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Climate Change: Looking at 400 ppm and Beyond

David Hone's picture
Chief Climate Change Adviser Shell International Ltd.

David Hone serves as the Chief Climate Change Advisor for Royal Dutch Shell. He combines his work with his responsibilities as a board member of the International Emissions Trading Association...

  • Member since 2018
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  • May 18, 2013

The first full day of 400+ ppm CO2 as recorded at Mauna Loa in Hawaii last week produced an outpouring of sentiment and grief from many, but the news has seemingly passed. Unfortunately, the arrival of such a day had become inevitable. Since the early days of the Keeling Curve at 315 ppm when it became clearly apparent that anthropogenic CO2 emissions were accumulating in the atmosphere, we have counting up the ppm to this day.

Despite an early clear warning to the Johnson Administration at 321 ppm, it wasn’t long before there was a brief worry about global cooling. Then, with atmospheric chemistry growing as a discipline (probably on the back of concerns about a cold war nuclear winter), we were distracted at 332 ppm by the first major anthropogenic global concern, the hole in the ozone layer. But with a treaty negotiated and ratification underway by 349 ppm (only 17 ppm to sort that one out), it didn’t take long for the science community to remember that another big issue was lurking in the shadows.

At 352 ppm and nearly 40 ppm on from the start of the Keeling Curve, James Hansen stated to a US Congressional Committee that;

  • The earth is warmer in 1988 than at any time in the history of instrumental measurements.
  • Global warming is now large enough that we can scribe with a high degree of confidence a cause and effect relationship to the greenhouse affect.
  • Computer simulations indicate that the greenhouse effect is already large enough to begin to effect the probability of extreme events such as summer heat waves.

But it was another 13 ppm before the Kyoto Protocol was adopted by parties to the UNFCCC and 14 ppm more before it was finally ratified. 21 ppm later and it is a shadow of its former self, but at least with the legacy of some beginnings of a global carbon market. However, it is trading close to zero!! In the interim there was a valiant attempt at a new global deal, but even that was 12 ppm ago.

400 ppm and climbing


Our goal to be avoided, 450 ppm, is now feeling a bit close for comfort, given we are already at 400 ppm and 300 ppm was only passed under the previous British monarch.

Not to worry, it should only be another 15 ppm before a new global deal comes into force, although after more than 3ppm of discussion, the negotiations don’t really seem to have started. So we wait again, hopeful that someone has got a plan.

But a lot can happen in 50 ppm if we try hard and we really want something!! After all, the first world wide web page was posted only 43 ppm ago!

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Tim Havel's picture
Tim Havel on May 18, 2013

Great article!

Schalk Cloete's picture
Schalk Cloete on May 18, 2013

I’m afraid that our decision-making systems make any meaningful climate change action pretty much impossible before climate change actually starts having a direct, consistent and clearly attributable negative impact on the lives of a large portion of the electorate. It will probably take many more ppm for this to happen.

In the meantime, the best we can do is to prepare for very rapid changes to our energy systems when climate change finally becomes real to the average man on the street (and hope that the warnings about positive feedbacks are overly-pessimistic). Perhaps most importantly, we really need to make sure that highly efficient second generation CO2 capture technology is commercially available by that time. The capacity for rapid deployment and retrofitting of CCS could turn out to be vital in such a scenario. 

Robert Bernal's picture
Robert Bernal on May 18, 2013

I can’t believe this day has already come. I havn’t seen it on the news, not under “science news”, not under “google news” and not even under a “global warming” search! I was about to question this very fact until I searched “CO2 ppm”. Now, I see it.

If solar grows at a 22% rate (which seems to be about half of its recent), by the time we reach 450 ppm, about 13,000 GW  of capacity will have been installed (based upon 90GW as of late 2012) which is FAR short of the 256,000GW or so needed to account for like “everything”. However, with a continued such growth rate, that will happen just 15 years later, or forty years from now. Unfortunately (per my crude projecting techniques), the CO2 ppm will have increased to over 500!

