A couple of months ago, we discussed a short paper by Matthews and Weaver on the ‘climate change commitment’ – how much change are we going to see purely because of previous emissions. In my write up, I contrasted the results in M&W (assuming zero CO2 emissions from now on) with a constant concentration scenario (roughly equivalent to an immediate cut of 70% in CO2 emissions), however, as a few people pointed out in the comments, this exclusive focus on CO2 is a little artificial.
I have elsewhere been a big advocate of paying attention to the multi-faceted nature of the anthropogenic emissions (including aerosols and radiatively and chemically active short-lived species), both because that gives a more useful assessment of what it is that we are doing that drives climate change, and also because it is vital information for judging the effectiveness of any proposed policy for a suite of public issues (climate, air pollution, public health etc.). Thus, I shouldn’t have neglected to include these other factors in discussions of the climate change commitment.
Luckily, some estimates do exist in the literature of what happens if we ceased all human emissions of climatically important factors. One such estimate is from Hare and Meinshausen (2006), whose results are illustrated here:
The curve (1) is the result for zero emissions of all of the anthropogenic inputs (in this case, CO2, CH4, N2O, CFCs, SO2, CO, VOCs and NOx). The conclusion is that, in the absence of any human emissions, the expectation would be for quite a sharp warming with elevated temperatures lasting almost until 2050. The reason is that the reflective aerosols (sulphates) decrease in abundance very quickly and so their cooling effect is removed faster than the warming impact of the well-mixed GHGs disappears.
This calculation is done with a somewhat simplified model, and so it might be a little different with a more state-of-the-art ESM (for instance, including more aerosol species like black carbon and a more complete interaction between the chemistry and aerosol species), but the basic result is likely to be robust.
Obviously, this is not a realistic scenario for anything that could really happen, but it does illustrate a couple of points that are relevant for policy. Firstly, the full emissions profile of any particular activity or sector needs to be considered – exclusively focusing on CO2 might give a misleading picture of the climate impact. Secondly, timescales are important. The shorter the time horizon, the larger the impact of short-lived species (aerosols, ozone, etc.). However, the short-lived species provide both warming and cooling effects and the balance between them will vary depending on the activity. Good initial targets for policy measures to reduce emissions might therefore be those where both the short and long-lived components increase warming.
Re #230
Sorry, my second link was to Comment 92 after “Climate Change Commitments”. That also discussed methane release.
Incidentally, if you are worried about a repeat of the PETM, then there is a big difference between Pliocene temperatures (~3 degrees hotter than pre-industrial) and Paleocene temperatures just before the PETM itself (probably >6 degrees hotter than pre-industrial). A PETM rerun could happen if we continue burning fossil fuels through the 21st century, but it seems unlikely that we’ve set it off already. The Pliocene was stable with CO2 levels like today’s.
In fact the Earth has been through some very hot times before and survived… can’t say the same for us unfortunately. See
last 65 million years and
last 500 million years
“I never said a decline in temperature is responsible for economic growth. That’s what you were implying with your correlation talk”
No, Rod, your errant memory or just plain lying tongue again changes the past in the hope that nobody is watching.
Ray was pointing out that the contention (that YOU have made too!) that GDP will increase in higher temperature climates is not shown in actual measurements.
Not once has anyone here said that cooling causes economic growth until you pulled that out of your nethers to wave about as a strawman.
What Ray was implying with his correlation talk is that the correlation of GDP and temperature is negative, not positive as you and other denialerati would have it.
Failing to counter these facts, you make up arguments and assert them against others, to enable a Gish Gallop off into the misty marshes where you hope to hide.
“I should have known you would merely dismiss the problem and be rude,”
Uh, you’re the one saying that there is no problem, the solution is that we grow dwarf wheat.
I’m saying that YOU are dismissing the problem.
Talk about getting the facts wrong…
ccpo, just one question about your 278 post: how do we know that Arctic ice is not as thick or stable as satellite imagery tells us?
