This week, the international court of justice (ICJ) opened two weeks of hearings on states’ climate-related legal obligations – and the consequences, if “significant harm” is caused.
The case stems from a unanimous UN general assembly (UNGA) request for an “advisory opinion” from the ICJ.
It is taking place against a backdrop of rapidly escalating climate impacts. Emissions continue to rise, rather than falling rapidly, as needed to avoid dangerous levels of global warming.
It is the ICJ’s largest ever case, with more than 100 countries and international organisations making interventions, deploying a wide variety of legal arguments.
Ralph Regenvanu, climate envoy for Vanuatu, which led the campaign for the ICJ hearings, said in his opening address: “[T]his may well be the most consequential case in the history of humanity.”
Below, Carbon Brief interviews leading international law scholar Prof Philippe Sands – who drafted the pleadings for Mauritius, but is speaking here in a personal capacity – to find out more about the legal issues at stake and the wider significance of the ICJ case.
- On the significance of the case: “It’s the first time the ICJ has been called upon to address legal issues relating to climate change.”
- On the key legal arguments: “There’s just a huge number of issues that are coming up.”
- On climate obligations under the UN: “Will the court open the door to the situation that the 1992 [UN climate] convention … [is] not the be all and end all?”
- On where outcomes could come from: “Essentially, it’s the whole of international law!”
- On the responsibility of states: “The question at the beating heart of this case, really, is the consequences of emissions over time.”
- On historical emissions: “The big issue is, are you liable for the continuing consequences of your past emissions?”
- On applying international law: “When drafting the climate treaty regime, [did] states…exclude the application of general international law?”
- On expectations for the case: “What I’m interested in, really, is an advisory opinion that is capable of having hard, practical application.”
- On the state of the science: “A procedure in which the judges hear privately from any person…is unusual. It’s unorthodox.”
- On the significance of the submissions: “The oral phase is very important, because it basically concentrates the issues down to the most significant and narrow set of issues.”
- On the question of the UN or wider law: “It’s a tough situation for the judges.”
Carbon Brief: Would you be able to start by just situating this case in its wider legal context and explaining why it could be so consequential?
Philippe Sands: Well, it’s the first time the international court of justice has been called upon to address legal issues relating to climate change. The ICJ is the principal judicial organ of the United Nations and, although the advisory opinion that it hands down will not be binding on states, it is binding on all UN bodies. The determinations that the court makes will have consequences that go very far and that will have a particular authority, in legal and political terms. Of course, everything turns on what the court actually says.
CB: Would you be able to summarise the key legal arguments that are being fought over in this case?
PS: No! I mean, there’s just a huge number of issues that are coming up. But, essentially, the court has been asked two questions by the UN General Assembly – the first time, I believe, that a request from the General Assembly has been consensual, with no objections. The two questions are, firstly, what are the obligations for states under international law to protect the climate system? And, secondly, what are the legal consequences under these obligations, where, by their acts and emissions, [states] cause significant harm to the climate system? So, there are two distinct questions – and about 100 states and international organisations of various kinds have made submissions on the vast range of issues that are raised by these two questions. The questions are very, very broad and that signals to me that the court’s response may be quite general. But, for me, the crucial issues are, firstly, what the court says about the state of the science: is it established, or is there any room for doubt? Secondly, what are the obligations of states having regard to the clarity of the science? Thirdly, are there legal obligations on states in relation to the climate system that exist and arise outside of the treaty regime – the 1992 [UN Framework] convention [on climate change], the Kyoto Protocol, the Paris Agreement and so on and so forth. And, related to that, fourthly – this is the most intense, legally interesting aspect – what are the responsibilities of states for historic emissions under general international law? And, in particular, are the biggest contributors liable under international law to make good any damages that may arise from their historic actions? But, I mean, there’s just such a vast array of questions that are addressed, it’s impossible to summarise briefly.
CB: This is the challenge I found when I was trying to write questions!
