A scientific critique of the two-degree climate change target

A scientific critique of the two-degree climate change target (Reto Knutti,Joeri Rogelj, Jan Sedláček & Erich M. Fischer; Nature Geoscience (2015) doi:10.1038/ngeo2595): sounds like a good idea, and vair topical. Since its short, I'll nick the abstract in full:

The world's governments agreed to limit global mean temperature change to below 2 °C compared with pre-industrial levels in the years following the 2009 climate conference in Copenhagen. This 2 °C warming target is perceived by the public as a universally accepted goal, identified by scientists as a safe limit that avoids dangerous climate change. This perception is incorrect: no scientific assessment has clearly justified or defended the 2 °C target as a safe level of warming, and indeed, this is not a problem that science alone can address. We argue that global temperature is the best climate target quantity, but it is unclear what level can be considered safe. The 2 °C target is useful for anchoring discussions, but has been ineffective in triggering the required emission reductions; debates on considering a lower target are strongly at odds with the current real-world level of action. These debates are moot, however, as the decisions that need to be taken now to limit warming to 1.5 or 2 °C are very similar. We need to agree how to start, not where to end mitigation.

I've bolded the important bits that people always forget.

[I haven't read the paper itself, of course, because it is paywalled. Ah, but AFS found it:

More like this

@-"This 2 °C warming target is perceived by the public as a universally accepted goal, identified by scientists as a safe limit that avoids dangerous climate change.”

'Perceived' by which public, when and how measured?

I think I have only ever seen the claim made that 2degC is universally accepted to avoid dangerous change in the context of its refutation.

Interesting that it is described as a public perception and not a conclusion. That implies that it is something the public has seen claimed, so perceived, not understood or reasoned for themselves.

In which case the significant question is not whether this is a correct claim, but where it came from.

[I don't think it is a strawman. I think they are correct in saying its a commonplace. See misc meetings -W]

Quoting an article that you (appear to) agree with, William? That's unusual behaviour for you.

I agree with it too, though "perceived by the public as a universally accepted goal" is a bit strong IMHO.

By Mark Hadfield (not verified) on 16 Dec 2015 #permalink

The 2 °C meme is due to the misreading of one of Hansen's earlier papers.

To put in perspective so far there has been 1 °C global warming since, say, 1880 CE. That is clearly already too much for safety.

By David B. Benson (not verified) on 16 Dec 2015 #permalink

Its the word 'target' that bothers me. To my mind its something you aim for or achieve

Documentation of another failed AGW sales job.
"The [unscientific but sold as scientific point of no return for danger not catastrophe, -H] 2 °C target is useful for anchoring discussions, but has been ineffective in triggering the required emission reductions; debates on considering a lower target are strongly at odds with the current real-world level of action."
Perhaps more republican ridicule will help get their support for emission reductions. It isn't a science problem, it's a politics and engineering problem. Until someone can figure out how to make decarbonization a huge pork project (bigger than Phillips Petroleum) in Inhofe's district, nothing will happen.

I'm baffled by this idea that 2 C has not been universally recognized as a "safe" target. We have been carpet-bombed with that idea for 5 years now.

David Benson - You really think the climate we live with now is dangerous vs. 1880s climate? It is not yet possible to detect a change in any extreme weather with confidence, let alone a dangerous change.

The US west just went through the most serious wildfire season ever. Washington state is now on its third declared emergency, these last two being flooding related. About 3 weeks ago Spokane had hurricane force winds causing power outages to over 200,000 service addresses. Some took 10 days to restore the power. It was the worst wind storm since electricity service was first started there in 1889.

And that just around here. Go check the typhoon news for the last few years, especially the Philippines.

By David B. Benson (not verified) on 18 Dec 2015 #permalink


Until someone can figure out how to make decarbonization a huge pork project (bigger than Phillips Petroleum) in Inhofe’s district, nothing will happen.

