Climate Change and the Monsoon - impacts

Melting ice will strengthen the monsoon in northern Australia – but cause drier conditions north of the Equator

Sebnem Coskun/Anadolu via Getty Images

Corey J. A. Bradshaw, Flinders University; Cassandra Rowe, James Cook University, and Michael Bird, James Cook University

Almost two-thirds of the world’s population is affected by the monsoon – the annual arrival of intense rains in areas north and south of the Equator. These drenching rains tend to arrive during each hemisphere’s summer.

The East Asian monsoon north of the equator is the best known and best studied, because it affects the largest land area and the most people. But the southern Indo-Australian monsoon is vitally important to northern Australia, Indonesia and Papua New Guinea. To date, it has been studied much less.

To help fill this gap in knowledge, we analysed deep sediment from an unusual lagoon near Darwin in northern Australia. We looked at ancient pollen and chemical isotopes (different versions of the same chemical element) to look about 150,000 years back in time and glimpse changes to the monsoon. When types of pollen change, it tells us the monsoon has changed. Drier conditions favour the emergence of grasslands, while wetter climates favour forests.

Our new research suggests as the world gets hotter, the Indo-Australian monsoon will intensify and northern Australia will get wetter. This finding is consistent with research suggesting the East Asian monsoon could weaken, threatening agriculture and nature in heavily populated countries.

Location of Girraween Lagoon in monsoonal north Australia. Insert shows approximate dominant flows of the East Asian and Indo-Australian summer monsoons. Corey Bradshaw/Flinders University, CC BY-NC

The past held in a single lagoon

To examine how monsoons change over time, researchers drill sediment cores to track changes in pollen and chemical isotopes. For example, changes in hydrogen isotopes indicate changes in the intensity of the monsoon rain.

The problem is, these cores have to come from long-undisturbed lake sediments, because such places provide a continuous record of change.

To reconstruct past changes in monsoon patterns, undisturbed sediments have to be sampled carefully by extracting a thin “core” from the bottom sediments. Once researchers have this precious core, they can examine the changing proportions of pollen, chemical isotopes and other properties. The deeper you drill the core, the farther back in time you can look.

These exacting requirements are one reason the Indo-Australian monsoon is not as well understood as its northern cousin.

Fortunately, we have found one place which has kept a detailed environmental record over a long period: Girraween Lagoon on the outskirts of Darwin in the Northern Territory.

This lagoon was created after a sinkhole formed more than 200,000 years ago. It has contained permanent water ever since, and is slowly filling with sediment and pollen blown in from the surrounding landscape.

The 18-metre core from Girraween’s sediments gave us a 150,000-year record of environmental change in Australia’s northern savannahs.

It took hard work to extract the core from Girraween Lagoon.

Dipping into the past

If you walk around Girraween Lagoon today, you’ll see a tall and dense tree canopy with a thick grass understory in the wet season. But it hasn’t always been that way.

During the last ice age 20,000–30,000 years ago, the sea level was much lower and the polar ice caps much larger. As a result, the lagoon was more than 300 kilometres from the coast. At that time, the lagoon was surrounded by an open, grassy savannah with fewer, shorter trees.

A schematic showing the depth of the Girraween core and the associated time periods. Emma Rehn/Centre of Excellence for Australian Biodiversity and Heritage, CC BY-NC

About 115,000 years ago (and again 90,000 years ago), Australia was dotted with gigantic inland “megalakes”. At those times, the lagoon expanded into a large, shallow lake surrounded by lush monsoon forest, with almost no grass.

At times, tree cover changed radically. In fact, over one 3,000-year period, the percentage of tree pollen soared from 15% to 95%. That suggests a sweeping change from grassland to dense forest – meaning a switch from drier to wetter climate at a rate too fast to be explained by changes in Earth’s orbit.

Some of these changes are linked to the shifting distance between coastline and lagoon as well as predictable variation in how much solar energy reaches Earth.

A connection to the North Atlantic

Huge ice sheets covered large areas of the Northern Hemisphere during previous ice ages.

Remarkably, the evidence of their melting at the end of previous ice age was there in the sediment core from Girraween Lagoon.

When glacial ice melts rapidly, huge volumes of fresh water flood into the North Atlantic. These rapid pulses are known as Heinrich events. These pulses can shut down the warm Gulf Stream current up the east coast of North America. As a result, the Northern Hemisphere cools and the Southern Hemisphere warms.

Over the last 150,000 years, there have been 14 of these events. We could see evidence of them in the sediment cores. Every gush of fresh water in the Atlantic triggered higher rainfall over northern Australia because of the buildup of heat in the Southern Hemisphere as the Gulf Stream slowed.

What does this mean for the monsoon?

All this suggests the Indo-Australian monsoon will get more intense as the world gets hotter and more ice melts.

That would mean a wetter northern Australia. It could also bring more rainfall to other Australian regions, and neighbouring countries. At this stage, it’s too uncertain to predict what an intensifying monsoon would do to the southern parts of Australia.