PS: To be honest, the questions [put by the UN General Assembly] are rather general, so I have concerns about the burden that has been imposed on the court. My general approach has been that, with advisory opinions, the best questions are those which require a yes or no answer. But the moment you have questions of such generality, you impose on the 15 judges an especially onerous burden, because the questions are open to interpretation.

CB: Some countries are arguing, effectively, that states’ climate obligations start and finish with the UN climate regime, as you’ve already mentioned.
PS: Exactly. Well, that’s a central aspect of what’s coming up. Will the court open the door to the situation that the 1992 [UN climate] convention and the subsequent agreements [Kyoto, Paris] are not the be all and end all, and that the rules of general international law [also] apply? And, if so, what are those rules? And what are the consequences of breaching those rules? Some states say there can’t be any liability under general international law because the whole matter is governed by the treaty regime. Other states say that’s not right, that, although the treaty regime is a distinct “lex specialis” – a specialised area of law – that does not preclude the application of the general principles of international law. So that may be a really interesting issue for the court to determine.
CB: Could you say a bit more about the other areas of international law, where obligations could come from, whether it’s human rights, or customary law, or whatever it might be?
PS: The difficulty, if you look at the first part of the question [put to the court]…the drafters of the question invite the court to have regard to the Charter of the United Nations, the Covenant on Civil and Political Rights, the Covenant on Economic and Social Rights, the Framework Convention on Climate Change, the Paris Agreement, the UN Convention on the Law of the Sea, the duty of due diligence, human rights law, the principle of prevention, and the duty to protect and preserve the marine environment. That is a vast array of international legal obligations and it’s not exhaustive. It says, having particular regard to, so, essentially, it’s the whole of international law! So the court is being asked to address the application of the whole of international law to the issue of climate change and, in particular, issues of legal consequences, and in particular, the issues of state responsibility. So, it’s vast, vast.
CB: Another set of arguments that I’ve seen…is around the idea of the “responsibility of states for internationally wrongful acts”, which might lead to a requirement for cessation of the acts and reparation of the harm done. Can you just say a bit more about what that idea means and where it comes from?
PS: There’s an area of international law called the law of state responsibility. That law of state responsibility says that when you have committed a wrongful act and violated a rule of international law, you are liable for all of the consequences. That rule has not been incorporated, as such, or at all, into the treaty regime [on climate change]. So, essentially, by raising those issues, there are a number of legal issues that arise – but there are two of particular interest. Firstly, in relation to damage that is caused by climate change, are those states most responsible, liable for the consequences of that damage in, let us say, for example, in financial terms? And, secondly – and this relates to something called the principle of “common but differentiated responsibility” – does the fact that certain states have historic emissions going back 200 years mean that their entitlement to the remaining “carbon budget” is reduced. So, the question, I think, at the beating heart of this case, really, is the consequences of emissions over time, looking back and looking forward. That’s one aspect the court may have at the forefront of its mind.
CB: Historical greenhouse gas emissions, but also the rights of future generations, have both come up quite a lot in some of the submissions. Can you just say a bit more about the legal arguments around these?
PS: The big issue is: are you liable for the continuing consequences of your past emissions? And does the nature and extent of your past emissions affect your ability to generate emissions in the future? Those are really the two issues and the treaty regime does not, as such, explicitly address [them]. The practicalities are that islands are disappearing with sea level rise. Are historic polluters of greenhouse gases responsible for the consequences of those disappearances? Or, if states are required to build sea walls to protect themselves, can they bring a case against the biggest polluters for the consequences of sea level rise? That’s the kind of complex issue the court may have in the back of its mind, because that’s essentially what’s being asked.
CB: In terms of how they will decide whether these other potential areas of law could give rise to obligations on states – and, therefore, potentially further consequences – how are they going to decide? To decide whether those [areas of law] do apply, or whether it is only the UN climate regime that gives rise to obligations.
PS: They are going to have to address whether, when drafting the climate treaty regime, states intended to, or did as a necessary consequence, exclude the application of general international law. That is an issue that they will do by looking at the climate regime and determining whether, by adopting it, there was an intention to exclude the application of general international law. So, that is a classical job for lawyers, for judges: to interpret the law, to interpret what the drafters of the treaty regime have done and what they intended, and to then form a view in applying the general rules of international law, whether a space is left which allows those general rules to apply. That’s classically what international judges will do.
