As the ongoing and often fractious debate over climate change and the environment swings to and fro, the Paris Agreement is usually cited emphasising the key target of limiting global temperature increases to no more than 1.5C. This is an incorrect explanation as the phrasing in the agreement is more nuanced. The Paris Agreement, adopted in December 2015 at COP21 has three goals -
to keep global temperature increase well below 2 degrees C with effort to limit it to 1.5C,
to strengthen adaptation and resilience capacities
to align financial flows with the other goals of the Agreement
The Paris Agreement is therefore aimed at preventing global temperatures increasing above 2 degrees C with a preference to limiting the increase to 1.5C. The actual upper temperature increase to be avoided is 2C not 1.5C.
The Agreement requires all countries both developed and developing, to submit "Nationally Determined Contributions (NDCs)". The NDCs are defined by each country and and an explanation provided as to what actions the country intends to take to respond to climate change. The implementation of actions is to be accompanied by an enhanced transparency regime.
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
Over the past four summers, Antarctic sea ice extent has hit new lows.
I’m part of a large group of scientists who set out to explore the consequences of summer sea ice loss after the record lows of 2022 and 2023. Together we rounded up the latest publications, then gathered new evidence using satellites, computer modelling, and robotic ocean sampling devices. Today we can finally reveal what we found.
It’s bad news on many levels, because Antarctic sea ice is vital for the world’s climate and ecosystems. But we need to get a grip on what’s happening – and use this concerning data to prompt faster action on climate change.
Sea ice around Antarctica waxes and wanes with the seasons, growing in the cold months and melting in warm ones. But this rhythmic cycle is changing.
What we did and what we found
Our team used a huge range of approaches to study the consequences of sea ice loss.
We used satellites to understand sea ice loss over summer, measuring everything from ice thickness and extent to the length of time each year when sea ice is absent.
Satellite data was also used to calculate how much of the Antarctic coast was exposed to open ocean waves. We were then able to quantify the relationship between sea ice loss and iceberg calving.
Data from free-drifting ocean robots was used to understand how sea ice loss affects the tiny plants that support the marine food web.
Every other kind of available data was then harnessed to explore the full impact of sea ice changes on ecosystems.
We also used computer models to simulate the impact of dramatic summer sea ice loss on the ocean.
In summary, our extensive research reveals four key consequences of summer sea ice loss in Antarctica.
1. Ocean warming is compounding
Bright white sea ice reflects about 90% of the incoming energy from sunlight, while the darker ocean absorbs about 90%. So if there’s less summer sea ice, the ocean absorbs much more heat.
This means the ocean surface warms more in an extreme low sea ice year, such as 2016 – when everything changed.
Until recently, the Southern Ocean would reset over winter. If there was a summer with low sea ice cover, the ocean would warm a bit. But over winter, the extra heat would shift into the atmosphere.
That’s not working anymore. We know this from measuring sea surface temperatures, but we have also confirmed this relationship using computer models.
What’s happening instead is when summer sea ice is very low, as in 2016, it triggers ocean warming that persists. It takes about three years for the system to fully recover. But recovery is becoming less and less likely, given warming is building from year to year.
Comparing an average sea ice summer (a) to an extreme low sea ice summer (b) in which there is less sea ice for wildlife and more sunlight is absorbed by the ocean. The ice shelf is more exposed to ocean waves, calving more icebergs. The ocean is also less productive and tourist vessels can make a closer approach.Doddridge, E., W., et al. (2025) PNAS Nexus., CC BY-NC-ND
2. More icebergs are forming
Sea ice protects Antarctica’s coast from ocean waves.
On average, about a third of the continent’s coastline is exposed over summer. But this is changing. In 2022 and 2023, more than half of the Antarctic coast was exposed.
Our research shows more icebergs break away from Antarctic ice sheets in years with less sea ice. During an average summer, about 100 icebergs break away. Summers with low sea ice produce about twice as many icebergs.
Antarctic ice sheets without sea ice are more exposed to waves.Pete Harmsen AAD
3. Wildlife squeezed off the ice
Many species of seals and penguins rely on sea ice, especially for breeding and moulting.
Entire colonies of emperor penguins experienced “catastrophic breeding failure” in 2022, when sea ice melted before chicks were ready to go to sea.
After giving birth, crabeater seals need large, stable sea ice platforms for 2–3 weeks until their pups are weaned. The ice provides shelter and protection from predators. Less summer sea-ice cover makes large platforms harder to find.
Many seal and penguin species also take refuge on the sea ice when moulting. These species must avoid the icy water while their new feathers or fur grows, or risk dying of hypothermia.
4. Logistical challenges at the end of the world
Low summer sea ice makes it harder for people working in Antarctica. Shrinking summer sea ice will narrow the time window during which Antarctic bases can be resupplied over the ice. These bases may soon need to be resupplied from different locations, or using more difficult methods such as small boats.
Supply ships typically unload their cargo directly onto the sea ice, but that may have to change.Jared McGhie, Australian Antarctic Division
No longer safe
Anarctic sea ice began to change rapidly in 2015 and 2016. Since then it has remained well below the long-term average.
