The world is inches from the dreaded "tipping points" of global warming

The world is inches from the dreaded "tipping points" of global warming: 5 catastrophic scenarios.

The effects of climate change are usually evident over decades and centuries, but they seem to be everywhere this summer:

• Temperature records are constantly being broken.
• Ocean waters are warm as hot tubs.
• World leaders are so anxious that they've dubbed this "the age of the global boil."

In connection with these developments, scientists have long worried that more dramatic, looming, and irreversible changes to the planet could happen quickly. Even in the past year, there is evidence that some of these scenarios have become more likely.

A paper published in Science in 2022 investigated various climatic "tipping points" — conditions after which changes become self-perpetuating and difficult or impossible to reverse. While the concept angered some scientists, who suggested it was too simplistic, the paper suggested that the possibility of such points of no return provides compelling reasons for limiting warming as much as possible.

About a year later, many of the world systems that scientists have worried about are showing signs of becoming increasingly fragile.

Antarctic sea ice is at a record low, fires in Canada are reshaping the terrain, air is polluting, and record ocean temperatures are threatening coral reefs. Even new research published in July suggests critical Atlantic ocean currents could break sooner than expected, leading to rapid changes in weather and climate.

But the news isn't all bad: There is some good news out there for Amazon. And scientists say that if humanity takes climate threats seriously and moves quickly to end carbon emissions, the scenarios below become less likely or less extreme.

Here are five tipping points that scientists say could start to swing sooner rather than later:

Melting ice sheets could flood the oceans.

What could happen: Melting of the Antarctic and Greenland ice sheets, causing worldwide ocean levels to rise by an inch or, in the worst-case scenario, causing sea levels to rise by several feet.

When could it happen: Although it could take much longer, one paper suggested that the melt could severely affect Antarctica as quickly as 100 years from now and 300 years in Greenland.

What would the impact on Earth be: If the Antarctic Thwaites Glacier were to retreat later this century suddenly, it could add enough water to the world's oceans to raise sea levels by more than 10 feet. This could take hundreds of years, but every bit that melts makes high-altitude flooding worse, endangering the 680 million people living in low-lying coastal areas.

What has changed since last year? Sea ice in Antarctica has fallen by a record amount this year.

As of July 18, Antarctic sea ice was more than a million square miles less than the 1981-2010 average. According to the National Snow and Ice Data Center, that area is larger than the seven southwestern states, including Utah and Texas. It's also over half a million square miles less than last year, a previous record low.

In Greenland, temperatures over the ice sheet in the center and north of the country between 2001 and 2011 were the warmest in the past 1,000 years, said Maria Horhold, a glaciologist at the Alfred Wegener Institute for Polar and Marine Research in Germany and an author of a study that published this year.

What could happen: The massive ocean currents that move hot and cold water around could halt. Some studies have described it as an "irreversible transition."

When could it happen: New research suggests it could happen this century.

What the effect will be on Earth: Scientists aren't sure, but some say the pause could lead to rapid changes in the weather and climate in the United States, Europe, and elsewhere. It could lead to an ice age in Europe, rising sea levels in cities like Boston and New York, and more powerful storms and hurricanes along the East Coast.

What has changed since last year? Recent analysis shows that the current is weakening or slowing down.

The Atlantic Meridian Circulation (AMOC), a large system of ocean currents that transports warm water from the tropics to the North Atlantic, could collapse by mid-century, or perhaps anytime from 2025 onwards, due to human-caused climate change. , notes a study published last week.

It's far from a certainty, and many scientists say there isn't enough data yet to know if a trend could mean an imminent flash crash.

What could happen: The Amazon rainforest could transform from a lush to arid savanna. Far fewer species will live there, and much less carbon will be sequestered.

When could that happen? One estimate suggested it could happen as early as 2039.

What could be the effect on Earth? Sometimes called the "lungs of plants," the 2.5 million square miles of Amazon rainforest is so vast that it creates half of its rainfall and is home to 10% of the world's species. It also stores a large amount of carbon in the world.

