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The Montreal Protocol was designed to heal the ozone layer. It may have also fended off several degrees of warming—and a collapse of forests and croplands.

James Temple – August 18, 2021

The world has already banded together to enact an international treaty that prevented significant global warming this century—even though that wasn’t the driving goal.

In 1987, dozens of nations adopted the Montreal Protocol, agreeing to phase out the use of chlorofluorocarbons and other chemicals used in refrigerants, solvents, and other industrial products that were breaking down Earth’s protective ozone layer.

It was a landmark achievement, the most successful example of nations pulling together in the face of a complex, collective threat to the environment. Three decades later, the atmospheric ozone layer is slowly recovering, preventing additional levels of ultraviolet radiation that cause cancer, eye damage, and other health problems.

But the virtues of the agreement, ultimately ratified by every country, are more widespread than its impact on the ozone hole. Many of those chemicals are also powerful greenhouse gases. So as a major side benefit, their reduction over the last three decades has already eased warming and could cut as much as 1 ˚C off worldwide average temperatures by 2050.

Now, a new study in Nature highlights yet another crucial, if inadvertent, bonus: reducing the strain that ultraviolet radiation from the sun puts on plants, inhibiting photosynthesis and slowing growth. The Montreal Protocol avoided “a catastrophic collapse of forests and croplands” that would have added hundreds of billions of tons of carbon to the atmosphere, Anna Harper, a senior lecturer in climate science at the University of Exeter and a coauthor of the paper, said in an email.

The Nature paper, published August 18, found that if production of ozone-depleting substances had continued ticking up 3% each year, the additional UV radiation would have curtailed the growth of trees, grasses, ferns, flowers, and crops across the globe.

The world’s plants would absorb less carbon dioxide, releasing as much as 645 billion tons of carbon from the land to the atmosphere this century. That could drive global warming up to 1 ˚C higher over the same period. It would also have devastating effects on agricultural yields and food supplies around the globe.

The impact of rising CFCs levels on plants, plus their direct warming effect in the atmosphere, could have pushed temperatures around 2.5 ˚C higher this century, the researchers found. That would all come on top of the already dire warming projections for 2100.

“While it was originally intended as an ozone protection treaty, the Montreal Protocol has been a very successful climate treaty,” says Paul Young, a climate scientist at Lancaster University and another author of the paper.

All of which poses a question: Why can’t the world enact a similarly aggressive and effective international treaty designed explicitly to address climate change? At least some scholars think there are crucial but largely overlooked lessons in the success of the Montreal Protocol, which are becoming newly relevant as global warming accelerates and the next UN climate conference approaches.

A fresh look

At this point, the planet will continue warming for the next several decades no matter what, as the dire UN climate report warned last week. But how much worse it gets still depends heavily on how aggressively the world cuts climate pollution in the coming decades.

To date, nations have failed, both through the Kyoto Treaty and the Paris climate accord, to pull together an agreement with sufficiently ambitious and binding commitments to phase out greenhouse-gas emissions. Countries will assemble at the next UN conference in Glasgow in early November, with the explicit goal of stepping up those targets under the Paris agreement.

Scholars have written lengthy papers and entire books examining lessons from the Montreal Protocol, and the commonalities and differences between the respective efforts on CFCs and greenhouse gases.

A common view is that the relevance is limited. CFCs were a far simpler problem to solve because they were produced by a single sector—mostly by a few major companies like DuPont—and used in a limited set of applications.

On the other hand, nearly every component of every sector of every nation pumps out greenhouse gases. Fossil fuels are the energy source that drives the global economy, and most of our machines and physical infrastructure are designed around them.

But Edward Parson, a professor of environmental law at the University of California, Los Angeles, says it’s time to take a fresh look at the lessons from the Montreal Protocol.

That’s because as the dangers of climate change become more evident and dire, more and more countries are pushing for stricter rules, and companies are increasingly approaching the stage that those like DuPont did: switching from steadfastly disputing the scientific findings to grudgingly accepting that new rules were inevitable, so they had better figure out how to operate and profit under them.

In other words, we’re reaching a point where enacting more proscriptive rules may be feasible, so it’s crucial to use the opportunity to create effective ones.

Strict rules, consistently enforced

Parson is the author of Protecting the Ozone Layer: Science and Strategy, an in-depth history of the Montreal Protocol published in 2003. He stresses that phasing out ozone-depleting compounds was a more complex problem than is often appreciated, because a sizable fraction of the worldwide economy relied on them in one way or another.