Now, I would hope that (by then, and to prove me wrong!) there would be machines mass produced in the likeness of solar and batteries that convert the excess CO2 into calcium carbonate AND that some other form of clean energy such as LFTR nuclear paralleled at least this expected solar growth. But I question the nuclear idea almost as much as “everyone else”, because it is not 100% proliferation proof.

Therefore we must do whatever we can to increase the solar growth rate, first by continuing subsidies ONLY for the most efficiently made solar and for the continued improvements in the machine automation required. A massive increase of installation jobs shall be the reward, long enough to ease humanity from the pain, and to learn how to adapt to whatever peaceful social structure required, caused from lots of other jobs displaced by machine.

Same for batteries (such as the LiFePO4 or better) and carbon capture catalyst. Perhaps, in lessor amount of time, exponential growth will finally become manifest in these essential components. In the meantime, humanity could use “paint everything white” tactics as a cheap mitigation.

For those that think we do not have the material resources, I must add “There ARE enough resources to build many billions of electric cars” and the hundreds of thousands of square miles of solar needed. See 

I K's picture
I K on May 20, 2013

In the last hour I just put on 0.5kg of mass increasing my weight by 0.7%, if this rate continues in just 365 days I shall be bigger than jupiter

I K's picture
I K on May 20, 2013

Why did you feel the need to base your pretty graph at 300ppm and not start it at 0ppm?

Do you fell it necessary to make it look like we are now some 5x higher than at the beginning of your pretty graph rather than 400/315 = 27% higher?

Do things like that aid or abate reasonable debates?

I K's picture
I K on May 20, 2013

Which internet expert did you get those numbers from?

256TW of PV is far in excess of anything we would ever need for even 10B people living like Americans do today.

It’s also interesting to note, that that much solar would require you to first build and install 2,000 billion, yes TWO THOUSAND BILLION times 128 watt panels. And then you need to install 20 billion, yes 20 billion times 128 watt panels every year in perpetuity to maintain its output and that is assuming an overall degrade/damage/replace rate of just 1%

How “green” or even feasible is that?

Contrary to popular fantasy once you install a PV panel its not a happily ever after fairytale there is a lot more to it.

Paul O's picture
Paul O on May 20, 2013

Most renewables enthusiasts, refuse to acknowledge that Solar Panels fade over time and eventually die.  Worse, solar panels cease to be of  much practical use long before they completely die, hence the need to continually replace dead and dud panels..

Enthusiasts also refuse to acknowledge that solar panels need to be cleaned regularly, and  they produce no power at all at night and very little at dusk or dawn (capacity factor woes). The most horrible myopia of enthusiasts is that we have no good and affordable way to store sunlight. I certainly hope for better Lithium technologies in batteries, but seriously, do we even have enough Lithium mines to cover what we’ll need? Are we going to recycle the toxic metals/chemicals involved in such massive battery making? I would think that Aluminium Air batteries are better for the task at hand,

Lest solar enthusiasts unleash their wrath at me for stating the obvious (above), I want to state that in a recent debate with you (IK), I was persuaded by you of  possibility of a practical Global Solar grid as a solution.

I’ve said it before and will repeat it here. We need to look very well at technologies for remediating AGW by geo-engineering. We also need to learn to adapt to the unpleasant effects of GW, we are not going to avoid GW any time soon, so we have to be able to adapt to it or ameliorate it.

Finally if the Earth does end up melting away, The Anti-Nuclear Renewables and GW Enthusiasts will share a large blame for it, because by their irrational opposition to nuclear power, they are practically hobbling us in our effectiveness inm trying to replace FFs.

I K's picture
I K on May 20, 2013

A global grid powered by distributed solar is a distant possibility but degrade&damage rates need to fall.

Perhaps in the region of 300 billion dollars has been spent on solar worldwide. That may have been enough to build 100 reactors to kick start the nuclear industry to produce subsequent reactor at 2 dollars a watt.

Also I think your negative predictions of global warming are probably too dire. Anyway over half of what the world burns does not stay in the air so if fossil fuel consumption is reduced by half co2 concentration should stabilise or even fall slightly.

