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EmissionsGreenhouse gases, climate change and the transition from coal to low-carbon electricity is the snappy title of an interesting paper published recently by the journal Environmental Research Letters, writes Stephen Gardner.

The paper is made slightly more interesting because one of the authors is Nathan Myhrvold, who was Microsoft's Chief Technology Officer, making him both highly intelligent (Cambridge University, studied under Stephen Hawking, etc) and very rich, which in turn makes him more likely to be listened to, because rich people always find it easier to get an audience, even if they have nothing to say (viz. Bono).

The paper describes the implications of the switch to low-carbon electricity in terms of the time it takes and the temperature change it produces, taking into account economic growth and consequently global demand for electricity. It notes, in particular, that a wide-ranging programme to build nuclear power plants or set up wind turbines would cause a short-term spike in greenhouse gas emissions because of the construction effort, electricity for which would be provided by the current fossil-fuel infrastructure. Over the long-term however, whereas coal-fired power plants keeping pumping out carbon for years, renewable facilities will settle into a long-term pattern of low-carbon generation.

The crucial issue is timing. The coal-fired plants exist now and are producing energy, and will continue to do so as they are phased out in favour of renewable generation. The carbon dioxide they are pumping out will remain in the atmosphere for decades. Considering the short-term spike in greenhouse gas emissions that the building of low-carbon power facilities will produce, how long will it take before there is an actual reduction in global warming resulting from the switch to renewables?

The answer is at least 20 years even in the best case. To achieve even a 25 percent reduction in the forecast warming, compared to business as usual, will require up to 30 years. In some cases, it will take even longer to produce a smaller reduction. If all coal-fired plants could start to be phased out today in favour of natural gas, it would take more than a century to effect a 25 percent reduction. The best options, according to the paper, would be wind, solar and nuclear power, which would cause greater greenhouse gas emissions over a year or two as the facilities are constructed, but would then result in a 25 percent reduction in warming after 20-30 years compared to what could be expected otherwise.

This is hardly enough considering that emissions overall (not just those from power generation) should be cut by half by mid-century (compared to 1990) if there is to be about a 50 percent chance of stabilising the global temperature rise at 2 degrees Celsius, as per the Intergovernmental Panel on Climate Change's scenario. A 25 percent reduction in warming attributed to power generation would be about 10 percent overall because power generation produces about 40 percent of greenhouse gas emissions.

Timing is everything

One can argue with this and say "it's only a model", but the paper illustrates the scale of change required if carbon dioxide concentrations are to be stabilised at 450 part per million (the benchmark used in the paper). Timing is everything. As the authors say "rapid deployment of low-emission energy systems can do little to diminish the climate impacts in the first half of this century". If we're lucky, renewables could produce "substantial benefits" in the second half of the century, but natural gas is a waste of time. From a climate perspective, the only option is a rapid shift to nuclear power and renewables. The idea that natural gas can be a temporary solution would simply delay the transition too much.

Of course in the real world, the switch to renewables is gradual, progress on conserving energy is limited, and coal-fired power capacity continues to be added in countries such as China and India. A discussion on concerted global action to tackle greenhouse gas emissions has been put off until about 2015, with any decision to come into effect in 2020, even though the International Energy Agency has explicitly stated that "without further action, by 2017, all CO2 emissions permitted by the 450 scenario will be 'locked in'". In the EU, Poland blocks even limited further action, showing that the Poles either completely misunderstand the urgency of timely action, or that they don't believe the science.

So in short, without drastic action (which won't happen – it's been put off), emissions and the associated temperature rise will be locked in. Even with drastic action, all but a short proportion of the temperature rise is locked in. Enjoy what's left of the Holocene and prepare to man the lifeboats!

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