We might already be seeing this shift. Weather records since the 1960s show northern Australia getting steadily wetter, and less rain in Australia’s southeast and southwest.

Trends in total annual rainfall in Australia from 1960 to 2020. Commonwealth of Australia Bureau of Meteorology, CC BY

What would this mean for people? Australia’s tropical north is not densely populated, which would reduce the human impact of an intensifying monsoon.

But while our research suggests the Indo-Australian monsoon strengthens during Heinrich events, earlier research has shown the East Asian and other Northern Hemisphere monsoons will weaken. Without reliable monsoonal rains, food and water supplies for billions of people could be at risk.

Corey J. A. Bradshaw, Matthew Flinders Professor of Global Ecology and Node Leader in the ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, Flinders University; Cassandra Rowe, Senior Research Fellow, ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, and College of Science and Engineering, James Cook University, and Michael Bird, JCU Distinguished Professor, ARC Centre of Excellence for Indigenous and Environmental Histories and Futures, James Cook University

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

Heat is being trapped on Earth in greater levels than modelled

Earth is trapping much more heat than climate models forecast – and the rate has doubled in 20 years

NASA, CC BY-NC-ND

Steven Sherwood, UNSW Sydney; Benoit Meyssignac, Université de Toulouse, and Thorsten Mauritsen, Stockholm University

How do you measure climate change? One way is by recording temperatures in different places over a long period of time. While this works well, natural variation can make it harder to see longer-term trends.

But another approach can give us a very clear sense of what’s going on: track how much heat enters Earth’s atmosphere and how much heat leaves. This is Earth’s energy budget, and it’s now well and truly out of balance.

Our recent research found this imbalance has more than doubled over the last 20 years. Other researchers have come to the same conclusions. This imbalance is now substantially more than climate models have suggested.

In the mid-2000s, the energy imbalance was about 0.6 watts per square metre (W/m2) on average. In recent years, the average was about 1.3 W/m2. This means the rate at which energy is accumulating near the planet’s surface has doubled.

These findings suggest climate change might well accelerate in the coming years. Worse still, this worrying imbalance is emerging even as funding uncertainty in the United States threatens our ability to track the flows of heat.

Energy in, energy out

Earth’s energy budget functions a bit like your bank account, where money comes in and money goes out. If you reduce your spending, you’ll build up cash in your account. Here, energy is the currency.

Life on Earth depends on a balance between heat coming in from the Sun and heat leaving. This balance is tipping to one side.

Solar energy hits Earth and warms it. The atmosphere’s heat-trapping greenhouse gases keep some of this energy.

But the burning of coal, oil and gas has now added more than two trillion tonnes of carbon dioxide and other greenhouse gases to the atmosphere. These trap more and more heat, preventing it from leaving.

Some of this extra heat is warming the land or melting sea ice, glaciers and ice sheets. But this is a tiny fraction. Fully 90% has gone into the oceans due to their huge heat capacity.

Earth naturally sheds heat in several ways. One way is by reflecting incoming heat off of clouds, snow and ice and back out to space. Infrared radiation is also emitted back to space.

From the beginning of human civilisation up until just a century ago, the average surface temperature was about 14°C. The accumulating energy imbalance has now pushed average temperatures 1.3-1.5°C higher.

Ice and reflective clouds reflect heat back to space. As the Earth heats up, most trapped heat goes into the oceans but some melts ice and heats the land and air. Pictured: Icebergs from the Jacobshavn glacier in Greenland, the largest outside Antarctica. Ashley Cooper/Getty

Tracking faster than the models

Scientists keep track of the energy budget in two ways.

First, we can directly measure the heat coming from the Sun and going back out to space, using the sensitive radiometers on monitoring satellites. This dataset and its predecessors date back to the late 1980s.

Second, we can accurately track the build-up of heat in the oceans and atmosphere by taking temperature readings. Thousands of robotic floats have monitored temperatures in the world’s oceans since the 1990s.

Both methods show the energy imbalance has grown rapidly.

The doubling of the energy imbalance has come as a shock, because the sophisticated climate models we use largely didn’t predict such a large and rapid change.

Typically, the models forecast less than half of the change we’re seeing in the real world.

Why has it changed so fast?

We don’t yet have a full explanation. But new research suggests changes in clouds is a big factor.

Clouds have a cooling effect overall. But the area covered by highly reflective white clouds has shrunk, while the area of jumbled, less reflective clouds has grown.

It isn’t clear why the clouds are changing. One possible factor could be the consequences of successful efforts to reduce sulfur in shipping fuel from 2020, as burning the dirtier fuel may have had a brightening effect on clouds. However, the accelerating energy budget imbalance began before this change.

Natural fluctuations in the climate system such as the Pacific Decadal Oscillation might also be playing a role. Finally – and most worryingly – the cloud changes might be part of a trend caused by global warming itself, that is, a positive feedback on climate change.

Dense blankets of white clouds reflect the most heat. But the area covered by these clouds is shrinking. Adhivaswut/Shutterstock

What does this mean?