The Tragedy of the Commons, American style. Silent Cal summed it up pretty well:

After all, the chief business of the American people is business. They are profoundly concerned with producing, buying, selling, investing and prospering in the world.

The purpose of our "one dollar, one vote" system for electing our representatives is to externalize as much of the costs of business as possible. The main difference between Democrats and Repubiicans may be that Republicans are more upfront about it.

By Mal Adapted (not verified) on 19 Dec 2015 #permalink

Mal: We go to save the planet with the politics we have, not the politics we wish to have.

The Tragedy of the Commons has been progressively mitigated by popular democratic pressures. Your one dollar one vote is really a sliding scale. The environmental groups have much more political power per dollar than the Koch Bros because they can deliver votes at a significantly lower cost.

Environmental progress in the US has been paid mostly with private money against government pressure. The exception is underground fuel tank leaks that has a penny gas tax funded insurance program.

More overt externalizing (socializing) of environmental impact would, IMO be a net benefit. Everyone prospers from cheap power, cheap food, cheap motor fuel and reliable transport. These are all economically progressive benefits as the poor consume these basics at a similar rate to the middle, upper middle and lower wealthy classes.

We already pay for motor fuel cleanup through the gas tax. The same model could be applied to agricultural pollution, energy pollution and industrial pollution. IMO, we should start with toxics (and thereby the short-term GHG's), then move on to decarbonization. Rather than use a focused tax to punish and force behavior changes, use a widely distributed tax to help pay for the technological changes required to fix the problems.

A not particularly scientific critique of your good self:


William M. Connolley is a British Wikipedia editor known for his fanaticism in promoting the theory of anthropogenic global warming (AGW) and in censoring the views of critics and skeptics. He is the ringleader of the infamous global warming cabal at Wikipedia, a powerful pro-AGW group that has an iron grip on global warming-related articles.  


[I am sinfully proud of my conservapedia article. Not many have such fame. Its also nice to see my name arousing fear and loathing in the Curryite's, though I'm afraid I'm rather forgotten over there -W]

By Verytallguy (not verified) on 19 Dec 2015 #permalink


The environmental groups have much more political power per dollar than the Koch Bros because they can deliver votes at a significantly lower cost.

Assessing the global accrual of externalities our country is disproportionately responsible for, of which climate change is only the largest, one has to dismiss your assertion as yet to be demonstrated, if not counter-factual.

The reality is that globally, economic development has been a matter of liquidizing natural capital for largely private benefit while socializing much of the costs. In the US, the individuals, families and corporations who've gained fortunes thereby have mobilized to prevent further progress after the environmental victories of the 1960s through the 80s, and are attempting to roll back the gains, by restricting the funding of regulatory and land-management agencies for example.

Regardless, proposals for a carbon tax aren't intended to "punish and force" behavior change, they are to intended to harness market forces to promote the transition to a carbon-neutral energy economy, by motivating creative solutions on both the demand and supply sides. Internalizing the climate-change cost of fossil fuel production obviously threatens the private wealth of the Koch family, but offers the vastly greater public benefit of mitigating global climate chaos.

By Mal Adapted (not verified) on 19 Dec 2015 #permalink

Conservapedia? I know most of their math discussions are blatantly wrong, so I assume the rest of the items there are just as bad? (As in, whatever, they say, turn 180 degrees to head toward reality wrong?)

Mal: Your point is wrong, the US continues to advance environmentally through increasing regulation and the feedback of 40-years of practical science that has been conducted largely by private funds. We still have a lot to do, but the US environment is significantly better off than it was in the 1980's. I don't know about Europe, I suppose it's better than the past.

I will make your point that you failed to make: Global environmental degradation of the developing world has significantly increased as the West shifted manufacturing to those shores with little or no environmental control. This is a negative externality of Western environmental regulation. The here and now PM2.5 cloud from India and China is quite horrific and needs to be dealt with as the top global environmental priority and the West should help pay for it by renaming all those stores to Two Dollar General.