CB: You’ve already said a little bit about this, but what would your expectations be for this advisory opinion, which I gather is expected next year?
PS: Normally, it takes six months from after they’ve done the hearings for an advisory opinion to come up. I don’t really have any expectations. There’s been a previous advisory opinion in relation to the Law of the Sea proceedings. The Tribunal for the Law of the Sea came up with an advisory opinion which, in a sense, was rather general. What I’m interested in, really, is an advisory opinion that is capable of having hard, practical application, as happened, for example, in the advisory opinion on the Chagos Archipelago, where the court was asked two questions, essentially, “yes/no” questions, and the court gave a very clear advisory opinion, which has had significant political and legal consequences. The difficulty with asking very general questions is you get very general answers, and very general answers are less easily capable of practical application. So, the best-case scenario for me, is that the court comes up with an advisory opinion of sufficient clarity on the facts, which is basically the state of the science and on the applicable legal principles, which then allows other courts and, in particular, national courts, to take the advisory opinion, in interpreting and applying domestic law, which is, ultimately, going to be where the rubber hits the road. So my expectations turn on the nature and generality of the opinion that the court is able to give. But where the questions posed are so general, I would be concerned that the answers may also be rather general and that limits my expectations.
CB: You mentioned the state of the science as being very important. We know that the court met with a delegation of IPCC [Intergovernmental Panel on Climate Change] authors and I gather there’s some sort of question mark about the procedure used to do that?
PS: The normal process is that if scientists are going to provide information to the judges, it would be in the form of submissions made in writing, or in open court, publicly and transparently. A procedure in which the judges hear privately from any person, however authoritative – and the IPCC is authoritative – is unusual. It’s unorthodox. It does raise questions. We don’t know who attended. We don’t know what they said. We don’t know what the exchanges were with the judges. I have to assume that it was done by the judges, at their request, as a way of informing themselves on the state of science, which is understandable. But the more usual way for this to happen would be, as I said, in written submissions made to the court and in open submissions made already in the courtroom. So it is unusual.
CB: You mentioned already, there’s more than 100 submissions from countries and international organisations. And we’ve obviously got these two weeks of hearings, with some of those same entities making oral statements. How significant are those submissions in terms of shaping the advisory opinion of the court?
PS: My experience before the court, having been involved in a number of cases involving advisory opinions and contentious cases, is that the written pleadings are very important in setting out the generality of the arguments and the totality of the arguments. And, essentially, what you see is a narrowing down. There are essentially three rounds. The first round is the first written statement of the participating states and international organisations. Then they have a second written round, which tends to narrow down the issues and be responsive to the first round of others. And then you’ve got the oral arguments, which are limited, of course, to half an hour for each participant. And so it’s a real narrowing down and homing in. Essentially, what the oral arguments are doing is signaling to the judges what the states participating think are the most significant issues. That’s why the oral phase is very important, because it basically concentrates the issues down to the most significant and narrow set of issues. And so it gives the judges a sense of what states think are the most important issues to be addressed. Secondly, it provides states with an opportunity to hear what responses each state has made to the written submissions of other states. So the oral phase is significant.
CB: If you were going to make a bet, which way would you say the court would go on that key question of whether it’s just the [UN] climate regime that gives rise to obligations [on states], or whether there could be obligations from other parts of the law?
PS: I think the court will proceed very carefully. I don’t think it will want to close the door to the application of other rules of international law. Rather, as the International Tribunal for the Law of the Sea did, which opened the door to the application of the Law of the Sea Convention to the issue of climate change – and opened it quite widely. I don’t know precisely where the court will go. But I would be surprised if they said general international law does not govern issues related to climate change.
