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dairy cows are methane producing machines

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Authors: Milena Bojovic, PhD Candidate, Macquarie University


This article is republished from The Conversation under a Creative Commons license. Read the original article.

Milena Bojovic, Macquarie University

New Zealand’s dairy sector faces an uncertain future due to several challenges, including water pollution, high emissions, animal welfare concerns and market volatility.

All of these issues are building tensions and changing public perceptions of dairy farming.

In my new research, I argue the time has come for the dairy sector to adopt a “just transition” framework to achieve a fair and more sustainable food future and to navigate the disruptions from alternative protein industries.

The concept of a just transition is typically applied to the energy sector in shifting from fossil fuels to renewable energy sources.

But a growing body of research and advocacy is calling for the same principles to be applied to food systems, especially for shifting away from intensive animal agriculture.

Aotearoa New Zealand’s dairy sector is an exemplary case study for examining the possibilities of a just transition because it is so interconnected in the global production and trade of dairy, with 95% of domestic milk production exported as whole-milk powder to more than 130 countries.

Environmental and economic challenges

New Zealand’s dairy sector faces significant threats. This includes environmental challenges such as alarming levels of nitrate pollution in waterways caused by intensive agriculture.

The sector is also a major source of emissions of biogenic methane from the burps of almost six million cows in the national dairy herd.

Debates about how to account for these emissions have gone on for many years in New Zealand. But last month, the coalition government passed legislation to keep agriculture out of the Emissions Trading Scheme.

This means livestock farmers, agricultural processors, fertiliser importers and manufacturers won’t have to pay for on-farm emissions. Instead, the government intends to implement a pricing system outside the Emissions Trading Scheme by 2030. To meet emissions targets, it relies on the development of technologies such as methane inhibitors.

A cheese board with soem bread and a cheese made from cashews
The development of plant-based and fermentation proteins poses another threat to the dairy sector. Getty Images

In addition to environmental challenges, global growth and domestic initiatives in the development of alternative dairy products are changing the future of milk production and consumption.

New Zealand dairy giant Fonterra is pursuing the growth of alternative dairy with significant investments in a partnership with Dutch multinational corporation Royal-DSM. This supports precision fermentation start-up Vivici, which already has market-ready products such as whey protein powder and protein water.

Fonterra’s annual report states it anticipates a rise in customer preference towards dairy alternatives (plant-based or precision-fermentation dairy) due to climate-related concerns. The company says these shifting preferences could pose significant business risks for future dairy production if sustainability expectations cannot be met.

Pathways to a just transition for dairy

What happens when one the pillars of the economy becomes a major contributor to environmental degradation and undermines its own sustainability? Nitrate pollution and methane emissions threaten the quality of the land and waterways the dairy sector depends on.

In my recent study which draws on interviews with people across New Zealand’s dairy sector, three key transition pathways are identified, which address future challenges and opportunities.

  • Deintensification: reducing the number of dairy cows per farm.

  • Diversification: introducing a broader range of farming practices, landuse options and market opportunities.

  • Dairy alternatives: government and industry support to help farmers participate in emerging plant-based and precision-fermentation industries.

While the pathways are not mutually exclusive, they highlight the socioeconomic and environmental implications of rural change which require active participation and engagement between the farming community and policy makers.

The Ministry of Business, Innovation and Employment recently published a guide to just transitions. It maps out general principles such as social justice and job security.

But the guide is light on advice for agricultural transitions. My work puts forward recommendations to shape future policy for a more just and sustainable dairy future. This includes issues such as navigating intensification pressures, supporting the development of alternative proteins and fundamentally supporting farmer agency in the transition process.

For the dairy transition to be fair and sustainable, we need buy-in from leadership and support from government, the dairy sector and the emerging alternative dairy industry to help primary producers and rural communities. This needs to be specific to different regions and farming methods.

The future of New Zealand’s dairy industry depends on its ability to adapt. Climate adaptation demands balancing social license, sustainable practices and disruptions from novel protein technologies.The Conversation

Milena Bojovic, PhD Candidate, Macquarie University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Plastic bags in ocean image: Naja Bertolt Jensen

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With the failure of a global plastics treaty—oil-rich nations and the petrochemical industry putting up the strongest opposition—the following article should give food for thought, especially as every mouthful of seafood contains microplastics.


