The shape of things to come.. CO2 at 800ppm by 2100?

How alarming!

An interesting article by William D. Nordhaus from Yale University in the most recent Proceedings of the National Academy of Science (PNAS). The same PNAS who in the spirit of true debate deniers such as Jo Nova like now claim to be practising ‘witch craft“.

Titled “Economic aspects of global warming in a post-Copenhagen environment“, Nordhaus’ examines some of the most likely outcomes for the planet following the failure of COP15:

“The world is far along in what Roger Revelle and Hans Suess called “our great geophysical experiment”. The failure of nations in Copenhagen in December 2009 to reach a concrete agreement to extend and broaden the Kyoto Protocol raises the prospect that attempts to limit atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases (GHGs), with the resulting global temperature increases, may prove politically difficult. This study reports improved estimates of the likely trajectories of global output, GHG emissions…”

Putting a price on carbon is a vital strategy, and as part of his modelling, Nordhaus calculates a “true price” for coal:

“The model also calculates the path of carbon prices necessary to keep the increase in global mean temperature to 2 °C or less in an efficient manner. The carbon price for 2010 associated with that goal is estimated to be $59 per ton (at 2005 prices), compared with an effective global average price today of around $5 per ton. However, it is unlikely that the Copenhagen temperature goal will be attained even if countries meet their ambitious stated objectives under the Copenhagen Accord…”

As many of us know, the “Accord” was a face-saving exercise that does nothing to limit CO2 emissions. Thus, some of the conclusions of the paper are gloomy:

“The reality behind the accord is not encouraging. To begin with, even if the high-income countries fulfilled their commitments, these would probably not achieve anything close to the 2 °C target, as is shown below. Meanwhile, progress on reaching a more binding agreement has been glacial at best. At present, a global agreement is waiting for the United States to take credible legislated steps. Continued delay in adoption of climate change policies by the United States may lead to a domino effect in which other countries follow the US inaction…”

I think we know where we can place the blame for inaction.

The RICE model: basis for criticism?

Nordhaus’ used a model to calculate possible outcomes:

The RICE model views climate change in the framework of economic growth theory. In a standard neoclassical optimal growth model known as the Ramsey model, society invests in capital goods, thereby reducing consumption today so as to increase consumption in the future. The RICE model modifies the Ramsey model to include climate investments…

..The model divides the world into 12 regions. Some are large countries such as the United States or China; others are large multicountry regions such as the European Union or Latin America. Each region is assumed to have a well-defined set of preferences, represented by a social welfare function, and to optimize its consumption, GHG policies, and investment over time.”

The bulk of the paper is a fascinating discussion of the model developed by Nordhaus and the most likely outcomes of different policies designed to reduce CO2 and greenhouse gas (GHG) emissions.

The “baseline” projection in which we do nothing – the one the world is actually following at present – may see CO2 reach 800 parts per million (ppm) by centuries end.

You’ll note my little widget there on the right states where at 392 ppm as of May 2010. Over the last century that has seen a rise in temperatures by 1 degrees and a 5% increase in moisture, the effects of which are noticeable already.

Of course climate change sceptics deny the validity of any computer models (my response to that is here).

The point of models is to evaluate possible outcomes, not make exact predictions such as “sea levels will rise by 10cm by June 2035”.

No scientist has ever made such a claim, which makes the accusation “models are useless” chanted by the denial industry both facile and disingenuous.

Models are designed to help us evaluate risk: there isn’t a major industry that does not do some form of modelling of future outcomes.

Should we really be listening to people who want us to be blind to the future?

My take away from the paper by Nordhaus: the longer we delay, the greater the risk.


One thought on “The shape of things to come.. CO2 at 800ppm by 2100?

  1. John R T says:

    ¨…by centuries [the century´s] end.

    You’ll note my little widget there on the right states where [we’re] at 392 ppm ¨

    Welcome back; I trust the busy season has been productive and profitable.

    I will be happy to be a first reader.

    Your blog came to my attention recently; I try to keep up with developments in atmospherics. re ´Tools,´ ´Research a climate commentators expertise:´ you will find me at Citizen Audit. I was delighted to be involved in the crowd source audit. I garden and read, after retiring from decades in environmental compliance.

    Hansen found a willing accomplice in my fellow Southerner, Al Gore. Freeman Dyson pegged them both, over a year ago. Stewart Brand and others have identified both problems with AGW and with IPCC-led mis-direction.

    I hope to find here something worth addressing.

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