The Times Australia
The Times World News

.

these changes are now irreversible, but we have to act to slow them down

  • Written by Nick Golledge, Professor of Glaciology, Te Herenga Waka — Victoria University of Wellington

After three years of writing and two weeks of virtual negotiations to approve the final wording, the Sixth Assessment Report (AR6[1]) of the Intergovernmental Panel on Climate Change (IPCC[2]) confirms that changes are happening in Earth’s climate across every continent and every ocean.

My contribution was as one of 15 lead authors to a chapter about the oceans, the world’s icescapes and sea level change — and this is where we are now observing changes that have become irreversible over centuries, and even millennia.

Read more: This is the most sobering report card yet on climate change and Earth's future. Here’s what you need to know[3]

Overall, the world is now 1.09℃ warmer than it was during the period between 1850 and 1900. The assessment shows the ocean surface has warmed slightly less, by about 0.9℃ as a global average, than the land surface since 1850, but about two-thirds of the ocean warming has taken place during the last 50 years.

Underwater canyon in the Pacific ocean. The world’s oceans are warming and acidifying. Shutterstock/Damsea

We concluded that it is virtually certain the heat content of the ocean will continue to increase for the rest of the current century, and will likely continue until at least 2300, even under low-emissions scenarios.

We also concluded that carbon dioxide emissions are the main driver of acidification in the open ocean and that this has been increasing faster than any time in at least 26,000 years.

We can also say with high confidence that oxygen levels have dropped in many ocean regions since the mid-20th century and that marine heatwaves have doubled in frequency since 1980, also becoming longer and more intense.

Past greenhouse gas emissions, since 1750, mean we are now committed to future ocean warming throughout this century. The rate of change depends on our future emissions, but the process itself is now irreversible on centennial to millennial time scales.

Glacier calving on the Antarctic Peninsula. A warming ocean is melting ice from below in West Antarctica. Shutterstock/Steve Allen

Ice loss in Antarctica

All this heat is bad news for the area I work in: Antarctica. With a warming ocean, the Antarctic ice sheet is left vulnerable to melting because so much of it rests on bedrock below sea level.

As the ocean warms and the ice sheet melts, sea level goes up around the world. We have very high confidence that the ice lost from West Antarctica in recent decades has exceeded any gain in mass from snowfall. We are also confident this loss has largely been due to increased melting of ice below sea level, driven by warming ocean water.

This melting has allowed the acceleration and thinning of grounded ice further inland — and this is what contributes to sea level rise. On the other side of the world, the Greenland ice sheet has also been losing mass over recent decades, but in Greenland this is principally due to warmer air, rather than warming ocean water.

Read more: If warming exceeds 2°C, Antarctica's melting ice sheets could raise seas 20 metres in coming centuries[4]

It is virtually certain that the melting of the two great ice sheets, in Greenland and Antarctica, as well as the many thousands of glaciers around the world, will continue to raise sea levels globally for the rest of the current century.

By 2100, we project global mean sea level to be between 0.4m (for the lowest emission scenario, in which CO₂ emissions would have to drop to net zero by 2050) and 0.8m (for the highest emissions scenario) above the 1995–2014 average. How high the seas rise this century clearly depends on how much and how quickly we manage to cut greenhouse gas emissions.

The time to act is now

There are processes at play which we still cannot fully capture in computer models, mostly because they take place over periods of time longer than we have direct (satellite-based) observations for. In Antarctica, some of these uncertain processes could greatly accelerate the loss of ice, and potentially add one metre to the projected sea level by 2100.

Whether or not this worst-case scenario plays out or not remains uncertain, but what is increasingly beyond doubt is that global mean sea level will continue to rise for centuries to come. The magnitude of this depends very much on the extent to which we are able, collectively, to reduce greenhouse gas emissions right now.

