For over a decade, the world has been trying to limit global warming to 1.5°C.
That’s no longer possible, according to a new United Nations report. We will likely pass 1.5°C in 2030. That’s not good news for anyone, least of all Australia’s Pacific Island neighbours who face rapidly rising seas.
In response to the report, Palau’s President Surangel Whipps Jr said:
It is hard to overstate the depth of emotion for those of us living on the frontline after having fought so hard to put the 1.5 degree limit at the heart of the Paris Agreement […] calls for greater ambition are no longer enough — we need to see an urgent and unprecedented increase in political will and investment in a climate safe future
The small silver lining is that it’s still possible for this to be a temporary overshoot of the target. If nations redouble their efforts to phase out fossil fuels and reduce other sources of emissions, they could limit peak warming to 1.8°C and then use carbon removal methods to bring temperatures back to 1.5°C or below this century.
There are no good outcomes if we remain above 1.5°C. Urgent cuts to emissions and efforts to protect the most vulnerable are our best remaining options. Failure to do so risks irreversible harm.
Why does 1.5°C matter so much?
The 2015 Paris Agreement established a shared goal for the world: keep the rise in global average temperatures above pre-industrial levels “well below” 2°C and “pursue efforts” to hold warming to 1.5°C.
This goal was set based on expert scientific assessments that warming of more than 2°C would be dangerous and that limiting warming to 1.5°C was necessary to minimise climate risks.
Pacific nations fought hard to include 1.5°C in the agreement, arguing it was essential for their communities to “stay alive” in the face of rising sea levels and other climate-fuelled threats.
Last year, the world’s top court – the International Court of Justice – ruled that 1.5°C is the primary temperature limit nations have committed to work towards.
This ruling means that if governments fail to act as ambitiously as they can, they could be sued in international courts.
In May this year, a majority of nations voted in the UN General Assembly to endorse the court’s ruling and urge action to keep to 1.5°C.
It’s not time to give up
Warming of 1.5°C will be bad. But 1.6°C will be worse, and 1.7°C worse again. Every increase will bring more extreme weather, more loss of nature, more loss of land to the sea and more harm to humans.
If we stay over 1.5°C, we risk triggering climate tipping points – sudden shifts which cannot be undone on human timescales. These include the Greenland and West Antarctic ice sheets melting, the collapse of crucial heat-distributing currents in the Atlantic Ocean or the Amazon rainforest becoming a source of emissions.
Overshooting 1.5°C doesn’t mean it’s time to throw out the Paris Agreement. It’s not working fast enough, but it is working.
Solar power and electric vehicles have boomed and electrification has accelerated. Nations have cut emissions enough to avoid the worst climate futures of a 3°C rise or even higher. According to the Climate Action Tracker, the Paris Agreement has averted the equivalent of 1°C of warming. Rather than hitting 3.6°C by 2100, the world is on track for 2.6°C.
While this is progress, it is not enough. Global emissions are plateauing, but have still not begun to fall in earnest.
As damage from climate change mounts, leaders must do the work and begin rapidly cutting emissions to keep the goal of net-zero by 2050 alive.
To get temperatures back under 1.5°C, we will also need to pull gigatonnes of carbon dioxide back out of the atmosphere using tree planting and nature restoration. We may also need technological approaches such as rock weathering or ocean alkalinity enhancement, though these are not proven at scale and can come with other risks.
We are all in this together
It may seem as if climate action faces impossible headwinds, as populism surges and the current United States administration doubles down on fossil fuels.
It’s worth looking beyond these headlines. It took almost 70 years for the world to install a terawatt of solar power, but then just two years for the second and another two for the third terawatt. In ten years, that figure will likely have tripled. Developing nations are moving rapidly to take up non-polluting electric transport.
Climate change can no longer be ignored. As damage mounts, nations will have to cooperate to cut emissions as rapidly as possible and figure out how to safely and equitably pull carbon back out of the atmosphere. Action depends on strong political will, inclusive governance, and finance to help developing countries cut emissions and adapt.
In November, Australia will lead negotiations at the next international climate summit, COP31, in Turkey. Leaders and diplomats will work to keep 1.5°C in reach – even after overshoot. Australia can point to its own rapid clean energy transition and urge others to set clear pathways to go electric – and wean themselves off the production and use of fossil fuels.
Climate change has been described as a super wicked problem – big, complex and impossible to solve simply. The solution is to see the urgency of the issue and act cooperatively to tackle it. If we make it a problem for the next generation, there may be no way back to a safe climate.
Records are tumbling and impacts not expected until mid-century are now hitting every continent – what happened?
AI generated graphic: Collin & Harris
If you wanted to summarise the countless published observations and studies on climate disruption in a single word, it would be the noun: underestimation.
This is in no way a criticism of the scientific community. The unprecedented climate impacts we are now experiencing are occurring at a pace tens of times faster than those seen in previously stable climates of the geologic past. No evolution of CO₂ levels this rapid has been observed in the 800,000 years of ice core data, nor in the last 66 million years of geological data, and the current level of 430 ppm has not been seen for 5 to 8 million years. Even the Palaeocene Eocene Thermal Maximum (PETM), 56 million years ago, only saw CO₂ levels and temperatures rise at one tenth of today’s rate. The closest parallels are from Heinrich Events during the last glacial period which were caused by dramatic changes and collapse episodes of the Atlantic Meridional Overturning Circulation (AMOC). Scientists therefore do not have comparable past examples for many of today’s rapid changes, from which to draw comparisons or create prognoses for the future.
Even though today’s temperatures have existed in the past, and today’s CO₂ concentrations have also been reached in the past, they have never occurred at the same time before. This is due to the incredible speed by which we have accumulated CO₂ emissions in the atmosphere, overwhelming nature’s ability to respond with anything like an equilibrium. Even the peak volcanic emissions of the PETM, which created a 5-8°C temperature rise over 5,000 years, are dwarfed by our current burn rate of fossil fuels. We are in uncharted territory.1
Antarctica has long been seen as a remote, unchanging environment. Not any more.
The ice-covered continent and the surrounding Southern Ocean are undergoing abrupt and alarming changes. Sea ice is shrinking rapidly, the floating glaciers known as ice shelves are melting faster, the ice sheets carpeting the continent are approaching tipping points and vital ocean currents show signs of slowing down.
Published today in Nature, our new research shows these abrupt changes are already underway – and likely to significantly intensify in the future.
