Tipping points for the planet

A series of recent reports have made clear that our planet's complex environmental systems are undergoing profound changes as a result of human activities.

Glaciers around the world, from Greenland from Switzerland to Antarctica, are melting faster than expected as the heat of the atmosphere and oceans reaches new highs.

New research shows that up to half of the Amazon rainforest could quickly turn into grasslands or weakened ecosystems in the coming decades due to deforestation, climate change and drought. These stresses could ultimately push the entire forest ecosystem, home to a tenth of the Earth's land species, beyond a tipping point that would lead to the collapse of the entire forest.

And a new study suggests a crucial network of ocean currents transporting warm water to the North Atlantic shows early signs of collapse by the influx of fresh water from melting glaciers.

At first glance, all these developments seem worrying. But most worrying of all, they raise the specter that the planet is approaching some of the so-called tipping points that could bring about serious and irreversible changes.

Tim Lenton, a professor who studies climate and earth systems at the University of Exeter, said tipping points were characterized by “amplifying feedback within a system that becomes strong enough to cause self-propelling change.”

What that means in layman's terms: Once the key threshold is crossed, change accelerates and deep transformation becomes inevitable. Change begets more change in a self-reinforcing loop.

There is no consensus that large-scale tipping points have been reached, although there is debate about whether some, on the Greenland Ice Sheet and in many of the world's coral reefs, are close or have already tipped.

“Things we're actually seeing in the climate look a lot like tipping point changes, or serious harbingers of those changes,” Lenton said.

The turning points of the planet

The expression 'tipping point' has a complicated and controversial history. Scientists started talking regularly about climate tipping points in the early 2000s. They quickly came to the conclusion that some of those tipping points were quickly approaching, or perhaps had already passed.

The self-driving mechanism of tipping points usually consists of several feedback loops. Here are examples of how some of them work.

• Some of the most concerning are the world's vast ice sheets. For example, if the Greenland ice sheet collapses, global sea levels could rise by seven meters in the coming centuries. Feedback loops: As the ice melts, the surface decreases in height, meaning the air on top of it becomes warmer, leading to more melting. And disappearing ice means there are fewer white surfaces to reflect sunlight back into space, warming the atmosphere even more.

• Thawing permafrost could release gigatons of planet-warming methane into the atmosphere. Feedback: Methane causes the atmosphere to warm further, causing more permafrost to melt, and so on.

• Earth's ecosystems – such as forests, coral reefs and lakes – are also at risk, with far-reaching consequences. For example, the collapse of the boreal forests, which burned at an unprecedented rate last year, could send huge amounts of carbon into the atmosphere. Feedback: Fires cause water stress, which reduces trees' ability to resist insect pests, making them more vulnerable to fires.

• Currents and monsoons that regulate the oceans and atmosphere can slow, warm and change in many ways. For example, if the currents that bring warm water to the North Atlantic Ocean collapse, average temperatures in Western Europe could plummet within decades. Feedback: These currents move saltier water from one part of the ocean to another. As they weaken, less salt is transported and the surface water becomes less salty, making it less dense and less likely to sink, further weakening the current.

Since researchers began identifying tipping points, the list of systems close to the edge has grown steadily to the current twenty; some closer, some further from the collapse. You can check them all in a report on global tipping points that Lenton and his colleagues published a few months ago.

Good turning points

It's not just the planet that can experience tipping points. There are also industrial, technological and economic turning points. And some of them can help combat global warming.

Take the rapid decline in renewable energy costs. Last year we reported on a study that argued that solar energy had already passed a tipping point, as market forces alone, without help from policymakers, could make it the cheapest source of electricity by 2027. A similar dynamic could benefit wind energy, batteries and other energy sources. parts of the transition to clean energy.

The new economics of green energy is leading to an influx of spending in the sector. Last year, for the first time, total global investments in solar energy exceeded investments in oil.

Solar panels, wind turbines and batteries all experience surprising efficiency gains as well. And adoption of electric vehicles and heat pumps continues to rise as they become more affordable.

Lenton, who is writing a book about tipping points, noted that social norms can also change quickly, virtually overnight. (The phrase “tipping point” was used in the social sciences to describe a sudden stream of white families moving out of a particular neighborhood as black families moved in.)

Some people believe that we are the livestock industry that we consider unacceptable today in the future. Would it be objectionable to eat meat every day in the future? Will burning fossil fuels ever become unthinkable?

“Sometimes change really comes naturally and something big happens out of nowhere,” says Lenton. 'It can be very bad, if it is bad. But it can also be very good, if it is good.”

Rewilding the golf course

Shuttered golf courses across the country are being transformed into nature reserves, parks and wetlands. They include locations in Detroit, Pennsylvania, Colorado, the Finger Lakes in upstate New York and at least four in California.

While redesigning a golf course may disappoint players, it can have major benefits for animals, plants and non-golfers. On land owned by the University of California, Santa Barbara, the 64-acre area that was once the Ocean Meadows Golf Course is now an estuary surrounded by grasslands, a salt marsh and islands of coastal sage scrub. Two federally endangered plants, the Ventura marsh vetch and the salt marsh bird's beak, have also been established at the site, as part of an effort to move some plants north as their natural habitat becomes too warm.

Turning a golf course into a public green space requires an unlikely set of stars to align. There must be a willing seller and, crucially, a conservation-oriented buyer who can afford to not only buy the land, but also restore it. But the numbers are growing. Between 2010 and October 2022, approximately 28 former golf courses have been transformed into public green spaces. — Cara Buckley