This article is republished from The Conversation under a Creative Commons license. Read the original article.
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We’ve all seen the impact of our plastic addiction. It’s hard to miss the devastating images of whales and sea birds that have died with their stomachs full of solidified fossil fuels. The recent discovery of a plastic bag in the Mariana Trench, at over 10,000 metres below sea level, reminds us of the depth of our problem. Now, the breadth is increasing too. New research suggests that chemicals leaching from the bags and bottles that pepper our seas are harming tiny marine organisms that are central to sustained human existence.

Once plastic waste is out in the open, waves, wind and sunlight cause it to break down into smaller pieces. This fragmentation process releases chemical additives, originally added to imbue useful qualities such as rigidity, flexibility, resistance to flames or bacteria, or a simple splash of colour. Research has shown that the presence of these chemicals in fresh water and drinking water can have grave effects, ranging from reduced reproduction rates and egg hatching in fish, to hormone imbalances, reduced fertility or infertility, cardiovascular diseases, diabetes and cancer in humans.

But very little research has looked at how these additives might affect life in our oceans. To find out, researchers at Macquarie University prepared seawater contaminated with differing concentrations of chemicals leached from plastic bags and PVC, two of the most common plastics in the world. They then measured how living in such water affected the most abundant photosynthesising organism on Earth – Prochlorococcus. As well as being a critical foundation of the oceanic food chain, they produce 10% of the world’s oxygen.

Prochlorococcus are miniscule, but there are as many of them in the oceans as there are atoms in a ton of gold. Chisholm Lab/Flickr

The results indicate that the scale and potential impacts of plastic pollution may be far greater than most of us had imagined. They showed that the chemical-contaminated seawater severely reduced the bacteria’s rate of growth and oxygen production. In most cases, bacteria populations actually declined.

What can be done?

Given the importance of oxygen levels to the rate of global heating, and the vital role these phytoplankton play in ensuring thriving marine ecosystems, it is essential that we now conduct research outside of the laboratory into the effects of plastic additives on bacteria in the open seas. In the meantime, we need to take active steps to reduce the risks of chemical plastic pollution.

The clear first step is to reduce the amount of plastic entering the ocean. Recent EU and UK bans on single-use plastics are a start, but much more radical policies are needed now to reduce the role plastic plays in our lives as well as to stop the plastic we do use being released into waterways and dramatically improve appallingly low recycling rates.

At an international level, we must make addressing the waste produced by the fishing industry a priority. Broken fishing nets alone account for almost half of the plastic in the Great Pacific Garbage Patch – and lost or discarded fishing gear accounts for one-third of the plastic litter in European seas. EU incentives announced in 2019 to tackle this waste do not go far enough.

Discarded fishing nets and other fishing gear make up a significant proportion of the plastic in our oceans. Aqua Images/Shutterstock

Legislation is also urgently needed to limit the industrial use of harmful chemical additives to a level that is absolutely necessary. As an example, bisphenol A, found in myriad products ranging from receipt paper to rubber ducks, is now listed as a “substance of very high concern” due to its hormone-disrupting effects. But as yet the few existing laws regulating the chemical do not cover the majority of industrial use. This needs to change – as quickly as possible.

Of course, even if we can completely stop new chemicals from reaching the oceans, we will still have a legacy of plastic and associated chemical pollution to deal with. At the moment, we have no idea whether we’ve already done irreversible damage, or if marine ecosystems are resilient to current levels of plastic pollution in the open oceans. But the health of our oceans is not something we can risk. So, in addition to physical removal schemes such as The Ocean Clean Up, we need to invest in chemical removal technologies as well.

In salty ocean environments, such technologies are under-researched. We are currently in the early stages of developing a floating device that uses a small electric circuit to transform BPA into easily retrievable solid matter, but our work alone is not enough. Scientists and governments need to ramp up their efforts to both understand and eliminate the problem of chemical contamination of our oceans, before it’s too late.

While ocean bacteria may seem far removed from our daily lives, we are dependent on these tiny organisms to maintain the balance of our ecosystems. We ignore their plight at our peril.The Conversation

Carbon trading

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Author:

Kate Dooley, Senior Research Fellow, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Negotiators at the COP29 climate conference in Baku have struck a landmark agreement on rules governing the global trade of carbon credits, bringing to a close almost a decade of debate over the controversial scheme.

The deal paves the way for a system in which countries or companies buy credits for removing or reducing greenhouse gas emissions elsewhere in the world, then count the reductions as part of their own climate efforts.

Some have argued the agreement provides crucial certainty to countries and companies trying to reach net-zero through carbon trading, and will harness billions of dollars for environmental projects.

However, the rules contain several serious flaws that years of debate have failed to fix. It means the system may essentially give countries and companies permissions to keep polluting.

What is carbon offsetting?