Several authors of this article have witnessed these startling changes during fieldwork on the ice. These changes spell bad news for wildlife, both iconic and lesser known. But the changes will reach much further. What’s happening in Antarctica right now will affect the world for generations to come, from rising sea levels to extreme changes in the climate system.
Antarctica’s enormity can give the illusion of permanence. But abrupt changes are arriving. Image: Sonny Whitelaw
What is an abrupt change?
Scientists define an abrupt change as a climatic or environmental shift taking place much faster than expected.
What makes abrupt changes so concerning is they can amplify themselves. For example, melting sea ice allows oceans to warm more rapidly, which melts more sea ice. Once triggered, they can be difficult or even impossible to reverse on timescales meaningful to humans.
While it’s common to assume incremental warming will translate to gradual change, we’re seeing something very different in Antarctica. Over past decades, the Antarctic environment had a much more muted response overall to human-caused climate warming compared to the Arctic. But about a decade ago, abrupt changes began to occur.
Shrinking sea ice brings cascading change
Antarctica’s natural systems are tightly interwoven. When one system is thrown out of balance, it can trigger cascading effects in others.
Sea ice around Antarctica has been declining dramatically since 2014. The expanse of sea ice is now shrinking at double the rate of Arctic sea ice. We found these unfolding changes are unprecedented – far outside the natural variability of past centuries.
The implications are far reaching. Sea ice has a reflective, high-albedo surface which reflects heat back to space. When there’s less sea ice, more heat is absorbed by darker oceans. Emperor penguins and other species reliant on sea ice for habitat and breeding face real threats. Less sea ice also means Antarctica’s ice shelves are more exposed to waves.
The expanse of ocean covered by sea ice began shrinking in 2014 and the rate is accelerating. image: Sonny Whitelaw
Vital ocean currents are slowing
The melting of ice is actually slowing down the deep ocean circulation around Antarctica. This system of deep currents, known as the Antarctic Overturning Circulation, plays a critical role in regulating Earth’s climate by absorbing carbon dioxide and distributing heat.
In the northern hemisphere, the Atlantic Meridional Overturning Circulation is facing a slowdown.
We’re now observing a similar risk in Southern Ocean currents. Changes to the Antarctic Overturning Circulation may unfold at twice the rate of the more famous North Atlantic counterpart.
A slowdown could reduce how much oxygen and carbon dioxide the ocean absorbs and leave vital nutrients at the seafloor. Less oxygen and fewer nutrients would have major consequences for marine ecosystems and climate regulation.
The West Antarctic Ice Sheet alone has enough ice to raise global sea levels by more than five metres – and scientists warn we could be nearing the point where this ice sheet could collapse even without substantial further warming, though this might take centuries to millennia.
These enormous ice sheets represent the risk of a global tipping point. They contribute the greatest uncertainty to projections of future sea level rise because we don’t know just how quickly they could collapse.
Antarctica’s biological systems are also undergoing sudden shifts. Ecosystems both under the sea and on land are being reshaped by warming temperatures, unreliable ice conditions and human activity bringing pollution and the arrival of invasive species.
It’s essential to protect these ecosystems through the Antarctic Treaty, including creating protected areas of land and sea and restricting some human activities. But these conservation measures won’t be enough to ensure emperor penguins and leopard seals survive. That will require decisive global action to reduce greenhouse gas emissions.
Which future?
Antarctica is often seen as a symbol of isolation and permanence. But the continent is now changing with disturbing speed – much faster than scientists anticipated.
These abrupt changes stem largely from the extra heat trapped by decades of unchecked greenhouse gas emissions. The only way to avoid further abrupt changes is to slash emissions rapidly enough to hold warming as close to 1.5°C as possible.
Even if we achieve this, much change has already been set in motion. Governments, businesses and coastal communities must prepare for a future of abrupt change. What happens in Antarctica won’t stay there.
The stakes could not be higher. The choices made now will determine whether we face a future of worsening impacts and irreversible change or one of managed resilience to the changes already locked in.
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.
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.
Antarctic ice sheets without sea ice are more exposed to waves.Image: Sonny Whitelaw
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.
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. Photo: Cody Whitelaw
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. Image: Vladimir Anikeev | Unsplash.
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 ocean around Antarctica is rapidly getting saltier at the same time as sea ice is retreating at a record pace. Since 2015, the frozen continent has lost sea ice similar to the size of Greenland. That ice hasn’t returned, marking the largest global environmental change during the past decade.
This finding caught us off guard – melting ice typically makes the ocean fresher. But new satellite data shows the opposite is happening, and that’s a big problem. Saltier water at the ocean surface behaves differently than fresher seawater by drawing up heat from the deep ocean and making it harder for sea ice to regrow.
The loss of Antarctic sea ice has global consequences. Less sea ice means less habitat for penguins and other ice-dwelling species. More of the heat stored in the ocean is released into the atmosphere when ice melts, increasing the number and intensity of storms and accelerating global warming. This brings heatwaves on land and melts even more of the Antarctic ice sheet, which raises sea levels globally.
Our new study has revealed that the Southern Ocean is changing, but in a different way to what we expected. We may have passed a tipping point and entered a new state defined by persistent sea ice decline, sustained by a newly discovered feedback loop.
The Southern Ocean surrounds Antarctica, which is fringed by sea ice. Image: NASA
A surprising discovery
Monitoring the Southern Ocean is no small task. It’s one of the most remote and stormy places on Earth, and is covered in darkness for several months a year. Thanks to new European Space Agency satellites and underwater robots which stay below the ocean surface measuring temperature and salinity, we can now observe what is happening in real time.
Our team at the University of Southampton worked with colleagues at the Barcelona Expert Centre and the European Space Agency to develop new algorithms to track ocean surface conditions in polar regions from satellites. By combining satellite observations with data from underwater robots, we built a 15-year picture of changes in ocean salinity, temperature and sea ice.
What we found was astonishing. Around 2015, surface salinity in the Southern Ocean began rising sharply – just as sea ice extent started to crash. This reversal was completely unexpected. For decades, the surface had been getting fresher and colder, helping sea ice expand.
The annual summer minimum extent of Antarctic sea ice dropped precipitously in 2015. Image: NOAA Climate.gov/National Snow and Ice Data Center
To understand why this matters, it helps to think of the Southern Ocean as a series of layers. Normally, the cold, fresh surface water sits on top of warmer, saltier water deep below. This layering (or stratification, as scientists call it) traps heat in the ocean depths, keeping surface waters cool and helping sea ice to form.
