Today the UN’s Intergovernmental Panel on Climate Change dropped the latest in its string of damning reports on the current state of the climate and its prognosis. The big picture: The effects are appearing much faster than scientists expected two decades ago, and they’re more severe and pervasive. Today, some three and a half billion people are highly vulnerable to the ravages of climate change—rising seas, heat waves, droughts, wildfires.
“One of the most striking conclusions in our report is that we're seeing adverse impacts being much more widespread, and being much more negative than expected in prior reports,” said coauthor Camille Parmesan of the University of Plymouth and University of Texas at Austin, speaking at a Sunday press conference announcing the findings.
The report—authored by hundreds of researchers from 67 countries, who reviewed more than 34,000 scientific references—finds that if the world reaches 2 degrees Celsius of warming above pre-industrial temperatures, extinction will very likely threaten up to 18 percent of species in terrestrial ecosystems. And it notes that mortality is already rising among some species, like corals killed by bleaching, trees damaged by drought, and the mass die-off among kelp forests. People are no exception to the health risks of a warmer world: The report calls out the increased risk of illness from food or water-borne pathogens like freshwater cyanobacteria, as well as cardiovascular and respiratory problems caused by wildfire smoke and atmospheric dust.
Rapid warming is also compromising the planet’s capacity to sequester excess carbon from the atmosphere, an ability which has so far helped save humanity from itself. “Some places,” Parmesan continued, “even in areas that are undisturbed, such as intact, old-growth Amazon rainforest and parts of the permafrost in undisturbed areas in North America and northern Siberia, are starting to turn from being overall net sinks of carbon—so sucking up more carbon than they put out—to turning into overall net sources of carbon.”
The report also spills significant ink about the fates of cities, both in terms of their vulnerabilities and their power to fight climate change. “I think one of the things that comes out of the report is that cities in and of themselves provide that classic example of a challenge as well as opportunity,” said coauthor William Solecki, of the City University of New York’s Hunter College, at the press conference. “We recognize the world is very rapidly urbanizing—up to 70 percent of the world's population by 2050 will live in cities.”
“We're concentrating lots of lots and lots of people in these very small places that are bull's-eyes for any kind of natural disaster, let alone a human-compounded natural disaster from climate change,” adds Jonathan Foley, executive director of Project Drawdown, which advocates for climate action but wasn't involved in the report. “That's actually increasing the risk for really bad things to happen to lots of people all at once. But the good news is that cities could be designed so much better than they are now."
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That's urgent because the world’s cities are rapidly getting hotter, the new IPCC report emphasizes: By the end of the century, up to three quarters of humans could be exposed to deadly heat stress, up from a third of people today. If the world ends up warming more than 4 degrees Celsius by the year 2100, outdoor workers in South Asia, tropical sub-Saharan Africa, Central and South America could see up to 250 more days a year of stressfully hot working conditions. In Europe, heat stress will affect two to three times the number of people if the world warms 3 degrees C compared to 1.5 degrees C.
Urbanization will expose billions of people to the dreaded “urban heat-island effect,” in which the built environment absorbs the sun’s energy during the day and releases it slowly throughout the night. This can make a city significantly hotter than surrounding rural areas, where vegetation releases water vapor, essentially sweating to cool the air. Within cities, richer areas also have more trees and are cooler than poorer areas, which might be more industrialized and scabbed over with heat-absorbing concrete. In New Orleans, for instance, a separate team of scientists previously found that one neighborhood can be far hotter than another, largely due to the lack of vegetation.
When combined with bad air quality, this exacerbates health problems already driven by racial and economic inequity, the new report notes. “In many places, climate change is intersecting with existing socio-economic inequities with long-standing histories of marginalization of some populations, including through the legacy of colonialism,” says Rachel Cleetus, policy director of the Climate and Energy Program at the Union of Concerned Scientists and a report coauthor. “Because of that, some people in places are even more highly exposed and at risk.” For instance, higher temperatures combined with increased rain (a warmer atmosphere holds more water) and flooding have boosted the occurrence of diarrheal diseases like cholera.
