CNN  — 

Climate change is on course to transform life on Earth as we know it, and unless global warming is dramatically slowed, billions of people and other species will reach points where they can no longer adapt to the new normal, according to a major report published Monday.

The UN-backed report, based on years of research from hundreds of scientists, found that the impacts from human-caused climate change were larger than previously thought. The report’s authors say these impacts are happening much faster and are more disruptive and widespread than scientists expected 20 years ago.

The authors point to enormous inequities in the climate crisis, finding that those who contribute the least to the problem are the worst affected, and warn of irreversible impacts if the world exceeds 1.5 degrees Celsius of global warming.

UN Secretary-General António Guterres called the report “an atlas of human suffering and a damning indictment of failed climate leadership,” and he warned that “delay means death.”

“The facts are undeniable. This abdication of leadership is criminal,” Guterres said in a statement. “The world’s biggest polluters are guilty of arson of our only home.”

He also said that “current events” showed the world was too reliant of fossil fuels, calling them “a dead end,” in an apparent reference to the Ukraine conflict and energy crisis.

Here are the report’s key takeaways:

Warming beyond 1.5 degrees could have irreversible consequences

Bleaching of the coral reefs around French Polynesia in 2019.

Scientists have warned for decades warming needs to stay below 1.5 degrees Celsius above preindustrial levels.

Monday’s report, from the UN Intergovernmental Panel on Climate Change (IPCC), showed if that limit is breached, some changes will be irreversible for hundreds — if not thousands — of years. And some changes may be permanent, even if the planet cools back down.

The world is already 1.1 degrees Celsius warmer than before industrialization, according to the IPCC’s estimate, which is considered conservative. We are now rapidly barreling toward 1.5 degrees.

With every extreme event, ecosystems are being pushed more toward so-called tipping points beyond which irreversible changes can happen, according to the report.

At warming of 2 degrees, for example, as many as 18% of all land species will be at high risk of extinction, according to the report. At 4 degrees, 50% of species are threatened.

“There are many challenges already with 1.5 degrees for several systems that we know about,” said Hans-Otto Pörtner, a co-chair on the report and a scientist at the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research.

“Clearly for coral reefs, we must say that in many locations, they are already beyond tipping points. They are on the downslide.”

A man works in the Swiss Alps at the Rhone Glacier in October 2021, which is partially covered with insulating foam to prevent it from melting due to global warming.

Highly vulnerable ecosystems in the Arctic, mountains and on the coasts are at the greatest risk to these changes, the authors say. Ice sheet and glacier melt will cause accelerated sea level rise, irreversible for centuries.

Forests, peatlands and permafrost — places where greenhouse gas is naturally stored — risk being pushed into a situation where they are emitting those gases into the atmosphere, causing even more warming.

We’re running out of ways to adapt

“Adaptation” is finding ways to live with the change — like putting up walls to ward off sea level rise or implementing new building codes to ensure homes can withstand more extreme weather.

Scientists note some of our adaptations have blunted the impact of the climate crisis so far, but they are not adequate in the long-term. Our options to adapt will become even more limited at 1.5 degrees.

A flood defense wall being constructed on the east side of Manhattan in New York City on December 11, 2021.

And although the natural world has adapted to changing climates over millions of years, the pace of human-caused global warming is pushing many of the planet’s most critical systems — like rainforests, coral reefs and the Arctic — to the brink. More extreme weather doesn’t just affect humans, it is causing mass die-offs in plants and animals.

Population growth and development, which has not been carried out with long-term adaptation in mind, are also luring people into harm’s way. As many as 3.6 billion people live in places already highly vulnerable to climate hazards, some of which will increase beyond the ability to adapt once the planet hits the 1.5-degree mark.

A lot of the world’s resources, particularly international finance, goes toward reducing greenhouse emissions, which is known as mitigation. At the COP26 climate talks in Glasgow, Scotland, last year, developing nations complained that the rich world was failing to help adequately fund adaptation in their countries.

“We have seen that the vast majority of climate finance goes towards mitigation rather than adaptation,” said Adelle Thomas, an author on the report and a climate scientist at the University of the Bahamas. “So although adaptation is taking place, there is not enough funding, and it is not a high priority, which are then leading to these limits.”

Up to 3 billion people will experience ‘chronic water scarcity’

Residents fill water containers during a shortage in Nairobi, Kenya, in January.

Around half of the world’s population experiences severe water scarcity each year in part due to climate-related factors, the report showed. Water will become even more scarce at higher global temperatures.

At 2 degrees of warming — which scientists predict the planet will reach by midcentury — as many as three billion people around the world will experience “chronic water scarcity,” according to the report. It increases to four billion people at 4 degrees.

Water shortages will put enormous pressure on food production and increase the world’s already dire food-security challenges.

A water crisis is already brewing in the Western United States. Multiyear drought has drained reservoirs and triggered unprecedented water cuts for the region. Lake Mead, the country’s largest reservoir, plunged to record lows in recent months, threatening water supply for tens of millions of people.

Dead almond trees lie in an open field after they were removed by a farmer because of a lack of water to irrigate them, in Huron, California, in July 2021. The authors say drought has put a hard limit on adaptation for almond growing.