The dataset we use relies on measurements from US Department of Defense satellites. Late last month, the department announced it would no longer provide this data to the scientific community. While this has since been delayed to July 31, significant uncertainty remains.
One of the biggest challenges in climate science is gathering and maintaining consistent long-term datasets. Without these, we don’t accurately know how much our climate is changing. Observing the entire Earth is hard enough when we all work together. It’s going to be almost impossible if we don’t share our data.
Antarctic sea ice extent anomalies (the difference between the long-term average and the measurement) for the entire satellite record since the late 1970s.Edward Doddridge, using data from the US NSIDC Sea Ice Index, version 3., CC BY
Recent low sea ice summers present a scientific challenge. The system is currently changing faster than our scientific community can study it.
But vanishing sea ice also presents a challenge to society. The only way to prevent even more drastic changes in the future is to rapidly transition away from fossil fuels and reach net zero emissions.
Since US President Donald Trump took office this year, one theme has come up time and again: his rule is a threat to the US-led international order.
As the US political scientist John Mearsheimer famously argued, the liberal international order was destined to fail from the start, as it contained the seeds of its own destruction.
This perspective has gained traction in recent years. And now, Trump’s actions have caused many to question whether a new world order is emerging.
Trump has expressed a desire for a new international order defined by multiple spheres of influence — one in which powers like the US, China and Russia each exert dominance over distinct regions.
This vision aligns with the idea of a “multipolar” world, where no single state holds overarching global dominance. Instead, influence is distributed among several great powers, each maintaining its own regional sphere.
This architecture contrasts sharply with earlier periods – the bipolar world of the Cold War, dominated by the US and the Soviet Union; and the unipolar period that followed, dominated by the US.
What does this mean for the world order moving forward?
Shifting US spheres of influence
We’ve seen this shift taking place in recent months. For example, Trump has backed away from his pledge to end the war between Russia and Ukraine and now appears to be leaving it to the main protagonists, and Europe, to find a solution.
Europe, which once largely spoke in a unified voice with the US, is also showing signs of policy-making which is more independent. Rather than framing its actions as protecting “Western democratic principles”, Europe is increasingly focused on defining its own security interests.
In the Middle East, the US will likely maintain its sphere of influence. It will continue its unequivocal support for Israel under Trump.
Amid shifting global alliances, the Trump administration will continue to support Israel, led by Prime Minister Benjamin Netanyahu.noamgalai/Shutterstock
The US will also involve itself in the region’s politics when its interests are at stake, as we witnessed in its recent strikes on Iranian nuclear facilities.
This, along with increasing economic ties between the US and Gulf states, suggests US allies in the region will remain the dominant voices shaping regional dynamics, particularly now with Iran weakened.
Yet it’s clear Trump is reshaping US dynamics in the region by signaling a desire for reduced military and political involvement, and criticising the nation building efforts of previous administrations.
The Trump administration now appears to want to maintain its sphere of influence primarily through strong economic ties.
Russia and China poles emerging elsewhere
Meanwhile, other poles are emerging in the Global South. Russia and China have deepened their cooperation, positioning themselves as defenders against what they frame as Western hegemonic bullying.
Trump’s trade policies and sanctions against many nations in the Global South have fuelled narratives (spread by China and Russia) that the US does not consistently adhere to the rules it imposes on others.
Trump’s decision to slash funding to USAID has also opened the door to China, in particular, to become the main development partner for nations in Africa and other parts of the world.
And on the security front, Russia has become more involved in many African and Middle Eastern countries, which have become less trustful and reliant on Western powers.
Russian President Vladimir Putin and Chinese leader Xi Xinping see opportunities to spread their influence in the Global South.plavi011/Shutterstock
In the Indo-Pacific, much attention has been given to the rise of China and its increasingly assertive posture. Many of Washington’s traditional allies are nervous about its continued engagement in the region and ability to counter China’s rise.
Chinese leader Xi Jinping has sought to take advantage of the current environment, embarking on a Vietnam, Malaysia and Cambodia push earlier this year. But many nations continue to be wary of China’s increasing influence, in particular the Philippines, which has clashed with China over the South China Sea.
Strategic hedging
Not all countries, however, are aligning themselves neatly with one pole or another.
For small states caught between great powers, navigating this multipolar environment is both a risk and an opportunity.
Ukraine is a case in point. As a sovereign state, Ukraine should have the freedom to decide its own alignments. Yet, it finds itself ensnared in great power politics, with devastating consequences.
Other small states are playing a different game — pivoting from one power to another based on their immediate interests.
Slovakia, for instance, is both a NATO and EU member, yet its leader, Robert Fico, attended Russia’s Victory Day Parade in May and told President Vladimir Putin he wanted to maintain “normal relations” with Russia.
Then there is Central Asia, which is the centre of a renewed “great game,” with Russia, China and Europe vying for influence and economic partnerships.