These findings suggest recent extremely hot years are not one-offs but may reflect a strengthening of warming over the coming decade or longer.

This will mean a higher chance of more intense climate impacts from searing heatwaves, droughts and extreme rains on land, and more intense and long lasting marine heatwaves.

This imbalance may lead to worse longer-term consequences. New research shows the only climate models coming close to simulating real world measurements are those with a higher “climate sensitivity”. That means these models predict more severe warming beyond the next few decades in scenarios where emissions are not rapidly reduced.

We don’t know yet whether other factors are at play, however. It’s still too early to definitively say we are on a high-sensitivity trajectory.

Our eyes in the sky

We’ve known the solution for a long time: stop the routine burning of fossil fuels and phase out human activities causing emissions such as deforestation.

Keeping accurate records over long periods of time is essential if we are to spot unexpected changes.

Satellites, in particular, are our advance warning system, telling us about heat storage changes roughly a decade before other methods.

But funding cuts and drastic priority shifts in the United States may threaten essential satellite climate monitoring.

Steven Sherwood, Professor of Atmospheric Sciences, Climate Change Research Centre, UNSW Sydney; Benoit Meyssignac, Associate Research Scientist in Climate Science, Université de Toulouse, and Thorsten Mauritsen, Professor of Climate Science, Stockholm University

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

As Los Angeles burns the World has crossed the 1.5C threshold

The highly destructive wildfires in Los Angeles US, in January 2025 are a warning to the World at large of the threat posed by climate change and its impact. Similar fires have been seen in the Mediterranean during their Summer period with similar devastating effects particularly in Greece.

The Copernicus Institute summarised the situation thus:  

“2024 saw unprecedented global temperatures, following on from the remarkable warmth of 2023. It also became the first year with an average temperature clearly exceeding 1.5°C above the pre-industrial level – a threshold set by the Paris Agreement to significantly reduce the risks and impacts of climate change. Multiple global records were broken, for greenhouse gas levels, and for both air temperature and sea surface temperature, contributing to extreme events, including floods, heatwaves and wildfires. These data highlight the accelerating impacts of human-caused climate change”.

Key points -

• 2024 was the warmest year in a multi-dataset record of global temperature going back to 1850.
• 2024 had a global average temperature of 15.10°C; 0.12°C higher than the previous highest annual value in 2023.
• 2024 was 0.72°C warmer than the 1991–2020 average, and 1.60°C warmer than the pre-industrial level, making it the first calendar year to exceed 1.5 above that level.
• The last ten years have been the warmest ten years on record.
• Each month from January to June 2024 was warmer than the corresponding month in any previous year. August 2024 equalled the record warmth of August 2023 and the remaining months from July to December were each the second warmest for the time of year, after the corresponding months in 2023.
• On 22 July 2024, the daily global average temperature reached a new record high of 17.16°C.

The link to the report (click): Global Climate Highlights 2024 

State of the Climate 2024 Report - continuing inconvenient truths abound

The State of the Climate Report 2024 from a consortium of scientists in mulitple institutions paints a grim picture for the direction of climate change with rising temperatures and greenhouse gas emissions. To quote an opening section of the report -

 “We are on the brink of an irreversible climate disaster. This is a global emergency beyond any doubt. Much of the very fabric of life on Earth is imperiled. We are stepping into a critical and unpredictable new phase of the climate crisis. For many years, scientists, including a group of more than 15,000, have sounded the alarm about the impending dangers of climate change driven by increasing greenhouse gas emissions and ecosystem change (Ripple et al. 2020 ). For half a century, global warming has been correctly predicted even before it was observed—and not only by independent academic scientists but also by fossil fuel companies (Supran et al. 2023 ). Despite these warnings, we are still moving in the wrong direction; fossil fuel emissions have increased to an all-time high, the 3 hottest days ever occurred in July of 2024.”

The graphs below from the report (figure 2) categorically demonstrate the upwards trends across a whole range of measures such as carbon dioxide emissions, methane emissions, nitrous oxide emissions, ocean heat, ocean levels and so on.

The report can be accessed at this link: State of the Climate Report 2024

No improvement in climate change measurements

Unprecedented peril: disaster lies ahead as we track towards 2.7°C of warming this century

Thomas Newsome, University of Sydney and William Ripple, Oregon State University

You don’t have to look far to see what climate change is doing to the planet. The word “unprecedented” is everywhere this year.

We are seeing unprecedented rapidly intensifying tropical storms such as Hurricane Helene in the eastern United States and Super Typhoon Yagi in Vietnam. Unprecedented fires in Canada have destroyed towns. Unprecedented drought in Brazil has dried out enormous rivers and left swathes of empty river beds. At least 1,300 pilgrims died during this year’s Hajj in Mecca as temperatures passed 50°C.

Unfortunately, we are headed for far worse. The new 2024 State of the Climate report, produced by our team of international scientists, is yet another stark warning about the intensifying climate crisis. Even if governments meet their emissions goals, the world may hit 2.7°C of warming – nearly double the Paris Agreement goal of holding climate change to 1.5°C. Each year, we track 35 of the Earth’s vital signs, from sea ice extent to forests. This year, 25 are now at record levels, all trending in the wrong directions.

