The Times Australia
The Times World News

.

Even temporary global warming above 2℃ will affect life in the oceans for centuries

  • Written by Tilo Ziehn, Principal Research Scientist, CSIRO
Even temporary global warming above 2℃ will affect life in the oceans for centuries

There is growing consensus[1] that our planet is likely to pass the 1.5℃ warming threshold. Research[2] even suggests global warming will temporarily exceed the 2℃ threshold, if atmospheric carbon dioxide (CO₂) peaks at levels beyond what was anticipated.

Exceeding our emissions targets is known as a climate overshoot[3]. It may lead to changes that won’t be reversible in our lifetime.

These changes include sea-level rise, less functional ecosystems, higher risks of species extinction, and glacier and permafrost loss. We are already seeing many of these changes.

Our newly published research[4] investigates the implications of a climate overshoot for the oceans. Across all climate overshoot experiments and all models, our analysis found associated changes in water temperatures and oxygen levels will decrease viable ocean habitats.

The decrease was observed for centuries. This means humanity will continue to feel its impacts long after atmospheric CO₂ levels have peaked and declined.

Read more: Ocean heat is off the charts – here's what that means for humans and ecosystems around the world[5]

What did the study look at?

Our analysis is based on simulations with Earth system models as part of the Coupled Model Intercomparison Project (CMIP6[6]). The project underpins the latest assessment reports[7] by the Intergovernmental Panel on Climate Change (IPCC).

We looked at multi-model results from two different CMIP6-developed experiments that simulate a climate overshoot.

One corresponds to a climate scenario simulating an overshoot this century.

The other experiment is from the Carbon Dioxide Model Intercomparison Project (CDRMIP[8]). It was designed to explore the reversibility of a climate overshoot and how this impacts the Earth system.

An insight into the world of climate modelling, particularly the Coupled Model Intercomparison Project (CMIP).

Read more: How much will our oceans warm and cause sea levels to rise this century? We've just improved our estimate[9]

We studied the combined effects of changes in ocean temperature and oxygen levels. These changes are linked because the warmer the water, the less dissolved oxygen it can hold.

In this study we explored what warmer oceans and deoxygenation mean for the long-term viability of marine ecosystems. These changes have already begun[10] under climate change.

To quantify these impacts we used a metabolic index, which describes the (aerobic) energy balance of individual organisms. In viable ecosystems the supply of oxygen needs to exceed their demand. The closer supply is to demand, the more precarious ecosystems become, until demand exceeds supply and these ecosystems are no longer viable.

Under global warming in the ocean we are already seeing an increase in metabolic demand and reduction in supply due to deoxygenation.

The index gives us the ability to assess how changing ocean temperatures impact the long-term viability of different marine species and their habitats. This allows us to explore how ecosystems across the world’s oceans respond to a climate overshoot, and for how long these changes will persist.

As conditions changed under the scenarios, we followed the evolution of the global ocean volume that can or cannot support the metabolic demands of 72 marine species.

Read more: The Southern Ocean absorbs more heat than any other ocean on Earth, and the impacts will be felt for generations[11]

What did the study find?

Across all climate overshoot experiments and all models, our findings show the water volumes that can provide viable habitats will decrease. This decrease persisted on the scale of centuries – well after global average temperature recovers from the overshoot.

Our study findings raise concerns about shrinking habitats. For example, species like tuna live in well-oxygenated surface waters and are restricted by low oxygen in deeper waters. Their habitat will be compressed towards the surface for hundreds of years, according to our study.

Fisheries that rely on such species will need to understand how changes in their distribution will affect fishing grounds and productivity. What is clear is that ecosystems would need to adapt to these changes or risk collapsing with significant environmental, societal and economic implications.

A shoal of fish swims beneath the ocean surface
Tuna and other species of importance for fisheries need well-oxygenated water. Shutterstock

Read more: Managing fish stocks shared by nations must focus on the impacts of climate change[12]

What are the implications of shrinking marine habitats?

To date, most research has focused on ocean warming[13]. The combination of temperature and deoxygenation we studied shows warming may harm marine ecosystems for hundreds of years after global mean temperatures have peaked. We will have to think more about resource management to avoid compromising species abundance and food security.

Climate overshoots not only matter in terms of their peak value but also in terms of how long temperature remains above the target. It is better to return from an overshoot than staying at the higher level, but a lot worse than not overshooting in the first place.

If we significantly overshoot the temperature targets of the Paris Agreement, many climate change impacts will be irreversible. Therefore, every effort should be made to drastically reduce emissions now. We can then avoid a significant climate overshoot, reach net-zero emissions by mid-century and keep warming “well below” 2℃.