Apparently you require euphemisms (it's a common reality avoidance crutch), but "harness market forces to promote transition" and "punish and force" means the same thing with fewer words.

A carbon tax will send the money to a black hole in the general fund. It's not going to get approved in the US unless the WAIS cheese slides off the pizza. Targeted taxes that go into an insurance fund won't be spent on papering over the social security debt. It's not magic, everyone needs to pay more money for everything to implement greater pollution controls.

"global climate chaos" Is that your euphemism for CAGW so the cool kids won't tease you?

“harness market forces to promote transition” and “punish and force” means the same thing with fewer words.

No, not at all. The big difference is that punish and force requires governmental action, but harnessing market forces to promote transition requires only the voluntary actions of individuals acting in concert.

By Paul Kelly (not verified) on 20 Dec 2015 #permalink


I will make your point that you failed to make: Global environmental degradation of the developing world has significantly increased as the West shifted manufacturing to those shores with little or no environmental control.

That is a penetrating insight, for which you are to be congratulated. As for the rest of your comment:


Whether the US is environmentally better off now than it was in the 80's depends on your criteria. Urban air quality has improved by some measures, but as you suggest, that's arguably due to off-shoring of heavy industry. Ozone is still injuring people and vegetation, in some cases hundreds of miles downwind of its sources. Surface waters are less polluted by and large, but groundwater supplies are still being discovered to be contaminated while others are being overdrawn, and both surface and ground water supplies are now threatened by AGW-related drought. Meanwhile, biodiversity continues to dwindle, the Endangered Species Act not-withstanding. Wildfires are destroying larger and larger tracts of forest, and other causes of habitat degradation continue unabated.

All those impacts are held external to the business of individual Americans, but someone has to pay for them even if not in dollars. They are mostly tangential to AGW, however, which is what we're talking about here. Assuming you're actually interested in a dialogue...


From your insistence that the intent of a carbon tax is to "punish and force", I gather you're not a market-oriented conservative. Neither am I, but I recognize the role of price as a motivator of economic choice. If a carbon tax is imposed on producers at the mine, well or port of entry, rational producers will pass their increased cost on to consumers. Some consumers may choose simply to pay more for gasoline for their high-performance autos; some will trade in their 20-mpg vehicles for 40-mpg ones; some wil leave their cars at home and ride a bicycle to work. Nobody will be forced to make the choices they make, unless it's by the other choices they've made. And if paying $2.00 for a gallon of gas isn't punishment, why is paying $3.00?

On the supply side, some fossil-fuel producers will see their profits dwindle along with demand for their product, and decide to exit the business. While the supply of fossil fuels shrinks, alternative energy suppliers will respond to increased demand for their product by investing in more capacity. Entrepreneurs like Elon Musk will invest in R&D of energy storage technology, while selling more of their initial products to an expanded population of early adopters. Other innovators will take note of the increasing supply of small-scale wind and solar energy developments as well as electrical storage capacity, and invest in building "smart" micro-grid distribution systems. If history is a guide, the ramp-up of alternative energy sources and infrastructure will lead to increasing efficiencies, tending to bring prices down until they match what we're paying for fossil energy now. Mission accomplished, no-one still complaining except maybe the guys whose investments in fossil-fuel assets are stranded. Nobody forced them to buy those oil wells, though, and having to write them off as a loss isn't punishment, it's just life in the business world.


I have some sympathy for "black hole" concerns, but it's not that hard to ensure revenue neutrality. Consider James Hansen's "fee" (tax, duh) and dividend proposal, whereby all revenue from the tax is divided equally among all legal US residents and returned to them as a monthly check. A per-ton-equivalent carbon tax on producers keeps the revenue stream easy to audit, and the promise of a dividend guarantees that every voter is watching the watchers. In any case, when you pay your income taxes, you're relying on our existing institutions to discourage chicanery. How would a carbon tax be different?

