The carbon dioxide emissions accumulated since the start of industrialization already comprise two-thirds of the carbon quota consistent with limited global warming of less than two degrees Celsius. How current emissions rates are diminishing the remaining quota and how global strategies can help to share this quota are discussed in a special joint Focus published online this week in Nature Geoscience and Nature Climate Change.
Pierre Friedlingstein and colleagues update estimates of accumulated carbon emissions to 2013 and project future emissions up to 2019 based on forecasts of global economic activity. In their Nature Geoscience Review Article, they report that the remaining carbon dioxide emissions quota is diminishing rapidly and at current rates is likely to be exhausted by the middle of the century. Reducing current emissions trends in the immediate future is critical while nations work towards the onset of a potential new climate agreement in 2020.
The most viable option for sharing the remaining emissions quota between countries combines the commonly debated approaches of equal allocation on a per-capita basis and continuation of current emissions, concludes a Perspective article by Michael Raupach and colleagues in Nature Climate Change. Regardless of the exact mix of sharing principles, long-term mitigation rates for meeting a temperature warming threshold of two degrees Celsius are challenging, they say, because current emissions rates are expected to persist in the short-term as a consequence of existing infrastructure.
Both groups conclude that actions to expedite the transition to low-carbon societies around the globe and cooperative agreements among countries on how to share the remaining quota are urgently needed if we are to avoid a global mean temperature rise above two degrees Celsius compared with pre-industrial temperatures.