Our assessment of potential future changes relies heavily on Earth system models. To better answer key questions about climate overshoots and the reversibility of the climate system, we need to further improve our models.

This includes sustained observations to validate our models. We must also develop new experimental frameworks[14] to explore what can be done in the event of a climate overshoot to minimise its long-term impact.

References

  1. ^ consensus (www.nature.com)
  2. ^ Research (www.pnas.org)
  3. ^ climate overshoot (www.overshootcommission.org)
  4. ^ newly published research (www.nature.com)
  5. ^ Ocean heat is off the charts – here's what that means for humans and ecosystems around the world (theconversation.com)
  6. ^ CMIP6 (www.wcrp-climate.org)
  7. ^ assessment reports (www.ipcc.ch)
  8. ^ CDRMIP (www.wcrp-climate.org)
  9. ^ How much will our oceans warm and cause sea levels to rise this century? We've just improved our estimate (theconversation.com)
  10. ^ changes have already begun (www.science.org)
  11. ^ The Southern Ocean absorbs more heat than any other ocean on Earth, and the impacts will be felt for generations (theconversation.com)
  12. ^ Managing fish stocks shared by nations must focus on the impacts of climate change (theconversation.com)
  13. ^ ocean warming (www.nature.com)
  14. ^ new experimental frameworks (theconversation.com)

Read more https://theconversation.com/even-temporary-global-warming-above-2-will-affect-life-in-the-oceans-for-centuries-214251

Times Magazine

Headless CMS in Digital Twins and 3D Product Experiences

Image by freepik As the metaverse becomes more advanced and accessible, it's clear that multiple sectors will use digital twins and 3D product experiences to visualize, connect, and streamline efforts better. A digital twin is a virtual replica of ...

The Decline of Hyper-Casual: How Mid-Core Mobile Games Took Over in 2025

In recent years, the mobile gaming landscape has undergone a significant transformation, with mid-core mobile games emerging as the dominant force in app stores by 2025. This shift is underpinned by changing user habits and evolving monetization tr...

Understanding ITIL 4 and PRINCE2 Project Management Synergy

Key Highlights ITIL 4 focuses on IT service management, emphasising continual improvement and value creation through modern digital transformation approaches. PRINCE2 project management supports systematic planning and execution of projects wit...

What AI Adoption Means for the Future of Workplace Risk Management

Image by freepik As industrial operations become more complex and fast-paced, the risks faced by workers and employers alike continue to grow. Traditional safety models—reliant on manual oversight, reactive investigations, and standardised checklist...

From Beach Bops to Alpine Anthems: Your Sonos Survival Guide for a Long Weekend Escape

Alright, fellow adventurers and relaxation enthusiasts! So, you've packed your bags, charged your devices, and mentally prepared for that glorious King's Birthday long weekend. But hold on, are you really ready? Because a true long weekend warrior kn...

Effective Commercial Pest Control Solutions for a Safer Workplace

Keeping a workplace clean, safe, and free from pests is essential for maintaining productivity, protecting employee health, and upholding a company's reputation. Pests pose health risks, can cause structural damage, and can lead to serious legal an...

The Times Features

Duke of Dural to Get Rooftop Bar as New Owners Invest in Venue Upgrade

The Duke of Dural, in Sydney’s north-west, is set for a major uplift under new ownership, following its acquisition by hospitality group Good Beer Company this week. Led by resp...

Prefab’s Second Life: Why Australia’s Backyard Boom Needs a Circular Makeover

The humble granny flat is being reimagined not just as a fix for housing shortages, but as a cornerstone of circular, factory-built architecture. But are our systems ready to s...

Melbourne’s Burglary Boom: Break-Ins Surge Nearly 25%

Victorian homeowners are being warned to act now, as rising break-ins and falling arrest rates paint a worrying picture for suburban safety. Melbourne residents are facing an ...

Exploring the Curriculum at a Modern Junior School in Melbourne

Key Highlights The curriculum at junior schools emphasises whole-person development, catering to children’s physical, emotional, and intellectual needs. It ensures early year...

Distressed by all the bad news? Here’s how to stay informed but still look after yourself

If you’re feeling like the news is particularly bad at the moment, you’re not alone. But many of us can’t look away – and don’t want to. Engaging with news can help us make ...

The Role of Your GP in Creating a Chronic Disease Management Plan That Works

Living with a long-term condition, whether that is diabetes, asthma, arthritis or heart disease, means making hundreds of small decisions every day. You plan your diet against m...