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Six Degrees: Choosing Our Future

Updated on February 3, 2016

This Hub is the final part of a larger series examining in detail Mark Lynas's 2008 classic, Six Degrees. The book looks at what science says about the consequences of various levels of climate change, from one degree of warming to the six degrees of the title. The 'main article' describes and evaluates the book as a whole, chapter by chapter.

Each chapter also has a summary Hub, which gives Lynas's points in tabular form for easy reference. Because the science has been rapidly advancing, and continues to do so, I will provide periodic updates, usually in these 'summary' Hubs. (Note: the first update has been posted; see below.)

The present Hub is the summary for the crucial final chapter, Choosing Our Future. It's about options: what can humans do to improve our chances of a reasonably prosperous and secure future?

Lynas, always a realist, gives unblinking assessments of our choices--but still finds possibilities for hope.

Four possible futures, viewed through the lens of soil moisture (in millimeters.)  Figure 12.23, AR5 final draft, page 12-147.  Caution downloading--large file!
Four possible futures, viewed through the lens of soil moisture (in millimeters.) Figure 12.23, AR5 final draft, page 12-147. Caution downloading--large file! | Source

Note--Update, 12/14/13: Making realistic choices about our future is far more urgent than most of us realize. As shown in the table below, Lynas assessed the available time for emissions reductions as being roughly "a decade." That time frame seems seems as realistic as it is dismaying, according to the recently released draft of the International Panel on Climate Change's Fifth Assessment Report. (The "IPCC AR5," for short.)

Given this urgency, I'm placing this update before the summary table, in order to highlight it as much as I can.

A really excellent summary of the AR5 was made by Canadian blogger Steve Easterbrook. It can be found via the sidebar link at the right. In this update I will focus on one implication of AR5, as highlighted by Mr. Easterbrook's comments. It is his point #8:

To stay below 2°C of warming, most fossil fuels must stay buried in the ground.

That is a radical idea; rarely, if ever, have humans collectively deliberately renounced a wealth-creating resource available for the exploitation--let alone one which is central to the existing economy. But that is what the science says.

Two degrees of warming is the consensus 'danger level.' Partly that reflects the fact that costs begin rapidly to escalate beyond that amount of warming; partly it reflects the possibility (discussed in considerable detail by Mr. Lynas) that that may be enough warming to trigger climate feedbacks that would make yet more warming inevitable even without additional greenhouse gas emissions.

Consider the graph below:

Figure SPM.10, AR5, as given by Easterbrook and processed for clarity by author.
Figure SPM.10, AR5, as given by Easterbrook and processed for clarity by author.

Its implications are probably not clear for most of us, just at a glance. Here's Mr. Easterbrook's summation:

...whichever experiment we carry out, the results tend to lie on a straight line on this graph. You do get a slightly different slope in one experiment, the “1%/yr” experiment, where only CO2 rises, and much more slowly than it has over the last few decades. All the more realistic scenarios lie in the orange band, and all have about the same slope.

This linear relationship is a useful insight, because it means that for any target ceiling for temperature rise (e.g. the UN’s commitment to not allow warming to rise more than 2°C above pre-industrial levels), we can easily determine a cumulative emissions budget that corresponds to that temperature.

And what is the "cumulative emissions budget" for 2 degrees?

AR5 gives the budget in terms of probabilities, since there are still too many uncertainties for complete precision. To have one chance in three of avoiding 2 C, we must not emit more than 880 gigatons of carbon to the atmosphere. If that seems a bit risky--as it seems to this writer!--then we can flip the odds to 2 chance in three by holding emissions to just 800 gigatons.

The trouble is, we've already emitted 500 gigatons since the beginning of the Industrial Revolution, leaving a budget of only 300 gigatons. Unfortunately, proven reserves amount to three times that amount, amply validating Lynas' 2008 assessment that peak oil will not save us.

Mr. Easterbrook summarizes this well, if not encouragingly:

There is no political or economic system anywhere in the world currently that can persuade an energy company to leave a valuable fossil fuel resource untapped. There is no government in the world that has demonstrated the ability to forgo the economic wealth from natural resource extraction, for the good of the planet as a whole. We’re lacking both the political will and the political institutions to achieve this. Finding a way to achieve this presents us with a challenge far bigger than we ever imagined.

Nevertheless, there are options, and even some reasons for hope. Some are given by Mr. Lynas; others will be subject for future updates. Read on, and 'stay tuned.'