Carbon trading is a system where countries, companies or other entities buy or sell “credits”, or permits, that allow the buyer to offset the greenhouse gas emissions they produce.

For example, an energy company in Australia that produces carbon emissions by burning coal may, in theory, offset their impact by buying credits from a company in Indonesia that removes carbon by planting trees.

Other carbon removal activities include renewable energy projects, and projects that retain vegetation rather than cutting it down.

Carbon trading was a controversial part of the global Paris climate deal clinched in 2015.

The relevant part of the deal is known as “Article 6”. It sets the rules for a global carbon market, supervised by the United Nations, which would be open to companies as well as countries. Article 6 also includes trade of carbon credits directly between countries, which has begun operating even while rules were still being finalised.

Rules for carbon trading are notoriously complex and difficult to negotiate. But they are important to ensure a scheme reduces greenhouse gas emissions in reality, not just on paper.

A long history of debate

Over the past few years, annual COP meetings made some progress on advancing the carbon trading rules.

For example, COP26 in Glasgow, held in 2021, established an independent supervisory body. It was also tasked with other responsibilities such as recommending standards for carbon removal and methods to guide the issuing, reporting and monitoring of carbon credits.

But the recommendations were rejected at COP meetings in 2022 and 2023 because many countries viewed them as weak and lacking a scientific basis.

At a meeting in October this year, the supervisory body published its recommendations as “internal standards” and so bypassed the COP approval process.

At this year’s COP in Baku, the Azerbaijani hosts rushed through adoption of the standards on day one, prompting claims proper process had not been followed

For the remaining two weeks of the conference, negotiators worked to further develop the rules. A final decision was adopted over the weekend, but has attracted criticism.

For example, the Climate Land Ambition and Rights Alliance says the rules risk “double counting” – which means two carbon credits are issued for only one unit of emissions reduction. It also claims the rules fail to prevent harm to communities – which can occur when, say, Indigenous Peoples are prevented from accessing land where tree-planting or other carbon-storage projects are occurring.

Getting to grips with carbon removal

The new agreement, known formally as the Paris Agreement Trading Mechanism, is fraught with other problems. Most obvious is the detail around carbon removals.

Take, for example, the earlier scenario of a coal-burning company in Australia offsetting emissions by buying credits from a tree-planting company in Indonesia. For the climate to benefit, the carbon stored in the trees should remain there as long as the emissions produced from the company’s burning of coal remains in the atmosphere.

But, carbon storage in soils and forests is considered temporary. To be considered permanent, carbon must be stored geologically (injected into underground rock formations).

The final rules agreed to at Baku, however, fail to stipulate the time periods or minimum standards for “durable” carbon storage.

Temporary carbon removal into land and forests should not be used to offset fossil fuel emissions, which stay in the atmosphere for millennia. Yet governments are already over-relying on such methods to achieve their Paris commitments. The weak new rules only exacerbate this problem.

To make matters worse, in 2023, almost no carbon was absorbed by Earth’s forests or soils, because the warming climate increased the intensity of drought and wildfires.

This trend raises questions about schemes that depend on these natural systems to capture and store carbon.

Temporary carbon removal into land and forests should not be used to offset fossil fuel emissions.
Temporary carbon removal into land and forests should not be used to offset fossil fuel emissions.

What next?

Countries already can, and do, trade carbon credits under the Paris Agreement. Centralised trading will occur under the new scheme once the United Nations sets up a registry, expected next year.

Under the new scheme, Australia should rule out buying credits for land-based offsets (such as in forests and soil) to compensate for long-lasting emissions from the energy and industry sectors.

Australia should also revise its national carbon trading scheme along the same lines.

We could also set a precedent by establishing a framework that treats carbon removals as a complement — not a substitute — for emissions reduction.The Conversation

Ilulissat Greenland, midnight sun. Photo: Cody Whitelaw

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Authors:

Laurie Menviel, Post-doctoral Research Fellow, Climate Change Research Centre, UNSW Sydney and Gabriel Pontes, Post-doctoral Research Fellow, Climate Change Research Centre, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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A vast network of ocean currents nicknamed the “great global ocean conveyor belt” is slowing down. That’s a problem because this vital system redistributes heat around the world, influencing both temperatures and rainfall.

The Atlantic Meridional Overturning Circulation funnels heat northwards through the Atlantic Ocean and is crucial for controlling climate and marine ecosystems. It’s weaker now than at any other time in the past 1,000 years, and global warming could be to blame. But climate models have struggled to replicate the changes observed to date – until now.