He adds that one of the most persistent misunderstandings about the deal is the notion that the industry had already developed commercially comparable alternative products and therefore was more willing to go along with the agreement in the end.

On the contrary, the development of alternatives happened after the regulations were in place. Rapid innovation continued as the rules tightened, and industry, experts, and technical bodies hashed out how much progress could be achieved and how quickly. That produced ever more and better alternatives “in a repeated positive feedback,” Parson says.

To be sure, the prospect of lucrative new markets also helped.

“DuPoint’s decision to support a CFC ban was based on a belief that it could obtain a significant competitive advantage through the sale of new chemical substitutes because of its proven research and development capabilities to develop chemicals, its (limited) progress already made in developing substitutes and the potential for higher profits in selling new speciality chemicals,” a pair of MIT researchers wrote in an analysis in the late 1990s.

All of this suggests the world shouldn’t wait around for innovations that will make it cheaper and easier to address climate change. Countries need to implement rules that increasingly ratchet down emissions, forcing industries to figure out cleaner ways of generating energy, growing food, producing products, and moving things and people around the world.

Another lesson is to adopt sector-wide rules that force all companies in all countries to abide by the same regulations, avoiding the so-called free-rider problem. This could be especially key for high-emitting companies with stiff international competition. For steel, cement, and other industrial sectors, developing and switching to new products will almost inevitably increase costs at first.

Still, Parson says, there are limits to the comparisons here. The oil and gas sector isn’t in the same position as DuPont, able to reengineer substitutable products and largely keep its businesses and markets intact.

The fossil-fuel sector is certainly making the case that it can carry on in climate-friendly ways, talking up means of capturing emissions from power plants, balancing out pollution through reforestation projects and other sorts of offsets, or sucking carbon out of the atmosphere.

But as studies and articles continually show, it’s difficult to ensure that companies are doing these things in reliable, verifiable, long-lasting, and credible ways. Those tensions are likely to continue complicating international efforts to enact the firm rules required and ensure we’re making the progress that we must.

Still, the Montreal Protocol offers a reminder that international rules binding the global behavior of companies and regulating their products do work, if strictly and consistently enforced. Companies will adapt to survive—even to thrive.

Date: August 18, 2021

Source: Lancaster University

Summary: New modelling by the international team of scientists paints a dramatic vision of a scorched planet Earth without the Montreal Protocol, what they call the ‘World Avoided’. This study draws a new stark link between two major environmental concerns — the hole in the ozone layer and global warming. The research team reveals that if ozone-destroying chemicals, which most notoriously include CFCs, had been left unchecked then their continued and increased use would have contributed to global air temperatures rising by an additional 2.5°C by the end of this century.

Without the global CFC ban we would already be facing the reality of a ‘scorched earth’, according to researchers measuring the impact of the Montreal Protocol.

Their new evidence reveals the planet’s critical ability to absorb carbon from the atmosphere could have been massively degraded sending global temperatures soaring if we still used ozone-destroying chemicals such as CFCs.

New modelling by the international team of scientists from the UK, USA and New Zealand, published today in Nature, paints a dramatic vision of a scorched planet Earth without the Montreal Protocol, what they call the “World Avoided.” This study draws a new stark link between two major environmental concerns — the hole in the ozone layer and global warming.

The research team, led by a Lancaster University scientist, reveals that if ozone-destroying chemicals, which most notoriously include CFCs, had been left unchecked then their continued and increased use would have contributed to global air temperatures rising by an additional 2.5°C by the end of this century.

Their findings, outlined in the paper ‘The Montreal Protocol protects the terrestrial carbon sink’, show that banning CFCs has protected the climate in two ways — curbing their greenhouse effect and, by protecting the ozone layer, shielding plants from damaging increases in ultraviolet radiation (UV). Critically, this has protected plant’s ability to soak up and lock in carbon dioxide from the atmosphere and so prevented a further acceleration of climate change.

The research team developed a new modelling framework, bringing together data on ozone depletion, plant damage by increased UV, the carbon cycle and climate change. Their novel modelling shows an alternative future of a planet where the use of CFCs continued to grow by around three per cent a year.

Their modelling reveals:

• Continued growth in CFCs would have led to a worldwide collapse in the ozone layer by the 2040s.
• By 2100 there would have been 60 per cent less ozone above the tropics. This depletion above the tropics would have been worse than was ever observed in the hole that formed above the Antarctic.
• By 2050 the strength of the UV from the sun in the mid-latitudes, which includes most of Europe including the UK, the United States and central Asia, would be stronger than the present day tropics.

