5 takeaways from the latest United Nations climate change report

Monday’s IPCC report is a warning letter to the world. Here’s what you need to know from the more than 3,500-page document.

The downtown skyline is shrouded in darkness after Hurricane Ida knocked out power in New Orleans in 2021. (Michael Robinson Chavez/The Washington Post)
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The latest report from the United Nations Intergovernmental Panel on Climate Change is a warning letter to a world on the brink. A sweeping survey of the most advanced climate science on the planet, it recounts the effects rising temperatures are already having and projects the catastrophes that loom if humans fail to make swift and significant cuts to greenhouse gas emissions.

The more than 3,500-page document is rife with devastating details about the toll of rising sea levels, scorching heat and escalating natural disasters. Here are five key points from the report about what the world stands to lose and all that can still be salvaged.

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A certain amount of suffering is inevitable, though adaptation can help

Humanity has unleashed more than a trillion tons of carbon dioxide since the start of the Industrial Revolution, fueling an average global temperature rise of more than one degree Celsius (1.8 degrees Fahrenheit) compared to the late 19th century. Those emissions, even if they ceased tomorrow, have set in motion a certain amount of irreversible change.

Postcards from Earth’s climate futures

Already, fish species are dying in oceans that have become warmer, more acidic and depleted of oxygen. Ravenous wildfires, ferocious hurricanes and unprecedented flooding have claimed lives and destroyed communities across the globe. One study of the world’s 150 biggest cities found that these areas have seen a 500 percent increase in extreme heat since 1980.

Near-term deterioration of environmental conditions could result in as much as 14 percent of species facing a “very high risk of extinction,” with even worse outcomes the more the world warms, the IPCC report finds. Even the best-case scenarios, which limit temperature rise to 1.5 degrees Celsius (2.7 degrees Fahrenheit), project the demise of an overwhelming majority of coral reefs and irreversible loss of glaciers and polar ice by the end of the century.

In coming decades, changes in temperature and weather patterns will make some agricultural areas unsuitable for the crops that are currently grown. Sea level rise will continue to threaten coastal communities. Annual deaths from climate-related illnesses such as extreme heat exposure, diarrheal disease and childhood malnutrition are projected to increase by 250,000 within the next 30 years.

But in many cases, the scientists say, adaptation can make a significant dent in the suffering.


Every incremental increase in temperature will lead to dramatically more disease, death and frequent, costly disasters

World leaders vowed in the Paris climate agreement to limit Earth’s warming to “well below” 2 degrees Celsius (3.6 Fahrenheit), and if possible to stop at 1.5 Celsius. While nations remain woefully far from hitting those goals, the science could not be clearer: Each increment of additional warming brings more devastation, more death — and more dollars spent on coping.

“Climate change is a threat to human well-being and planetary health,” the IPCC authors write. “Any further delay in concerted anticipatory global action on adaptation and mitigation will miss a brief and rapidly closing window of opportunity to secure a livable and sustainable future for all.”

The difference between 1.5 degrees and 2 degrees Celsius of temperature rise, Monday’s report states, would mean an additional 65 million people exposed to “exceptionally” extreme heat waves every five years.

Already, between 1.5 and 2.5 billion people live in areas exposed to water scarcity. These numbers are projected to increase continuously, with estimates of up to 3 billion at 2 degrees Celsius of warming. In the worst-case warming scenarios, projections show an additional 9 million annual deaths from climate-related illnesses by 2100, compared to the period from 1961 to 1990.

Climate change will make some current crop production areas unsuitable and force millions more humans to face hunger by mid-century. Some regions could experience 200 or more days a year where outdoor work is not feasible.

No place on Earth will be left unscathed by climate change. But the regions that contributed the least to the problem — particularly Africa, Central America, South Asia and small island states — will suffer some of the harshest consequences.

And coming generations will inherit a much harsher planet than the one their parents knew. For instance, people younger than 10 in the year 2020 are projected to experience a nearly fourfold increase in extreme events at 1.5 degrees Celsius of global warming and a fivefold increase if temperatures rise by 3 degrees Celsius (5.4 degrees Fahrenheit).