Our modelling suggests the recent weakening of the oceanic circulation can potentially be explained if meltwater from the Greenland ice sheet and Canadian glaciers is taken into account.

Our results show the Atlantic overturning circulation is likely to become a third weaker than it was 70 years ago at 2°C of global warming. This would bring big changes to the climate and ecosystems, including faster warming in the southern hemisphere, harsher winters in Europe, and weakening of the northern hemisphere’s tropical monsoons. Our simulations also show such changes are likely to occur much sooner than others had suspected.

The Atlantic Meridional Overturning Circulation (AMOC): what is it and why is it so important? (National Oceanography Centre)

Changes in the Atlantic Meridional Overturning Circulation

The Atlantic ocean circulation has been monitored continuously since 2004. But a longer-term view is necessary to assess potential changes and their causes.

There are various ways to work out what was going before these measurements began. One technique is based on sediment analyses. These estimates suggest the Atlantic meridional circulation is the weakest it has been for the past millennium, and about 20% weaker since the middle of the 20th century.

Evidence suggests the Earth has already warmed 1.5ºC since the industrial revolution.

The rate of warming has been nearly four times faster over the Arctic in recent decades.

Meltwater weakens oceanic circulation patterns

High temperatures are melting Arctic sea ice, glaciers and the Greenland ice sheet.

Since 2002, Greenland lost 5,900 billion tonnes (gigatonnes) of ice. To put that into perspective, imagine if the whole state of New South Wales was covered in ice 8 metres thick.

This fresh meltwater flowing into the subarctic ocean is lighter than salty seawater. So less water descends to the ocean depths. This reduces the southward flow of deep and cold waters from the Atlantic. It also weakens the Gulf Stream, which is the main pathway of the northward return flow of warm waters at the surface.

The Gulf Stream is what gives Britain mild winters compared to other places at the same distance from the north pole such as Saint-Pierre and Miquelon in Canada.

Our new research shows meltwater from the Greenland ice sheet and Arctic glaciers in Canada is the missing piece in the climate puzzle.

When we factor this into simulations, using an Earth system model and a high-resolution ocean model, slowing of the oceanic circulation reflects reality.

Our research confirms the Atlantic overturning circulation has been slowing down since the middle of the 20th century. It also offers a glimpse of the future.

Simplified schematic of the Atlantic Meridional Overturning Circulation in the North Atlantic
As they travel northwards, the Gulf Stream and North Atlantic Current cool as they lose heat to the atmosphere. The waters then become dense enough to sink to depth and form North Atlantic deep water, which travels southward at depth and feeds the other ocean basins. Modified from Nature Reviews Earth & Environment (2020)

Connectivity in the Atlantic Ocean

Our new research also shows the North and South Atlantic oceans are more connected than previously thought.

The weakening of the overturning circulation over the past few decades has obscured the warming effect in the North Atlantic, leading to what’s been termed a “warming hole”.

When oceanic circulation is strong, there is a large transfer of heat to the North Atlantic. But weakening of the oceanic circulation means the surface of the ocean south of Greenland has warmed much less than the rest.

Reduced heat and salt transfer to the North Atlantic has meant more heat and salt accumulated in the South Atlantic. As a result, the temperature and salinity in the South Atlantic increased faster.

Our simulations show changes in the far North Atlantic are felt in the South Atlantic Ocean in less than two decades. This provides new observational evidence of the past century slow-down of the Atlantic overturning circulation.

Infographic showing how the North Atlantic is connected to the South Atlantic by the overturning circulation
The addition of meltwater in the North Atlantic leads to localised cooling in the subpolar North Atlantic and warming in the South Atlantic. https://www.nature.com/articles/s41561-024-01568-1


What does the future hold?

The latest climate projections suggest the Atlantic overturning circulation will weaken by about 30% by 2060. But these estimates do not take into account the meltwater that runs into the subarctic ocean.

The Greenland ice sheet will continue melting over the coming century, possibly raising global sea level by about 10 cm. If this additional meltwater is included in climate projections, the overturning circulation will weaken faster. It could be 30% weaker by 2040. That’s 20 years earlier than initially projected.

Such a rapid decrease in the overturning circulation over coming decades will disrupt climate and ecosystems. Expect harsher winters in Europe, and drier conditions in the northern tropics. The southern hemisphere, including Australia and southern South America, may face warmer and wetter summers.

Our climate has changed dramatically over the past 20 years. More rapid melting of the ice sheets will accelerate further disruption of the climate system.