But the report also notes that as cities grow, there’s a critical opportunity to make them more equitable and more resilient to climate change. “As we invest in upgrading our public housing infrastructure, let's do it in a way that's forward looking—let's make sure it's energy efficient,” says Cleetus. “There's really opportunities to upgrade our infrastructure in a way that both addresses long-standing inequities and also invests in climate resilience.”
Creating more green spaces is the obvious choice: That would both cool and beautify a neighborhood. But scientists are also experimenting with higher-tech solutions like reflective pavements and paints for roofs, which deflect the sun’s energy back into space, or rooftop gardens shaded by solar panels that generate power and cool a building, and roads that capture rainwater instead of just shuttling it to the sea. Urban planners are also investigating how to build out charging infrastructure in poorer neighborhoods, which would encourage the adoption of electric vehicles and decrease local air pollution. And on the national scale, the US Congress has considered reviving the Depression-era Civilian Conservation Corps, which could task workers with jobs like retrofitting buildings with better insulation and windows.
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These are good examples of a strategy called multisolving, or reducing emissions while fixing a second problem at the same time. “We feel like multisolving is a bit of an underground movement that many, many people are doing, but they don't really realize they're part of a bigger thing,” says Elizabeth Sawin, director of the US-based nonprofit Multisolving Institute. “They're just addressing problems in their community in a way that makes sense.”
The new IPCC report uses a different term for a similar idea—they call it “climate resilient development,” meaning solutions that combine climate adaptations with strategies to reduce emissions. “Evidence shows that climate resilient development processes link scientific, Indigenous, local, practitioner and other forms of knowledge,” the report reads, “and are more effective and sustainable because they are locally appropriate and lead to more legitimate, relevant and effective actions.”
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That local buy-in is important, Sawin says, because otherwise legislators risk implementing “solutions” that a community doesn’t want. Or, they might inadvertently trigger green gentrification, if these climate improvements make the area more desirable to outsiders, drive up the value of real estate, and price out the long-time residents. “When you look across these projects, you see that the way that they're working is very similar in terms of this inclusiveness for community voices, or focus on equity,” says Sawin of multi-solving efforts. “Often they are sort of organic and iterative, as opposed to kind of top-down plans imposed on a place.”
Take, for example, one of the key threats to urban environments mentioned in the new IPCC report: sea level rise. The report notes that if global sea levels go up half a foot, the number of people exposed to a disastrous one-in-100-year coastal flood will jump by 20 percent. (On average, the coastlines of the US could see a foot of sea level rise by 2050, according to a recent federal report.) “For low-lying and coastal communities, the increasing intensity of tropical storms and hurricanes, combined with sea level rise, will result in losses and damages, despite our best efforts to adapt,” said report coauthor Adelle Thomas, senior Caribbean research associate for the IMPACT project at Climate Analytics, at the press conference Sunday. “And unfortunately, these negative impacts of climate change have disproportionate effects on those that are least able to respond—the poorest and most vulnerable communities.”
One fix is to throw up a giant sea wall, like the Army Corps of Engineers is proposing for Miami, which could see three and a half feet of sea level rise by the end of the century. But some local residents have criticized the idea because it’ll decrease property values, and instead are pushing for nature-based solutions like restoring wetlands, which naturally absorb excess water.
Adaptation is no substitute for cutting emissions, the new IPCC report emphasizes. And Sawin agrees: “We can't say that too many times: That the number one priority is keeping fossil fuels in the ground, so that what we have to adapt to is manageable.”
But while the world is changing fast, if there’s a silver lining to the report, it’s that cities can change fast, too. “It's been understood for a long time that climate risks don't just depend on how much climate change we get—they also depend on how vulnerable society is,” says Brian O’Neill, a coordinating lead author of the report and director of the Joint Global Change Research Institute, a partnership between the Pacific Northwest National Laboratory and the University of Maryland. Rapidly growing urban areas can be designed to protect residents from a warmer world, and to make sure disadvantaged groups aren’t left out. Cities don't have to be victims of climate change. They can become the crucibles that forge resilience against it.
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