Humans are not used to these conditions. Human civilisation emerged over the last 10,000 years under benign conditions – not too hot, not too cold. But this liveable climate is now at risk. In your grandchild’s lifetime, climatic conditions will be more threatening than anything our prehistoric relatives would have faced.

Our report shows a continued rise in fossil fuel emissions, which remain at an all-time high. Despite years of warnings from scientists, fossil fuel consumption has actually increased, pushing the planet toward dangerous levels of warming. While wind and solar have grown rapidly, fossil fuel use is 14 times greater.

This year is also tracking for the hottest year on record, with global daily mean temperatures at record levels for nearly half of 2023 and much of 2024.

Next month, world leaders and diplomats will gather in Azerbaijan for the annual United Nations climate talks, COP 29. Leaders will have to redouble their efforts. Without much stronger policies, climate change will keep worsening, bringing with it more frequent and more extreme weather.

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Bad news after bad news

We have still not solved the central problem: the routine burning of fossil fuels. Atmospheric concentrations of greenhouse gases – particularly methane and carbon dioxide – are still rising. Last September, carbon dioxide levels in the atmosphere hit 418 parts per million (ppm). This September, they crossed 422 ppm. Methane, a highly potent greenhouse gas, has been increasing at an alarming rate despite global pledges to tackle it.

Compounding the problem is the recent decline in atmospheric aerosols from efforts to cut pollution. These small particles suspended in the air come from both natural and human processes, and have helped cool the planet. Without this cooling effect, the pace of global warming may accelerate. We don’t know for sure because aerosol properties are not yet measured well enough.

Other environmental issues are now feeding into climate change. Deforestation in critical areas such as the Amazon is reducing the planet’s capacity to absorb carbon naturally, driving additional warming. This creates a feedback loop, where warming causes trees to die which in turn amplifies global temperatures.

Loss of sea ice is another. As sea ice melts or fails to form, dark seawater is exposed. Ice reflects sunlight but seawater absorbs it. Scaled up, this changes the Earth’s albedo (how reflective the surface is) and accelerates warming further.

In coming decades, sea level rise will pose a growing threat to coastal communities, putting millions of people at risk of displacement.

Accelerate the solutions

Our report stresses the need for an immediate and comprehensive end to the routine use of fossil fuels.

It calls for a global carbon price, set high enough to drive down emissions, particularly from high-emitting wealthy countries.

Introducing effective policies to slash methane emissions is crucial, given methane’s high potency but short atmospheric lifetime. Rapidly cutting methane could slow the rate of warming in the short term.

Natural climate solutions such as reforestation and soil restoration should be rolled out to increase how much carbon is stored in wood and soil. These efforts must be accompanied by protective measures in wildfire and drought prone areas. There’s no point planting forests if they will burn.

Governments should introduce stricter land-use policies to slow down rates of land clearing and increase investment in forest management to cut the risk of large, devastating fires and encourage sustainable land use.

We cannot overlook climate justice. Less wealthy nations contribute least to global emissions but are often the worst affected by climate disasters.

Wealthier nations must provide financial and technical support to help these countries adapt to climate change while cutting emissions. This could include investing in renewable energy, improving infrastructure and funding disaster preparedness programs.

Internationally, our report urges stronger commitments from world leaders. Current global policies are insufficient to limit warming to 1.5°C above pre-industrial levels.

Without drastic changes, the world is on track for approximately 2.7°C of warming this century. To avoid catastrophic tipping points, nations must strengthen their climate pledges, reduce dependence on fossil fuels, and accelerate the transition to renewable energy.

Immediate, transformative policy changes are now necessary if we are to avoid the worst effects of climate change.

Climate change is already here. But it could get much, much worse. By slashing emissions, boosting natural climate solutions and working towards climate justice, the global community can still fend off the worst version of our future.

Thomas Newsome, Associate Professor in Global Ecology, University of Sydney and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

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

Coral reefs in jeopardy

Devastating coral bleaching will be more common, start earlier and last longer unless we cut emissions

Sarah_lewis/Shutterstock

Camille Mellin, University of Adelaide and Damien Fordham, University of Adelaide

Coral bleaching is becoming much more common as a result of increasingly severe and frequent marine heatwaves. Four global mass bleaching events have happened since 1998. Two of these were in the past decade.

Unless greenhouse gas emissions are cut to slow global warming, our new research shows that, by 2080, coral bleaching will start in spring, rather than late summer. Some events will last into autumn. The Great Barrier Reef’s maximum annual heat stress will double by 2050 if emissions do not slow.

Marine heatwaves stress corals, which then expel the symbiotic algae living in their tissue. These corals are left white and weakened. While not all bleached corals die immediately, prolonged heat stress harms their health and reproduction.

Our research used daily data on sea surface temperatures (instead of monthly data that models typically use) and supercomputing to produce high-resolution projections of marine heatwaves. We showed the risk of coral bleaching will be greatest along the equator. That’s also where the most biodiverse coral reefs are found.

