Bryan Lawrence : Stern Facts

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Stern Facts

Like William Connolley I doubt I'll ever read the whole thing, but it's intriguing to wade through the 27 page executive summary at least.

The Bad News

Under a BAU scenario, the stock of greenhouse gases could more than treble by the end of the century, giving at least a 50% risk of exceeding 5?C global average temperature change during the following decades. This would take humans into unknown territory. An illustration of the scale of such an increase is that we are now only around 5?C warmer than in the last ice age.

Well, that 5 degree figures is a bit hard to fathom (although I think he uses that with respect to the period 2100-2200), but the comparison with the scale to the last ice age is rather a good one. Even if the real number might be 2 to 3 degrees C, it puts things in perspective somewhat - even those of us who may claim to be professionals still have to get a grip on the emotional reaction that a few degrees C isn't that much really. Put like that, it obviously is!

The disaster list is pretty awesome:

  • Water supply problems (Melting glaciers: initially a flood risk, lead to a fall in water availability, not to mention changes in water availability associated with changing weather patterns) ...

  • Declining crop yields (particularly in the higher range of predictions)

  • Death rates from malnutrition, heat stress and vector borne diseases (malaria dengue fever etc) increase ...

  • Rising sea levels ... threatening the homes of 1 in 20 people!

  • Ecosystem melt down (15-40% of species for only a 2C increase!) (Plus ocean acidification with unquantifiable impact on fish stocks)


Impacts on this scale could spill over national borders, exacerbating the damage further. Rising sea levels and other climate-driven changes could drive millions of people to migrate ...rise in sea levels, which is a possibility by the end of the century... Climate-related shocks have sparked violent conflict in the past, and conflict is a serious risk in areas such as West Africa, the Nile Basin and Central Asia.

But maybe this will get more attention in the City:

At higher temperatures, developed economies face a growing risk of large-scale shocks - for example, the rising costs of extreme weather events could affect global financial markets through higher and more volatile costs of insurance.

I find all the arguments about changes in GDP difficult to follow, possibly because one never really knows where the baseline is (unless one is an economist), but this seems a pretty straight forward statement:

In summary, analyses that take into account the full ranges of both impacts and possible outcomes - that is, that employ the basic economics of risk - suggest that BAU climate change will reduce welfare by an amount equivalent to a reduction in consumption per head of between 5 and 20%. Taking account of the increasing scientific evidence of greater risks, of aversion to the possibilities of catastrophe, and of a broader approach to the consequences than implied by narrow output measures, the appropriate estimate is likely to be in the upper part of this range.

I've blogged before (Jan 2005a, Jan 20005b, Jul 2005, and Aug 2005) about the future of the oil economy, but maybe I've been on the wrong tack:

The shift to a low-carbon global economy will take place against the background of an abundant supply of fossil fuels. That is to say, the stocks of hydrocarbons that are profitable to extract (under current policies) are more than enough to take the world to levels of greenhouse-gas concentrations well beyond 750ppm CO2e, with very dangerous consequences. Indeed, under BAU, energy users are likely to switch towards more carbon-intensive coal and oil shales, increasing rates of emissions growth.

The economic analysis makes it clear that there is a high price to delay. As he says:

Delay in taking action on climate change would make it necessary to accept both more climate change and, eventually, higher mitigation costs. Weak action in the next 10-20 years would put stabilisation even at 550ppm CO2e beyond reach ? and this level is already associated with significant risks.

The Good News

He thinks there is a way out:

Yet despite the historical pattern and the BAU projections, the world does not need to choose between averting climate change and promoting growth and development. Changes in energy technologies and the structure of economies have reduced the responsiveness of emissions to income growth, particularly in some of the richest countries. With strong, deliberate policy choices, it is possible to ?decarbonise? both developed and developing economies on the scale required for climate stabilisation, while maintaining economic growth in both.

I think the Aussie and the American governments understand the last part of this (opportunities), but they want to somehow avoid the fist part ... (costs):

Reversing the historical trend in emissions growth, and achieving cuts of 25% or more against today?s levels is a major challenge. Costs will be incurred as the world shifts from a high-carbon to a low-carbon trajectory. But there will also be business opportunities as the markets for low-carbon, high-efficiency goods and services expand.

For those of us in paranoid Europe, worried about Russian control of our gas supplies:

National objectives for energy security can also be pursued alongside climate change objectives. Energy efficiency and diversification of energy sources and supplies support energy security, as do clear long-term policy frameworks for investors in power generation.

In Britain today the headlines are all about the taxation that will result from doing something about this, but Stern also points out that while

the social cost of carbon will also rise steadily over time ... This does not mean that consumers will always face rising prices for the goods and services that they currently enjoy, as innovation driven by strong policy will ultimately reduce the carbon intensity of our economies, and consumers will then see reductions in the prices that they pay as low-carbon technologies mature.

I've got that in the good news section on the grounds that the clear message is that the cost of doing something about this isn't going to rise and rise, but it isn't good news for our next thirty years. I fear for the tourism and export agriculture of countries a long way from anywhere else (e.g. New Zealand!)

At this point I'm on page seventeen, and I'm tired ... more soon!

Update, 31 Oct: See James Annan for a critique of the science part ..

Categories: climate environment

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The Stern Way Forward (from "Bryan's Blog" on Tuesday 31 October, 2006)

Yesterday I waded through the first two thirds of the Executive Summary ... I thought it best to finish it today, otherwise I would be at risk of not only not reading the whole thing, but not making it through the executive summary :-)

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This page last modified Tuesday 31 October, 2006
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