Saltier water is denser and therefore heavier. So, when surface waters become saltier, they sink more readily, stirring the ocean’s layers and allowing heat from the deep to rise. This upward heat flux can melt sea ice from below, even during winter, making it harder for ice to reform. This vertical circulation also draws up more salt from deeper layers, reinforcing the cycle.
A powerful feedback loop is created: more salinity brings more heat to the surface, which melts more ice, which then allows more heat to be absorbed from the Sun. My colleagues and I saw these processes first hand in 2016-2017 with the return of the Maud Rise polynya, which is a gaping hole in the sea ice that is nearly four times the size of Wales and last appeared in the 1970s.
What happens in Antarctica doesn’t stay there
Losing Antarctic sea ice is a planetary problem. Sea ice acts like a giant mirror reflecting sunlight back into space. Without it, more energy stays in the Earth system, speeding up global warming, intensifying storms and driving sea level rise in coastal cities worldwide.
Wildlife also suffers. Emperor penguins rely on sea ice to breed and raise their chicks. Tiny krill – shrimp-like crustaceans which form the foundation of the Antarctic food chain as food for whales and seals – feed on algae that grow beneath the ice. Without that ice, entire ecosystems start to unravel.
What’s happening at the bottom of the world is rippling outward, reshaping weather systems, ocean currents and life on land and sea.
Feedback loops are accelerating the loss of Antarctic sea ice. Image: University of Southampton
Antarctica is no longer the stable, frozen continent we once believed it to be. It is changing rapidly, and in ways that current climate models didn’t foresee. Until recently, those models assumed a warming world would increase precipitation and ice-melting, freshening surface waters and helping keep Antarctic sea ice relatively stable. That assumption no longer holds.
Our findings show that the salinity of surface water is rising, the ocean’s layered structure is breaking down and sea ice is declining faster than expected. If we don’t update our scientific models, we risk being caught off guard by changes we could have prepared for. Indeed, the ultimate driver of the 2015 salinity increase remains uncertain, underscoring the need for scientists to revise their perspective on the Antarctic system and highlighting the urgency of further research.
We need to keep watching, yet ongoing satellite and ocean monitoring is threatened by funding cuts. This research offers us an early warning signal, a planetary thermometer and a strategic tool for tracking a rapidly shifting climate. Without accurate, continuous data, it will be impossible to adapt to the changes in store.
Under the landmark 2015 Paris Agreement on climate change, humanity is seeking to reduce greenhouse gas emissions and keep planetary heating to no more than 1.5°C above the pre-industrial average. In 2024, temperatures on Earth surpassed that limit.
This was not enough to declare the Paris threshold had been crossed, because the temperature goals under the agreement are measured over several decades, rather than short excursions over the 1.5°C mark.
But the two papers just released use a different measure. Both examined historical climate data to determine whether very hot years in the recent past were a sign that a future, long-term warming threshold would be breached.
The answer, alarmingly, was yes. The researchers say the record-hot 2024 indicates Earth is passing the 1.5°C limit, beyond which scientists predict catastrophic harm to the natural systems that support life on Earth.
2024: the first year of many above 1.5°C
Climate organisations around the world agree last year was the hottest on record. The global average temperature in 2024 was about 1.6°C above the average temperatures in the late-19th century, before humans started burning fossil fuels at large scale.
Earth has also recently experienced individual days and months above the 1.5°C warming mark.
But the global temperature varies from one year to the next. For example, the 2024 temperature spike, while in large part due to climate change, was also driven by a natural El Niño pattern early in the year. That pattern has dissipated for now, and 2025 is forecast to be a little cooler.
These year-to-year fluctuations mean climate scientists don’t view a single year exceeding the 1.5°C mark as a failure to meet the Paris Agreement.
However, the new studies published today in Nature Climate Change suggest even a single month or year at 1.5°C global warming may signify Earth is entering a long-term breach of that vital threshold.
What the studies found
The studies were conducted independently by researchers in Europe and Canada. They tackled the same basic question: is a year above 1.5°C global warming a warning sign that we’re already crossing the Paris Agreement threshold?
Both studies used observations and climate model simulations to address this question, with slightly different approaches.
In the European paper, the researchers looked at historical warming trends. They found when Earth’s average temperature reached a certain threshold, the following 20-year period also reached that threshold.
This pattern suggests that, given Earth reached 1.5°C warming last year, we may have entered a 20-year warming period when average temperatures will also reach 1.5°C.
The Canadian paper involved month-to-month data. June last year was the 12th consecutive month of temperatures above the 1.5°C warming level. The researcher found 12 consecutive months above a climate threshold indicates the threshold will be reached over the long term.
Both studies also demonstrate that even if stringent emissions reduction begins now, Earth is still likely to be crossing the 1.5°C threshold.
Heading in the wrong direction
Given these findings, what humanity does next is crucial.
For decades, climate scientists have warned burning fossil fuels for energy releases carbon dioxide and other gases that are warming the planet.
But humanity’s greenhouse gas emissions have continued to increase. Since the Intergovernmental Panel on Climate Change released its first report in 1990, the world’s annual carbon dioxide emissions have risen about 50%.
Put simply, we are not even moving in the right direction, let alone at the required pace.
The science shows greenhouse gas emissions must reach net-zero to end global warming. Even then, some aspects of the climate will continue to change for many centuries, because some regional warming, especially in the oceans, is already locked in and irreversible.
If Earth has indeed already crossed the 1.5°C mark, and humanity wants to get below the threshold again, we will need to cool the planet by reaching “net-negative emissions” – removing more greenhouse gases from the atmosphere than we emit. This would be a highly challenging task.
Feeling the heat
The damaging effects of climate change are already being felt across the globe. The harm will be even worse for future generations.
Australia has already experienced 1.5°C of warming, on average, since 1910.
Our unique ecosystems, such as the Great Barrier Reef, are already suffering because of this warming. Our oceans are hotter and seas are rising, hammering our coastlines and threatening marine life.
These studies are a sobering reminder of how far short humanity is falling in tackling climate change.
They show we must urgently adapt to further global warming. Among the suite of changes needed, richer nations must support the poorer countries set to bear the most severe climate harms. While some progress has been made in this regard, far more is needed.
A major shift is also needed to decarbonise our societies and economies. There is still room for hope, but we must not delay action. Otherwise, humanity will keep warming the planet and causing further damage.
A vast network of ocean currents nicknamed the “great global ocean conveyor belt” is slowing down. That’s a problem because this vital system redistributes heat around the world, influencing both temperatures and rainfall.