Pardon me for butting in, but the argument that warmer temps lead to increased GDP is rather silly and deceptive. What does it matter if they correlate? More to the point, it’s an exercise in semantics. Even if warmer temps correlate to higher GDP, the argument warmer temps contribute or lead to GDP is backwards. Warmer temps are a symptom, a byproduct, not a driver. If anything, this is an argument for more efficient use of energy, not promoting more ‘heat’.
Seriously, this is almost a silly as Sarah Palin blaming the Gulf oil spill on environmentalists.
JRC (282) you say, “…If anything increased rates of temps…” and “…don’t think that anyone is saying it’s a universal law…” but then follow with, “…increased rates of temps correlate to lower GDP, and the data proves that. (emphasis mine)” Sounds like a contradiction in terms. You make a good point about the uncertainty (and probably not) that increased temps enhance GDP and then hurt your credibility by saying that on the other hand the data proves that increased temp does reduce GDP. Why is one side of the coin flaky and the other side certain?
CFU, FYI, the Horowitz paper said GDP, NOT GDP growth. Though ‘course you probably could have read that yourself…
The difference between DDR and FRG was small? So small??!! That’s probably why West Germans were desperately trying to get into East Germany!
CFU says in #285, “…“I (and others) have been saying correlations between temp and GPD is devoid of any substance.”
No, you’ve been saying correlations between temp and GDP are in the opposite way of the measurements.”
I have not, at all.
I’ll try to get my syntax down to the ‘see Jane run’ level so maybe you can grasp what I write.
“305
J.S. McIntyre says:
8 June 2010 at 8:40 AM
Pardon me for butting in, but the argument that warmer temps lead to increased GDP is rather silly and deceptive. What does it matter if they correlate? ”
What’s silly and deceptive is asking that question.
There is no evidence of warmer temps lead to increased GDP, the only evidence of a link is in the reverse direction, therefore anyone (such as rod) who wishes to say that GDP increases with temperature (as rod has said in this thread) have to prove not only the causation but the reason why the correlation is the reverse of what their thesis would make it.
“how do we know that Arctic ice is not as thick or stable as satellite imagery tells us?”
We don’t have to know.
What we have to know is “is the ice thinner than it was before”. A 50% reduction in thickness still halves the volume of ice, even if the total volume is different.
Steckis, Again point to where I have claimed that climate change will destroy ALL agriculture. It doesn’t have to in a world where we must feed 9 billion people. All it has to do is cause a couple of critical crops to fail (rice, potatos, wheat…).
Rod, again, I posted the data and study to illustrate that the claim that a warmer world will be more productive is unsupported by the data. Interesting that you’ve never taken issue with those making that claim. It appears that you only take an interest when the studies show inverse correlation between temperature and economic growth.
Again, I have mentioned some of the ideas that have been debated wrt this data. It appears that you are more interested in denying the correlation rather than in the possible explanations.
“Why is one side of the coin flaky and the other side certain?”
Because a coin as three sides: top, bottom AND EDGE.
Therefore just because “it’s not top” doesn’t mean “it’s bottom”.
BPL, the assertions are 1) a one degree increase in global temperature will lower global GDP by 3.8% (or roughly 4%). — period. 2) “the relationship is roughly 1.1% decrease in GDP per degree of warming” (62, et al). 3) “a 2 degree C rise in temperature results in GDP growth rate declining by 2.2 [%] per doubling” (51).
Those are pretty definitive and explicit. Whether it is THE primary cause is a real strawman and doesn’t matter. It clearly is implied to be a definite and A primary cause. Your song and dance to rationalize the correlations and causation is not cutting it. You and others seem to be hoping against hope that we will just close our eyes, succumb to the intimidation, accept entirely the implication, and quit pointing to evident faults and asking questions that can only be answered with a juggling act.
There is one clear actual and measurable example for the 1st claim above. That is the global temperature and global GDP over some period like 1900 to 2000 (or any 30 year or more period you want). Looks really bad. Quit the tap dancing and re-coloring the argument mid-stream.
[this is not directed solely to BPL. Actually BPL is not even a primary target — just handy ;-)]
J.S. McIntyre (305), the debate was whether warmer temps lowered GDP. There has been a bunch of scrambling trying to change the debate.
Is this getting tiresome, or what??
Guys, guys — GDP is Gross Domestic Product.