This means we have even less time to stabilise the climate. So it is imperative that humanity acts to reduce emissions as fast as possible.The Conversation

Living planktonic foraminifera photos by Haruka Takagi, Katsunori Kimoto, Tetsuichi Fujiki, Hiroaki Saito, Christiane Schmidt4 , Michal Kucera and Kazuyoshi Moriya5, CC BY-SA 4.0 via Wikimedia Commons

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1) Orbulina universa, (2) Sphaeroidinella dehiscens, (3) Globigerinoides sacculifer, (4) Globigerinoides conglobatus, (5) Globigerinoides ruber (white), (6) Globigerinoides ruber (pink), (7) Globoturborotalita rubescens, (8) Globoturborotalita tenella, (9) Globigerinella calida, (10) Globigerinella siphonifera Type I, (11) Globigerinella siphonifera Type II, (12) Globigerinella adamsi, (13) Globigerina bulloides, (14) Turborotalita quinqueloba, (15) Turborotalita humilis, (16) Hastigerina pelagica, (17) Hastigerinella digitata, (18) Neogloboquadrina incompta, (19) Neogloboquadrina pachyderma, (20) Neogloboquadrina dutertrei, (21) Pulleniatina obliquiloculata, (22) Globorotalia inflata, (23) Globorotalia menardii, (24) Globorotalia scitula, (25) Globorotalia crassaformis, (26) Globorotalia truncatulinoides, (27) Candeina nitida, (28) Globigerinita glutinata, (29) Globigerinita uvula, and (30) Tenuitella fleisheri. Images by Haruka Takagi, Katsunori Kimoto, Tetsuichi Fujiki, Hiroaki Saito, Christiane Schmidt , Michal Kucera and Kazuyoshi Moriya CC BY-SA 4.0 via Wikimedia Commons

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This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Global temperature records are expected to exceed the 1.5 °C threshold for the first time this year. This has happened much sooner than predicted. So can life on the planet adapt quickly enough?

In our new research, published today in Nature, we explored the ability of tiny marine organisms called plankton to adapt to global warming. Our conclusion: some plankton are less able to adapt now than they were in the past.

Plankton live in the top few metres of ocean. These algae (phytoplankton) and animals (zooplankton) are transported by ocean currents as they do not actively swim.

Climate change is increasing the frequency of heatwaves in the sea. But predicting the future effects of climate change is difficult because some projections depend on ocean physics and chemistry, while others consider the effects on ecosystems and their services.

Some data suggest that current climate change have already altered the marine plankton dramatically. Models project a shift of plankton towards both poles (where ocean temperatures are cooler), and losses to zooplankton in the tropics but might not predict the patterns we see in data. Satellite data for plankton biomass are still too short term to determine trends through time.

To overcome these problems, we have compared how plankton responded to past environmental change and modelled how they could respond to future climate changes. As the scientist Charles Lyell said, “the past is the key to the present”.

We explored one of the best fossil records from a group of marine plankton with hard shells called Foraminifera. This comprehensive database of current and past distributions, compiled by researchers at the University of Bremen, has been collected by hundreds of scientists from the seafloor across the globe since the 1960s. We compared data from the last ice age, around 21,000 years ago, and modern records to see what happened when the world has previously warmed.

We used computational models, which combine climate trends with traits of marine plankton and their effect on marine plankton, to simulate the oceanic ecosystems from the last ice age to the pre-industrial age. Comparing the model with the data from the fossil record is giving us support that the model simulated the rules determining plankton growth and distribution.

We found that some subtropical and tropical species’ optimum temperature for peak growth and reproduction could deal with seawater warming in the past, supported by both fossil data and model. Colder water species of plankton managed to drift to flourish under more favourable water temperatures.

Our analysis shows that Foraminifera could handle the natural climate change, even without the need to adapt via evolution. But could they deal with the current warming and future changes in ocean conditions, such as temperature?

Future of the food chain

We used this model to predict the future under four different degrees of warming from 1.5 to 4 °C. Unfortunately, this type of plankton’s ability to deal with climate change is much more limited than it was during past warming. Our study highlights the difference between faster human-induced and slower-paced geological warming for marine plankton. Current climate change is too rapid and is reducing food supply due to ocean stratification, both making plankton difficult to adapt to this time.

Phytoplankton produce around 50% of the world’s oxygen. So every second breath we take comes from marine algae, while the rest comes from plants on land. Some plankton eat other plankton. That in turn gets eaten by fish and then marine mammals, so energy transfers further up the food chain. As it photosynthesises, phytoplankton is also a natural carbon fixation machine, storing 45 times more carbon than the atmosphere.