The depleted ozone layer would have seen the planet, and its vegetation, exposed to far more of the sun’s UV.

Plants absorb carbon dioxide (CO₂) through photosynthesis and studies have shown that large increases in UV can restrict plant growth, damaging their tissues, and impairing their ability to undertake photosynthesis. This means the plants absorb less carbon.

Less carbon in vegetation also results in less carbon becoming locked into soils, which is what happens to a lot of plant matter after it dies. All of this would have happened on a global scale.

The researchers’ models show that in a world without the Montreal Protocol the amount of carbon absorbed by plants, trees and soils dramatically plummets over this century. With less carbon in plants and soils, more of it remains in the atmosphere as CO₂.

Overall, by the end of this century without the Montreal Protocol CFC ban:

• There would have been 580 billion tonnes less carbon stored in forests, other vegetation and soils.
• There would be an additional 165-215 parts per million of CO₂ in the atmosphere, depending on the future scenario of fossil fuel emissions. Compared to today’s 420 parts per million CO₂, this is an additional 40-50%.
• The huge amount of additional CO₂ would have contributed to an additional 0.8°C of warming through its greenhouse effect.

Ozone depleting substances, such as CFCs, are also potent greenhouse gases and previous research has shown that their ban prevented their contribution to global warming through their greenhouse effect. By the end of this century, their greenhouse effect alone would have contributed an additional 1.7°C global warming. This is in addition to the newly quantified 0.8°C warming, coming from the extra CO₂ that would have resulted from damaged vegetation, meaning that temperatures would have risen 2.5°C overall.

Dr Paul Young, lead author from Lancaster University, said: “Our new modelling tools have allowed us to investigate the scorched Earth that could have resulted without the Montreal Protocol’s ban on ozone depleting substances.

“A world where these chemicals increased and continued to strip away at our protective ozone layer would have been catastrophic for human health, but also for vegetation. The increased UV would have massively stunted the ability of plants to soak up carbon from the atmosphere, meaning higher CO₂ levels and more global warming.

“With our research, we can see that the Montreal Protocol’s successes extend beyond protecting humanity from increased UV to protecting the ability of plants and trees to absorb CO₂. Although we can hope that we never would have reached the catastrophic world as we simulated, it does remind us of the importance of continuing to protect the ozone layer. Entirely conceivable threats to it still exist, such as from unregulated use of CFCs.”

The planet has already seen 1°C warming from pre-industrial temperatures. Even if we had somehow managed to get to net zero CO₂ emissions, the additional 2.5°C rise would take us to a rise of 3.5°C. This is far in excess of the 1.5°C rise above pre-industrial levels that many scientists see as the most global temperatures can rise in order to avoid some of the most damaging effects of climate change.

Dr Chris Huntingford of the UK Centre for Ecology & Hydrology said: “This analysis reveals a remarkable linkage, via the carbon cycle, between the two global environmental concerns of damage to the ozone layer and global warming.”

Background information

The ozone layer is an essential barrier that protects us by filtering the sun’s harmful UV — when a hole in the layer was discovered above Antarctica in the 1980s, it caused great alarm because of the damage UV can cause to human health through conditions such as skin cancers.

The Montreal Protocol, which was signed in 1987, is championed as an exemplar in environmental diplomacy. By agreeing to a worldwide ban on ozone depleting substances, including CFCs, international leaders were able to save the planet’s ozone layer. Thanks to the Montreal Protocol the ozone layer is undergoing a long process of repair.

Funders: The research was supported by the Engineering and Physical Science Research Council, Natural Environment Research Council, Lancaster University, the UK and New Zealand governments, NASA and the United States’ National Science Foundation.

The study brings together experts across atmospheric chemistry, physicists, plant scientists, and land surface modellers from Lancaster and Exeter Universities, the UK Centre for Ecology & Hydrology, NASA, the National Center for Atmospheric Research, and the National Institute for Water and Atmospheric Research.

Story Source:

Materials provided by Lancaster University. Note: Content may be edited for style and length.

Journal Reference:

1. Paul J. Young, Anna B. Harper, Chris Huntingford, Nigel D. Paul, Olaf Morgenstern, Paul A. Newman, Luke D. Oman, Sasha Madronich, Rolando R. Garcia. The Montreal Protocol protects the terrestrial carbon sink. Nature, 2021; 596 (7872): 384 DOI: 10.1038/s41586-021-03737-3