Coral reefs cover only 1% of our oceans, but host at least 25% of all marine species. More than half a billion people worldwide depend on coral reefs for food.

So coral reefs are vital for the health of the ocean and people. They are also among the ecosystems most at risk from climate change.

Longer bleaching season will hit spawning

The US National Oceanic and Atmospheric Administration monitors marine heatwaves globally. Seasonal coral bleaching alerts are based on this data. Predicting coral bleaching risk over entire decades has proved much more challenging.

Recent improvements in climate modelling now allow marine heatwaves and coral bleaching risks to be predicted with high accuracy. Using daily projections of heat stress from many global climate models, we show the severity and duration of coral bleaching will soon reach uncharted territory.

By mid-century coral bleaching is expected to start in spring for most of Earth’s reefs, rather than late summer as is typical today. In equatorial regions, corals will be at high risk of bleaching all year round by the end of the century.

In many regions, corals spawn only once a year. These spectacular mass spawning events happen in a single week following a full moon in spring.

By 2040, this spawning event could coincide with severe bleaching risk. This would greatly reduce their reproductive success, causing large-scale coral loss.

Acropora coral spawning on Magnetic Island in Queensland, Australia. Coral Brunner/Shutterstock

Equatorial regions most at risk

We show the future risk of severe coral bleaching is uneven globally.

The greatest risk is along the equator. Equatorial regions are home to the most biodiverse coral reefs, including conservation hotspots such as the Coral Triangle. To make matters worse, marine life in these regions is particularly vulnerable to accelerated climate change.

Many equatorial species are already living at temperatures near their upper tolerance. They also generally have low abilities to move to track shifting climates. This leaves them at high risk of extinction.

Future risk of coral bleaching under a high-emission scenario (top) and benefit from climate mitigation (bottom). Adapted from Mellin et al. Science Advances 2024

Our research shows equatorial regions are set to benefit least from efforts to curb emissions. We expect significant emission cuts will reduce the annual duration of severe bleaching conditions in all areas except these regions.

The projected highest climate impacts coincide with highest social reliance on coral reefs. This will challenge human populations that rely heavily on their local reefs for their livelihoods and nutrition.

Improving coral reef management

Our research identifies Earth’s reef regions that are at lowest risk of increased bleaching. This will help conservation managers and policymakers prioritise efforts to limit loss of coral reef biodiversity.

We predict much less risk of coral bleaching in regions such as the northern coasts of Venezuela and Colombia, Socotra Island (opposite the Gulf of Aden) and Alor Kecil in Indonesia. Seasonal upwellings occur here, bringing cooler water to the surface that’s likely to limit the severity of heatwaves.

Identifying these future havens for coral reefs will help maximise the success of coral conservation strategies such as assisted evolution, coral restoration or transplantation.

These strategies can help maintain healthy coral populations at local scales, particularly if used on reefs where future climate impacts will be lower. By pinpointing these havens, our research will strengthen coral conservation.

Our research includes a user-friendly web-based tool for mapping future coral bleaching. It will help pinpoint locations for effective management interventions.

Curbing greenhouse gas emissions is the main solution to reduce future climate impacts on corals. However, other strategies are also vital to maximise coral reefs’ adaptation to climate change.

Camille Mellin, Senior Lecturer and ARC Future Fellow, School of Biological Sciences, University of Adelaide and Damien Fordham, Associate Professor of Global Change Ecology, University of Adelaide

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

Has the world crossed the 1.5C warming threshold already ?

                                                                                                      Shutterstock

Earlier this week, the media carried a series of articles suggesting that the threshold of limiting increased global temperature to 1.50 C had already been crossed. The articles are based on new research on ocean temperatures that surmised that "hotter land temperatures, together with the earlier onset of industrial-era warming, indicate that global warming was already 1.7 +/- 0.1C above pre-industrial levels by 2020".  In short, this research and possible discovery means that the temperature is 0.5C higher than IPCC estimates with 20  C projected by the late 2020s, nearly two decades earlier than expected.

A team led by Professor Malcolm McCulloch from the University of Western Australia studied 300 years of records preserved in the skeletons of long-lived sea sponges from the Eastern Carribean. Of particular importance the sclerosponge thermometry shows that global warming has already exceeded 1.50 C. The focus of the research was changes in the amount of a chemical known as 'strontium' in the sponges skeletons. The changes in the amount of strontium reflects variations in seawater temperatures over the sponges' life.

The conclusion reached is that the Earth may already have reached at least 1.7C warming since pre-industrial times, well above the Paris Climate target of 1.5C. The opportunity for controlling climate change at the first milestone has already been lost.

Link to Nature article: 300 years of sclerosponge thermometry

The warming of Antarctica

DM Bergstrom, Author provided

A heatwave in Antarctica totally blew the minds of scientists. They set out to decipher it – and here are the results

Dana M Bergstrom, University of Wollongong

Climate scientists don’t like surprises. It means our deep understanding of how the climate works isn’t quite as complete as we need. But unfortunately, as climate change worsens, surprises and unprecedented events keep happening.