Hurricane swamps New Orleans — rebuilding — increases GDP
Earthquake — rebuilding — increases GDP
Fish getting scarce — new deeper smarter fishing gear — increases GDP
You’re acting like spending money on new stuff and wasting stuff is a good thing.
Conservation doesn’t increase GDP.
RS 284: You seem to think that all food production will be lost. I think it won’t. You are still engaging in extremist thinking (a severe cognitive distortion). i.e. climate change will destroy all agriculture, which is patently untrue.
BPL: If we do nothing about global warming, we will reach the point where human agriculture collapses completely. But if even a third of the world suddenly found itself starving, that would be an unprecedented disaster. Maybe “some” food will still be possible to produce when 70% of the world is in severe drought. But the important distinction is not “some,” but “enough.”
Gilles 285: I never said that “human civilization” as a whole was dependent on FF, and I agree to call “civilization” the greek, roman, chinese, aztec , etc.. who lived without them. I said that the modern way of life (a GDP and a energy consumption per capita several dozens times as large as previously) was only possible with FF.
BPL: You’re still wrong.
Furry 290: I’m with Frank on this one — there are entirely too many variables to say that temperature and GDP have =any= relationship (except at the extremes).
BPL: Such things can be MEASURED, Furry. Crack an introductory statistics book, will you?
I vote for “Correlation between temperature and GDP” as the most pointless and insoluble discussion entertained so far in the history of Real Climate. But I’ve not looked comprehensively at the paleo record so perhaps I’m mistaken.
How about ditching dubious correlations and instead taking a look at Scafetta’s latest paper, now in review, where recent climate change is ascribed to “vibrations of the solar system?” That should produce a much more entertaining argument.
Get good vibrations here: Empirical evidence for a celestial origin of the climate oscillations and its implications
Comment by Rod B — 8 June 2010 @ 8:48 AM
Rod, you are correct, I shouldn’t have said “the data proves that.” My apologies. As far as the coin, in my opinion, it’s more like one side is flaky and the other side is more flaky.
Many people could mistake large methane fuel-air explosions for nuclear explosions. Smaller methane fuel-air explosions will still seem like an attack. It will happen on Russia’s northern coast. It would help if everybody were warned ahead of time. Methane fuel-air explosions can kill people and other animals.
http://climateprogress.org/2010/03/04/science-nsf-tundra-permafrost-methane-east-siberian-arctic-shelf-venting/
Frank Giger (#268),
> I’d think good governance (…) would have far more impact on GDP than
> temperature.
That may well be, but differences in governance between rich and poor countries apparently leave unexplained most of the strong negative correlation between temperature and economic output. Check out Nordhaus (2006): He separated out “national” factors from geographical ones by using sub-national gridded economic data (in cells measuring 1 x 1º latitude/longitude). About 2/3 of the relationship between mean temperature and per capita output could not be explained by “country-specific factors such as institutional differences, history, major locational advantages…”
” If anything, this is an argument for more efficient use of energy, not promoting more ‘heat’.”
Spot on.
Does climate effect GDP? Sure, on the baseline. The Congo won’t become a grain belt in the near (or distant) future, for an example.
However, stating that one can quanitify the ups and downs of GDP based on temperature ignores modern economic realities. A 2% swing in GDP up or down can be caused by so many factors that pegging it to global temperature is grasping for a rung too high up the ladder.
If the paper had gone after sectors of economy I’d probably be right on board, nodding my head, particularly if they chose agriculture. But they didn’t – they went after the whole of the economy.
Global temperatures have gone up since WWII, but Global GDP has as well. In the USA, agricultural output has gone crazy efficient since then. Not because of global temperatures, but because of mechanization, pesticides, practices, fertilization, crop variety optimizations, etc.
The counter argument that increasing global temperatures somehow automatically increases GDP is equally specious.
BPL @ 315:
I have. As I’ve noted before, I’ve actually studied statistics at the graduate level, used it in my work for 25 years, and have a pretty good grasp on =how= what you’ve become so attached to can be completely unrelated to “temperature”.
Need I remind you? Correlation does NOT NOT NOT imply causation.
