animals but could ripple through the marine ecosystem."