Around the world, many people depend heavily on food from the ocean as their primary protein sources. When climate change threatens marine plankton, this has huge knock-on effects throughout the rest of the marine food web. Plankton-eating marine mammals like whales won’t have enough food to prey on and there’ll be fewer fish to eat for predators (and people). Reducing warming magnitude and slowing down the warming rate are necessary to protect ocean health.

Global warming will continue to rise: image Peggy Anke

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Authors: Andrew King, Senior Lecturer in Climate Science, The University of Melbourne and Tilo Ziehn, Principal Research Scientist, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The world is striving to reach net-zero emissions as we try to ward off dangerous global warming. But will getting to net-zero actually avert climate instability, as many assume?

Our new study examined that question. Alarmingly, we found reaching net-zero in the next few decades will not bring an immediate end to the global heating problem. Earth’s climate will change for many centuries to come.

And this continuing climate change will not be evenly spread. Australia would keep warming more than almost any other land area. For example if net-zero emissions are reached by 2060, the Australian city of Melbourne is still predicted to warm by 1°C after that point.

But that’s not to say the world shouldn’t push to reach net-zero emissions as quickly as possible. The sooner we get there, the less damaging change the planet will experience in the long run.

Reaching net-zero is vital

Global greenhouse gas emissions hit record highs in 2023. At the same time, Earth experienced its hottest year.

Analysis suggests emissions may peak in the next couple of years then start to fall. But as long as emissions remain substantial, the planet will keep warming.

Most of the world’s nations, including Australia, have signed up to the Paris climate agreement. The deal aims to keep global warming well below 2°C, and requires major emitters to reach net-zero as soon as possible. Australia, along with many other nations, is aiming to reach the goal by 2050.

Getting to net-zero essentially means nations must reduce human-caused greenhouse gas emissions as much as possible, and compensate for remaining emissions by removing greenhouse gases from the atmosphere elsewhere. Methods for doing this include planting additional vegetation to draw down and store carbon, or using technology to suck carbon out of the air.

Getting to net-zero is widely considered the point at which global warming will stop. But is that assumption correct? And does it mean warming would stop everywhere across the planet? Our research sought to find out.

Centuries of change

Computer models simulating Earth’s climate under different scenarios are an important tool for climate scientists. Our research used a model known as the Australian Community Climate and Earth System Simulator.

Such models are like lab experiments for climate scientists to test ideas. Models are fed with information about greenhouse gas emissions. They then use equations to predict how those emissions would affect the movement of air and the ocean, and the transfer of carbon and heat, across Earth over time.

We wanted to see what would happen once the world hit net-zero carbon dioxide at various points in time, and maintained it for 1,000 years.

We ran seven simulations from different start points in the 21st century, at five-year increments from 2030 to 2060. These staggered simulations allowed us to measure the effect of various delays in reaching net-zero.

We found Earth’s climate would continue to evolve under all simulations, even if net-zero emissions was maintained for 1,000 years. But importantly, the later net-zero is reached, the larger the climate changes Earth would experience.

Warming oceans and melting ice

Earth’s average temperature across land and sea is the main indicator of climate change. So we looked at that first.

We found this temperature would continue to rise slowly under net-zero emissions – albeit at a much slower rate than we see today. Most warming would take place on the ocean surface; average temperature on land would only change a little.

We also looked at temperatures below the ocean surface. There, the ocean would warm strongly even under net-zero emissions – and this continues for many centuries. This is because seawater absorbs a lot of energy before warming up, which means some ocean warming is inevitable even after emissions fall.

Over the last few decades of high greenhouse gas emissions, sea ice extent fell in the Arctic – and more recently, around Antarctica. Under net-zero emissions, we anticipate Arctic sea ice extent would stabilise but not recover.

In contrast, Antarctic sea ice extent is projected to fall under net-zero emissions for many centuries. This is associated with continued slow warming of the Southern Ocean around Antarctica.

Importantly, we found long-term impacts on the climate worsen the later we reach net-zero emissions. Even just a five-year delay would affect on the projected climate 1,000 years later.

Delaying net-zero by five years results in a higher global average surface temperature, a much warmer ocean and reduced sea ice extent for many centuries.

Australia’s evolving climate

The effect on the climate of reaching net-zero emissions differs across the world.

For example, Australia is close to the Southern Ocean, which is projected to continue warming for many centuries even under net-zero emissions. This warming to Australia’s south means even under a net-zero emissions pathway, we expect the continent to continue to warm more than almost all other land areas on Earth.

