The world can keep global warming to below 1.5 degrees, but for that to happen it needs “rapid and far-reaching transitions” that include a deep cut in greenhouse gas emissions and a greater reliance on nuclear power, according to a U.N. climate science report published on Monday.
“Limiting warming to 1.5 degrees is possible within the laws of chemistry and physics but doing so would require unprecedented changes,” said Jim Skea, a professor at Imperial College London and one of the authors of the report by the Intergovernmental Panel on Climate Change, the U.N. body that aims to give a scientific view of climate change.
The summary was vetted and endorsed by all 195 governments that are parties to the Paris Agreement in Incheon, South Korea, on Saturday, despite attempts by oil-exporting Saudi Arabia to block it, and leaked U.S. comments that criticized the report for downplaying the role of fossil fuels in lifting countries out of poverty.
The 2015 Paris Agreement sets a global goal of limiting warming to “well below” 2 degrees Celsius above preindustrial levels, and to “pursue efforts” to limit warming to no more than 1.5 degrees Celsius. The earth has already warmed roughly 1 degree, and is on track for 3 degrees of warming.
The IPCC report, which assesses published literature and publicly available data, spells out the difference between 2 degrees of warming and 1.5 degrees. It finds at the lower temperature rise, the risks of flooding, Arctic ice melting, sea level rise, species extinction and droughts are all lower.
But hitting that lower target demands a radical effort.
Keeping the global temperature rise to within 1.5 degrees of preindustrial levels would require carbon dioxide emissions to be cut by about 45 percent by 2030 compared to 2010 levels. By 2050, the world would have to achieve “net zero” emissions, meaning as much carbon would have to be absorbed as is emitted.
By 2100, a balance of zero would require removing anywhere from 100 to 1,000 gigatons of carbon dioxide from the atmosphere.
Methods for carbon removal range from natural solutions such as planting trees and embracing farming practices that retain more CO2 in the soil, to technological solutions that capture and store CO2 emissions underground.
The authors warned against betting on technological fixes alone, because these ideas have not been deployed at scale and come with high costs and limited social acceptability.
“While it’s clear that some [carbon dioxide removal] is needed, it is really a policy choice which actions we want to go through,” said Joeri Rogelj, another of the report’s authors and a researcher at the Austrian International Institute for Applied Systems Analysis.
Avoiding over-reliance on carbon removal requires the world to peak carbon dioxide emissions “well before” 2030. This in turn has huge implications for the energy sector.
By 2050 renewables will have to produce 70 percent to 85 percent of power.
Coal will have to be phased out, and gas will have a limited role — generating only 8 percent of global electricity, and only as long as it’s used in combination with carbon capture and storage technology.
An area ranging from 1 million to 7 million square kilometers — the size of Egypt and Australia respectively — will have to be dedicated to growing crops used to generate energy.
Because of the competition with food crops, this transition will have to be “carefully managed,” but is indispensable, according to authors, especially as biofuels are the only alternative to fossil fuels in high-emission sectors like aviation and shipping.
“Only if we find technologies that can decarbonize air transport or freight, it would be possible to eliminate bioenergy,” said Skea.
Similarly, under all scenarios compatible with 1.5 degrees, the contribution of nuclear power increases.
The U.N. report, commissioned by governments in Paris in 2015, will feed into the discussions at December’s COP24 climate summit in Katowice, Poland.
EU environment ministers are meeting on Tuesday to discuss the bloc’s position for the summit, and green groups are calling on them to increase the EU’s 2030 target of cutting greenhouse gas emissions from 40 percent to “well beyond 45 percent,” said Wendel Trio, director of NGO Climate Action Network Europe.
Updated targets for renewable energy and energy efficiency — 32 percent and 32.5 percent by 2030 — respectively would already allow the EU to increase its 2030 target from 40 percent to at least 45 percent, the European Commission said in June.
But an updated target is not on the table at Tuesday’s meeting. According to draft conclusions seen by POLITICO and dated October 1, ministers will note that the new energy and energy efficiency targets “have an impact on our level of ambition,” without pledging a higher level of emissions cuts.
This article has been updated with more detail from the report.