The next thing you’ll tell me is that temperature causes Banana Republics, rather than political corruption from a legacy of European colonialism …
CM @ 320:
Did they study the counter-example presented by the migration of industry from the Rust Belt to the Sun Belt? Did the Sun Belt get colder, and the Rust Belt get warmer, and that’s why the population and per-capita GDP shift happened?
CFU @ 253 “You can breed the American plains grasses to produce wheat. It just takes much, much longer than 19 years to do it.”
RS @ 283 “No you can’t. If you could then it would have already been done or at least attempted.
It IS being attempted, at The Land Institute in Kansas, but it will take decades to accomplish. See
http://www.landinstitute.org/vnews/display.v/ART/2007/03/15/45fac62e11c35
in the perennial grains research subsection
301 Dr. Nick Bone: Thanks much.
http://climateprogress.org/2010/03/04/science-nsf-tundra-permafrost-methane-east-siberian-arctic-shelf-venting/
has a comment which leads to
http://www.newscientist.com/article/dn17625-as-arctic-ocean-warms-megatonnes-of-methane-bubble-up.html
which quantifies the release compared to global average release, and it is small compared to the global average.
CM, from your link:
At the same time, three reservations should be emphasized. First,the estimates of the impact of geographic variables on output leave a significant fraction of output unexplained. Until output variations
are fully and robustly explained, we cannot be confident about a projection based on an incomplete model. Second, these estimates include only market output and do not incorporate any nonmarket
impacts or abrupt climate changes. Hence, impacts on ecosystems or amenities, and particularly the potential for abrupt climate change, need to be included in a full impacts analysis (21, 22). Finally, the model underlying the estimates here, particularly the
assumption of climate-economy equilibrium, is highly simplified. The dynamic nature of economic growth cannot be adequately captured in cross-sectional estimates. Given the sluggish reactions of population distributions to changing conditions, existing settlement and economic patterns may still be adjusting to economic and climatic conditions. Pursuing each of these issues requires further data and methodological developments.
Using the assumptions taken in the paper, one need only draw a latitude line and predict GDP….or not, as they themselves admit.
Making a buck in the tropics has the same pitfalls as making a buck in the artic…weather and soil works against a person. That’s not a news flash.
The economic system is still too dynamic to pin GDP on temperature to where one can predict output based on it. And yeah, if one is saying “one degree = 2.2% reduction in GDP” one is doing exactly that.
Similarly, the studies don’t explain why the other side of the globe that matches North America and Europe aren’t a match in GDP. Why aren’t Angola, Zaire, and Zimbabwe the peers of the USA in GDP? The latter has not only roughly the same Latitude, but geography, weather patterns, and soil to support not only agriculture but has a wealth of mineral resources to back it up!
Re #230
Sorry, my second link was to Comment 92 after “Climate Change Commitments”. That also discussed methane release.
Incidentally, if you are worried about a repeat of the PETM, then there is a big difference between Pliocene temperatures (~3 degrees hotter than pre-industrial) and Paleocene temperatures just before the PETM itself (probably >6 degrees hotter than pre-industrial). A PETM rerun could happen if we continue burning fossil fuels through the 21st century, but it seems unlikely that we’ve set it off already. The Pliocene was stable with CO2 levels like today’s.
In fact the Earth has been through some very hot times before and survived… can’t say the same for us unfortunately. See
last 65 million years and
last 500 million years
I suspect here are some serious differences between then and now.
1. I doubt the geography was the same, let alone the geology. Now? We have very shallow continental shelves (Siberia) loaded with clathrates due to all the biomass deposited there during previous interglacials and submerged when the ice age retreated. Those may not have been there during the PETM.
2. The Siberian shelf is so shallow, we can expect a lot of instability as the pressure/temp ratio gets out of whack. Quickly. After all, all this melting is decades, many decades in some respects, ahead of expectations/projections. Clearly, we don’t model clathrates well at all. One scientists I e-mailed with a couple years ago swore we were a century or more from any serious threat. Scientists here at RealClimate have stated broadly similar comments. Clearly, they are incorrect.