Ocean ways against a coastal city. Globally, the seas will continue to rise for centuries to come. Shutterstock/JivkoM

The scientific updates in our AR6 chapter are in line with those from previous assessments. That’s encouraging, because every assessment report brings in new authors with different expertise. The fact the scientific conclusions remain consistent reflects the overwhelming agreement within the global scientific community.

For our chapter, we have assessed 1500 research papers, but across the entire AR6, over 14,000 publications were considered, with an emphasis on recent research that hasn’t been assessed in previous IPCC reports.

The report has been scrutinised carefully at every stage of its evolution, attracting nearly 80,000 individual review comments from experts all over the world. Every single comment had to be addressed by the author team, with written responses provided and any changes to the text carefully noted and tracked.

What changes with each assessment is the clarity of the trends we are observing, and the increasing urgency with which we must act. While some aspects of AR6 are new, the underlying message remains the same. The longer we wait, the more devastating the consequences.

Click here[5] to read more of The Conversation’s coverage of the IPCC report

Read more https://theconversation.com/rising-seas-and-melting-glaciers-these-changes-are-now-irreversible-but-we-have-to-act-to-slow-them-down-165527

Times Magazine

Building a Strong Online Presence with Katoomba Web Design

Katoomba web design is more than just creating a website that looks good—it’s about building an online presence that reflects your brand, engages your audience, and drives results. For local businesses in the Blue Mountains, a well-designed website a...

September Sunset Polo

International Polo Tour To Bridge Historic Sport, Life-Changing Philanthropy, and Breath-Taking Beauty On Saturday, September 6th, history will be made as the International Polo Tour (IPT), a sports leader headquartered here in South Florida...

5 Ways Microsoft Fabric Simplifies Your Data Analytics Workflow

In today's data-driven world, businesses are constantly seeking ways to streamline their data analytics processes. The sheer volume and complexity of data can be overwhelming, often leading to bottlenecks and inefficiencies. Enter the innovative da...

7 Questions to Ask Before You Sign IT Support Companies in Sydney

Choosing an IT partner can feel like buying an insurance policy you hope you never need. The right choice keeps your team productive, your data safe, and your budget predictable. The wrong choice shows up as slow tickets, surprise bills, and risky sh...

Choosing the Right Legal Aid Lawyer in Sutherland Shire: Key Considerations

Legal aid services play an essential role in ensuring access to justice for all. For people in the Sutherland Shire who may not have the financial means to pay for private legal assistance, legal aid ensures that everyone has access to representa...

Watercolor vs. Oil vs. Digital: Which Medium Fits Your Pet's Personality?

When it comes to immortalizing your pet’s unique personality in art, choosing the right medium is essential. Each artistic medium, whether watercolor, oil, or digital, has distinct qualities that can bring out the spirit of your furry friend in dif...

The Times Features

How much money do you need to be happy? Here’s what the research says

Over the next decade, Elon Musk could become the world’s first trillionaire[1]. The Tesla board recently proposed a US$1 trillion (A$1.5 trillion) compensation plan, if Musk ca...

NSW has a new fashion sector strategy – but a sustainable industry needs a federally legislated response

The New South Wales government recently announced the launch of the NSW Fashion Sector Strategy, 2025–28[1]. The strategy, developed in partnership with the Australian Fashion ...

From Garden to Gift: Why Roses Make the Perfect Present

Think back to the last time you gave or received flowers. Chances are, roses were part of the bunch, or maybe they were the whole bunch.   Roses tend to leave an impression. Even ...

Do I have insomnia? 5 reasons why you might not

Even a single night of sleep trouble can feel distressing and lonely. You toss and turn, stare at the ceiling, and wonder how you’ll cope tomorrow. No wonder many people star...

Wedding Photography Trends You Need to Know (Before You Regret Your Album)

Your wedding album should be a timeless keepsake, not something you cringe at years later. Trends may come and go, but choosing the right wedding photography approach ensures your ...

Can you say no to your doctor using an AI scribe?

Doctors’ offices were once private. But increasingly, artificial intelligence (AI) scribes (also known as digital scribes) are listening in. These tools can record and trans...