The interesting area to read, in what they say, will be the relationship between the general rules and the treaty rules. I mean, the broader issue here is that, essentially, the legislative system has broken down. The states have been unable to legislate effectively and efficiently to address the issues related to climate change. And so what has happened is that a group of states have essentially gone to the General Assembly and said: “The legislative system is broken down. Let’s now ask the judges to step in and tell us what the applicable principles and rules are.” The difficulty that that poses for the judges, who will be conscious that the legislative system has not delivered, is that it’s not the function of judges to legislate. The function of judges is limited to interpreting the law and applying it to the facts, to identify the existence of rules and then applying them to the facts. So I would have thought the instinct of the judges will be to do something, but not to want to overstep the proper boundaries on the judicial function. And that’s a difficult challenge for the judges that they find themselves in.
[It is] a very delicate and difficult situation in the face of, on the one hand, the urgent need for action, and, on the other hand, the failure of states, essentially, to deal with the situation and act as the scientists tell us is needed. I don’t know whether you’ve been through all the different pleadings. I drafted the pleadings for Mauritius – I’m speaking here in a personal capacity. Mauritius decided not to participate in the oral hearings, but you can go on to the Mauritius statement and, if you look at the second Mauritius statement filed in August, you’ll find attached to it as an annex, a report by Prof James Hansen, one of the world’s leading scientists. And that really indicates, with crystal clarity, the urgency of the situation. He’s one of the world’s leading scientists on this issue and that’s the kind of submission that could concentrate the minds of the judges and, I think, impel them to want to go as far as they can. But they’ll be acutely conscious of the limits of judicial function. And, of course, you know, some countries like the UK are basically saying, butt out, leave it to the treaty negotiators, leave it to the treaty system. And the US has said essentially the same thing yesterday. So, it’s a tough situation for the judges.
An abridged version of this interview was published in DeBriefed, Carbon Brief’s weekly email newsletter. Sign up for free.
The interview was conducted by Simon Evans via phone on 5 December 2024.
The post Interview: Prof Philippe Sands on UN court’s landmark climate-change hearing appeared first on Carbon Brief.
Interview: Prof Philippe Sands on UN court’s landmark climate-change hearing
Climate Change
Germany election 2025: What the manifestos say on energy and climate change
A federal election is taking place in Germany on 23 February, following the collapse of the coalition government at the end of last year.
Germans will vote to elect 630 members of the nation’s parliament.
Polling suggests there will be a political shift to the right, with the centre-right Christian Democratic Union (CDU) in the lead and far-right Alternative for Germany (AfD) set to make significant gains.
A “traffic light” coalition of parties has ruled since 2021, led by the centre-left Social Democratic Party (SPD), alongside the Green Party and the Free Democratic Party (FDP).
However, successive crises led to its breakup at the end of 2024, when the liberal, free market-oriented FDP split from the rest.
This prompted a vote of no confidence by the German parliament, which, in turn, triggered a snap election several months earlier than previously scheduled.
The coalition government has been plagued by ideological differences, particularly between the FDP and its two centre-left partners.
Climate policies were at the heart of many of the disputes.
The centre-left SPD and Greens have broadly favoured more public spending on climate issues, while the FDP is opposed to state intervention of any sort.
In the interactive grid below, Carbon Brief tracks the commitments made by each of the main parties in their election manifestos, across a range of issues related to climate and energy.
The parties covered are:
- Christian Democratic Union (CDU)/Christian Social Union (CSU): The centre-right CDU and its regional Bavarian “sister party”, CSU, has been the dominant political force in modern Germany and is currently polling highest ahead of the election.
- Social Democratic Party (SPD): The centre-left SPD has led the ruling coalition in Germany since the last election in 2021 and has traditionally been the other dominant party in the nation’s politics.
- Green Party: The centre-left and environmentalist Greens have been part of the coalition government since 2021.
- Free Democratic Party (FDP): The FDP is an economically liberal party that prioritises free markets and privatisation. It was part of the coalition government, but its departure at the end of 2024 ultimately triggered the federal election.
- Left Party: In recent years, this left-wing, democratic-socialist party has lost much of its support base in the east of the country.