Stabilization wedges (original version.)
Stabilization wedges (original version.) | Source

Summary Table for "Choosing Our Future"

Intro--p. 269
It is probably too late for "the Alpine glaciers, the Nebraska grazing lands, and the resplendent coral reefs." Perhaps too late for the Arctic ice cap. Possibly (by the Pliocene analogy) it is too late too avoid 3 C warming--and an eventual 25 meters of sea level rise. "My conclusion in this book... is that we have less than a decade remaining to peak and begin cutting global emissions. This is an urgent timetable, but not an impossible one. It seems to me that the dire situation that we find ourselves in argues no for fatalism, but for radicalism."
Knowing What we Don't Know--p. 271
Uncertainties affecting the prediction of climate change and its speed: future emissions, climate sensitivity, aerosols, characteristic time scales.
Setting A Target--p. 275
Why avoid 2 C warming? Because Amazonian collapse--considered possible at such a level--could yield 250 ppm CO2, and an additional 1.5 C warming. (Presto! We'd be in the 4 C world.) Permafrost melt could then do likewise. (Hey! 5 C!) Would that perhaps then lead to methane hydrate release and a 6 C 'extinctron' world? "Contraction and convergence" is explained on p. 281. In essence, the historic emitters would cut emissions much more heavily in proportion to countries in the developing world. Overall emissions would contract and per capita emissions would converge Carbon trading would allow for flexibility and economic efficiency. "The poor would get equality, while all (including the rich) would get survival."
A Reality Check--p. 282.
Kicking fossil fuels is hard, and for good reason--they provide enormous benefits and are intertwined with modern life in innumerable ways.
States of Denial--p. 286.
The psychology of climate denialism (mostly as phenomenon, not as an organized ideology.) " could argue that the whole economic system of modern Western society is founded on denial, in particular the denial of resource limitations. Schoolchildren are taught--and Nobel Prize-winning economics professors apparently still believe--that Earth-provided resources, from iron ore to fisheries, come into the category of "free goods," appearing as if by magic at the start of the economic process."
Peak Oil, p. 290.
Rarity of oil fields discussed. However: "The picture is complicated, but it seems unlikely that peak oil will save us from global warming. Even if cheap oil does indeed begin to run out sooner rather than later, the world is a long way from running short of hydrocarbons. More's the pity."
Knocking In Wedges, p. 293.
Useful discussion of Socolow and Pacala's 'Stabilization Wedges' concept. In it, each technology/technique for reducing emissions by one billion tonnes of carbon by 2055 counts as a 'wedge.' As of writing '6 Degrees,' seven wedges were needed to stabilize emissions by 2055. All represent existing technologies or practices. (See list of wedges below.)

Emissions Stabilization Wedges

  1. Halve vehicle emissions (double fuel efficiency or halve miles travelled.)
  2. Energy efficient buildings. (Lynas doesn't say how many are needed.)
  3. Less carbon intensive electrical generation. (Again, no number is specified.)
  4. Quadruple gas-fired electrical generation, displacing coal-fired.
  5. Add 700 GW of nuclear capacity displacing coal.
  6. CCS at 800 1-GW coal plants.
  7. Deploy 2 TW of wind power. (50x increase from writing of '6 Degrees.)
  8. Deploy solar to 700x then-level.
  9. "Massive" reforestation and an end to tropical clear-cutting.

Update--10/23/14: Renewable Energy Capacity

For the first time, one stabilization wedge worth of wind power has been projected as a realistic possibility. The Global Wind Energy Council released a report showing the world reaching an installed generation capacity of 2 Terawatts in 2030. Of course, that number is an estimate, depending upon policy choices made around the world. But even their 'moderate scenario' had capacity exceeding that mark by 2040.

That's good news--but still considerably short of what is needed to avoid the 2 C world. The 2 TW mark is just one stabilization wedge; we needed 7, as of the writing of Six Degrees.

Meanwhile in the observed world, global wind capacity reached 318 Gigawatts at the end of 2013, with a further 45 expected in the current year, for an expected 2014 cumulative total of 363 GW.

2014-15 Upate: 2/3/16

For 2014, cumulative global wind capacity reached roughly 370 GW, exceeding the projected results reported just above. And early reports for 2015 indicated that approximately 62 GW more were added in that year, a record-breaking performance which would take installed wind capacity to over 430 GW. China alone accounted for 29 GW of that total.

Clearly, such results auger well for a continuing rapid increase in wind capacity, especially in the context of climate change policy following on from the successful Paris Treaty. But we still need exponential growth to continue for some time if we are to reach 'stabilization wedge' levels.

Gobal cumulative wind capacity, to 2014
Gobal cumulative wind capacity, to 2014 | Source

...and back to 2013!

