The retreat of sea ice in the Arctic has long been a prominent symbol of climate change.
Observations reveal that Arctic sea ice extent at the end of summer has halved, since satellite records began in the late 1970s.
Yet, since the late 2000s, the pace of Arctic sea ice loss has slowed markedly, with no statistically significant decline for about 20 years.
In new research, published in Geophysical Research Letters, my colleagues and I explore the reasons for the recent slowdown of Arctic sea ice – and turn to climate models to understand what might happen next.
Our findings show that, rather than being an unexpected or rare event, climate model simulations suggest we should expect periods like this to occur relatively frequently.
This current slowdown is likely caused by natural fluctuations of the climate system – just as they played a part in an acceleration of sea ice loss in the decades prior.
Were it not for human-caused warming, it is likely that sea ice would have increased over this period.
According to our simulations, the slowdown could even last for another five or 10 years – even as the world continues to warm.
Widespread slowdown
The changes in the Arctic are one of the most clear and well-known indicators of a warming climate.
With the Arctic warming up to four times the rate of the global average, the region has lost more than 10,000 cubic kilometres of sea ice since the 1980s. (The volume of ice lost is roughly equivalent to 4bn Olympic swimming pools).
Arctic sea ice reached its smallest extent on record in September 2012, dwindling to 3.41m square kilometres (km2). This triggered discussions of when the Arctic might see its first “ice-free” summer, where sea ice extent drops below 1m km2.
Research has shown that human-caused warming is responsible for up to two-thirds of this decline, with the remainder down to natural fluctuations in the climate system, also known as “internal climate variability”.
Despite the record low of 2012, satellite data reveals a widespread slowdown in Arctic sea ice loss over the past two decades.
Climate model simulations of Arctic sea ice thickness and volume further reinforce these observations, indicating little or no significant decline over the past 15 years.
This data is laid out in the charts below, which show average sea ice extent in September (left) and for the whole year (middle), as well as how annual average sea ice volume differs from the long-term average (right).
(September is typically the point in the year where sea ice reaches its annual minimum, at the end of the Arctic summer.)
The coloured lines indicate that the data originates from the National Snow and Ice Data Centre (NSIDC, orange), the Ocean and Sea Ice Satellite Application Facility (OSISAF, red) and the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS, blue).

These observational records show how the precipitous decline in sea ice seen over much of the satellite data has slowed since the late 2000s.
It also shows that the slowdown is not limited to summer months, but is occurring year-round.
Our study is not the first to highlight this slowdown – several recent studies have also examined various aspects of this phenomenon. Meanwhile, a 2015 paper was remarkably prescient in suggesting such a slowdown could occur.
Is the slowdown surprising?
The loss of sea ice around the north pole is both a cause and effect of Arctic amplification – the term given to the rapid warming in the region.
Melting snow and ice reduces the reflectiveness, or “albedo”, of the Arctic’s surface, meaning less incoming sunlight is reflected back out to space. This causes greater warming and even more melting of ice and snow.
This “surface-albedo feedback” is one of several drivers of Arctic amplification.
Given global warming is caused by the continued rise in greenhouse gas emissions, it might seem puzzling – or even impossible – that Arctic sea ice loss could slow down.
However, the recent generations of climate models used for the Coupled Model Intercomparison Project (CMIP) – the international modelling effort that feeds into the influential reports from the Intergovernmental Panel on Climate Change (IPCC) – illustrate why this might be happening.
Models from CMIP5 and CMIP6, which simulate the historical period and explore different future warming scenarios, indicate that slowdowns in Arctic sea ice loss lasting multiple decades are relatively common – happening in roughly 20% of model runs.
This is due to natural variability in the climate system, which can temporarily counteract decline of sea ice – even under high-emission scenarios.
One way that climate scientists investigate natural variability is by running multiple simulations of a model, each with identical levels of human-caused emissions of carbon dioxide, aerosols and methane. These are known as “ensembles”.