In March 2022, Antarctica experienced an extraordinary heatwave. Large swathes of East Antarctica experienced temperatures up to 40°C (72°F) above normal, shattering temperature records. It was the most intense heatwave ever recorded anywhere in the world.

So shocking and rare was the event, it blew the minds of the Antarctic climate science community. A major global research project was launched to unravel the reasons behind it and the damage it caused. A team of 54 researchers, including me, delved into the intricacies of the phenomenon. The team was led by Swiss climatologist Jonathan Wille, and involved experts from 14 countries. The collaboration resulted in two groundbreaking papers published today.

The results are alarming. But they provide scientists a deeper understanding of the links between the tropics and Antarctica – and give the global community a chance to prepare for what a warmer world may bring.

Head-hurting complexity

The papers tell a complex story that began half a world away from Antarctica. Under La Niña conditions, tropical heat near Indonesia poured into the skies above the Indian Ocean. At the same time, repeated weather troughs pulsing eastwards were generating from southern Africa. These factors combined into a late, Indian Ocean tropical cyclone season.

Between late February and late March 2022, 12 tropical storms had brewed. Five storms revved up to become tropical cyclones, and heat and moisture from some of these cyclones mashed together. A meandering jet stream picked up this air and swiftly transported it vast distances across the planet to Antarctica.

Below Australia, this jet stream also contributed to blocking the eastward passage of a high pressure system. When the tropical air collided with this so-called “blocking high”, it caused the most intense atmospheric river ever observed over East Antarctica. This propelled the tropical heat and moisture southward into the heart of the Antarctic continent.

Luck was on Antarctica’s side

The event caused the vulnerable Conger Ice Shelf to finally collapse. But the impacts were otherwise not as bad as they could have been. That’s because the heatwave struck in March, the month when Antarctica transitions to its dark, extremely cold winter. If a future heatwave arrives in summer – which is more likely under climate change – the results could be catastrophic.

Despite the heatwave, most inland temperatures stayed below zero. The spike included a new all-time temperature high of -9.4°C (15.1°F) on March 18 near Antarctica’s Concordia Research Station. To understand the immensity of this, consider that the previous March maximum temperature at this location was -27.6°C (-17.68°F). At the heatwave’s peak, 3.3 million square kilometres in East Antarctica – an area about the size of India – was affected by the heatwave.

The impacts included widespread rain and surface melt along coastal areas. But inland, the tropical moisture fell as snow – lots and lots of snow. Interestingly, the weight of the snow offset ice loss in Antarctica for the year. This delivered a temporary reprieve from Antarctica’s contribution to global sea-level rise.

These images, acquired by the Copernicus Sentinel-2 satellites on January 30 2022 (left) and March 21 2022 (right), show the Conger ice shelf before and after the collapse, which was triggered by a shocking heatwave. European Union, Copernicus Sentinel-2 satellite imagery, CC BY

Learning from the results

So what are the lessons here? Let’s begin with the nice bit. The study was made possible by international collaboration across Antarctica’s scientific community, including the open sharing of datasets. This collaboration is a touchstone of the Antarctic Treaty. It serves as a testament to the significance of peaceful international cooperation and should be celebrated.

Less heartwarmingly, the extraordinary heatwave shows how compounding weather events in the tropics can affect the vast Antarctic ice sheet. The heatwave further reduced the extent of sea ice, which was already at record lows. This loss of sea ice was exacerbated this year resulting in the lowest summer and winter sea ice ever recorded. It shows how disturbances in one year can compound in later years.

The event also demonstrated how tropical heat can trigger the collapse of unstable ice shelves. Floating ice shelves don’t contribute to global sea-level rise, but they acts as dams to the ice sheets behind them, which do contribute.

This research calculated that such temperature anomalies occur in Antarctica about once a century, but concluded that under climate change, they will occur more frequently.

The findings enable the global community to improve its planning for various scenarios. For example, if a heatwave of similar magnitude hit in summer, how much ice melt would there be? If an atmospheric river hit the Doomsday glacier in the West Antarctic, what rate of sea level rise would that trigger? And how can governments across the world prepare coastal communities for sea level rise greater than currently calculated?

This research contributes another piece to the complex jigsaw puzzle of climate change. And reminds us all, that delays to action on climate change will raise the price we pay.

This article has been amended to correct an error in converting a 40°C temperature difference from Celsius to Fahrenheit.