So the challenge isn’t the near impossible task of stopping FF burn completely but the far more manageable task of halving current burn.

Offshore wind also offers potential with a many nation grid and its fairly high 40-50% CFs but the near and medium term is simply fossil fuels nuclear and hydro. 

David Hone's picture
David Hone on May 20, 2013

Dear IK,

I think we all know that the base line in this case is much closer to 300 ppm than 0 ppm.


Robert Bernal's picture
Robert Bernal on May 20, 2013

Unlike most people, I actually did the research myself. It’s about as easy as pressing 90 x 1.22 and then hitting “=” forty times. Yes, that’s how exponential growth works.

Robert Bernal's picture
Robert Bernal on May 20, 2013

Are we so stupid that we won’t even recycle (what an insult)…Anyways, Earth’s crust contains more lithium than we’ll ever need, and the ocean has enough to power something like one hundred trillion Tesla’s… We only need 1%! Sure, the price will double, but then extraction will go up by an order of magnitude… and so on.

You see, there ARE NO physical limitations, just made up ones… as long we hurry up and DEMAND that industrialism (and machine automation) trumps over life sucking regulations! We already know how to mine things without destroying the planet, but if we don’t, then we will destroy the planet in our decline (by burning the Rain forest, etc).

FF’s will continue to rise in price and push the limits of XSCO2, so they must be used to build this solar whether you like it or not because I like the idea of the jobs… unlimited install (and cleaning) jobs that may actually enable humanity to be able to afford the next step… focusing on all the real solutions and endeavors

I do NOT like your idea of geoengineering unless it is merely “painting everything white” because we can not risk causing a more serious chain reaction (and it ain’t right to put ‘shade thingys’ in outer space as some idiots propose). At least with GW, all we have to do is use the same kind of machine automation that WILL build the panels and build devices that sequester the XSCO2 back into limestone??? or better yet, use part of the profits from all those solar jobs to mandate organic soils (because they sequester CO2 much better than the farming practices used today).

I like the nuclear idea only IF it is 100% proliferation proof, otherwise, it might take away momentum from the machine automation of solar. Preferably, I want both LFTR and solar!

A complete doubling of co2 will cause an additional radiative forcing of 3.6 watts/ sq meter which can only raise the temps 1C… Better hope the feedbacks don’t kick in before that time! Because that’s plenty of time for solar to do EXACTLY what I want. I will boast a little. Even if solar’s growth rate DROPS to 22%, it will still have covered four hundreds thousand sq mi by the year 2053 (assuming 15% eff). The math is: 90GW installed as of late 2012 x 1.22 = (and so on for forty times). This adds up to 256,000GW which is needed to power the world at that time assuming 23% capacity factor and a LiFePO4 battery eff of 95%. I call this the ‘upper limit’ because that is just under 1% of Earth’s land space. So I imagine that the dark color (if they are still made darker ‘than they need to be’) will cause heating… but I know that is trivial compared to the effects of the excess GHG’s emitted without this amount.

I K's picture
I K on May 21, 2013

Try 90 x 1.22^40 it will save you hitting = forty times90GW growing at 22% a year for 40 years will equal 256TW if you can keep that rate up for 40 years which you cannot

Robert Bernal's picture
Robert Bernal on May 21, 2013

Thanks. I forgot it’s the same thing.

Anyways, I do get a little carried away with the idea of solar’s growth. I know it won’t continue its 78% or even 33% rate for long, however, I ‘think’ that advanced machine automation is still in its developmental stage, and that the price of oil will go up. I believe the subsidy for solar should instead go for developing this automation so that it can be at least as cheap as it is now… with subsidies.

What gets me is all that LFTR and fast reactor research has been canceled. T think that makes other people afraid of it even more.

Pieter Siegers's picture
Pieter Siegers on May 24, 2013

You both forget to mix energy efficiency and emerging energy storage techniques like supercapacitors as well as upcoming innovation – if only we could shoot the 1% into space that fights those welcome changes!

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