Jeff Tollefson reports that a team of climate scientists has delivered a rare bit of good news: it could be easier than previously thought to limit global warming to 1.5°C above pre-industrial levels, as called for in the 2015 Paris climate agreement. But even if the team is right, and some researchers are already questioning the conclusions, heroic efforts to curb greenhouse-gas emissions will still be necessary to limit warming.
Published on 18 September in Nature Geoscience, the analysis focuses in part on the fact that global climate models used in the 2013 report from the Intergovernmental Panel on Climate Change (IPCC) tend to overestimate the extent of warming that has already occurred. After adjusting for that discrepancy and running further models, the authors of the latest study found that the amount of carbon that humanity can emit from 2015 onward while holding temperatures below 1.5°C is nearly three times greater than estimated by the IPCC, or even larger if there is aggressive action on greenhouse gases beyond carbon dioxide.
The implications for global policymakers are significant. Humanity is poised to blow through the IPCC carbon budget for a 1.5°C rise within a few years, leading many scientists to declare the goal impossible. But the new analysis suggests that it could be met with a modest strengthening of the current Paris pledges up to 2030, followed by sharp cuts in carbon emissions thereafter. The Paris goal of 1.5°C is not impossible, it is just very, very difficult, says lead author Richard Millar, a climate researcher at the University of Oxford, UK. That is true for science as well as for climate policy. For a lot of people, it would probably be easier if the Paris goal was actually impossible, Millar says. We are showing that it is still possible. But the real question is whether we can create the policy action that would actually be required to realize these scenarios.
Reasonable goals can be reached if coal burning is curtailed especially dirty coal such as brown coal in Germany and lignite in Texas and Louisiana. Natural gas needs to phased out over the nexy few decades. Nuclear power and hydro-power (dams and forced pumping) are the only two sources of clean energy with the proven grid potential at reasonable prices, with renewable energy (wind and solar) in remote regions or on rooftops.
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