- Alternative for Germany (AfD): The far-right party has become a major force in the country’s politics over the past decade, particularly in eastern Germany.
- Sahra Wagenknecht Alliance (BSW): The party was only founded last year, as an offshoot of the Left Party, but it has rapidly risen in popularity with a left-wing economic message and a conservative approach to some social and cultural issues.
Each entry in the grid represents a direct quote from a manifesto document.
Net-zero and climate framing
Climate action has become a divisive topic in German politics.
This is evident in the major parties’ manifestos, which range from supporting more ambitious net-zero goals to outright climate scepticism.
Germany is currently aiming to reach net-zero greenhouse gas emissions by 2045, with interim targets including a 65% cut by 2030.
Government climate advisors on the Council of Experts on Climate Change have stated that the nation is on track to miss the 2030 target.
Despite starting out with ambitious aims, the coalition’s climate progress has faltered, with the FDP successfully pushing for weaker climate policies. Moreover, a major court ruling curtailed the government’s climate spending by enforcing Germany’s limit on debt.
Amid these wider tensions, Germany’s two traditionally dominant parties still want to retain the nation’s headline climate target. The CDU, which is leading the polls in the run-up to election day, commits to meeting the Paris Agreement goals in its manifesto, saying its sights are “firmly set” on net-zero by 2045.
The SPD, which is currently third in the polls and likely to end up in coalition with the CDU, also supports the 2045 net-zero target, as well as the interim goals.
However, the two parties differ substantially in their approach to meeting the 2045 target. The CDU prioritises carbon pricing and rejects the tougher policies to decarbonise heating and transport favoured by the SPD. (See: Heating dispute and Combustion engine phaseout.)
Meanwhile, the AfD manifesto repeatedly questions the “supposed scientific consensus” on “man-made climate change”. The party, which is currently second in the polls, “therefore rejects every policy and every tax that is related to alleged climate protection”.
Mainstream German parties across the spectrum have long agreed to a “firewall” against far-right groups, meaning they will not form coalitions with the AfD. However, the CDU recently sparked controversy when it backed an anti-immigration policy with the AfD.
The Green Party also supports the 2045 net-zero target in its manifesto, emphasising Germany’s status as the EU member state with the highest emissions. The Left Party goes further, calling for a 2040 net-zero goal.
As for the FDP, its manifesto argues for the 2045 net-zero goal to be pushed back to 2050, stating that this would align Germany with the EU target. Prior to exiting the coalition government last year, the party had demanded this policy change, claiming that it would be a way to boost the German economy.
(Germany already revised its net-zero target, bringing it forward by five years, following a supreme court ruling in 2021 that its 2050 goal was insufficient. Moreover, even with a later goal, Germany would still need to align with wider EU targets, meaning its climate policies may not change much due to its “effort sharing” obligations.)
Finally, the BSW is not specific about when the net-zero goal should be achieved, but pushes for a “departure from the wishful thinking of quickly achieving complete climate neutrality”.
It does not reject climate policies outright, stating that climate change should be “taken seriously”. However, it frames many climate policies as being “extremely expensive and often unrealistic”.
Heating dispute
Home heating has become a major political issue in Germany. Along with transport, buildings make up one of the key German sectors that have repeatedly missed their decarbonisation goals, prompting the coalition government to take action.
Towards the end of 2023, the German parliament passed an amendment to the Building Energy Act, meaning that newly installed heating systems had to be powered by at least 65% renewable energy.
This covered heat pumps, “hydrogen-ready” gas boilers and other low-carbon systems. There are caveats to ensure the law is phased in gradually in different areas and types of homes, starting with new builds.
The amendment had been watered down compared to the coalition’s initial proposal, with allowances for people to keep gas boilers for longer. This followed relentless campaigning by the AfD and the right-leaning tabloid newspaper Bild, which dubbed the policy the “heizhammer” – or “heating hammer”.
There were also attacks from within the coalition, with the FDP criticising the law proposed by its partners in the Greens and SDP. Opponents framed the policy as an excessive burden on consumers.