Scary? The former said clathrates were within 1 and 2 degrees of instability. Given the shallow seas, the influx of warm water shown in a previous link, and the emissions we have already seen coupled with the state of the ice, I’d say it’s a minor miracle we don’t have evidence of even greater emissions.
3. The permafrost above sea level alone holds 2 times the carbon in the atmosphere and melt is well underway with thermokarst lakes tripling in size, e.g., over short periods of time. (See K. Walter, et al.)
4. Rate of change. The speed of warming is simply much faster than most other transitions have been. Events such as the Younger Dryas and such were relatively rapid, but those weren’t shifts to new climates, merely big blips along the road.
5. With the Swiss Cheese that is the Arctic Sea Ice, all bets are off.
Cheers
Ah, I forgot all about this little gem from a link provided above:
“Shakhova notes that the Earth’s geological record indicates that atmospheric methane concentrations have varied between about .3 to .4 parts per million during cold periods to .6 to .7 parts per million during warm periods. Current average methane concentrations in the Arctic average about 1.85 parts per million, the highest in 400,000 years, she said. Concentrations above the East Siberian Arctic Shelf are even higher.”
Comment by Doug Bostrom: I vote for “Correlation between temperature and GDP” as the most pointless and insoluble discussion entertained so far in the history of Real Climate.
I second the motion. Particularly on a topic about ‘commitment’.
Ray, I made a clear statement that one can find a correlation with all four combinations of temp and GDP, and claimed they all prove no causality of anything — including the case of higher temps causing greater GDP. You will not find where I made a case for the latter anywhere. However, speaking of correlations and ‘no data exists’, as some have said, I’m still waiting for someone to explain the data from the single best actual scenario — global temp vs. global GDP over the last hundred years or so within the context of this debate.
I think one can find scenarios where increased temperatures have had a non-exclusive causality of enhanced GDP. I also think one can present scenarios where higher temperatures are clearly — even irrefutably — the primary cause of reduced GDP, as I did one in an earlier post. But the limited scenarios in the linked references are interesting but miss proving the case by a country mile. I can’t figure out why you all want to keep it on its very shaky pedestal — even more so than the authors it seems.
JRC (318), I’ll buy that!
Hank (#312),
Thank you for being a voice of sanity. You are quite right: mind your theories of value! I think most people don’t understand GDP.
I can’t bring myself to comment directly on this ludicrous GDP/temperature discussion but let me say this: there’s no objective way to compare GDP between countries, regions or periods. This doesn’t make comparisons from a year to the next (growth) or between similar countries useless (though there is some controversy regarding how the numbers should be adjusted) but any comparison between very dissimilar economies such as comparisons of estimates of premodern to current global GDP would yield arbitrary values. What theory of value would one use as a basis? One can’t use a chain deflator, purchasing power parity or labour time and even the value of commodities has varied widely.
“BPL: You’re still wrong.”
You didn’t answer my question : can you give me a statistical method that I could blindly apply to correlate GDP against temperature, or FF (for instance without knowing which is which in “reduced units”), and that would show a better correlation with temperature than with FF ?
and more generally, can you give me a method of reasoning , which, equally applied to judge the influence of temperature and FF consumption on human society, would obviously show that the first one is much more important than the second one to explain the wealth of modern countries ?
Again, if you postulate that “we could find in the future a magic solution to replace FF”, the same thought applied to temperature could equally give “we could find in the future a magic solution to adapt to warming”.
And conversely, if you estimate the influence of temperature on societies by extrapolating present known facts and correlations, then you should also estimate the influence of FF by extrapolating present known facts and correlations.
So please, before saying that I’m wrong, give me a rational, scientific method to justify it.
The 1870’s European didn’t have access to modern composite materials to make high efficiency wind turbines from, Gilles. Neither did they have access to modern amorphous silicon production techniques to make photovoltaic cells.
We do.
Therefore in 20 years time, there will be a modern industrial society that will have an idiot like you look back and say “electricity from renewable resources is how any modern society created, tell me one modern society that wasn’t created without it? And don’t start me on that ancient ‘civilisation’ of the Victorians… I mean MODERN.”.
Why?