For example, the models predict Melbourne would experience 1°C of warming over centuries if net-zero was reached in 2060.

Net-zero would also lead to changes in rainfall in Australia. Winter rainfall across the continent would increase – a trend in contrast to drying currently underway in parts of Australia, particularly in the southwest and southeast.

Knowns and unknowns

There is much more to discover about how the climate might behave under net-zero.

But our analysis provides some clues about what climate changes to expect if humanity struggles to achieve large-scale “net-negative” emissions – that is, removing carbon from the atmosphere at a greater rate than it is emitted.

Experiments with more models will help improve scientists’ understanding of climate change beyond net-zero emissions. These simulations may include scenarios in which carbon removal methods are so successful, Earth actually cools and some climate changes are reversed.

Despite the unknowns, one thing is very clear: there is a pressing need to push for net-zero emissions as fast as possible.The Conversation

Extreme weather in a changing climate

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Authors:

Simon H. Lee, Lecturer in Atmospheric Science, University of St Andrews; Hayley J. Fowler, Professor of Climate Change Impacts, Newcastle University, and Paul Davies, Chief Meteorologist, Met Office and Visiting Professor, Newcastle University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Extreme weather is by definition rare on our planet. Ferocious storms, searing heatwaves and biting cold snaps illustrate what the climate is capable of at its worst. However, since Earth’s climate is rapidly warming, predominantly due to fossil fuel burning, the range of possible weather conditions, including extremes, is changing.

Scientists define “climate” as the distribution of possible weather events observed over a length of time, such as the range of temperatures, rainfall totals or hours of sunshine. From this they construct statistical measures, such as the average (or normal) temperature. Weather varies on several timescales – from seconds to decades – so the longer the period over which the climate is analysed, the more accurately these analyses capture the infinite range of possible configurations of the atmosphere.

Typically, meteorologists and climate scientists use a 30-year period to represent the climate, which is updated every ten years. The most recent climate period is 1991-2020. The difference between each successive 30-year climate period serves as a very literal record of climate change.

This way of thinking about the climate falls short when the climate itself is rapidly changing. Global average temperatures have increased at around 0.2°C per decade over the past 30 years, meaning that the global climate of 1991 was around 0.6°C cooler than that in 2020 (when accounting for other year-to-year fluctuations), and even more so than the present day.

A moving target for climate modellers

If the climate is a range of possible weather events, then this rapid change has two implications. First, it means that part of the distribution of weather events comprising a 30-year climate period occurred in a very different background global climate: for example, northerly winds in the 1990s were much colder than those in the 2020s in north-west Europe, thanks to the Arctic warming nearly four times faster than the global average. Statistics from three decades ago no longer represent what is possible in the present day.

Second, the rapidly changing climate means we have not necessarily experienced the extremes that modern-day atmospheric and oceanic warmth can produce. In a stable climate, scientists would have multiple decades for the atmosphere to get into its various configurations and drive extreme events, such as heatwaves, floods or droughts. We could then use these observations to build up an understanding of what the climate is capable of. But in our rapidly changing climate, we effectively have only a few years – not enough to experience everything the climate has to offer.

Extreme weather events require what meteorologists might call a “perfect storm”. For example, extreme heat in the UK typically requires the northward movement of an air mass from Africa combined with clear skies, dry soils and a stable atmosphere to prevent thunderstorms forming which tend to dissipate heat.

Such “perfect” conditions are intrinsically unlikely, and many years can pass without them occurring – all while the climate continues to change in the background. Based on an understanding of observations alone, this can leave us woefully underprepared for what the climate can now do, should the right weather conditions all come together at once.

Startling recent examples include the extreme heatwave in the Pacific north-west of North America in 2021, in which temperatures exceeded the previous Canadian record maximum by 4.6°C. Another is the occurrence of 40°C in the UK in summer 2022, which exceeded the previous UK record maximum set only three years earlier by 1.6°C. This is part of the reason why the true impact of a fixed amount of global warming is only evident after several decades, but of course – since the climate is changing rapidly – we cannot use this method anymore.

Playing with fire

To better understand these extremes, scientists can use ensembles: many runs of the same weather or climate model that each slightly differ to show a range of plausible outcomes. Ensembles are routinely used in weather prediction, but can also be used to assess extreme events which could happen even if they do not actually happen at the time.

When 40°C first appeared in ensemble forecasts for the UK before the July 2022 heatwave, it revealed the kind of extreme weather that is possible in the current climate. Even if it had not come to fruition, its mere appearance in the models showed that the previously unthinkable was now possible. In the event, several naturally occurring atmospheric factors combined with background climate warming to generate the record-shattering heat on July 19 that year.