These disputes are reflected in the election manifestos, with many parties outright rejecting the amended law. The CDU, FDP and AfD all say they would abolish it, as does the populist left BSW.
Meanwhile, the Green Party pledges to provide more government support for the installation of new heating systems by covering up to 70% of the price. The Left Party commits to covering 100% of the cost for low-income households.
(The current law covers 30% of the cost as a starting subsidy, with more available for low-income households and people who replace their boilers before 2028.)
Combustion engine phaseout
Several German political parties are pushing back against the EU-wide ban on the sale of new petrol and diesel cars, which is set to come into effect in 2035.
The CDU says the “ban on combustion engines must be reversed”, while the AfD says the “one-sided preference for electromobility must be stopped immediately”.
(EVs are “likely crucial” for tackling transport emissions, according to the Intergovernmental Panel on Climate Change [IPCC].)
The FDP and the BSW also argue that the 2035 phaseout date should be dropped, with less focus on the transition to electric cars. (This is in spite of Germany being the second-biggest manufacturer of electric cars in the world.)
These parties also favour getting rid of supposed “anti-car” policies. For example, they oppose speed limits on the German “autobahns” and support funding for alternative fuels, such as synthetic fuels.
The issue with ending the 2035 ban on new combustion-engine cars is that this policy is set at the EU level. Far-right and centre-right coalitions within the EU, including German parties, have been pushing hard to weaken the ban across the bloc.
However, the centre-left parties that may end up forming a coalition with the CDU, notably the SPD, stand by the 2035 phaseout date.
There is growing pressure on Germany’s car industry, linked to global competition and slow economic growth. Some German industry figures have stressed the need for consistent policy signals from the government, regarding the transition to electric vehicles.
Clean energy and fossil fuels
Broadly speaking, German parties on the left tend to be more supportive of renewables, while strongly opposing nuclear power. Those on the right are generally more open to nuclear and in some cases coal power.
Germany, which uses more coal than any other EU member state, has a coal power phaseout date of 2038. This is supported by the CDU and the FDP, but the Greens and the Left Party want a quicker phaseout by 2030.
(When the coalition government formed in 2021, the parties agreed to “ideally” move the coal phaseout date to 2030, but this has not happened formally. The SPD manifesto does not include any mention of coal power,)
Only the AfD advocates for the construction of new coal power plants, framing them as filling a gap until new nuclear plants are built.
Last year, Germany closed down its final nuclear reactors, bringing an end to a long-term plan to phase out the power source. However, nuclear power continues to be a politicised topic, with some arguing that its continued use is necessary to ensure the nation’s energy security.
Notably, the CDU suggests in its manifesto that it is open to reviving nuclear power in the future. It proposes an “expert review” around restarting closed plants and advocates for research on advanced nuclear technologies, such as small modular reactors.
Despite this wording, CDU leader Friedrich Merz has conceded that it is unlikely any old reactors will be restarted. This echoes views expressed by German utility companies and energy experts.
Both the CDU and the SPD support the expansion of renewables in their manifestos. The Greens include a specific target to achieve a net-zero electricity grid by 2035. By contrast, the AfD calls for an end to wind power expansion, in favour of other technologies.
Finally, both the far-right AfD and the BSW say the German government should repair the damaged Nord Stream pipelines in order to import what the BSW refers to as “cheap” gas from Russia. (The Baltic Sea pipelines were blown up in 2022 under mysterious circumstances.)
Germany has tried to wean itself off Russian gas since the country’s invasion of Ukraine, with considerable success. However, both the AfD and the BSW are more open to cooperating with Russia, and less supportive of Ukraine, than mainstream German parties.
The post Germany election 2025: What the manifestos say on energy and climate change appeared first on Carbon Brief.
Germany election 2025: What the manifestos say on energy and climate change
Climate Change
Guest post: How atmospheric rivers are bringing rain to West Antarctica
“Atmospheric rivers” are bringing rain to the frozen slopes of the West Antarctic ice sheet, hitting the ice shelves that play a major role in holding back rapidly retreating glaciers.