[edit]
You’re like an Apple Fanboi who defends the iPad not having a card reader by saying “Hey, we have ‘the cloud’ and email and FTP, who needs sneakernet with SD cards?”. Refusing to see the utlility of another technology because that would be admitting something is wrong with the technology you’re in love with.
I would stress that the correlation between temperature and GDP is totally equivalent to the correlation between temperature and FF consumption, both being much looser than the correlation between FF and GDP. Arguing that we must act on FF consumption to lower temperatures, and hence raise GDP, as if it would influence the GDP only through the second effect, and not the first one (which is much more strongly correlated) , is plainly stupid, just from a mathematical point of view.
BPL wrote: “But if even a third of the world suddenly found itself starving, that would be an unprecedented disaster. Maybe ‘some’ food will still be possible to produce when 70% of the world is in severe drought. But the important distinction is not ‘some,’ but ‘enough.'”
The people who are driving BP, ExxonMobil, Koch Industries et al — the paymasters for the denialist propaganda machine — are more than willing to risk starvation for a third of the Earth’s human population in return for the prospect of trillions of dollars in profit from several more decades of business-as-usual consumption of their products.
If there is food for the “top one percent” then that’s “enough”.
To Edward G at 319:
Doesn’t that need some kind of a spark to set off the gas? Can it happen spontaneously? Are you thinking that lightening would set it off?
If there really are 10,000 gigatons of the stuff under the East Siberian Arctic Shelf, and if a substantial proportion of that was released suddenly and ignited, I’m guessing there would be greater consequences than a few birds or people in the nearby (mostly desolate) local area being killed.
Back to the graph, I’m having trouble understanding the difference between curve one and curve two. Is the second curve just ignoring the whole aerosol situation–pretending they don’t exist?
From todays nytimes: http://www.nytimes.com/2010/06/09/opinion/09krosnick.html?hp
“ON Thursday, the Senate will vote on a resolution proposed by Lisa Murkowski, Republican of Alaska, that would scuttle the Environmental Protection Agency’s plans to limit emissions of greenhouse gases by American businesses.
— and then:a new survey by my Political Psychology Research Group show just the opposite: huge majorities of Americans still believe the earth has been gradually warming as the result of human activity and want the government to institute regulations to stop it.
When senators vote on emissions limits on Thursday, there is one other number they might want to keep in mind: 72 percent of Americans think that most business leaders do not want the federal government to take steps to stop global warming. A vote to eliminate greenhouse gas regulation is likely to be perceived by the nation as a vote for industry, and against the will of the people.”
Unfortunately most Americans don’t want carbon taxes which is the most efficient way to reduce CO2 emissions.
OT, but this will be welcome news for many here:
http://www.cbc.ca/technology/story/2010/06/09/globalwarming-americans.html
“You can’t fool all the people all the time. . .”
“So please, before saying that I’m wrong, give me a rational, scientific method to justify it.”
You can’t refute the Flying Spaghetti Monster with a rational scientific method. What makes you think that it’s possible with your fantasies?
Fossil Fuels were the only way Victorians had of collecting concentrated sunlight.
We have the technology to bypass that slow and dangerous method.
What was wanted was energy. Not oil. Energy.
John E. Pearson quoted the NY Times: “When senators vote on emissions limits on Thursday … A vote to eliminate greenhouse gas regulation is likely to be perceived by the nation as a vote for industry, and against the will of the people.”
In other words, business as usual for the US Senate.
As Frederik Pohl and Cyril Kornbluth suggested over 50 years ago in The Space Merchants, perhaps it is time to drop the pretense that Senators represent the citizens of their states, and acknowledge that they represent corporations, i.e. “Lisa Murkowski, Republican from ExxonMobil”.
We should impose a tax on poverty. In the same way a carbon tax will discourage carbon based fuels, a tax on poverty will discourage poverty. As with carbon, each year we can raise the tax on poverty, making it more and more expensive to be poor, which will encourage people to stop being poor and encourage them to be rich.
Over time we will have less and less poor people, and more and more rich people. This will allow us to afford the switch from a carbon based economy to a green economy. After all, a poor person does not choose to own an inefficient car, they simply can’t afford the latest hybrid. After our tax on poverty makes everyone rich, we can all afford to buy new, fuel efficient green cars.