Yet if any Central Asian countries were to be invaded by Putin, would other powers intervene? It’s a difficult question to answer. Major powers are reluctant to engage in direct conflict unless their core interests or borders are directly threatened.
While it is still early to draw definitive conclusions, the events of the past few months underscore a growing trend. Smaller countries are expressing solidarity with one power, but pragmatic cooperation with another, when it suits their national interests.
For this reason, regional power blocs seem to be of increasing interest to countries in the Global South.
For instance, the China-led Shanghai Cooperation Organisation has become a stronger and larger grouping of nations across Eurasia in recent years.
Trump’s focus on making “America Great Again,” has taken the load off the US carrying liberal order leadership. A multipolar world may not be the end of the liberal international order, but it may be a reshaped version of liberal governance.
How “liberal” it can be will likely depend on what each regional power, or pole, will make of it.
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.
The timing and targets of Israel’s attacks on Iran tell us that Prime Minister Benjamin Netanyahu’s short-term goal is to damage Iran’s nuclear facilities in order to severely diminish its weapons program.
But Netanyahu has made clear another goal: he said the war with Iran “could certainly” lead to regime change in the Islamic republic.
It’s no secret Israel has wanted to see the current government of Iran fall for some time, as have many government officials in the US.
But what would things look like if the government did topple?
How is power wielded in today’s Iran?
Founded in 1979 after the Iranian Revolution, the Islamic Republic of Iran has democratic, theocratic and authoritarian elements to its governing structure.
The founding figure of the Islamic republic, Ayatollah Ruhollah Khomeini, envisioned a state run by Islamic clerics and jurists who ensured all policies adhered to Islamic law.
Iran has a unicameral legislature (one house of parliament), called the Majles, and a president (currently Masoud Pezeshkian). There are regular elections for both.
But while there are democratic elements within this system, in practice it is a “closed loop” that keeps the clerical elite in power and prevents challenges to the supreme leader. There is a clear hierarchy, with the supreme leader at the top.
Khamenei has been in power for more than 35 years, taking office following Khomeini’s death in 1989. The former president of Iran, he was chosen to become supreme leader by the Assembly of Experts, an 88-member body of Islamic jurists.
While members of the assembly are elected by the public, candidates must be vetted by the powerful 12-member Guardian Council (also known as the Constitutional Council). Half of this body is selected by the supreme leader, while the other half is approved by the Majles.
In last year’s elections, the Guardian Council disqualified many candidates from running for president, as well as the Majles and Assembly of Experts, including the moderate former president Hassan Rouhani.
As such, the supreme leader is increasingly facing a crisis of legitimacy with the public. Elections routinely have low turnout. Even with a reformist presidential candidate in last year’s field – the eventual winner, Masoud Pezeshkian – turnout was below 40% in the first round.
The supreme leader also directly appoints the leaders in key governance structures, such as the judiciary, the armed forces and Islamic Revolutionary Guard Corps (IRGC).
The all-powerful IRGC
So, Iran is far from a democracy. But the idea that regime change would lead to a full democracy that is aligned with Israel and the US is very unlikely.
Iranian politics is extremely factional. Ideological factions, such as the reformists, moderates and conservatives, often disagree vehemently on key policy areas. They also jockey for influence with the supreme leader and the rest of the clerical elite. None of these factions is particularly friendly with the US, and especially not Israel.
There are also institutional factions. The most powerful group in the country is the clerical elite, led by the supreme leader. The next most powerful faction would be the IRGC.
The IRGC is extremely hardline politically. At times, the IRGC’s influence domestically has outstripped that of presidents, exerting significant pressure on their policies. The guard only vocally supports presidents in lockstep with Islamic revolutionary doctrine.
In addition to its control over military hardware and its political influence, the guard is also entwined with the Iranian economy.
Given all of this, the IRGC would be the most likely political institution to take control of Iran if the clerical elite were removed from power.
In peacetime, the general consensus is the IRGC would not have the resources to orchestrate a coup if the supreme leader died. But in a time of war against a clear enemy, things could be different.
Possible scenarios post-Khamenei
So, what might happen if Israel were to assassinate the supreme leader?
One scenario would be a martial law state led by the IRGC, formed at least in the short term for the purposes of protecting the revolution.
In the unlikely event the entire clerical leadership is decimated, the IRGC could attempt to reform the Assembly of Experts and choose a new supreme leader itself, perhaps even supporting Khamenei’s son’s candidacy.
Needless to say, this outcome would not lead to a state more friendly to Israel or the US. In fact, it could potentially empower a faction that has long argued for a more militant response to both.
Another scenario is a popular uprising. Netanyahu certainly seems to think this is possible, saying in an interview in recent days:
The decision to act, to rise up this time, is the decision of the Iranian people.
We’ve seen enough revolutions to know this is possible – after all, modern Iran was formed out of one. But once again, new political leadership being more friendly to Israel and the West is not a foregone conclusion.
It is possible for Iranians to hold contempt in their hearts for both their leaders and the foreign powers that would upend their lives.
