How Close Are Planetary Weather Tips Points?

Right now, every minute of every day, we humans are slowly reorganizing the Earth’s climate. Hot summer and wet storms. High seas and more intense wildfires. It’s a constant, escalating turn of the dial on the multitude of threats that inhabit our homes, our communities and the environment around us.

It is also possible that we are changing the climate in an even bigger way.

For the past two decades, scientists have been warning major ecosystems that warming, caused by carbon emissions, may be headed for collapse. These systems are so large that they can remain somewhat balanced even as temperatures rise. But only the point.

If we warm the planet above certain levels, this balance may be lost, scientists say. The consequences can be severe and difficult to reverse. Not like the turn of a dial, but the flip of a switch. One that would not be easily turned back.

The Great Dying of Coral Reefs

When corals turn ghostly white, they are not really dead, and their reefs are not gone forever. Extreme heat in the water causes corals to release the algae that live inside their tissues. If conditions improve, they may survive this bleaching. Over time, reefs can grow back. However, as the world warms, the occasional dimming becomes more frequent. A little cleaning has become very white.

The latest predictions of scientists are bad. Even if humanity takes immediate action to control global warming, 70 to 90 percent of today’s reef-building corals could die in the coming decades. If we don’t, the toll could be 99 percent or more. An ocean can look healthy until its corals begin to decay and die. Finally, it is a grave.

This does not mean that coral reefs will disappear. Strong ones may endure in pockets. But the living ecosystem that supports these creatures will not be seen. There is no going back anytime soon, not in coral reefs today, not on any scale.

Where possible: It may continue.

Rapid Melting of Permafrost

On the ground below the coldest parts of the world, the accumulated remains of long-dead plants and animals contain as much carbon, almost twice as much as is currently in the atmosphere. As heat, wildfires and rains melt and thaw the frozen ground, microbes get to work, turning this carbon into carbon dioxide and methane. These greenhouse gases make heat and fire and rain worse, causing melting.

Like many of these large, spontaneous shifts in our climate, the melting of permafrost is difficult to predict. Large areas are already unfrozen, Western Canada, Alaska, Siberia. But how quickly some of the rest would decompose, how much that would add to global warming, how much carbon might remain trapped there because melting causes new vegetation to grow on top of it – all of that is hard to pin down. down.

“Because these things are so uncertain, there’s a bias to not talk about it or to dismiss it,” said Tapio Schneider, a climate scientist at the California Institute of Technology. “That, I think, is a mistake,” he said. “It’s still important to assess the risk, even if the likelihood of it happening in the future is relatively small.”

Where possible: Time will vary from place to place. The effects of global warming can accumulate over a century or more.

The collapse of the Greenland Ice

Large sheets of ice that blanket The poles of the earth don’t melt the way an ice cube melts. Because of their size and geometric complexity, many factors shape how quickly ice loses its mass and adds to the rising ocean. Among these factors, scientists are particularly concerned about those that may start to feed on themselves, causing rapid melting that would be very difficult to stop.

In Greenland, the problem is altitude. As the surface of the ice loses altitude, some of it settles in a cooler area, exposed to warmer air. That makes it melt faster.

Scientists know, from geological evidence, that large parts of Greenland were once ice-free. They also know that the effects of another major meltdown could reverberate around the world, affecting ocean currents and rainfall that reach the tropics and beyond.

Where possible: Irreversible melting may begin this century and unfold over hundreds, even thousands of years.

The breakup of the West Antarctic ice sheet

In another end of the world from Greenland, the ice of western Antarctica is less threatened by warm air than by warm water.

Most of the West Antarctic glaciers flow into the ocean, meaning their bottoms are exposed to constant ocean currents. As the water warms, these floating ice shelves melt and weaken from below, especially where they sit on the ocean floor. Like a dancer holding a difficult pose, the shelf begins to lose its place. With less floating ice blocking it, more ice from the interior of the continent can slide into the ocean. Eventually, the ice at the water’s edge may fail to support its own weight and break into pieces.

The West Antarctic ice sheet has probably fallen before, in Earth’s past. How close today’s ice is to the same suffering is something scientists are still trying to figure out.

“If you think about the future of the world’s coastal areas, 50 percent of the story will be the melting of Antarctica,” said David Holland, a scientist at New York University who studies the northern regions. And yet, he said, when it comes to understanding how continental ice can break up, “we’re at Day Zero.”

Where possible: As in Greenland, the ice may begin to retreat irreversibly this century.

Sudden Changes in the West African Monsoon

About 15,000 years ago, the Sahara began to turn green. It started when small shifts in the Earth’s orbit made North Africa sunny every summer. This warmed the land, causing the winds to shift and draw in more moist air from over the Atlantic. The moisture fell like hurricane rain, which ate the grass and filled the lakes, some as big as the Caspian Sea. Animals flourished: elephants, giraffes, cattle. So it was with people, as evidenced by rock carvings and paintings from that time. Only about 5,000 years ago did this region change into the harsh desert we know today.

Scientists now understand that the Sahara has flipped several times over the years between dry and wet, between barrenness and temperature. They are less sure if, and how, the heavy rainfall in West Africa could change or become stronger due to today’s warming. (Despite its name, the rain of this region also releases rain in parts of East Africa.)

Whatever happens will be of great importance in an area of ​​the world where the sustenance and livelihood of many people depend on the sky.

Where possible: It’s hard to predict.

The loss of the Amazon rainforest

Except being at home hundreds of Indigenous communities, millions of animals and 400 billion plants and trees; besides containing innumerable numbers of other organisms which have not yet been discovered, named and described; and apart from storing an abundance of carbon that may be warming the planet, the Amazon rainforest plays another big role. It is a living, moving, breathing weather engine.

The collective breathing of all those trees causes clouds of moist oil. When this moisture falls, it helps keep the area green and forested.

Now, however, farmers and ranchers are cutting down trees, and global warming is fueling wildfires and drought. Scientists are concerned that once the forest is gone, this rain machine could collapse, causing the entire forest to wither and become grassy plains.

By 2050, a large part of today’s Amazon rainforest could be at risk of this type of destruction, researchers recently estimated.

Where possible: It will depend on how quickly people clear it, or how much they protect the remaining forest.

Closure of the Atlantic Currents

Sweeping across the Atlantic Ocean, from the west coast of Africa, around the Caribbean and up to Europe before receding again, more ocean water sets temperatures and precipitation over much of the world. Salty, dense water sinks to the depths of the ocean while softer, lighter water rises, keeping this conveyor belt turning.

However, now the melting of the Greenland ice sheet is disrupting this balance by flooding the North Atlantic with a new flow of fresh water. Scientists fear that if the engine slows down too much, it could stop, changing the climate for billions of people in Europe and the tropics.

Scientists have already seen signs of inflation in these currents, which go by a mysterious name: the Atlantic Meridional Overturning Circulation, or AMOC. The hard part is predicting when the slowdown might be a shutdown. At the moment, our data and records are very limited, says Niklas Boers, a climate scientist at the Technical University of Munich and the Potsdam Institute for Climate Impact Research.

However, we know enough to be sure of one thing, said Dr. “With every additional gram of CO2 in the atmosphere, we increase the likelihood of giving events,” he said. He said: “The longer we wait” to reduce pollution, “the more we reach a dangerous point.”

Where possible: It is very difficult to predict.