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Limiting temperature rise to less than 1.5°C by 2100 is feasible – at least from a purely technological standpoint. That’s the conclusion of a study, published in the journal Nature Climate Change, by researchers at the International Institute for Applied Systems Analysis (IIASA) and the Potsdam Institute for Climate Impact Research (PIK).
The new study examines scenarios for the energy, economy and environment that are consistent with limiting climate change to 1.5°C above pre-industrial levels, and compares them with scenarios for limiting climate change to 2°C.
The authors note that the economic, political and technological requirements to meet even the 2°C target are ‘substantial’. In the run-up to climate negotiations in December 2015, this information is important for policymakers considering long-term goals and how to achieve them.
‘Actions for returning global warming to below 1.5°C by 2100 are in many ways similar to those limiting warming to below 2°C. However, the more ambitious 1.5°C goal leaves no space to further delay global mitigation action and emission reductions need to scale up swiftly in the next decades.’
Joeri Rogelj, IIASA researcher and a lead author of the study
Still, the research authors make clear that increased international effort to cut greenhouse gases is vital if we want the 1.5°C target to remain within reach.
‘The 1.5°C target leaves very little leeway. Any imperfections – be it a further delay of meaningful policy action, or a failure to achieve negative emissions at large scale – will make the 1.5°C target unattainable during this century.’
Gunnar Luderer, PIK researcher and study co-leader
The study identifies key elements that would need to be in place in order to reach the 1.5°C target by 2100. One fundamental feature is the tight constraint on future carbon emissions.
‘In 1.5°C scenarios, the remaining carbon budget for the 21st century is reduced to almost half compared with 2°C scenarios.
‘As a consequence, deeper emissions cuts are required from all sectors, and global carbon neutrality would need to be reached 10-20 years earlier than projected for 2°C scenarios.’
Gunnar Luderer, PIK researcher and study co-leader
Faster improvements in energy efficiency are another key factor for achieving a 1.5°C target. All the scenarios show that, at some point this century, carbon emissions would have to become negative on a global scale. That means significant amounts of CO2 would need to be actively removed from the atmosphere.
This could occur through technological solutions such as bioenergy use combined with carbon capture and storage – a technology that remains untested on a large scale, increases the pressure on food supply systems and lacks social acceptance – or through efforts to grow more forests, sequestering carbon in tree trunks and branches. Just like bioenergy plantations, afforestation would need to be carefully balanced against food production and other land use requirements.
Most of the scenarios examined in recent research set 2°C as the absolute limit, with no margin for error. The recent Fifth Assessment Report from the IPCC didn’t explain how to limit warming to below 1.5°C as the scenarios available didn’t allow for an in-depth analysis.
Yet over 100 countries worldwide – over half of the countries in the United Nations Framework Convention on Climate Change (UNFCCC), including the Alliance of Small Island States (AOSIS) and the Least-Developed Countries (LDCs) – have declared their support for a 1.5°C target on climate change. The target is one of the many things up for debate at the upcoming climate negotiations.
The full report, Energy system transformations for limiting end-of-century warming to below 1.5°C, is published in Nature Climate Change.
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