The 2013 GWEC report also noted expected carbon emissions savings:

In cumulative terms, the IEA New Policies scenario has wind power saving 7 billion tonnes by 2020, and over 19 [billion] tonnes by 2030. The GWEO Moderate scenario results in over 7.5 billion tonnes in cumulative savings by 2020, and 24.1 billion tonnes of CO2 savings by 2030. The GWEO Advanced scenario yields cumulative CO2 savings of nearly 7.9 billion tonnes by 2020, and 28.6 billion tones by 2030.

On the solar side, the prestigious International Energy Agency reported that cumulative solar installations had reached 140 GW at the end of 2013. That puts the two categories together at something like a quarter of one stabilization wedge today. However, there is some additional good news in the report, which is that the growth curve has not [yet] begun to flatten from its roughly exponential trend. That means future growth will be much faster than in the past--though for how long that continues to be true remains unknown.



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    • Doc Snow profile imageAUTHOR

      Doc Snow 

      4 years ago from Camden, South Carolina

      Yes, if we reduced population, each person could use more energy, certainly. But hard limits still exist to how much energy can be accessed and used. As long as we are growing, we will be approaching those limits. Therefore at some point we need to transition to a ZEG economy. The best illustration would be to read the first article I linked.

      But essentially, it's just a matter of what those limits are, and when we would hit them--not a matter of 'if they exist.' They do. The linked pieces offer some good illustrative math to show that even granting quite fantastically optimistic premises, we hit growth limits sooner than one might perhaps think. Ultimately, the only way human society can keep using more and more energy is to expand off-planet. Though (spoiler alert!) even in that case, we hit limits that are surprisingly short in historical terms.

      Here's a couple of the illustrative cases from the 'energy' post I linked. In another 2450 years--a long time hence, sure, but remember that 2450 years *ago* still only gets us back to the year Alexander the Great smashed the Persian Empire--the somewhat conservative annual growth rate of 2.3% would see humanity consuming the equivalent of *the total energy output of all suns in the galaxy*.

      Less fantastically, just 275 years would see us using the equivalent of the total solar energy intercepted by all land everywhere (with a 20% conversion efficiency.)

      Well, what, you might ask, would happen if we cut the Earth's population by a factor of ten? That should help, shouldn't it? Well, yes. It would give us another century of expansion. But it doesn't change the ultimate result.

      In reality, of course, the constraints are considerably more stringent. So I think we need to be thinking about this now--it's going to take quite a while to figure out...

    • Jay C OBrien profile image

      Jay C OBrien 

      4 years ago from Houston, TX USA

      ZEG, Zero Energy Growth? If we had far less population (1 billion worldwide? 100 million?) each person could consume More energy and still not harm the environment.

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      4 years ago from Camden, South Carolina

      You are more than welcome, Jay.

      I don't know about the relative costs of 'space umbrella' versus 'acid spray' options. I'm sure there are some estimates that have been done, but I'm also sure that the numbers can't be very firm, given that both notions are pretty much at a conceptual stage.

      I'm working from memory here, but to the best of my recollection, the 'acid spray' strategy shouldn't directly affect the ozone layer. (Indirectly, I think it's possible that using radiation management to ameliorate warming might have some indirect effect, because ozone depletion occurs at low temperatures--that's why ozone holes develop in the winter at the poles--and rad/man would imply that we failed to address carbon emissions. That affects ozone because one of the under-appreciated consequences of greenhouse warming of the lower atmosphere is cooling of the stratosphere--something we already observe.)

      I agree with you on the population issue. But it will, I think, also be necessary to create economic structures that, at a minimum, do not assume or depend upon, continual growth in energy use. Even if we could create energy at will, at some point it becomes impossible to radiate enough of it away from the planet to maintain equilibrium:

      So at some point, we *must* transition to a ZEG ('zero-energy-growth') economy.

      The same blogger looks at the possibilities for continued economic growth in a ZEG economy:

    • Jay C OBrien profile image

      Jay C OBrien 

      4 years ago from Houston, TX USA

      Thank you for the link. Would a space umbrella to block sunlight be better that spraying sulfuric acid into the air? What would be the relative cost? Ozone concerns? Long term I am in favor of decreasing consumption and pollution by people. That circles back to population reduction.

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      4 years ago from Camden, South Carolina

      Hi, Jay. Yes, I think vasectomies are a valuable option, and a smaller global population would definitely be more sustainable. It's not a silver bullet, though, as the will to use them is important! So it goes along with a suite of measures, like empowering and educating girls and women, and implementing cost-effective public health systems, to make small families desirable.