Dana M Bergstrom, Honorary Senior Fellow, University of Wollongong

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

State of the Climate Report 2022 - climate change continues to be mapped in Australia

BOM/CSIRO (c)

The latest State of the Climate Report for 2022 has been published by the CSIRO and the Bureau of Meteorology (BOM) continuing the unequivocal evidence of climate change and the impact on weather that is becoming the normal for this continent. The findings in summary provide sober reading at best and a portent of what is to come in the years ahead -

• Temperature: Australia’s climate has warmed by an average of 1.47 ± 0.24 °C since national records began in 1910.
• Sea temperature: Sea surface temperatures have increased by an average of 1.05 °C since 1900. This has led to an increase in the frequency of extreme heat events over land and sea. 
• Rainfall: There has been a decline of around 15 per cent in April to October rainfall in the southwest of Australia since 1970. Across the same region, May to July rainfall has seen the largest decrease, by around 19 per cent since 1970.
• There has been a decrease in streamflow at most gauges across Australia since 1975.
• Rainfall and streamflow have increased across parts of northern Australia since the 1970s.
• Fire: There has been an increase in extreme fire weather, and a longer fire season, across large parts of the country since the 1950s.
• There has been a decrease in the number of tropical cyclones observed in the Australian region.
• Decrease in snow: Snow depth, snow cover and number of snow days have decreased in alpine regions since the late 1950s.
• Ocean acidification: Oceans around Australia are acidifying and have warmed by more than 1 °C since 1900, contributing to longer and more frequent marine heatwaves.
• Sea level rise: Sea levels are rising around Australia, including more frequent extremes that are increasing the risk of inundation and damage to coastal infrastructure and communities.

The Report can be accessed at this link:CSIRO - BOM State of the Climate 2022 Report

Great Barrier Reef in Australia - coral bleaching increases in latest report

                      Aerial survey  (c) Great Barrier Marine Park Authority

The lastest surveillance report on Australia's Great Barrier Reef confirms the ongoing damage to the reef through increased temperatures as a result of climate change. Of particular alarm has been the repeated events of bleaching which now number 4 in seven years. The expected relief from a change in weather systems to La Nina did not occur and a mass bleaching resulted. This prolonged heat exposure is occuring across the wider reef system. 

The latest reef snapshot report published this month (May 2022) describes the current situation in clear terms which are not easily disputed -

• A total of 719 reefs were surveyed from the air between the Torres Strait and the Capricorn Bunker Group in the Great Barrier Reef Marine Park. Of these 654 reefs (91 per cent) exhibited some fomr of bleaching and a significant core of the central reef had severe or extreme bleaching. 
• Coral bleaching seen from the air is largely consistent with the spatial distribution of heat stress accumulation with a larger proportion of coral cover bleached on reefs that were exposed to the highest accumulated heat stress this last Summer (late 2021 and early 2022)
• The waters around the Great Barrier Reef exceeded historical summer maximums for the hottest summer months with three distinct heat waves increasing thermal stress throughout the Central and Northern Great Barrier Reef.
• The 2022 Aerial Survey Map [shown above] illustrates the variation in bleaching observed across the reef in the second half of March. The aerial surveys were conducted by trained observers from the Great Barrier Reef Marine Park Authority and the Australian Institute of Marine Science.

The full report can be accessed at this link: Great Barrier Reef Snapshot Report 2022

IPCC Report February 2022: Key global indictors on impact of climate change

As part of the Sixth Assessment Report, working group II of the IPCC published the 'report on impacts, adaptation and vulnerability'. This specific paper contains a list of impact indicators in a graphical presentation covering both ecological and human impact measures (as shown below). Copyright IPCC 2022.

Panel A

Panel B

IPCC Report February 2022: adaptation to climate change falls well behind

                                                              IPCC 2022

The latest report from Intergovernmental panel on climate change (IPCC) continues the well established trend of identifying the sadly lagging response to the threat of climate change globally. While a few concrete steps have been taken to address carbon emissions and mitigation, these efforts remain substantially insufficient and in many cases, badly misdirected.

A number of messages in the report emphasise the importance of close collaboration between all parts of society: Government, private sector, media, the scientific community, investors and essentially international cooperation.

There is also a sense that many of the 'soft limits' to human adaptation have been reached and increasingly the next steps will be harder to achieve with options now increasingly closing off with the risk of cascade events more likely.

Key points covered in this report -

• it is unequivocal that climate change has already disrupted human and natural systems. Past and current development trends (past emissions, development and climate change) have not advanced global climate resilient development.
• climate resilient development prospects are increasingly limited if current greenhouse gas emissions do not rapidly decline, especially if 1.5C global warming is exceeded in the near term.  the Report also noted that " evidence of observed impacts, projects risks, levels and trends in vulnerability, and adaptation limits, demonstrate that worldwide climate resilient development action is more urgent than previously assessed in the 5th Assessment Report".
• the rise in weather and climate extremes has led to some irreversible impacts as natural and humans systems are pushed beyond their ability to adapt.
• approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change.
• climate change impacts and risks are becoming increasingly complex and more difficult to manage. Multiple climate hazards will occur simultaneously and multiple climatic and non climatic risks will interact resulting in compounding overall risk and risks cascading across sectors and regions.
• Note a key caveat about global warming that transiently exceeds 1.5C which is termed 'overshoot'. "Depending on the magnitude and duration of overshoot, some impacts will cause the release of additional greenhouse gases and some will be irreversible even if global warming is reduced".