In a new study, my colleagues and I show how rain is occurring in sub-zero temperatures due to these “rivers in the sky” – long, narrow plumes of air which transport heat and moisture from the tropics to the mid-latitudes and poles.
Rain in Antarctica is significant, not only because it is a stark indicator of climate change, but because it remains an under-studied phenomenon which could impact ice shelves.
Ice shelves in Antarctica are important gatekeepers of sea level rise.
They act as a buffer for glaciers that flow off the vast ice sheet, slowing the rate at which ice is released into the ocean.
In the study, we explore the causes of rain falling on ice shelves in the Amundsen Sea embayment region, which stand in front of the critically important Thwaites and Pine Island glaciers.
Researchers have warned the collapse of ice shelves in this region could trigger the loss of the entire West Antarctic ice sheet over several centuries.
Rivers in the sky
Atmospheric rivers are typically associated with bringing extreme rainfall to the mid-latitudes, but, in the frigid Antarctic, they can deliver metres of snow in just a few days.
In West Antarctica, atmospheric rivers deliver a disproportionate quantity of the year’s snowfall. Research shows they account for around 13% of annual snowfall totals, despite occurring on just a few days per year.
But what makes atmospheric rivers in Antarctica so interesting is that snow is only part of the story. In extreme cases, they can also bring rain.
To explore how extreme precipitation affects the Amundsen Sea embayment region, we focused on two events associated with atmospheric rivers in 2020. The summer case took place over a week in February and the winter case over six days in June.
We used three regional climate models to simulate the two extreme weather events around the Thwaites and Pine Island ice shelves, then compared the results with snowfall observations.
During both the winter and summer cases, we find that atmospheric rivers dumped tens of metres of snow over the course of a week or so.
Meanwhile, the quantities of rain driven by these events were not insignificant. We observed up to 30mm of rain on parts of the Thwaites ice shelf in summer and up to 9mm in winter.

A mountain to climb
Antarctica’s cold climate and steep, icy topography make it unique. It also makes the region prone to rain in sub-zero temperatures.
The first reason for this is the foehn effect, which is when air forced over a mountain range warms as it descends on the downward slope.
Commonly observed across Antarctica, it is an important cause of melting over ice shelves on the Antarctic peninsula, the northernmost point of the continent.
When air passes over the mountainous terrain of the West Antarctic ice sheet during atmospheric river events, temperatures near the surface of the ice shelves can climb above the melting point of 0C.
This can accentuate the formation of rain and drizzle that stays liquid below 0C – also known as “supercooled drizzle”.
Another factor which leads to liquid drizzle, rather than snow, in sub-zero conditions is a lack of dust and dirt – particles which are usually needed to trigger the formation of ice crystals in clouds.
In the pristine Antarctic, these particles – which act as “ice nuclei” – are few and far between. That means that pure liquid water can exist even when temperatures are below 0C.
The origins of rain over ice shelves
It is easy to assume that rain that reaches the surface in Antarctica is just snow that has melted after falling through a warm layer of air caused by the foehn effect. Indeed, this is what we initially supposed.
But our research shows that more rain reaches the surface of Antarctica when the air near the ground is within a few degrees of freezing.
At times when the foehn effect is strongest, there is often little or no rainfall, because it evaporates before it gets a chance to reach the surface.
However, we saw rain falling well above the warm layer of air near the surface, where temperatures were universally below 0C – and, in some cases, as low as -11C.
Rare rain
Rain in Antarctica is a rare occurrence. The region’s normally frigid temperatures mean that most precipitation over the continent falls as snow.
However, exactly how rare rain is in the region remains relatively unknown, because there are virtually zero measurements of rainfall in Antarctica.
There are a number of reasons for this – rain falls infrequently, and it is very difficult to measure in the hostile Antarctic environment.
Our results show that extreme events such as atmospheric rivers can bring rain. And it is likely that rain will become a more common occurrence in the future as temperatures rise and extreme weather events occur more frequently.
However, until rain starts being measured in Antarctica, scientists will have to rely entirely on models to predict rain, as we did in this research.