      As to the 'radiation management' strategy you mention, yes, it is a (proposed) 'thing'. The substance proposed is sulfuric acid, in extremely fine droplets. (It would be injected high into the stratosphere, and so would react before descending to lower levels where it could cause acid rain.) Most people feel it's a pretty desperate strategy, though, because it's expensive and potentially politically destabilizing--which is a nice way of saying that, since the benefits and costs of it wouldn't apply equally to all nations, it might cause a war.

      The term of art is "geoengineering." Wikipedia has a reasonable summary, if you are interested in more:

    • Jay C OBrien profile image

      Jay C OBrien 

      4 years ago from Houston, TX USA

      Population control by vasectomies seems entirely plausible. We could maintain the high-tech society we desire, but with fewer people (100 million total population?). Vasectomies are fast, cheap and reliable. I got one before I had children.

      I heard of a solution to spray a substance into the atmosphere at high altitude to mimic a volcanic eruption. The theory is, the substance would reflect sunlight and lower temperature. What is the science on this theory?

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      7 years ago from Camden, South Carolina

      Thanks for the info--and a chuckle!

      Yes, I've seen some info on the thorium reactors. My fear, though, is that development just won't be fast enough, relative to the speed of the crisis.

    • profile image

      P. Orin Zack 

      7 years ago

      I think the StarShip Enterprise must have been flying through my head when I wrote that. I meant thorium. (They use dilithium crystals, if you recall.) Anyway, there's a wealth of information about thorium reactors, including one design that was proposed by a teenager:

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      7 years ago from Camden, South Carolina

      Good to hear from you, Orin!

      Can you provide more information on these lithium-based designs? I had no luck looking, though I did find this:

      Seems as if there was some confusion with this proposed unit:

    • profile image

      P. Orin Zack 

      7 years ago

      When people speak about nuclear power plants, they usually mean the kind of mega-size plants that have caused so much trouble in the past, the spent fuel from which is an even longer-term problem. There is an alternative, though, in smaller-scale lithium-fueled generators that convert heat directly to electricity, rather than using it to heat water so the steam can spin a turbine. The lithium design does not need water cooling, and in an emergency situation the fuel can be dumped into a holding tank where it cools and becomes relatively harmless. Our problems with nuclear power plants stems from an early design that used fuel that was friendly towards making weapons; lithium does not have that problem. I welcome a lithium-based future.

    • Doc Snow profile imageAUTHOR

      Doc Snow 

      7 years ago from Camden, South Carolina

      Thanks for asking! CCS is "carbon capture and sequestration," in which the carbon is scrubbed from the exhaust of the coal-fired boiler, and then pumped underground. (There's a Canadian plant doing this as a demo project, and in that case the carbon dioxide is being pumped down into an oil field to extract the last squeezings of petroleum, which somewhat counteracts the sequestering of the carbon.)

      Do I personally agree with increasing nuclear power to combat carbon pollution of the atmosphere? Sort of--that is, I think it would be much safer than continuing with fossil fuels as we have been doing. And I'm kind of sorry that Germany is closing down their nuclear capacity, post-Fukushima; were that not the case, their emissions would be falling with the aggressive adoption of renewable energy, not rising slightly, which was the case last year.

      But I don't think that there is any realistic prospect that anything like enough nuclear plants will be built. Financing them is already a big challenge, and while the risk of accidents is relatively low, when they do happen they can be absolutely devastating, as recent history shows. And as the price of renewables (especially solar) continues to plummet, nuclear energy will be increasingly uneconomical.

      Moreover, I'm not sure that building a large nuclear fleet at the global level is even reasonably feasible--I'm skeptical that there are enough skilled personnel to do the building on the scale that would be needed. Water is another big concern--like any thermal power generation (such as coal- or oil-fired, or even bio-mass-fired plants) nuclear uses water for cooling--and uses it in really massive quantities.

      As climate change continues, certain regions--among them northern China, the western US, and the Mediterranean basin--are likely to become increasingly water-stressed. That means that any thermal power plant could be increasingly hobbled by limited cooling capacity. This has already been an operational problem in some instances, in both the US and Europe:

      All that said, Mark Lynas is emphatically in favor of nuclear power to help solve climate change. He rightfully is concerned about the scale of the mitigation actions required, and our woefully inadequate response so far.

      As I am able to update these supplemental Hubs, I'll have more on this issue here.

    • i scribble profile image

      i scribble 

      7 years ago

      Excuse me, but what the heck is 'CCS at 800 1-GW coal plants'? Do you agree that increasing nuclear power is a good idea to reduce global warming? Sounds like jumping from the frying pan into the fire to me. But it's an interesting stabilization plan.


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