Wanted: Fair players and a climate leader

It requires one major economic power -- such as the United States, China or the European Union -- to set a benchmark emissions reduction target for others to follow, thereby capping global warming to within 2°C.

The work is published in the journal Nature Climate Change and is the first to propose this method of 'diversity-aware leadership'.

Lead author Dr Malte Meinshausen, from the University of Melbourne and the Australian-German Climate and Energy College, believes positive change is possible in the lead-up to the COP21 talks in Paris in December.

He says the model could be the first step to solving the question about how countries share the burden.

"The world is united in wanting to fend off drastic increases in weather extremes and sea-level rises, but has lost its leaders in that endeavor. The danger is that international negotiations are stuck in a gridlock about who should mitigate how much," Dr Meinshausen says.

High-level climate change negotiations continue to be plagued by conflicting interpretations of 'fair' shares.

"If the world waited to find an approach that is considered 'fair' by everybody, the outcome would be 'fair' only in the sense that all are hit by climate change"

Two broad views exist; one considers a future world where the burden is divided equally among the global population and where every person emits the same amount as the next. This is called 'distributive justice'.

The second camp, or 'corrective justice', takes into account what has already been emitted, for instance, placing more of the burden on Australia or the US, countries with historically high per-capita emissions.

This third and new model would require the leader to move first and set an ambitious target for reducing emissions.

Other nations would then match that amount of effort, but get to choose the justice model which defines its own fair share.

The researcher summarises the new idea as "acknowledging the diversity of views on what is fair."

"This study is therefore more closely related to the political realities. The approach also assumes that a large country leads by example, and one could argue that this is not on the horizon at the moment," Dr Meinshausen says.

For example, the US could assume the leadership role by pledging to reduce their emissions by 52 per cent off 2010 levels by 2025 (rather than the presently pledged 21-24 per cent below 2010, which is equivalent to the 26-28 per cent below 2005 levels).

For Australia, a doubling of proposed emission cuts (23-25 per cent below 2010 levels, which equals the pledged 26- 28 per cent below 2005 levels), would not be sufficient to assume a leadership position. Almost a tripling to 66 per cent would be needed, reflecting the high level of per-capita emissions that Australia currently presents.

Dr Meinshausen's team has shown that virtually all countries fall short of the mark when it comes to leadership as well as both interpretations of a fair share.

"One leader could catalyse a global consensus, where no one was doing more or less than the other," he says.

"But it's also vital we don't see the reverse in Paris, where a leader sets the bar too low, encouraging others to follow suit."