Wili (#341),
It looks like curve 2 assumes nothing will change (including aerosols) or that any change will be compensated exactly by another with the opposite sign. I guess the idea is to illustrate the heat inertia of the system. It’s certainly not meant as any kind of forecast.
Curve 1 is a forecast of sorts. It shows what is believed would happen in an unrealistic scenario. I guess your’re right and that the bump in curve 1 is mainly explained by aerosols being removed from the atmosphere faster than GHGs (and feedbacks).
Mr. Pearson, giving the EPA to legislate through regulation, without oversight, is a bad idea. Why bother to have a Congress – we’ll just appoint chairmen of agencies!
CFU (338) says, “Therefore in 20 years time, there will be a modern industrial society that will have [people] look back and say “electricity from renewable resources is how any modern society created, tell me one modern society that wasn’t created without it?””
Why do you think one/some/most/all people will 20 years from now suddenly become completely stupid and claim such obvious absurdities? Even if, hypothetically, all electricity is magically then being generated with renewables.
I think people have wandered rather far afield in the GDP-temperature debate.
Also, people on each side are now in positions where they refuse to budge. Every argument is immediately countered without proper consideration. It’s now a game, rather than an argument, and the point is to win, not to reach a logical and truthful conclusion.
Some points anyone should (individually) agree with:
A 2C to 3C increase in average global temperatures will mean that some regions of the Earth experience 6C+ seasonal increases. A 6C average increase will mean that some regions experience at least a 10C+ seasonal increase.
A regional temperature increase of 6C or more in areas of the globe, along with likely precipitation changes, will inevitably cause major agricultural problems. There will be farmland lost, transition of farmland to new crops, and the cultivation of potential new farmland, all at a large cost. Costs will include effort spent, as well as temporary or permanent loss of crop productivity, and the cascading effects of that on food supply and general productivity.
A regional temperature increase of 6C or more in areas of the globe will result in increased disease, in the short term (before the diseases can be battled) and possibly in the long term (i.e. situations which can only be partially mitigated but never completely corrected). This will happen with malaria and others. Battling the disease itself will cost, treating those afflicted will cost, and it will have cascading impacts on population health and therefore general productivity.
A regional temperature increase of 6C or more in areas of the globe will result in major water availability problems. As everything in human society has historically been greatly impacted by the availability of water resources, this will require mitigation, and in some areas be untenable. For instance, it may no longer be possible to grow cops in the lower Southwestern states, no matter what effort is undertaken. Worse, large cities may be simply unable to support their populations. This would certainly have a massive negative impact on productivity.
Sea level rise would displace large populations along ocean and river delta coasts, and interfere with ports and other elements of the infrastructure. Such changes may not occur for many, many, many decades, but would still have a pronounced cost.
Increases in storm strength and frequency (when I get a chance, I plan to download the historical tornado data, and see if there is a trend corresponding to global temperature) will cause not only repeated, large scale damage, but if recognized as a persistent, repeating pattern may make first cause repeated drops in productivity, and ultimately require a redistribution of infrastructure to move things to less volatile areas.
In the end, the details say that a major increase in temperature implies a drop in useful productivity. GDP may stay high, because people still have to work to do things, but what they put their time into will be an unnecessary distraction.
At the same time, if the combined impacts of climate change are too overwhelming (like the dust bowl of the 1930s), and it happens too quickly to simply “up and move” everything affected, then GDP may in fact plummet for a decade or three.
When a growing scarcity of fossil fuels is added to the picture, along with a growing reluctance to use “the cause” as part of “the cure,” things get dicey.
Stresses such as those described also, historically, lead to conflict and war, which is man’s single greatest method of reducing his own productivity, both in effort spent building an army, and then the inevitable destruction caused by their use.
The counter argument to this is that warm temperatures will make everything grow better, increasing productivity, while efforts spent finding alternatives to (limited and expiring) fossil fuel resources would be wasted, and damage overall productivity.
This all seems pretty clear to me. But I’m just one little guy with one little brain. Don’t mind me.