The United Nations’s climate panel has moved the goal posts for limiting climate change, setting the world a staggering challenge. A report released yesterday in Incheon, South Korea, by the Intergovernmental Panel on Climate Change (IPCC) says allowing the planet to warm by more than 1.5°C could have dire consequences, and that a speedy transformation of the world’s energy systems is needed to avoid breaching that limit, which is notably tighter than the target of 2°C cited in the Paris agreement of 2015. “Net [carbon dioxide] emissions at the global scale must reach zero by 2050,” said Valérie Masson-Delmotte, a climate scientist at France’s Alternative Energies and Atomic Energy Commission in Paris and a key participant in drafting the report.
There is no time for delay, the report warns, a consensus drawn from thousands of scientific studies. The world has already warmed by about 1°C since preindustrial times, two-thirds of the way toward the new target. “We have to alter course immediately; no longer can we say the window for action will close soon—we’re here now,” Drew Shindell, an atmospheric scientist at Duke University in Durham, North Carolina, wrote in an email to Science. Among other measures, the IPCC says, coal needs to be all but eliminated as a source of electricity, renewable power must be greatly expanded, and “negative-emissions” strategies that suck carbon dioxide (CO2) out of the atmosphere need to be adopted on a large scale, particularly if emissions reductions are delayed.
Under pressure from island nations at risk from sea-level rise, the United Nations agreed during the Paris negotiations to ask the IPCC to investigate the impact of 1.5°C of global warming. In what IPCC Chair Hoesung Lee, a South Korean economist, called “a Herculean effort,” more than 90 authors and reviewers from 40 countries examined 6000 scientific publications. The resulting picture is urgent and alarming. Given accumulated emissions, the report says, “Global warming is likely to reach 1.5°C between 2030 and 2052.”
It warns that overshooting 1.5°C will be disastrous. For example, with 1.5°C of warming, sea levels are projected to rise 26 to 77 centimeters by 2100; going to 2°C adds another 10 centimeters, which would affect an additional 10 million people living in coastal regions. Plants, insects, animals, and marine life will all be pushed farther out of current geographic ranges with 2°C of warming. Coral reefs are projected to decline 70% to 90% at 1.5°C, but at 2°C, 99% of reefs would be ravaged. Storms, flooding, and drought would exact an even higher toll. “Every bit of extra warming makes a difference,” said Abdalah Mokssit, director of Morocco’s National Meteorological Department in Casablanca and IPCC secretary.
The panel says keeping warming to 1.5°C is technically feasible, but the emissions cuts pledged so far by the nations that signed the Paris agreement fall far short of what’s needed. To hit and keep that 1.5°C target, net anthropogenic CO2 emissions must come down 45% from 2010 levels by 2030 and reach net zero around 2050. “We’re not on track, we’re currently heading for about 3° or 4° of warming by 2100,” Mark Howden, a climate change scientist at Australian National University in Canberra, said during an online briefing on Sunday. “The good news is that there’s actually movement in the right direction in many areas,” he added.
One bright spot is renewable energy. “There [has been] exponential growth in the last 5 years in solar, wind, and batteries that is significantly changing electricity systems around the world,” Peter Newman, a sustainability scientist at Curtin University in Bentley, Australia, said during the Sunday briefing. But efforts to reduce emissions are lagging in freight, aviation, shipping, and in industry, he said.
Because forests capture and sequester carbon, reforestation could help reduce net emissions. But forest loss is still outpacing reforestation globally. Other strategies to sequester carbon have yet to live up to their promise, Newman says. The report notes that one proposed approach, bioenergy with carbon capture, in which trees or other crops are grown on vast plantations, then burned in power plants that capture carbon emissions and store them underground, could encroach on agricultural land and undermine food security.
Meanwhile, coal’s share of global electricity must be cut from 37% today to no more than 2% by 2050, the report says. Technologically, economically, and politically the challenge is immense, “indicative both of the scale of the challenge and the resistance [the effort will] face,” notes Shindell, who also contributed to the report.
Jim Skea, a sustainable energy expert at Imperial College London, says achieving the needed emissions cuts will not be a matter of picking and choosing among options. “All options need to be exercised.”
With reporting by Paul Voosen.