News | August 10, 2011

Climate Change Committee's Assumptions ‘Implausible', Say Researchers

Researchers have questioned the ambitious assumption of the UK Committee on Climate Change (CCC) that global carbon emissions can peak by 2016.

Whilst the researchers agree that global emissions should peak ‘as soon as possible' – an aim agreed by the United Nations at a 2010 conference – their new research, published recntly, Tuesday 9 August, in IOP Publishing's Environmental Research Letters suggests that 2016 is implausibly early.

Instead, it suggests that 2020 might be a more realistic year as it allows more time for the global population to adjust to reduction strategies and change their own habits and preferences in favour of low-carbon alternatives.

Based at the University of Manchester, the researchers compared a 2008 study from the CCC with an independent 2009 study by Meinshausen et al.

Under the CCC's most ambitious emission scenario, after peaking in 2016, carbon emissions fall at 3.5% per year. The CCC states this reduction rate is compatible with economic growth and would result in a 55% probability of dangerous climate change. (In its study, the CCC resigns itself to the fact that achieving a 0% probability is impossible.)

According to the CCC's model, if emissions peak in 2020 instead, achieving a 55% probability of dangerous climate change would require the resultant yearly reductions to rise to 5% per year.

There is, however, a disparity between the CCC's model and the model used in the 2009 independent study. According to the independent study, a 2020 peak and a yearly reduction rate of 5% brings with it a 70% chance of dangerous climate change.

If this probability was brought down to 55%, the reduction rate would rise to 9% per year, compared with the 5% obtained by the CCC.

‘It would be good to know more about why these two studies differ so much', said lead author, Richard Starkey.

Despite these differences, the researchers found that according to both studies, reducing the probability of dangerous climate change to 50% would require reduction rates in carbon emissions of 10% or more per year if emissions peak in 2020. Such reduction rates, they suggest, are not compatible with continued economic growth.

Starkey explained, ‘Growth requires energy. If you're reducing CO2 emissions very rapidly, you're reducing fossil fuel combustion very rapidly and you've therefore got to plug the gap with either nuclear and renewable energy or energy efficiency. If emission reduction rates get above a certain level, this gap becomes too big to plug completely'.

The ultimate objective of the United Nations Framework Convention on Climate Change is the prevention of dangerous climate change. According to the researchers, this can reasonably be understood as achieving something close to a 0% probability of dangerous climate.

However, as Starkey remarked ‘Our research suggests that when a 2020 peak year is assumed, this objective is unachievable. Indeed, even achieving a 50% probability of dangerous climate change may be incompatible with economic growth'.

From Tuesday 9 August, this paper can be downloaded from

SOURCE: IOP Publishing