Climate change is already testing the limits of what human communities can survive, and if warming isn’t kept in check, some of the most crowded parts of the planet will become practically unlivable. The temperatures are already getting too hot, disasters are becoming too severe, and the costs of staying put are becoming unbearable for millions of people. And the greatest impacts are on those least able to cope.
These are some of the stark conclusions in the latest comprehensive assessment from the United Nations’ climate change research group, the Intergovernmental Panel on Climate Change (IPCC). The 3,600-page report published Monday focuses on the practical impacts of climate change, on humans and on nature. It follows the first installment of the assessment, released last August, that covered the basic science behind global warming.
“Today’s IPCC report is an atlas of human suffering and a damning indictment of failed climate leadership,” said UN Secretary-General Antonio Guterres during a press conference Monday.
Global average temperatures have already risen by 1.1 degrees Celsius, roughly 2 degrees Fahrenheit, leaving perilously little room for meeting the targets of the 2015 Paris climate agreement. The accord set a goal of limiting global warming to less than 2 degrees Celsius/3.6 degrees Farenheit compared to average temperatures before the industrial revolution in the 1800s. The agreement also set a more ambitious target of staying below 1.5°C/2.7°F.
Global warming has already raised global sea levels by 9 inches. It has left a distinct mark on extreme weather too, worsening heat waves, storm surges, and rainfall. Scientists can even quantify how much human-linked emissions of heat-trapping gases have made these events worse.
That means regardless of how much greenhouse gas emissions come down, a certain amount of warming is here to stay. “Near-term actions that limit global warming to close to 1.5°C would substantially reduce projected losses and damages related to climate change in human systems and ecosystems, compared to higher warming levels, but cannot eliminate them all,” according to the new report.
Around 3.5 billion people around the world already have no choice but to adapt to the warming that’s underway because they live in vulnerable hotspots, said Debra Roberts, co-chair of the team that produced the report, during a press conference.
Adaptation might entail building seawalls, planting different types of crops and trees, and improving governance. But these and other efforts are already proving to be a challenge, and some of those boundaries are already being surpassed. “Adaptation cannot prevent all losses and damages,” Roberts said. “Even with effective adaptation, limits will be reached with higher levels of warming.” And if people fail to adapt, much more suffering is in store.
IPCC reports generally don’t reveal new information but summarize and evaluate the strength of existing research. Since the last major IPCC report was released in 2013, the IPCC has developed a much better read of how warming will play out for the planet.
The new report defines two categories of limits to adaptation. “Soft” adaptation limits are scenarios where there may be options to cope with the impacts of climate change, but aren’t available due to cost or technological limitations. “Hard” limits are those where physical changes are so drastic that there is no way to reduce risks.
The natural world is passing some of the hard limits of what it can handle from climate change right now, leading to irreversible changes like extinction of species. “Ecosystems already reaching or surpassing hard adaptation limits include some warm water coral reefs, some coastal wetlands, some rainforests, and some polar and mountain ecosystems,” according to the report. Humans who are dependent on these ecosystems are deeply affected as well.
Coral reefs, for instance, are valuable ecosystems for tourism and coastal fisheries. They support more species per area than any other marine ecosystem and contribute about $375 billion to the global economy each year. Climate change causes several major problems for corals. Increased carbon dioxide dissolved in the water is making the ocean more acidic, harming the growth of corals. They also depend on a narrow range of optimal temperatures, between 73° and 84° Fahrenheit (23° to 29° Celsius), and warming water is pushing some species past their threshold of survivability.
There are hard limits to climate change adaptation that directly affect people too. Sea level rise is forcing residents of small islands to permanently evacuate. At least five islands in the Pacific Ocean have been lost to higher water levels. Rising temperatures are changing rainfall patterns and melting snowpacks, limiting freshwater for drinking and agriculture. This is driving migrations around the world.
One of the most important hard limits is the heat and humidity that people can endure. Scientists measure this using wet-bulb temperature, the highest temperature under a given amount of humidity where water will not evaporate. It serves as a proxy for how well the human body can cool itself off. For humans, the maximum tolerable wet-bulb temperature is 35 °C, or 95 °F, for six hours. Above that, even healthy people start experiencing severe, often fatal, health problems.
There are now regions in Iran, Pakistan, and India , all highly populated countries, that have approached or climbed above this threshold on several occasions. As climate change is raising global average temperatures, it’s also increasing the number and severity of extreme heat event. The frequency of places around the world approaching the human wet-bulb temperature limit has doubled since 1979.
In many parts of the world, it’s still possible for communities to adapt to higher temperatures and changing weather patterns, but they haven’t received enough resources to do so, according to the IPCC. Money in particular is one of the biggest soft barriers to adaptation.
For developing countries, adapting to climate change will cost around $127 billion per year by 2030, according to Edwin Castellanos, one of the IPCC report’s authors.
But investment in adaptation is falling woefully short, especially compared to efforts to curb emissions. “The overwhelming majority of global tracked climate finance was targeted to mitigation while a small proportion was targeted to adaptation,” according to the report.