The Atlantic Meridional Overturning Circulation funnels heat northwards through the Atlantic Ocean and is crucial for controlling climate and marine ecosystems. It’s weaker now than at any other time in the past 1,000 years, and global warming could be to blame. But climate models have struggled to replicate the changes observed to date – until now.
Our modelling suggests the recent weakening of the oceanic circulation can potentially be explained if meltwater from the Greenland ice sheet and Canadian glaciers is taken into account.
Our results show the Atlantic overturning circulation is likely to become a third weaker than it was 70 years ago at 2°C of global warming. This would bring big changes to the climate and ecosystems, including faster warming in the southern hemisphere, harsher winters in Europe, and weakening of the northern hemisphere’s tropical monsoons. Our simulations also show such changes are likely to occur much sooner than others had suspected.
The Atlantic Meridional Overturning Circulation (AMOC): what is it and why is it so important? (National Oceanography Centre)
Changes in the Atlantic Meridional Overturning Circulation
The Atlantic ocean circulation has been monitored continuously since 2004. But a longer-term view is necessary to assess potential changes and their causes.
There are various ways to work out what was going before these measurements began. One technique is based on sediment analyses. These estimates suggest the Atlantic meridional circulation is the weakest it has been for the past millennium, and about 20% weaker since the middle of the 20th century.
Since 2002, Greenland lost 5,900 billion tonnes (gigatonnes) of ice. To put that into perspective, imagine if the whole state of New South Wales was covered in ice 8 metres thick.
This fresh meltwater flowing into the subarctic ocean is lighter than salty seawater. So less water descends to the ocean depths. This reduces the southward flow of deep and cold waters from the Atlantic. It also weakens the Gulf Stream, which is the main pathway of the northward return flow of warm waters at the surface.
The Gulf Stream is what gives Britain mild winters compared to other places at the same distance from the north pole such as Saint-Pierre and Miquelon in Canada.
Our new research shows meltwater from the Greenland ice sheet and Arctic glaciers in Canada is the missing piece in the climate puzzle.
When we factor this into simulations, using an Earth system model and a high-resolution ocean model, slowing of the oceanic circulation reflects reality.
Our research confirms the Atlantic overturning circulation has been slowing down since the middle of the 20th century. It also offers a glimpse of the future.
As they travel northwards, the Gulf Stream and North Atlantic Current cool as they lose heat to the atmosphere. The waters then become dense enough to sink to depth and form North Atlantic deep water, which travels southward at depth and feeds the other ocean basins.Modified from Nature Reviews Earth & Environment (2020)
Connectivity in the Atlantic Ocean
Our new research also shows the North and South Atlantic oceans are more connected than previously thought.
The weakening of the overturning circulation over the past few decades has obscured the warming effect in the North Atlantic, leading to what’s been termed a “warming hole”.
When oceanic circulation is strong, there is a large transfer of heat to the North Atlantic. But weakening of the oceanic circulation means the surface of the ocean south of Greenland has warmed much less than the rest.
Reduced heat and salt transfer to the North Atlantic has meant more heat and salt accumulated in the South Atlantic. As a result, the temperature and salinity in the South Atlantic increased faster.
Our simulations show changes in the far North Atlantic are felt in the South Atlantic Ocean in less than two decades. This provides new observational evidence of the past century slow-down of the Atlantic overturning circulation.
The addition of meltwater in the North Atlantic leads to localised cooling in the subpolar North Atlantic and warming in the South Atlantic.https://www.nature.com/articles/s41561-024-01568-1
What does the future hold?
The latest climate projections suggest the Atlantic overturning circulation will weaken by about 30% by 2060. But these estimates do not take into account the meltwater that runs into the subarctic ocean.
The Greenland ice sheet will continue melting over the coming century, possibly raising global sea level by about 10 cm. If this additional meltwater is included in climate projections, the overturning circulation will weaken faster. It could be 30% weaker by 2040. That’s 20 years earlier than initially projected.
Such a rapid decrease in the overturning circulation over coming decades will disrupt climate and ecosystems. Expect harsher winters in Europe, and drier conditions in the northern tropics. The southern hemisphere, including Australia and southern South America, may face warmer and wetter summers.
Our climate has changed dramatically over the past 20 years. More rapid melting of the ice sheets will accelerate further disruption of the climate system.
This means we have even less time to stabilise the climate. So it is imperative that humanity acts to reduce emissions as fast as possible.
Record breaking fossil fuel production, all time high greenhouse gas emissions and extreme temperatures. Like the proverbial frog in the heating pan of water, we refuse to respond to the climate and ecological crisis with any sense of urgency. Under such circumstances, claims from some that global warming can still be limited to no more than 1.5°C take on a surreal quality.
For example, at the start of 2023’s international climate negotiations in Dubai, conference president, Sultan Al Jaber, boldly stated that 1.5°C was his goal and that his presidency would be guided by a “deep sense of urgency” to limit global temperatures to 1.5°C. He made such lofty promises while planning a massive increase in oil and gas production as CEO of the Abu Dhabi National Oil Company.
We should not be surprised to see such behaviour from the head of a fossil fuel company. But Al Jaber is not an outlier. Scratch at the surface of almost any net zero pledge or policy that claims to be aligned with the 1.5°C goal of the landmark 2015 Paris agreement and you will reveal the same sort of reasoning: we can avoid dangerous climate change without actually doing what this demands – which is to rapidly reduce greenhouse gas emissions from industry, transport, energy (70% of total) and food systems (30% of total), while ramping up energy efficiency.
This is also not surprising given that net zero and even the Paris agreement have been built around the perceived need to keep burning fossil fuels, at least in the short term. Not do so would threaten economic growth, given that fossil fuels still supply over 80% of total global energy. The trillions of dollars of fossil fuel assets at risk with rapid decarbonisation have also served as powerful brakes on climate action.
Overshoot
The way to understand this doublethink: that we can avoid dangerous climate change while continuing to burn fossil fuels – is that it relies on the concept of overshoot. The promise is that we can overshoot past any amount of warming, with the deployment of planetary-scale carbon dioxide removal dragging temperatures back down by the end of the century.
This not only cripples any attempt to limit warming to 1.5°C, but risks catastrophic levels of climate change as it locks us in to energy and material-intensive solutions which for the most part exist only on paper.
To argue that we can safely overshoot 1.5°C, or any amount of warming, is saying the quiet bit out loud: we simply don’t care about the increasing amount of suffering and deaths that will be caused while the recovery is worked on.
