By Yangyang Xu, Veerabhadran Ramanathan and David G. Victor
Prepare for the “new abnormal”. That was what California Governor Jerry Brown told reporters last month, commenting on the deadly wildfires that have plagued the state this year. He’s right. California’s latest crisis builds on years of record-breaking droughts and heatwaves. The rest of the world, too, has had more than its fair share of extreme weather in 2018. The Lancet Countdown on health and climate change announced last week that 157 million more people were exposed to heatwave events in 2017, compared with 2000.
Such environmental disasters will only intensify. Governments, rightly, want to know what to do. Yet the climate-science community is struggling to offer useful answers.
In October, the Intergovernmental Panel on Climate Change (IPCC) released a report setting out why we must stop global warming at 1.5 °C above pre-industrial levels, and how to do so1. It is grim reading. If the planet warms by 2 °C — the widely touted temperature limit in the 2015 Paris climate agreement — twice as many people will face water scarcity than if warming is limited to 1.5 °C. That extra warming will also expose more than 1.5 billion people to deadly heat extremes, and hundreds of millions of individuals to vector-borne diseases such as malaria, among other harms.
But the latest IPCC special report underplays another alarming fact: global warming is accelerating. Three trends — rising emissions, declining air pollution and natural climate cycles — will combine over the next 20 years to make climate change faster and more furious than anticipated. In our view, there’s a good chance that we could breach the 1.5 °C level by 2030, not by 2040 as projected in the special report (see ‘Accelerated warming’). The climate-modelling community has not grappled enough with the rapid changes that policymakers care most about, preferring to focus on longer-term trends and equilibria.
Policymakers have less time to respond than they thought. Governments need to invest even more urgently in schemes that protect homes from floods and fires and help people to manage heat stress (especially older individuals and those living in poverty). Nations need to make their forests and farms more resilient to droughts, and prepare coasts for inundation. Rapid warming will create a greater need for emissions policies that yield the quickest changes in climate, such as controls on soot, methane and hydrofluorocarbon (HFC) gases. There might even be a case for solar geoengineering — cooling the planet by, for instance, seeding reflective particles in the stratosphere to act as a sunshade.
Climate scientists must supply the evidence policymakers will need and provide assessments for the next 25 years. They should advise policymakers on which climate-warming pollutants to limit first to gain the most climate benefit. They should assess which policies can be enacted most swiftly and successfully in the real world, where political, administrative and economic constraints often make abstract, ‘ideal’ policies impractical.