The highest observed temperature each year in the UK, from 1900 to 2023

A graph showing the highest observed temperature in the UK between 1900 and 2023.
The hottest days are getting hotter in the UK. Met Office/Kendon et al. 2024

Later in summer 2022, after the first occurrence of 40°C, some ensemble weather forecasts for the UK showed a situation in which 40°C could be reached on multiple consecutive days. This would have posed an unprecedented threat to public health and infrastructure in the UK. Unlike the previous month, this event did not come to pass, and was quickly forgotten – but it shouldn’t have been.

It is not certain whether these model simulations correctly represent the processes involved in producing extreme heat. Even so, we must heed the warning signs.

Despite a record-warm planet, summer 2024 in the UK has been relatively cool so far. The past two years have seen global temperatures far above anything previously observed, and so potential extremes have probably shifted even further from what we have so far experienced.

Just as was the case in August 2022, we’ve got away with it for now – but we might not be so lucky next time.

Humidity forecasts over North America and the northeast Pacific Ocean. Kochov et al. / Nature

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Image: Humidity forecasts over North America and the northeast Pacific Ocean.
Kochov et al. / Nature Sanaa Hobeichi, UNSW Sydney




A new system for forecasting weather and predicting future climate uses artificial intelligence (AI) to achieve results comparable with the best existing models while using much less computer power, according to its creators.

In a paper published in Nature today, a team of researchers from Google, MIT, Harvard and the European Centre for Medium-Range Weather Forecasts say their model offers enormous “computational savings” and can “enhance the large-scale physical simulations that are essential for understanding and predicting the Earth system”.

The NeuralGCM model is the latest in a steady stream of research models that use advances in machine learning to make weather and climate predictions faster and cheaper.

What is NeuralGCM?

The NeuralGCM model aims to combine the best features of traditional models with a machine-learning approach.

At its core, NeuralGCM is what is called a “general circulation model”. It contains a mathematical description of the physical state of Earth’s atmosphere, and it solves complicated equations to predict what will happen in the future.

However, NeuralGCM also uses machine learning – a process of searching out patterns and regularities in vast troves of data – for some less well-understood physical processes, such as cloud formation. The hybrid approach makes sure that the output of the machine learning modules will be consistent with the laws of physics.

Google researchers explain the NeuralGCM model.

The resulting model can then be used for making forecasts of weather days and weeks in advance, as well as looking months and years ahead for climate predictions.

The researchers compared NeuralGCM against other models using a standardised set of forecasting tests called WeatherBench 2. For three- and five-day forecasts, NeuralGCM did about as well as other machine-learning weather models such as Pangu and GraphCast. For longer-range forecasts, over ten and 15 days, NeuralGCM was about as accurate as the best existing traditional models.

NeuralGCM was also quite successful in forecasting less-common weather phenomena, such as tropical cyclones and atmospheric rivers.

Why machine learning?

Machine learning models are based on algorithms that learn patterns in the data they are fed with, then use this learning to make predictions. Because climate and weather systems are highly complex, machine learning models require vast amounts of historical observations and satellite data for training.

The training process is very expensive and requires a lot of computer power. However, after a model is trained, using it to make predictions is fast and cheap. This is a large part of their appeal for weather forecasting.

The high cost of training and low cost of use is similar to other kinds of machine learning models. GPT-4, for example, reportedly took several months to train at a cost of more than US$100 million, but can respond to a query in moments.

A comparison of how NeuralGCM compares with leading models (AMIP) and real data (ERA5) at capturing climate change between 1980 and 2020. Google Research

A weakness of machine learning models is that they often struggle in unfamiliar situations – or in this case, extreme or unprecedented weather conditions. To do this, a model needs to be able to generalise, or extrapolate beyond the data it was trained on.

NeuralGCM appears to be better at this than other machine learning models, because its physics-based core provides some grounding in reality. As Earth’s climate changes, unprecedented weather conditions will become more common, and we don’t know how well machine learning models will keep up.

Nobody is actually using machine learning-based weather models for day-to-day forecasting yet. However, it is a very active area of research – and one way or another, we can be confident that the forecasts of the future will involve machine learning.The Conversation

Sanaa Hobeichi, Research Associate, Climate Change Research Centre, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

January 2024 ocean temperatures

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New extreme records have already been set for ocean temperatures. Not looking forward to what this means for ecosystems and extreme weather events around Aotearoa:

ocean temperatures Janaury 08

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