This article is part of Conversation Insights. Our co-editors commission long-form journalism, working with academics from many different backgrounds who are engaged in projects aimed at tackling societal and scientific challenges.
A key element of overshoot is carbon dioxide removal. This is essentially a time machine – we are told we can turn back the clock of decades of delay by sucking carbon dioxide directly out of the atmosphere. We don’t need rapid decarbonisation now, because in the future we will be able to take back those carbon emissions. If or when that doesn’t work, we are led to believe that even more outlandish geoengineering approaches such as spraying sulphurous compounds into the high atmosphere in an attempt to block out sunlight – which amounts to planetary refrigeration – will save us.
The 2015 Paris agreement was an astonishing accomplishment. The establishment of 1.5°C as being the internationally agreed ceiling for warming was a success for those people and nations most exposed to climate change hazards. We know that every fraction of a degree matters. But at the time, believing warming could really be limited to well below 2°C required a leap of faith when it came to nations and companies putting their shoulder to the wheel of decarbonisation. What has happened instead is that the net zero approach of Paris is becoming detached from reality as it is increasingly relying on science fiction levels of speculative technology.
There is arguably an even bigger problem with the Paris agreement. By framing climate change in terms of temperature, it focuses on the symptoms, not the cause. 1.5°C or any amount of warming is the result of humans changing the energy balance of the climate by increasing the amount of carbon dioxide in the atmosphere. This traps more heat. Changes in the global average temperature is the established way of measuring this increase in heat, but no one experiences this average.
Climate change is dangerous because of weather that affects particular places at particular times. Simply put, this extra heat is making weather more unstable. Unfortunately, having temperature targets makes solar geoengineering seem like a sensible approach because it may lower temperatures. But it does this by not reducing, but increasing our interference in the climate system. Trying to block out the sun in response to increasing carbon emissions is like turning on the air conditioning in response to a house fire.
In 2021 we argued that net zero was a dangerous trap. Three years on and we can see the jaws of this trap beginning to close, with climate policy being increasingly framed in terms of overshoot. The resulting impacts on food and water security, poverty, human health, the destruction of biodiversity and ecosystems will produce intolerable suffering.
The situation demands honesty, and a change of course. If this does not materialise then things are likely to deteriorate, potentially rapidly and in ways that may be impossible to control.
Au revoir Paris
The time has come to accept that climate policy has failed, and that the 2015 landmark Paris agreement is dead. We let it die by pretending that we could both continue to burn fossil fuels and avoid dangerous climate change at the same time. Rather than demand the immediate phase out of fossil fuels, the Paris agreement proposed 22nd-century temperature targets which could be met by balancing the sources and sinks of carbon. Within that ambiguity net zero flourished. And yet apart from the COVID economic shock in 2020, emissions have increased every year since 2015, reaching an all time high in 2023.
Despite there being abundant evidence that climate action makes good economic sense (the cost of inaction vastly exceeds the cost of action), no country strengthened their pledges at the last three COPs (the annual UN international meetings) even though it was clear that the world was on course to sail past 2°C, let alone 1.5°C. The Paris agreement should be producing a 50% reduction in greenhouse gas emissions by 2030, but current policies mean that they are on track to be higher than they are today.
We do not deny that significant progress has been made with renewable technologies. Rates of deployment of wind and solar have increased each year for the past 22 years and carbon emissions are going down in some of the richest nations, including the UK and the US. But this is not happening fast enough. A central element of the Paris agreement is that richer nations need to lead decarbonisation efforts to give lower income nations more time to transition away from fossil fuels. Despite some claims to the contrary, the global energy transition is not in full swing. In fact, it hasn’t actually begun because the transition demands a reduction in fossil fuel use. Instead it continues to increase year-on-year.
And so policymakers are turning to overshoot in an attempt to claim that they have a plan to avoid dangerous climate change. A central plank of this approach is that the climate system in the future will continue to function as it does today. This is a reckless assumption.
2023’s warning signs
At the start of 2023, Berkeley Earth, NASA, the UK Met Office, and Carbon Briefpredicted that 2023 would be slightly warmer than the previous year but unlikely to set any records. Twelve months later and all four organisations concluded that 2023 was by some distance the warmest year ever recorded. In fact, between February 2023 and February 2024 the global average temperature warming exceeded the Paris target of 1.5°C.
Currently we cannot fully explain why global temperatures have been so high for the past 18 months. Changes in dust, soot and other aerosols are important, and there are natural processes such as El Niño that will be having an effect.
But it appears that there is still something missing in our current understanding of how the climate is responding to human impacts. This includes changes in the Earth’s vital natural carbon cycle.
Around half of all the carbon dioxide humans have put into the atmosphere over the whole of human history has gone into “carbon sinks” on land and the oceans. We get this carbon removal “for free”, and without it, warming would be much higher. Carbon dioxide from the air dissolves in the oceans (making them more acidic which threatens marine ecosystems). At the same time, increasing carbon dioxide promotes the growth of plants and trees which locks up carbon in their leaves, roots, trunks.
All climate policies and scenarios assume that these natural carbon sinks will continue to remove tens of billions of tons of carbon from the atmosphere each year. There is evidence that land-based carbon sinks, such as forests, removed significantly less carbon in 2023. If natural sinks begin to fail – something they may well do in a warmer world – then the task of lowering global temperatures becomes even harder. The only credible way of limiting warming to any amount, is to stop putting greenhouse gasses into the atmosphere in the first place.
Science fiction solutions
It’s clear that the commitments countries have made to date as part of the Paris agreement will not keep humanity safe while carbon emissions and temperatures continue to break records. Indeed, proposing to spend trillions of dollars over this century to suck carbon dioxide out of the air, or the myriad other ways to hack the climate is an acknowledgement that the world’s largest polluters are not going to curb the burning of fossil fuels.
Over the following years we are going to see climate impacts increase. Lethal heatwaves are going to become more common. Storms and floods are going to become increasingly destructive. More people are going to be displaced from their homes. National and regional harvests will fail. Vast sums of money will need to be spent on efforts to adapt to climate change, and perhaps even more compensating those who are most affected. We are expected to believe that while all this and more unfolds, new technologies that will directly modify the Earth’s atmosphere and energy balance will be successfully deployed.