A Border Tax Adustment on imported goods, tied to the producing country's carbon policy, would help US manufacturers stay competitive while promoting decarbonization internationally, especially when our domestic tax has demonstrated our own good faith. The revenue from the BTA, added to the dividend consumers received, would be an additional stimulus to the US economy.


Your use of that AGW-denier dog-whistle makes me suspect I've just wasted my time writing all that. You know there's a lopsided consensAnd tus of working climate scientist that the globe is warming, and the cause is anthropogenic, hence "AGW". The "C" is implied by deniers to stand for "Catastrophic", a word that you won't see in a peer-reviewed scientific article. Deniers use it to suggest that supporters of the consensus aren't objective, because catastrophe is in the eyes of the beholder. So is "Chaotic" to an extent, but is less emotionally loaded while still conveying the sense of "unexpected".

For example, the recent multi-year drought in New Mexico was within the high inter-annual variability of the regional moisture regime, but its ecological and economic effects were exacerbated by warming. A die-off of pinyon pines occurred, as happened during the otherwise comparable drought of the 1950s, but tree mortality was greater and more widespread because both transpiration and respiration are functions of temperature during the growing season, while the bark beetle population is a function of winter minimum temperatures. The diminished winter snows were merely a disappointment to skiers in Santa Fe, but a serious problem for pecan farmers in the Mesilla valley, who don't know how much longer they can rely on the reservoirs on the Rio Grande for irrigation water. Some of them had to let their trees die when they didn't get their full annual allotment, and they either planted a less thirsty and perhaps less profitable crop or sold their land for housing development. Were the farmers forced to make those choices? Are they being punished for their parent's choices of fifty years ago?

Maybe you're a "lukewarmer", a species of AGW-denier who may accept that the climate is warming and that humans are responsible, but you don't believe it will affect you or anyone you care about enough to be worth having to take the bus to work instead of driving. But even if you never personally experience the slightest inconvenience as the world warms, AGW already threatens millions of people with the loss of their homes, livelihoods and lives. They are the ones who will pay the costs of our business, whether or not they've enjoyed the benefits. Will you stand before the survivors of Typhoon Yolanda and tell them AGW isn't catastrophic, or that it was punishment for them for being poor?

Cool kids don't use "CAGW", Howard, only deniers. Which one are you?

By Mal Adapted (not verified) on 20 Dec 2015 #permalink

G*dd*mn it. William, be so good as to delete the copy of my previous comment inserted at the top of my last, please!

[Done; though it might have been funnier not to. Its a shame that the right wing, who are normally more economically literate than then left, fail so badly in the case of carbon tax -W]

By Mal Adapted (not verified) on 20 Dec 2015 #permalink

Market forces punish each other all the time. Your carbon tax is another bad idea that 1) won't ever get passed and 2) will only benefit mega corporations.

Mal: TLDR... except the last line. You CAGW euphemistic folks are a hoot. I'm a big-time denier if you need to use that as a pacifier. I don't understand the fear of embracing the reality of what you believe in. Then again, I could never understand the passive-aggressive mind because it never produces a meaningful result.

Your carbon tax .. will only benefit mega corporations

I guess that's why they complain about it so much.

[It is an odd complaint, I agree. And on the face of it, implausible. Howard, would you care to elaborate? -W]

By Chris O'Neill (not verified) on 20 Dec 2015 #permalink

Mal and David Benson -

Your examples here meant to show that the catastrophe is upon us are pathetic. An anecdote here and there and no clear long term trends established with any scientific rigor.

In my limited anecdotal experience of the water pollution industry, it was clear that small manufacturers and small gas station companies started closing rapidly due to costs associated with environmental remediation while the big businesses were able to survive. My deterministic hypothesis is that large companies are much better suited to compete bureaucratically than they are technologically. Of course, both aspects of business have economies of scale, however, dealing with the huge load of paperwork and the procurement of outside consultants and contractors to fix problems not relating to the core business is more easily handled at scale.

