Today the UN’s Intergovernmental Panel on Climate Change is releasing what may become a pivotal document of human progress—or lack thereof, if we don’t heed its warnings. It’s a “synthesis” report, summarizing the findings from the six previous IPCC reports that laid out the science of climate change, like how the food system spews greenhouse gas emissions and how the oceans and polar regions are transforming . The report is a full-throated call for the massive—yet doable—changes our species must enact to limit the damage that comes with each fraction of a degree of warming. It’s a temporary adieu of sorts, as the next climate report from the IPCC won’t land for at least another five years. “There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all,” the report notes. “The choices and actions implemented in this decade will have impacts now and for thousands of years.” The more warming occurs, the harder it will be to mitigate it—to preserve human health, agriculture, and the natural world. Some effects, like the collapse of ecosystems, will be irreversible. “The Synthesis Report underlines how important it is to not only accelerate climate action, but to do it in a way that helps everyone in the world, not just those in the wealthiest countries and regions,” said report coauthor Christopher Trisos, director of the Climate Risk Lab at the African Climate and Development Initiative, in a statement. The science of climate change is “unequivocal,” the report stresses: We’ve already warmed the planet by 1.1 degrees Celsius above pre-industrial levels—spawning fiercer wildfires , heat waves , droughts , and storms , which are killing people and destabilizing ecosystems. But just how much the planet will keep warming, and how quickly, depends on a full deck of wild cards , such as future economic development and poorly understood feedback loops like permafrost thawing and carbon release . Scientists also don’t have a good handle on the global influence of the aerosols produced by burning fossil fuels, which tend to cool the atmosphere—if we decarbonize (and we must), we might actually lose some of that air conditioning . Still, it’s becoming increasingly clear that we’re going to blow past the
Paris Agreement’s goal of limiting warming to 1.5 degrees. To avoid that fate, we’d have to cut emissions in half by 2030. In fact, emissions are increasing, the report notes. “By now, even the most optimistic among scientists think that that train has left,” says Claudia Tebaldi, a climate scientist at the Pacific Northwest National Laboratory, who was a lead author on a previous IPCC report but wasn’t involved in the new synthesis. “We may be able to return to 1.5, but we would need a miracle to be able to stay below 1.5.” Negative emissions techniques, like sucking carbon out of the atmosphere , could reduce warming. Indeed, the new report says these technologies will be necessary to bring temperatures down from an “overshoot.” Yet they are not yet proven at anywhere near the scale needed to make a dent in atmospheric carbon. Today, the plummeting price of renewables is helping humanity decarbonize: Wind energy prices dropped by 55 percent in the 2010s, the new report notes, while solar power and lithium ion batteries got 85 percent cheaper—much cheaper than researchers had anticipated. Lower prices have allowed for the proliferation of solar panels, reducing dependence on fossil fuels. Scientists are scrambling to figure out where to put them all, like on rooftop gardens and croplands , over canals , or floating on reservoirs . The report “makes it clear that the world has made some progress on climate change—there is some good news,” says Zeke Hausfather, a research scientist at Stripe and the nonprofit Berkeley Earth, who wasn’t involved in the synthesis. “At the same time, there’s such a big gap between where we are right now—and even where countries have committed to be by 2030—and what is needed to meet our most ambitious climate targets.” The future is uncertain. When scientists model climate change, they imagine different scenarios in which humanity reduces emissions, keeps them steady, or increases them. These models spit out a range of figures for potential warming. Not long ago, scientists were estimating that an increase of 4 or 5 degrees could be possible, given emissions trajectories. But modeling last year by Hausfather and his colleagues found that if countries stick to their reduction pledges, we could keep warming under 2 degrees . “We can be cautiously optimistic about the direction of these trends, and also realize that technology’s not going to save us all by itself ,” says Hausfather. “Without stronger policies to propel these adoptions, we’re not going to meet our targets.” The new IPCC report lands in the middle of those ranges—it warns that unless policymakers get a lot more ambitious about reductions, we could be heading toward a rise of around 3 degrees by the year 2100. Given the severity of the environmental damage we’re already seeing at 1.1 degrees of warming, it would be an unfathomable escalation. Hausfather sees hope that we might head this future off. Last year, the
United States passed the Inflation Reduction Act, which allocates hundreds of billions of dollars toward juicing the green
economy and incentivizing people to climate-proof their homes . The invasion of
Ukraine has forced Europe to wean itself off of
Russian gas and adopt more clean technologies like heat pumps . “What
China is doing with electric vehicles is huge,” says Hausfather, referring to the country’s rapid adoption of EVs. And as the price of renewable energy falls, he continues, “solving this is probably going to be a lot cheaper than we thought it was a decade ago.” The food system, though, is going to be trickier to decarbonize. A study published earlier this month estimated that the industry alone could add a degree Celsius of warming by 2100 . But it also pointed to powerful levers that can be pulled to control emissions: Three quarters of that warming would come from methane-heavy industries like dairy and livestock production ( cows burp a lot ) and rice cultivation (bacteria that emit the gas grow in flooded rice fields). Methane is 80 times more potent than CO 2 , but disappears from the atmosphere in 10 years rather than centuries. Changes like driving down demand for beef or developing feed additives to keep cows from belching could all help reduce warming quickly. Decarbonization comes with other benefits, the report notes, known as multisolving. Adding a green space to a city, for instance, absorbs carbon, cools the air , mitigates flooding, improves mental health, and may let residents grow more of their own food , increasing food security while reducing shipping emissions. Switching from gasoline cars to EVs reduces both carbon dioxide and air pollution. “So suddenly, this transition to net zero is a major, major win for public health around the world,” says Elizabeth Sawin, founder and director of the Multisolving Institute, which focuses on climate solutions. The final installment in this IPCC series lands at a moment when humanity is reaching a crossroads: business as usual, or accelerating the green revolution. “If we act now,” said IPCC chair Hoesung Lee in a statement, “we can still secure a liveable sustainable future for all.”