Climate Feedback

Mitigation scenario a taste of things to come

Olive Heffernan

I’ve just returned from a two-day visit to the UK Met Office, where scientists are gathered this week to present and discuss the results of a five-year research initiative known as Ensembles. An EU-funded project led by the Met Office Hadley Centre, Ensembles brought together 66 research international institutes with the express aim of developing climate models and projections and applying the newly developed tools to studying climate impacts on agriculture, health and other sectors.

One of the most exciting outcomes from Ensembles is the development of a climate mitigation scenario and its analysis by a variety of state-of-the-art climate models, many of which include carbon cycle feedbacks. As I explain over on Nature News, this is a radically different approach from the gold-standard climate projections, which are run by Intergovernmental Panel on Climate Change (IPCC), the United Nation’s climate body.

Up until now, the IPCC has run models for a range of ‘what if’ scenarios that make various assumptions about the future, such as the level of emissions, technological and economic development. None of these scenarios account for the impact of policy on climate change.

The Ensembles scenario, known as E1, works the other way around. It assumes that atmospheric levels of CO2 equivalents cannot rise above 450 parts per million if we are to avoid ‘dangerous’ climate change of more than 2 ºC and then looks at the mitigation that policy-makers would need to pursue to achieve that.

Most of the models suggest that emissions will need to be near zero by 2100 in order to stabilize atmopsheric concentrations at 450 ppm. But the Hadley Centre model, HadCM3, suggests that we’ll need to start actively removing greenhouse gases from the atmosphere – by artifical or natural means – by 2050, if we are to keep temperatures within a ‘safe’ level.

Although E1 won’t be be used by the IPCC in its next report (AR5), due out in 2013, E1 is the forerunner of a very similar scenario that will feature prominently in AR5.

The full story is here [subscription].

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