What’s more, some of these technologies may need to operate for three hundred years in order for the consequences of overshoot to be avoided. Rather than quickly slow down carbon polluting activities and increasing the chances that the Earth system will recover, we are instead going all in on net zero and overshoot in an increasingly desperate hope that untested science fiction solutions will save us from climate breakdown.
We can see the cliff edge rapidly approaching. Rather than slam on the brakes, some people are instead pushing their foot down harder on the accelerator. Their justification for this insanity is that we need to go faster in order to be able to make the jump and land safely on the other side.
We believe that many who advocate for carbon dioxide removal and geoengineering do so in good faith. But they include proposals to refreeze the Arctic by pumping up sea water onto ice sheets to form new layers of ice and snow. These are interesting ideas to research, but there is very little evidence this will have any effect on the Arctic let alone global climate. These are the sorts of knots that people tie themselves up in when they acknowledge the failure of climate policy, but refuse to challenge the fundamental forces behind such failure. They are unwittingly slowing down the only effective action of rapidly phasing out fossil fuels.
That’s because proposals to remove carbon dioxide from the air or geoengineer the climate promise a recovery from overshoot, a recovery that will be delivered by innovation, driven by growth. That this growth is powered by the same fossil fuels that are causing the problem in the first place doesn’t feature in their analysis.
The bottom line here is that the climate system is utterly indifferent to our pledges and promises. It doesn’t care about economic growth. And if we carry on burning fossil fuels then it will not stop changing until the energy balance is restored. By which time millions of people could be dead, with many more facing intolerable suffering.
Major climate tipping points
Even if we assume that carbon removal and even geoengineering technologies can be deployed in time, there is a very large problem with the plan to overshoot 1.5°C and then lower temperatures later: tipping points.
The science of tipping points is rapidly advancing. Late last year one of us (James Dyke) along with over 200 academics from around the world was involved in the production of the Global Tipping Points Report. This was a review of the latest science about where tipping points in the climate system may be, as well as exploring how social systems can undertake rapid change (in the direction that we want) thereby producing positive tipping points. Within the report’s 350 pages is abundant evidence that the overshoot approach is an extraordinarily dangerous gamble with the future of humanity. Some tipping points have the potential to cause global havoc.
The melt of permafrost could release billions of tons of greenhouse gasses into the atmosphere and supercharge human-caused climate change. Fortunately, this seems unlikely under the current warming. Unfortunately, the chance that ocean currents in the North Atlantic could collapse may be much higher than previously thought. If that were to materialise, weather systems across the world, but in particular in Europe and North America, would be thrown into chaos. Beyond 1.5°C, warm water coral reefs are heading towards annihilation. The latest science concludes that by 2°C global reefs would be reduced by 99%. The devastating bleaching event unfolding across the Great Barrier Reef follows multiple mass mortality events. To say we are witnessing one of the world’s greatest biological wonders die is insufficient. We are knowingly killing it.
We may have even already passed some major climate tipping points. The Earth has two great ice sheets, Antarctica, and Greenland. Both are disappearing as a consequence of climate change. Between 2016 and 2020, the Greenland ice sheet lost on average 372 billion tons of ice a year. The current best assessment of when a tipping point could be reached for the Greenland ice sheet is around 1.5°C.
This does not mean that the Greenland ice sheet will suddenly collapse if warming exceeds that level. There is so much ice (some 2,800 trillion tons) that it would take centuries for all of it to melt over which time sea levels would rise seven metres. If global temperatures could be brought back down after a tipping point, then maybe the ice sheet could be stabilised. We just cannot say with any certainty that such a recovery would be possible. While we struggle with the science, 30 million tons of ice is melting across Greenland every hour on average.
The take home message from research on these and other tipping points is that further warming accelerates us towards catastrophe. Important science, but is anyone listening?
It’s five minutes to midnight…again
We know we must urgently act on climate change because we are repeatedly told that time is running out. In 2015, Professor Jeffrey Sachs, the UN special adviser and director of The Earth Institute, declared:
The time has finally arrived – we’ve been talking about these six months for many years but we’re now here. This is certainly our generation’s best chance to get on track.
In 2019 (then) Prince Charles gave a speech in which he said: “I am firmly of the view that the next 18 months will decide our ability to keep climate change to survivable levels and to restore nature to the equilibrium we need for our survival.”
“We have six months to save the planet,” exhorted International Energy Agency head Fatih Birol – one year later in 2020. In April 2024, Simon Stiell, executive secretary of the United Nations Framework Convention on Climate Change said the next two years are “essential in saving our planet”.
Either the climate crisis has a very fortunate feature that allows the countdown to catastrophe to be continually reset, or we are deluding ourselves with endless declarations that time has not quite run out. If you can repeatedly hit snooze on your alarm clock and roll over back to sleep, then your alarm clock is not working.
Or there is another possibility. Stressing that we have very little time to act is intended to focus attention on climate negotiations. It’s part of a wider attempt to not just wake people up to the impending crisis, but generate effective action. This is sometimes used to explain how the 1.5°C threshold of warming came to be agreed. Rather than a specific target, it should be understood as a stretch goal. We may very well fail, but in reaching for it we move much faster than we would have done with a higher target, such as 2°C. For example, consider this statement made in 2018:
Stretching the goal to 1.5 degrees celsius isn’t simply about speeding up. Rather, something else must happen and society needs to find another lever to pull on a global scale.
What could this lever be? New thinking about economics that goes beyond GDP? Serious consideration of how rich industrialised nations could financially and materially help poorer nations to leapfrog fossil fuel infrastructure? Participatory democracy approaches that could help birth the radical new politics needed for the restructuring of our fossil fuel powered societies? None of these.
The lever in question is Carbon Capture and Storage (CCS) because the above quote comes from an article written by Shell in 2018. In this advertorial Shell argues that we will need fossil fuels for many decades to come. CCS allows the promise that we can continue to burn fossil fuels and avoid carbon dioxide pollution by trapping the gas before it leaves the chimney. Back in 2018, Shell was promoting its carbon removal and offsets heavy Sky Scenario, an approach described as “a dangerous fantasy” by leading climate change academics as it assumed massive carbon emissions could be offset by tree planting.
Shell is far from alone in waving carbon capture magic wands. Exxon is making great claims for CCS as a way to produce net zero hydrogen from fossil gas – claims that have been subject to pointed criticism from academics with recent reporting exposing industry wide greenwashing around CCS.
