Even aggressive renewable energy adoption and a rapid peak in fossil fuel production will produce unacceptably high levels of global warming by 2100 unless technology or natural systems sequester much more atmospheric carbon, according to a paper published last week in the journal Nature Communications.
The latest “ambitious but not impossible” scenario for meeting the global warming targets in the Paris agreement concluded that greenhouse gas emissions must peak in 10 years, fossils must fall to less than 25% of global energy supply by 2100, renewable energy must show strong growth—and even then, some form of carbon capture will still be needed.
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“The study shows that the combined energy and land use system should deliver zero net anthropogenic emissions well before 2040 in order to assure the attainability of a 1.5°C target by 2100,” said co-author Michael Obersteiner, director of the ecosystems services and management program at Austria’s International Institute for Applied Systems Analysis.
“Earlier work on mitigation strategies by IIASA has shown the importance of demand-side measures, including efficiency, conservation, and behavioural change,” added IIASA Energy Program Director Keywan Riahi. “Success in these areas may explain the difference between reaching 1.5°C instead of 2°C.”
To limit average global warming to 1.5°C, global emissions would have to hit net zero by 2040, not by the second half of the century as envisioned by Paris negotiators, InsideClimate News reports. “That would mean 34% annual growth in the amount of carbon sequestered from 2016 through 2040, with continued growth through the century.”
Without carbon capture, a scenario based on “aggressive” renewable energy growth at 5% per year shows average global warming at 2.5° or 2.6°C by 2100. If fossil fuel use peaks around 2055, average warming will hit 3.5°C at the end of the century.
The growth rates envisioned in the study “would require a stark break from current trends,” InsideClimate notes. “While the authors said the renewable energy goals are realistic, carbon capture technology has lagged, plagued by high costs. There is one opportunity for improvement, the authors note: greater potential for land use and agriculture to sop up more carbon dioxide than their models considered.”