The IPCC report can be accessed at this link: IPCC Impacts, adaptation and vulnerability report

Global warming and the Earth's axis

                                                                                            Shutterstock

 

Most people would be aware that the Earth's rotational axis is not steady but tends to wobble as the planet is not a perfect unchanging sphere. Due to plate tectonics, erosion, weather masses moving around the surface, large ice masses weighting down sections of land, the poles actually move and this drift averages around 6 centimetres a year. This movement for example drew the North Pole towards Labrador in a Southerly direction.  For compass users, this situation will be familiar due to the adjustment calculation needed for grid to magnetic measurement to compensate for the drift when navigating using maps.

However in 2005 this drift suddenly altered and shifted to an Easterly direction and accelerated corresponding to an increase in the melt occuring in Greenland and Antarctica. Researchers at the University of Texas in Austin found using the GRACE (Gravity Recovery and Climate Experiment) satellites that around 600 gigatonnes of mass was being lost each year by the large glaciers in Greenland, Antarctica and the mountain glaciers. This mount of water being released from the glaciers into the oceans accounted for 90 % of the polar drift since 2005.  In short the planet's tilt was unexpectedly altered due to the effect of climate change.

IPCC 6th Assessment Report - the magnitude of the crisis defined

 

The 6th Assessment Report from the IPCC makes for sobering reading and was issued prior to COP26 in Glasgow.  In summary, the report has found that:

• Human induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones has strengthened since the 5th Assessment Report.
• Global surface temperatures will continue to increase until at least mid-century under all emission scenarios considered. Global warming of 1.5C and 2C will be exceeded during the 21st century unless deep reduction in carbon dioxide (CO2)  and other greenhouse gas emissions occur in the coming decades.
• Under scenarios with increasing CO2 emissions, the ocean and land carbon sinks are projected to be less effective at slowing the accumulation of CO2 in the atmosphere.
• Continued global warming is projected to further intensify the global water cycle including its variability, global monsoon precipitation and the severity of wet and dry events.
• With further global warming, every region is projected to increasingly experience concurrent and multiple changes in climatic impact-drivers.
• Low-likelihood outcomes such as ice sheet collapse, abrupt ocean circulation changes, some compound extreme events and warming substantially larger than the assessed 'very likely' range cannot be ruled out.
• Strong rapid and sustained reduction in CH4 (methane) would also limit the warming effect resulting from declining aerosol pollution and would improve air quality.

The report now finds that serious climate impacts that previously were thought to be less likely, are now considered to be possible due to the accelerated increase in global warming. 

The report can be accessed at this link: IPCC Sixth Assessment Report

A rise of 3 Degrees Celsius - the impact on Australia

In March this year, the Australian Academy of Science issued a stark warning on the future of this country if global warming is not actively slowed and ultimately stopped. The Academy's report charts both proven existing impacts and the effects of modelled temperature increases. The situation could not be more starkly or clearly demonstrated by the findings of the Academy which included -

Temperature rising

• the total emission reduction current pledged by the Australian and international government through the United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement, even if implemented on time will translate as an average global surface temperatures of 3 degrees Celsius (C) or more.
• the planet is well on its way to devastating climate change with average surface temperatures being at 1.1 degrees C above the pre-industrial period. Australia has had a worse outcome with warming on average by 1.4 degrees C.
• limiting climate change to 1.5 degrees Celsius in now virtually impossible.

Ecosystems

• land-based environments have been affected by drought, fire, extreme heatwaves, invasive species and disease, large scale mortality of trees, birds and tree-dwelling mammals
• rising sea levels are amplifying storm impacts damaging coastal ecosystems such as coral reefs and mangrove forests.

Australian agriculture, forestry, fisheries and food security

• reduced water availability and heat stress have contributed to reductions in profitability for broadacre crops such as wheat and barley in the magnitude of up to 22% since 2000.
• heat stress is a significant issue for livestock systems due to impacts on animal welfare, reproduction and production. Projected temperature and humidity changes suggest an increased number of heat stress days per year. 
• forestry is facing growing pressure from a warming and drying climate with increased fire risks, changes in rainfall patterns and species-specific pest impacts.

Australian cities and towns

• with close to 90% of Australians living in cities and towns, climate change experience will be manifested in various ways. 
• extreme heat wave conditions, bushfires and storms already place pressure on power stations and infrastructure while simultaneously increasing demand for energy supply for air conditioning.
• global sea level rises are already occuring and pose a severe risk to properties infrastructure and ecosystems with coastal flooding becoming a more regular feature. 160,000 to 250,000 coastal properties will be at risk with a rise of 1 metre in sea levels. 
• climate sensitive infectious diseases such as Ross River fever and other vector borne diseases shift their geographical distribution and intensity of transmission. This will only increase as climate change increases to above 2 degrees C.

The Academy's report provides sober reading and a reality check for those who believe that its only a question of avoiding a 1.5C temperature impact to avoid climate change. The climate crisis has already commenced - the only viable objective is to prevent it becoming worse.

The full report can be accessed at: Risks to Australia: three degrees Celsius