Here are three dangerous climate tipping points that the world is on track for
The goal of the international climate meeting taking place in Egypt is to limit global warming to 1.5°C, compared to temperatures in the late nineteenth century. Even at this level, communities will face more dangerous storms, floods, and heat waves.
But if the planet’s temperature rises above 1.5 degrees, the effects won’t get even slightly worse. Scientists warn that sudden changes could occur, with devastating effects around the world.
Global temperatures have risen by about 2 degrees Fahrenheit since the late 19th century. Here, federal scientists show this change using the average temperature over each 5-year period going back to 1880.
These changes are sometimes called climate tipping points, although they are not as sudden as the term suggests. Most of it will unfold over decades. Some may take centuries. Some may be partially reversible or avoidable. But they all have enormous and lasting effects on humans, plants, and animals on Earth. They are looming.
Such widespread disasters can still be avoided, but only if countries move more aggressively to reduce the pollution that leads to climate change. The Earth’s temperature has increased by 1°C so far. If countries, including the United States, stick to current promises to reduce greenhouse gas emissions, the latest estimates suggest that Earth’s temperature will remain above 2.8°C of warming.
Here are the top three well-studied changes, from the collapse of ice sheets to the melting of Arctic ice, to the disappearance of coral reefs.
Ryan Kellman / NPR
Change #1: Greenland and West Antarctica’s ice sheets may collapse
Ice sheets are the vast expanses of ice covering Greenland and Antarctica, which contain about two-thirds of Earth’s fresh water. Climate change is already causing them to melt and raise sea levels around the world.
But if the Earth stays at two degrees Celsius or above warming, as it is on the right track, the Earth’s melting will accelerate steadily. Scientists warn that this will cause parts of the ice sheets to collapse, sending huge amounts of water into the world’s oceans.
The million-dollar question is how fast that crash can happen. “Avalanche tends to be kind of a loaded world. People think of it as a building collapse,” says Ian Joughin, a glaciologist at the University of Washington who has spent decades studying how giant glaciers move and change.
“Maybe it’s a better time scale for an ice sheet [collapsing] It is the Roman Empire,” explains Jugin. Like a dying empire, the ice sheets in Greenland and West Antarctica are huge. And it would take decades or even centuries to break up.
This year marks the 26th anniversary that Greenland has lost more ice than it gained. Last year, precipitation was recorded at the highest point of the ice sheet, rather than snow, in an indication that warmer temperatures led to widespread melting.
As temperatures continue to rise, scientists say the two-mile-thick ice sheet is out of balance. Snow and ice melt faster than it is being replaced, and as the snow melts accelerate, the process is hard to stop. One study found that no matter how humans reduce future greenhouse gas emissions, melting Greenland’s ice sheet will likely cause 10 inches of sea level to rise.
Research suggests that the collapse of the West Antarctic ice sheet may already be underway. A massive glacier there, which covers an area roughly the size of Washington State, is rapidly melting in response to climate change, and could split into the ocean in the coming decades.
If this glacier melted completely, it would add so much water to the oceans that sea level would rise by about two feet. If the West Antarctic ice sheet completely melted, scientists estimate that sea levels would rise by about 12 feet.
Because of their enormous size, ice sheets have a great deal of inertia. Once the melting process begins, it is difficult to stop.
“It takes a few hundred years to really get started,” says Joughin. “It’s kind of a snowball effect, in that the faster it goes, the more it goes.”
But it will take a long time for people around the world to feel the severe effects of this melting. “It could range from two or three hundred years to a thousand years,” says Joughin.
If humans slow the pace of global warming, it will help slow the pace of ice melt, giving the billions of people who live along coasts more time to adapt.
Change #2: Permanently frozen ground can thaw
Climate change is causing permafrost — the permanently frozen land in the Arctic — to thaw. As global warming approaches two degrees Celsius, the melting of the Earth will lead to both local and global problems.
Let’s start locally. When the permafrost thaws, the ice trapped in the ground turns into water and then drains away. “This can have really serious consequences,” says Merritt Tursky, director of the Institute for Arctic and Alpine Research at the University of Colorado, Boulder. “We could see lakes drying up overnight. We could see ecosystems getting drier in some areas, because permafrost was trapping water at the surface.”
This is because when the floor freezes, it is impermeable to moisture, like a bathtub liner. “When it melts, we pull the drain out of the bathtub,” Turetsky explains.
Melting permafrost has profound effects on the millions of people living in the Arctic. In many places, the ground is sinking as the snow melts, cracking building foundations, winding roads and walkways, and twisting pipelines. This will accelerate as the Earth warms even more.
Melting permafrost also has global climate impacts. The permanently frozen earth is like a frozen world: thousands of years of dead plants and animals are trapped in the permafrost.
“When the permafrost thaws, it’s a bit like losing energy in your freezer. And that food starts to rot,” explains Ted Shore, a permafrost expert at Northern Arizona University. Bacteria and fungi begin to digest carbon-rich soil, releasing methane and carbon dioxide into the atmosphere.
Essentially, it’s an endless loop of greenhouse gases: human emissions are causing the planet to warm. This heat melts the permafrost, releasing more emissions.
But how much extra carbon the polar permafrost releases in the future is up to humans. “The faster we can remove carbon from a community today, the more permafrost carbon we can keep in the Arctic land where it belongs,” says Turetsky. For example, by using renewable energy instead of burning fossil fuels.
But she warns there will be a delay: The warming that has already occurred will continue to melt permafrost for decades. “The warming of our climate today will melt permafrost and cause that permafrost to lose carbon 50 years from now,” Turetsky explains.
Change #3: Coral reefs can disappear forever
By total area, coral reefs are a small part of the ocean. But it is a rocky ecosystem of marine life, supporting an estimated 25% of all species.
Coral reefs are very sensitive to heat, and as the oceans warm, the future of coral reefs is at risk. When marine heat waves hit, corals under stress expel their algae companions, which they need to survive. Coral reefs turn ghostly white.
Bleaching does not necessarily mean the end of coral reefs. Corals have the ability to recover, if given enough time. But frequent heat waves, as seen in Australia’s Great Barrier Reef, can kill coral reefs, leading to ecosystem collapse.
The oceans are also becoming more acidic, as they absorb the carbon dioxide that humans emit from burning fossil fuels. It also affects corals, making it difficult for them to build their skeletons.
If the world exceeds 2°C of heat, an estimated 99% of the world’s coral reefs could be lost. The damage happens faster than scientists expected. Besides the effects of pollution and human development, half of coral reefs worldwide will be in unlivable conditions by 2035, according to a new study.
“The next decades will bring, I think, unprecedented change to both coral reef systems and humanity in general,” says Erik Franklin, a professor at the Hawaii Institute of Marine Biology at the University of Hawaii at Manoa, who worked on the study.
It is estimated that half a billion people around the world depend on coral reefs for food, income and livelihoods. The loss of coral reefs will destabilize many countries, along with risking the extinction of marine life that can only be found in coral reefs.
“There are entire societies and economies built around coral reef systems, especially in the tropics and tropics,” Franklin says. So these communities will be in dire straits.”
Many scientists are looking for “shelters” – pockets of the ocean where conditions may still be right for coral reefs. The hope is that corals can survive there, surviving long enough so that humans can control their greenhouse emissions.
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