While it’s critical to avert future warming by drawing down emissions now, researchers say that there is alarmingly little money to deal with harms occurring in the present. “People are suffering and dying right now from climate change,” said Kristie Ebi, an IPCC author, during a press conference. “The major constraint for adaptation options in health is the insignificant investment in this area.”
Money is not the only barrier, however. Millions of people are experiencing unprecedented changes and have little training or guidance for dealing with them. Many governments may not be up to the task either, lacking the political will or urgency to help their people deal with the changes to the climate they can’t avoid.
Some of the worst consequences are playing out for people with the fewest resources. “For soft limits, we are particularly seeing them in low-lying coastal areas and for smallholder farmers,” said Adelle Thomas, and one of the lead authors of the report, during a press briefing. “They don’t have the resources to adapt any further and they are experiencing devastating impacts of climate change now.”
The report highlights how some subsistence farmers in South America, Africa, and Asia have suffered costly crop losses from extreme weather worsened by climate change, forcing them out of business. In the Philippines, Typhoon Rai in 2021 caused more than $215 million in damages to crops and farmland. These types of losses in turn are fueling migration, poverty, disease, and political strife.
The upshot is that soft limits to adaptation are solvable problems. Improvements in technology, more funding, and better governance could allow people who were suffering the impacts of climate change to thrive.
As bad as the situation is right now, climate change can still get much worse. Rising temperatures mean that many more areas of the world, spanning some of the most populated regions, will experience times when it’s too hot to survive.
“High-resolution climate change simulations suggest that due to deadly heat waves projected in some of the densely populated agricultural regions of South Asia (i.e. Ganges and Indus river basins), are likely to exceed the critical threshold of wet-bulb temperature of 35 °C under the business-as-usual scenario of future greenhouse gas emissions,” according to the report.
Parts of central Asia and China are also poised to see wet-bulb temperatures above what people can tolerate in the coming decades. That will likely result in millions more deaths, particularly in dense urban areas.
“For example, at 1.5°C warming, without adaptation, annual heat-related mortality in 27 major cities across China is projected to increase from 32.1 per million inhabitants annually in 1986–2005 to 48.8– 67.1 per million,” according to the report. “This number increases to 59.2–81.3 per million for 2°C warming.”
Sea level rise is also poised to become unbearable for many. More than 150 million people currently live on land that will be below the high-tide line by 2050.
And if the world doesn’t move quickly enough, the window to adapt may close. “[W]hen compounded with lack of finance, and high costs associated with disasters and poverty and environmental degradation, soft limits might become hard ones in the future,” the report notes.
Scientists also note that the full scale of economic damage from the changes the world cannot adapt to remains unknown. “The loss and damage associated with the future climate change impacts, beyond the limits to adaptation, is an area of increasing focus, although yet to be fully developed,” according to the report.
One of the key findings of the previous installment of this round of reports is that it’s still technically possible to meet the 1.5 degree Celsius target of the Paris climate agreement, but every scenario considered overshoots this mark. Only the most aggressive cuts to greenhouse gas emissions bring global temperatures back below this line.
IPCC authors say their goal is not to prescribe specific policies. But the immense harm they highlight that’s underway and the more severe damage that lies ahead point toward the need for an economy-wide effort to prepare for changes the world can’t avoid.
“Adaptation and mitigation must be pursued with equal force and urgency,“ Guterres said. “Delay means death.”
The new IPCC report also warns that some adaptation measures can backfire. High temperatures may increase the demand for air conditioning powered by fossil fuels. A coastal seawall could damage protective ecosystems and create a false sense of security, encouraging more construction in vulnerable areas.
“There is increasing evidence of adaptation that has caused unintended consequences, for example destroying nature, putting peoples’ lives at risk or increasing greenhouse gas emissions,” according to the report.
But there are effective ways to adapt. Rebuilding damaged natural systems like wetlands, forests, and coral reefs can help cushion the blow of higher temperatures and rising seas. These measures have the added benefit of helping mitigate climate change, absorbing carbon dioxide or providing local cooling. So adaptation to climate change and mitigation work hand-in-hand, and the more that’s done to avert warming, the lower the needs for adaptation.
“Keeping climate change down to the lower levels is going to rely on getting natural systems in better shape to suck up carbon,” said Camille Parmesan, a lead author of the report, during a press conference. “Emissions reductions alone are not going to do it; it’s going to take carbon reduction as well.”
Another key element to adapting to climate change is addressing the inherent injustice of the problem. The people who contributed the fewest greenhouse gas emissions stand to suffer the most, while the countries that became wealthy from burning fossil fuels have the tools to insulate themselves.
So far, some of the wealthiest countries have hesitated to even acknowledge their disproportionate responsibility for climate change, let alone paying for the damages and losses already taking place.
This may be one of the biggest challenges of climate change adaptation. Negotiations on how to pay for adaptation measures across borders were not resolved at the last major international climate meeting in Glasgow, Scotland, and are on the agenda for the next meeting this year in Egypt.
All the while, global greenhouse gas emissions are continuing to rise. Adaptation will only become more essential, and more difficult.