But the rot goes much deeper. All climate policy scenarios that propose to limit warming to near 1.5°C rely on the largely unproven technologies of CCS and BECCS. BECCS sounds like a good idea in theory. Rather than burn coal in a power station, burn biomass such as wood chips. This would initially be a carbon neutral way of generating electricity if you grew as many trees as you cut down and burnt. If you then add scrubbers to the power station chimneys to capture the carbon dioxide, and then bury that carbon deep underground, then you would be able to generate power at the same time as reducing concentrations of carbon dioxide in the atmosphere.
Unfortunately, there is now clear evidence that in practice, large-scale BECCS would have very adverse effects on biodiversity, and food and water security given the large amounts of land that would be given over to fast growing monoculture tree plantations. The burning of biomass may even be increasing carbon dioxide emissions. Drax, the UK’s largest biomass power station now produces four times as much carbon dioxide as the UK’s largest coal-fired power station.
Five minutes to midnight messages may be motivated to try to galvanise action, to stress the urgency of the situation and that we still (just) have time. But time for what? Climate policy only ever offers gradual change, certainly nothing that would threaten economic growth, or the redistribution of wealth and resources.
Despite the mounting evidence that globalised, industrialised capitalism is propelling humanity towards disaster, five minutes to midnight does not allow time and space to seriously consider alternatives. Instead, the solutions on offer are techno fixes that prop up the status quo and insists that fossil fuel companies such as Shell must be part of the solution.
That is not to say there are no good faith arguments for 1.5°C. But being well motivated does not alter reality. And the reality is that warming will soon pass 1.5°C, and that the Paris agreement has failed. In the light of that, repeatedly asking people to not give up hope, that we can avoid a now unavoidable outcome risks becoming counterproductive. Because if you insist on the impossible (burning fossil fuels and avoiding dangerous climate change), then you must invoke miracles. And there is an entire fossil fuel industry quite desperate to sell such miracles in the form of CCS.
Four suggestions
Humanity has enough problems right now, what we need are solutions. This is the response we sometimes get when we argue that there are fundamental problems with the net zero concept and the Paris agreement. It can be summed up with the simple question: so what’s your suggestion? Below we offer four.
1. Leave fossil fuels in the ground
The unavoidable reality is that we need to rapidly stop burning fossil fuels. The only way we can be sure of that is by leaving them in the ground. We have to stop exploring for new fossil fuel reserves and the exploitation of existing ones. That could be done by stopping fossil fuel financing.
At the same time we must transform the food system, especially the livestock sector, given that it is responsible for nearly two thirds of agricultural emissions. Start there and then work out how best the goods and services of economies can be distributed. Let’s have arguments about that based on reality not wishful thinking.
2. Ditch net zero crystal ball gazing targets
The entire framing of mid and end-century net zero targets should be binned. We are already in the danger zone. The situation demands immediate action, not promises of balancing carbon budgets decades into the future. The SBTi should focus on near-term emissions reductions. By 2030, global emissions need to be half of what they are today for any chance of limiting warming to no more than 2°C.
It is the responsibility of those who hold most power – politicians and business leaders – to act now. To that end we must demand twin targets – all net zero plans should include a separate target for actual reductions in greenhouse gas emissions. We must stop hiding inaction behind promises of future removals. It’s our children and future generations that will need to pay back the overshoot debt.
3. Base policy on credible science and engineering
All climate policies must be based on what can be done in the real world now, or in the very near future. If it is established that a credible amount of carbon can be removed by a proposed approach – which includes capture and its safe permanent storage – then and only then can this be included in net zero plans. The same applies to solar geoengineering.
Speculative technologies must be removed from all policies, pledges and scenarios until we are sure of how they will work, how they will be monitored, reported and validated, and what they will do to not just the climate but the Earth system as a whole. This would probably require a very large increase in research. As academics we like doing research. But academics need to be wary that concluding “needs more research” is not interpreted as “with a bit more funding this could work”.
4. Get real
Finally, around the world there are thousands of groups, projects, initiatives, and collectives that are working towards climate justice. But while there is a Climate Majority Project, and a Climate Reality Project, there is no Climate Honesty Project (although People Get Real does come close). In 2018 Extinction Rebellion was formed and demanded that governments tell the truth about the climate crisis and act accordingly. We can now see that when politicians were making their net zero promises they were also crossing their fingers behind their backs.
We need to acknowledge that net zero and now overshoot are becoming used to argue that nothing fundamental needs to change in our energy intensive societies. We must be honest about our current situation, and where we are heading. Difficult truths need to be told. This includes highlighting the vast inequalities of wealth, carbon emissions, and vulnerability to climate change.
The time for action is now
We rightly blame politicians for failing to act. But in some respects we get the politicians we deserve. Most people, even those that care about climate change, continue to demand cheap energy and food, and a constant supply of consumer products. Reducing demand by just making things more expensive risks plunging people into food and energy poverty and so policies to reduce emissions from consumption need to go beyond market-based approaches. The cost of living crisis is not separate from the climate and ecological crisis. They demand that we radically rethink how our economies and societies function, and whose interests they serve.
To return to the boiling frog predicament at the start, it’s high time for us to jump out of the pot. You have to wonder why we did not start decades ago. It’s here that the analogy offers valuable insights into net zero and the Paris agreement. Because the boiling frog story as typically told misses out a crucial fact. Regular frogs are not stupid. While they will happily sit in slowly warming water, they will attempt to escape once it becomes uncomfortable. The parable as told today is based on experiments at the end of the 19th century that involved frogs that had been “pithed” – a metal rod had been inserted into their skulls that destroyed their higher brain functioning. These radically lobotomised frogs would indeed float inert in water that was cooking them alive.
Promises of net zero and recovery from overshoot are keeping us from struggling to safety. They assure us nothing too drastic needs to happen just yet. Be patient, relax. Meanwhile the planet burns and we see any sort of sustainable future go up in smoke.
Owning up to the failures of climate change policy doesn’t mean giving up. It means accepting the consequences of getting things wrong, and not making the same mistakes. We must plan routes to safe and just futures from where we are, rather where we would wish to be. The time has come to leap.
Top image: Under a microscope, a tiny elongate poppy seed, small tan spikemoss megaspores and black soil fungus spheres found in soil recovered from under 2 miles of Greenland’s ice. Halley Mastro/University of Vermont, CC BY-NDPaul Bierman, University of Vermont and Halley Mastro, University of Vermont
As we focused our microscope on the soil sample for the first time, bits of organic material came into view: a tiny poppy seed, the compound eye of an insect, broken willow twigs and spikemoss spores. Dark-colored spheres produced by soil fungi dominated our view.
