Published: 14 April 2014

IPCC: Emissions accelerate, but effective cuts still possible

The latest report from the Intergovernmental Panel on Climate Change (IPCC) shows that global emissions of greenhouse gases have risen to unprecedented levels despite policies being implemented in some parts of the world to reduce climate change. Emissions rose faster between 2000 and 2010 than in each of the three previous decades.

Air samples from the past: one of many strands of scientific evidence showing atmospheric carbon dioxide levels are rising, forcing a rapid rise in global mean temperature. The IPCC’s latest report concludes that ‘only major institutional and technological change will give a better than even chance that global warming will not exceed the [2°C above pre-industrial levels] threshold’. Credit: Bruce Miller/CSIRO under CC BY 3.0 licence

Climate Change 2014: Mitigation of Climate Change, the Working Group III (WGIII) contribution to the IPCC’s Fifth Assessment Report, also concludes it still may be possible, using an array of technological measures and changes in behaviour, to limit the increase in global mean temperature to 2°C above pre-industrial levels.

However, because most emissions come from the energy and industry sectors, only major institutional and technological change will give a better than even chance that global warming will not exceed this threshold.

‘Climate policies in line with the 2°C goal need to aim for substantial emission reductions,’ said Ottmar Edenhofer, one of the three WGIII co-chairs. ‘There is a clear message from science: To avoid dangerous interference with the climate system, we need to move away from business as usual.’

‘Climate change is a global commons problem. International cooperation is key for achieving mitigation goals. Putting in place the international institutions needed for cooperation is a challenge in itself.’

Scenarios show that to have a likely chance of limiting the increase in global mean temperature to 2°C, humankind must limit its global greenhouse gas emissions by 40–70 per cent compared with 2010 by mid-century, and to near-zero by the end of this century.

Ambitious mitigation may even require removing carbon dioxide from the atmosphere. Scientific literature confirms that even less ambitious temperature goals would still require similar emissions reductions.

‘Many different pathways lead to a future within the boundaries set by the two degrees Celsius goal,’ said Edenhofer. ‘All of these require substantial investments. Avoiding further delays in mitigation and making use of a broad variety of technologies can limit the associated costs.’

Since the last IPCC assessment report, published in 2007, a wealth of new knowledge about climate change mitigation has emerged. The authors of the new, fifth Working Group III report have included about 10,000 references to scientific literature in 16 chapters.

Stabilizing greenhouse gas concentrations in the atmosphere requires emissions reductions from energy production and use, transport, buildings, industry, land use, and human settlements.

Cutting emissions from electricity production to near zero is a common feature of ambitious mitigation scenarios. But using energy efficiently is also important.

‘Reducing energy use would give us more flexibility in the choice of low-carbon energy technologies, now and in the future. It can also increase the cost-effectiveness of mitigation measures,’ said another co-chair, Ramón Pichs-Madruga.

Land is another key component for the 2°C goal. Slowing deforestation and planting forests have stopped or even reversed the increase in emissions from land use. Through afforestation, land could be used to draw carbon dioxide from the atmosphere. This could also be achieved by combining electricity production from biomass and carbon dioxide capture and storage. However, this combination is not available at the scale required, permanent underground carbon dioxide storage faces challenges, and the risks of increased competition for land need to be managed.

‘The core task of climate change mitigation is decoupling greenhouse gas emissions from the growth of economies and population,’ said the third co-chair, Youba Sokona.

The IPCC is the international body for assessing the science related to climate change. It was set up in 1988 by the World Meteorological Organization and the United Nations Environment Programme to provide policymakers with regular assessments of the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation.

The IPCC’s Fifth Assessment Report series in 2014 will be completed by a Synthesis Report to be finalised in October.

Source: IPCC

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