Gas station cleanups started bankrupting Mom and Pop gas stations all over California in the 1980's while Chevron, Shell, Mobil and Arco were untouched. In fact, many of the Mom and Pop stations who carried the corporate brands were left holding the environmental liability.

By instituting a state run cleanup fund, small businesses were able to keep operating, but much of the damage had already been done and the corporate takeover of retail gasoline was accomplished.

For electronics, we used to have thousands of small and and a handful of large manufacturers in the Bay Area. Now we have next to none in either category. Most of the large manufacturers were able to stay alive long enough to make it offshore while the small guys sunk under the weight of environmental cleanup costs and retooling costs to reduce the use of chlorinated solvents.

Currently, California is starting to regulate water pollution from nutrient and pesticide applications on farms. It's still early days, but there is no doubt in my mind that large corporate agribusiness will be in a better position to weather this storm.

This is one reason I am a proponent of socializing environmental costs. The other reason is that if left to market forces, only the absolute minimum will be done and the remaining powerful players will have a bigger influence on future regulation.

[You're mostly talking about regulatory burden. And yes, the vast weight of bureaucracy is indeed a burden, that larger companies have found easier to bear. But a carbon tax isn't a regulatory burden, so I think you're doing the wrong comparison: mom and pop businesses would be paying the tax when they bought fuel, just like large companies, but there's no extra paperwork. As to electronics; I'm doubtful you're looking at the right effect: I suspect that effects of scale matter, but are more to do with the changing nature of the products themselves -W]


I’m a big-time denier if you need to use that as a pacifier.

After COP21, I feel like the world has turned a corner. It's OK with me if you and Tom C are the last AGW-deniers. The rest of us are talking about solutions now. But thanks for letting us know we don't need to waste our time with you.

By Mal Adapted (not verified) on 21 Dec 2015 #permalink

Tom C:

Your examples here meant to show that the catastrophe is upon us are pathetic. An anecdote here and there and no clear long term trends established with any scientific rigor.

Heh. The people of Tacloban and the Mesilla valley aren't asking for rigor. It's the local and personal catastrophes that will get the attention of the disengaged, and drive a wedge between the Fox-News-watching dittoheads and the professionals AGW-deniers. Barstool ideologues like you and Howard don't have a role to play.

By Mal Adapted (not verified) on 21 Dec 2015 #permalink

Tom C @ #20 --- There is also a recently reported photographic study of Greenland glacier terminations since 1900 CE. The retreat became much more pronounced after 1950 CE.

So already the sea level marches upwards. That will be hard for many.

[If you're interested in SLR, why would you look at a complicated proxy like glacier terminations? Why not just look at SL? -W]

By David B. Benson (not verified) on 21 Dec 2015 #permalink

Fair enough William. Beyond paying the tax will be the technological changes that are required to reduce the tax burden to maintain current productivity with less carbon footprint. Here I think mega super corp has an advantage over their mid-sized and smaller competitors.

Mal: You should consider moving beyond the high school clique MO. I am a big believer in mitigation, starting with the deployment of currently available advanced air pollution controls to reduce short-lived GHGs: NOx, SOx, VOCs, Ozone (and precursors), BC, OC, PM (and precursors). I believe the west needs to take the lead, then help finance and provide these techno fixes to India and China. One way to do this is to switch to CH4 for the next 20 years. At the same time, the west needs to be pushing research advancement into electrical storage, advanced nuke that burns up the waste in a self-stabilizing reactor.

For myself, I have taken some of the atmospheric science I have learned reading climate papers (recommended here and elsewhere over the past 10-years) and have developed and patented several air pollution control methods that eliminate the short term GHGs and at the same time reducing energy consumption by 75%. You would be surprised how difficult it is to sell these systems without appropriate regulatory pressure, absent tax incentives and to customers who do not wish to waken the regulatory awareness of what the current BACT is doing. Fortunately, we figured out a way to make a product from the wastes we capture and concentrate and are finally getting greater interest.

What are you doing besides making comments on blogs?