These were unmistakably the remains of an arctic tundra ecosystem – and proof that Greenland’s entire ice sheet disappeared more recently than people realize.
These tiny hints of past life came from a most unlikely place – a handful of soil that had been buried under 2 miles of ice below the summit of the Greenland ice sheet. Projections of future melting of the ice sheet are unambiguous: When the ice is gone at the summit, at least 90% of Greenland’s ice will have melted.
Results of an ice sheet model show how much of Greenland’s ice sheet survives when the ice is gone from the Camp Century (white dot), GISP2 (red dot) and DYE-3 (black dot) ice coring sites.Modified from Schaefer et al., 2016, Nature
In 1993, drillers at the summit completed the Greenland Ice Sheet Project 2 ice core, or GISP2, nicknamed the two-mile time machine. The seeds, twigs and spores we found came from a few inches of soil at the bottom of that core — soil that had been tucked away dry, untouched for three decades in a windowless Colorado storage facility.
Our new analysis builds on the work of others who, over the past decade, have chipped away at the belief that Greenland’s ice sheet was present continuously since at least 2.6 million years ago when the Pleistocene ice ages began. In 2016, scientists measuring rare isotopes in rock from above and below the GISP2 soil sample used models to suggest that the ice had vanished at least once within the past 1.1 million years.
Now, by finding well-preserved tundra remains, we have confirmed that Greenland’s ice sheet had indeed melted before and exposed the land below the summit long enough for soil to form and for tundra to grow there. That tells us that the ice sheet is fragile and could melt again.
The GISP2 ice drilling camp at the Greenland ice sheet summit has an average temperature today of minus 7 degrees Fahrenheit (minus 22 Celsius).Christine Massey, CC BY
The frozen plant remains suggest that the center of Greenland probably once looked like this dry rocky tundra, photographed in northwest Greenland.Paul Bierman/University of Vermont, CC BY-ND
A landscape with Arctic poppies and spikemosses
To the naked eye, the tiny bits of past life are unremarkable – dark flecks, floating between shiny grains of silt and sand. But, under the microscope, the story they tell is astounding. Together, the seeds, megaspores and insect parts paint a picture of a cold, dry and rocky environment that existed sometime in the past million years.
Above ground, Arctic poppies grew among the rocks. Atop each stalk of this small but tenacious herb, a single cupped flower tracked the Sun across the sky to make the most of each day’s light.
Tiny insects buzzed above mats of diminutive rock spikemoss, creeping across the gravelly surface and bearing spores in summer.
Modern rock spikemoss (left) and rock spikemoss megaspores (tan spheres, right) from the GISP2 soil sample.J.F. Clovis/Courtesy of Smithsonian Institution (left), Halley Mastro/University of Vermont (right)
In the rocky soil were dark spheres called sclerotia, produced by fungi that team up with plants’ roots in soil to help both get the nutrients they need. Nearby, willow shrubs adapted to life in the harsh tundra with their small size and fuzzy hair covering their stems.
Three fragments of wood, shown under a high-power electron microscope, right, were Arctic willow – not from grand trees but rather the remains of ankle-high shrubs, left, that characterize Greenland’s tundra today.Peter Prokosch; (left), Barry Rock/University of New Hampshire (right)
Each of these living things left clues behind in that handful of soil – evidence that told us Greenland’s ice was once replaced by a hardy tundra ecosystem.
Greenland’s ice is fragile
Our discoveries, published on Aug. 5, 2024, in the Proceedings of the National Academy of Sciences, demonstrate that Greenland’s ice is vulnerable to melting at atmospheric carbon dioxide concentrations lower than today. Concerns about this vulnerability have driven scientists to study the ice sheet since the 1950s.
In the 1960s, a team of engineers extracted the world’s first deep ice core at Camp Century, a nuclear-powered Army base built into the ice sheet over 100 miles from the northwest Greenland coast. They studied the ice, but they had little use for the chunks of rock and soil brought up with the bottom of the core. Those were stored and then lost until 2019, when they were rediscovered in a lab freezer. Our team was among the scientists called in to analyze them.
George Linkletter, working for the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory, examines a piece of ice core in the science trench at Camp Century. The base was shut down in 1966.U.S. Army Photograph
Exquisitely preserved remains of 400,000-year-old moss, on the left, and a sedge seed, on the right – found in the soil core from beneath the Greenland ice sheet at Camp Century – help tell the story of what lived there when the ice was gone.Halley Mastro/University of Vermont
Another ice core, DYE-3 from south Greenland, contained DNA showing that spruce forests covered that part of the island at some point in the past million years.
The biological evidence makes a convincing case for the fragility of Greenland’s ice sheet. Together, the findings from three ice cores can only mean one thing: With the possible exception of a few mountainous areas to the east, ice must have melted off the entire island in the past million years.
Losing the ice sheet
When Greenland’s ice is gone, world geography changes – and that’s a problem for humanity.
As the ice sheet melts, sea level will eventually rise more than 23 feet, and coastal cities will flood. Most of Miami will be underwater, and so will much of Boston, New York, Mumbai and Jakarta.
Today, sea level is rising at more than an inch each decade, and in some places, several times faster. By 2100, when today’s kids are grandparents, sea level around the globe is likely to be several feet higher.
Using the past to understand the future
The rapid loss of ice is changing the Arctic. Data about past ecosystems, like we have collected from under Greenland’s ice, helps scientists understand how the ecology of the Arctic will change as the climate warms.
When temperatures rise, bright white snow melts and ice shrinks, exposing dark rock and soil that soaks up heat from the Sun. The Arctic is becoming greener with every passing year, thawing underlying permafrost and releasing more carbon that will further warm the planet.
The authors share their research and images of the ice core drilling. Quincy Massey-Bierman/University of Vermont.
Human-caused climate change is on pace to warm the Arctic and Greenland beyond temperatures they have experienced for millions of years. To save Greenland’s ice, studies show the world will need to stop greenhouse gas emissions from its energy systems and reduce carbon dioxide levels in the atmosphere.
Understanding the environmental conditions that triggered the ice sheet’s last disappearance, and how life on Greenland responded, will be crucial for gauging the future risks facing the ice sheet and coastal communities around the world.
Paul Bierman, Fellow of the Gund Institute for Environment, Professor of Natural Resources and Environmental Science, University of Vermont and Halley Mastro, Graduate Fellow of the Gund Institute for Environment. Graduate Research Assistant in Natural Resources and Environmental Science, University of Vermont