What has changed in the past year? There is already good news - decreased Forest degradation in the Brazilian part of the Amazon is at its lowest level in six years, possibly because the nation has a new president who has vowed to protect the rainforest. Illegal logging makes rainforests less resilient to climate change.

As temperatures rise and droughts become more common, the forest's ability to grow back after fires or logging is a concern. This is a particular problem in the Amazon, where the trees pick up water through their roots and then release the moisture back through their leaves. An estimated single tree can emit 265 gallons of water per day.

If drought or logging kills the trees, there may not be enough left to bring water to the area, meaning that what grows back in its place will instead be grassland.

Wildfires could reshape Alaska and Canada, turning forests into grasslands.

What could happen: Massive wildfires could mean North America's vast boreal forests - sometimes called "snow forests" - could face a future as mostly treeless grasslands.

When could it happen: In some areas, it could reach 50% by 2100.

What will the impact be on Earth: These cold-weather forests stretch across Alaska and Canada and are estimated to store more than 30% of all forest carbon. Without it, huge amounts of greenhouse gases would be released into the atmosphere, exacerbating global warming.

What changed last year? Fires in Canada this summer have burned more than 50,000 square miles of forest. But even now, the boreal snow forests seem resilient, though the species that grow where are beginning to change.

Forests have always been burning, but what's happening now is different in every part of the country, said Marc-Andre Parisien, a research scientist with the Canadian Forest Service.

This summer has been a historically bad fire season in Canada. As of August 4, 1,054 active fires are burning, according to the Canadian Interagency Forest Fire Center.

While boreal forests are highly adapted to wildfires, the climate in forest areas is now much hotter and windier, making it difficult for seedlings to re-establish themselves. The concern is that in some areas, what grows after these huge fires may not be today's endless forests but grasslands and shrubs interspersed with smaller stretches of trees.

"The climate in the boreal forests has always been changing since the end of the Ice Age," Parisian said. "But the speed with which things are happening now is amazing."

What could happen: Rising ocean temperatures are cooking coral to death. If local deaths occur across the world's oceans, they will fundamentally change and reduce life under the sea.

When could it happen: The Intergovernmental Panel on Climate Change has predicted that a 1.5°C warming could lead to the disappearance of between 70 and 90% of the world's coral reefs - which could happen in the early 2000s.

What will impact Earth: Coral reefs are vital to ocean health. Although it only covers 0.2% of the ocean floor, it is home to at least a quarter of all marine species. They submit

Safety of small fish It is home to small organisms and fish that provide food for large fish. A report released last year showed that nearly 15% of the planet's coral reefs have disappeared since 2009.

What has changed since last year? Ocean temperatures have reached levels as high as 101.1 degrees off the coast of Florida, and the National Oceanic and Atmospheric Administration says the ocean surface experienced the third month in a row of record temperatures. Scientists are racing to save coral samples off the coast of Florida by hauling them out of ocean waters that have reached up to 101 degrees in recent weeks into tanks where they can be kept until the waters cool.

Corals can survive in a relatively narrow range of temperatures. Reef-building corals get much of their food from the algae in their tissues. When the seawater is too warm, the reaction of the corals is to expel the algae, which causes the corals to turn white. This process is called coral bleaching, and if it continues for too long, corals can starve — turning a thriving ecosystem into a graveyard of dead white shells.

The Coral Reef Restoration Foundation, a group centered on restoring and protecting coral reefs in Florida, said it visited Sombrero Reef off the Florida Keys on July 20 and found a "100% coral mortality rate." The foundation said the discovery means that all of the reefs on Sombrero Reef, a popular diving spot, are dead, and the reefs will only recover independently with active restoration.

Businesses do not despair.

Although humanity appears to be on track to miss the hoped-for UN limit for a temperature rise of no more than 1.5°C, giving up is not the answer, said Anthony Leserowitz, director of the Yale Climate Change Communication Program. 

There is no specific number indicating that all hope is lost. Instead, it is a call to action.

"It's not like we're falling off the world's edge," he said. "We can still make a huge difference; every tenth of a degree counts."