Climate change is battering the places and populations least able to adapt, and that is all but certain to continue

The gap between rich and poor countries will likely widen as the world warms, Monday’s IPCC report makes clear.

In the past decade, the average number of deaths from floods, droughts and storms in countries considered “highly vulnerable” was 15 times higher than in places with low vulnerability, such as the United Kingdom, Canada and Sweden.

Even moderate scenarios for sea level rise would risk inundating coastlines where roughly 90 percent of all Pacific Islanders live. At high levels of warming, small island states and some tropical regions will hit limits on their ability to adapt to flooding and extreme heat. Depending on how much temperatures rise, between 31 million and 143 million people could become displaced in sub-Saharan Africa, South Asia and Latin America.

African nations will suffer some of the most extreme inequities. These countries have contributed less than 3 percent of cumulative global emissions, yet in the near term they are projected to experience over half of excess deaths from climate-related illnesses. The worst-case scenario for warming would increase extreme heat exposure in Africa to 118 times historical levels. By contrast, heat exposure in Europe would go up only fourfold.

Current financial support for adaptation projects in African nations falls billions of dollars short of what’s needed, the IPCC authors say — illustrating a problem that persists in vulnerable nations all over the world, where access to climate finance is slow and inadequate. This disparity extends to basic information needed for adaptation; just 3.8 percent of funding for climate research has gone to projects focused on Africa over the past three decades.


Global warming is wreaking havoc on plants and wildlife

By shifting seasonal weather patterns and intensifying disruptive disasters, human-caused warming imperils almost all forms of life on Earth. Plants and animals are unable to shift their habitats fast enough to keep up with rising temperatures. Catastrophic wildfires and fierce hurricanes can incinerate forests and obliterate coastal ecosystems. Creatures whose migrations are triggered by seasonal changes in daylight are falling out of sync with the plants they eat, which flower and leaf out in response to warmer weather.

The risk of sudden and severe die-offs becomes much higher if global temperatures rise by 2 degrees Celsius or more, scientists say.

The IPCC report estimates that 10 percent of all plant and animal species could face high risk of extinction even if the world limits warming to 2 degrees Celsius. In less than a century, the losses would equal the number of species driven to extinction by human activities over the last 12,000 years.

Yet threats to biodiversity also hurt humans, who depend on ecosystems to provide food and clean the water and air. By weakening wildlife populations and damaging habitats, climate change increases the chance of diseases jumping from animals to people, the IPCC warns.

Meanwhile, rising temperatures risk unleashing millions of tons of carbon currently stored in vegetation and soil. Projected loss of forests and thawing of permafrost under some of the worst-case warming scenarios would add the equivalent of 15 years’ worth of greenhouse gas emissions to the atmosphere. But curbing warming to below 2 degrees Celsius would cut emissions from these ecosystems by more than half.


For many locations on Earth, the capacity for adaptation is already significantly limited, even as it becomes more critical

For all the grim news packed in Monday’s findings, its overarching message is not one of hopelessness, but urgency.

The authors make clear that humans have the ability to adapt to some of the challenges posed by climate change. But they also underscore that time is running short. The world must make significant investments in the next few years if it hopes to adapt to the climatic shifts that are already happening and avert more drastic change in the future.

To date, the report found, adaptation responses around the world have largely been incremental, reactive and small in scale — “designed to respond to current impacts or near-term climate change risks” rather than the more profound changes that are coming.

One example is sea walls, which actually allow for more intense development in coastal areas, as well as inadequate infrastructure in cities that cannot easily or affordably be altered to deal with heavier rainfall and other extreme weather.

Nowhere is the imperative to adapt more acute than in developing nations and small island states that already are facing gut-wrenching climate damage — and that least can afford to cope. In these places, which have done little to cause global warming and where individuals have far lower carbon footprints than in the industrialized world, the lack of access to climate financing is crippling.

“There is a rapidly narrowing window of opportunity,” the report’s authors write, “to enable climate resilient development.”

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