It is also not yet known exactly how rain could impact ice in Antarctica.
We do know that rain falling on snow darkens the surface, which can enhance melting, leading to greater ice losses. Meanwhile, rain that refreezes in the snowpack or trickles to the base of the ice can change the way that glaciers flow, impacting the resilience of ice shelves to fracture.
So, if we want to understand the future of the frozen continent, we need to start thinking about rain too. Because while rain may be rare now, it may not be for long.
The post Guest post: How atmospheric rivers are bringing rain to West Antarctica appeared first on Carbon Brief.
Guest post: How atmospheric rivers are bringing rain to West Antarctica
Climate Change
Colombia’s COP16 presidency in suspense as minister resigns
Susana Muhamad, Colombia’s minister of environment since 2022 and president of the COP16 UN biodiversity negotiations, has announced she will step down from government, but has asked President Gustavo Petro to let her stay in her post to conclude the UN nature talks later in February.
In her resignation letter, addressed to the president and dated February 8, Muhamad said she was quitting as a minister but urged him to consider “the need to conclude COP16” – the summit left unfinished in Colombia last year and now scheduled to resume from February 25 to 27 in Rome.
“I’ve led the complex negotiations in progress and I exercise the role of president (of the COP). Therefore, if you so decide, this resignation could be made effective from March 3,” the letter reads.
Buenos días, para clarificar cualquier malentendido, presento renuncia irrevocable al cargo de Ministra de Ambiente y Desarrollo Sostenible. Por lo tanto, publico la carta que radiqué en el DAPRE el 8 de febrero, que es una carta motivada, no protocolaria. pic.twitter.com/71quT3CEdJ
— Susana Muhamad (@susanamuhamad) February 10, 2025
Muhamad has been one of the most vocal opponents of the recent appointment of former senator Armando Benedetti as Petro’s chief of staff. Benedetti has faced allegations of domestic abuse and corruption, and was previously fired as ambassador to Venezuela by Petro himself.
In a televised session of the council of ministers held last week, Muhamad heavily opposed Benedetti’s appointment and threatened to resign if he remained in the cabinet. “As a feminist and as a woman, I cannot sit at this table of our progressive project with Armando Benedetti,” she told Petro.
According to Oscar Soria, veteran biodiversity campaigner and CEO of think-tank The Common Initiative, the Colombian government is likely to keep Muhamad as COP president, but her resignation could have a negative impact on the talks.
“To have a good result in Rome, proactive and energetic diplomatic work by the presidency was needed in the last months. However, some key issues have not been discussed recently. The internal political crisis (in Colombia) has likely been a great distraction,” Soria told Climate Home.
Since Muhamad’s announcement, several other ministers have also resigned, leading Petro to place all of his cabinet on hold and asking for “protocolary resignations” from every member.
“It’s not clear how much support from the president and ministers (Muhamad) can count on when her counterparts from other countries need to be approached by the Colombian foreign service,” Soria added.
Upcoming nature talks
The COP16 biodiversity negotiations are set to resume later this month, with important decisions coming up on finance for nature and a monitoring framework to track progress on nature restoration. These decisions were left pending after negotiators ran out of time in Cali, Colombia, last year.
One of the most pressing issues is the future of the Global Biodiversity Framework Fund (GBFF), which currently sits under the Global Environment Facility (GEF) until 2030. Some developing countries have called for the creation of a new fund, citing barriers at the GEF to access the funds.
Observers said COP16 could play an important role in the future of biodiversity finance, especially as the new US president, Donald Trump, cuts development funding for climate and nature projects.
“In Rome, countries must give a firm response to the measures and visions promoted by the Trump administration, reaffirming [their] commitment to protecting biodiversity,” said Karla Maas, campaigner at Climate Action Network (CAN) Latin America.
“This implies guaranteeing public resources for conservation instead of depending on the will of private actors or philanthropy,” Maas added.
(Reporting by Sebastian Rodriguez; editing by Megan Rowling)
The post Colombia’s COP16 presidency in suspense as minister resigns appeared first on Climate Home News.
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