Due to the chaotic nature of the climate system, which results in different phases of natural variability, the different model runs produce different outcomes – even if the long-term climate change signal from human activity remains constant.
Large ensembles help us to understand how to interpret the Earth’s observed climate record, which has been influenced by both human-induced climate change and natural variations.
In our research, we examine how many individual model runs within the ensemble exhibit a similar or greater slowdown in sea ice loss than the observed record over 2005-24.
The models show that natural climate variability can accelerate sea ice loss, as seen during the dramatic record-lows in 2007 and 2012. However, this natural variability can also temporarily slow the longer-term downward trend.
The primary suspects behind this multi-decade variability are natural fluctuations linked to the tropical Pacific and the North Atlantic, although the precise causes are yet to be quantified.
For example, a shift from the positive, warm phase to the negative, cool phase of a natural cycle in the Interdecadal Pacific Oscillation is associated with bringing much cooler waters close to the North American coastline and into the Arctic. This could potentially lead to sea ice growth.
What might happen to Arctic sea ice cover next?
So how long could this current slowdown persist?
Climate model simulations suggest the current slowdown might continue for another five or 10 years.
However, there is an important caveat: slowdowns like this often set the stage for faster declines later.
Climate models suggest that when the slowdown inevitably ends, the rate of sea ice loss could rapidly accelerate.
Thousands of simulations analysed in our research reveal that September sea ice loss ramps up at a rate of more than 500,000km2 per decade after prolonged periods of minimal sea ice loss.
This would equate to more than 10% of current sea ice cover in September.
An analogy of Arctic sea ice extent behaving like a ball bouncing downhill – set out in a 2015 Carbon Brief article by Prof Ed Hawkins – is particularly apt here.
Just like the ball – which eventually reaches the bottom due to gravity, despite an erratic journey – Arctic sea ice loss may temporarily seem to defy expectations at present.
Ultimately, however, sea ice loss will resume, reflecting the underlying human-induced warming trend.
While it may seem contradictory that Arctic sea ice loss can slow even as global temperatures climb, climate models clearly show that such periods are expected parts of climate variability.
As a result, the recent slowdown in Arctic sea ice does not signal an end to climate change or lessen the urgency of cutting greenhouse gas emissions, if global goals are to be met.
While the current slowdown might persist for some years to come, when sea ice loss resumes, it could do so with renewed intensity.
The post Guest post: Why the recent slowdown in Arctic sea ice loss is only temporary appeared first on Carbon Brief.
Guest post: Why the recent slowdown in Arctic sea ice loss is only temporary
Climate Change
Introducing Project Cosmos: Carbon Brief’s ‘universe’ of climate science
Carbon Brief’s Project Cosmos is a major collaborative effort to build the world’s largest and most complete database of climate change research.
The Cosmos database – which features more than 1.8m individual publications linked by 40m citation relationships – captures the vast body of human knowledge about climate change that has accumulated over more than a century of academic study.
Cosmos is a major new resource, which has taken more than 18 months to research and build, with help and guidance from a specialist team of academics.
Carbon Brief embarked on Project Cosmos to map and analyse the scientific community’s foundational knowledge about climate change.
This includes, at first, ranking the most highly cited academic publications, authors and institutions.
Together, this series of rankings is known as the Cosmos 500.
But, over time, the database will reveal, for example, how interest in different areas of climate science has changed over time, plus identify potential knowledge gaps and, thus, opportunities for future research.
The post Introducing Project Cosmos: Carbon Brief’s ‘universe’ of climate science appeared first on Carbon Brief.
https://www.carbonbrief.org/introducing-project-cosmos-carbon-briefs-universe-of-climate-science/
Climate Change
Two to tango: How governments can unlock private investment for national climate goals
Even the most ambitious national climate plans aimed at cutting emissions to meet the 1.5C global warming goal in the Paris Agreement often lack a vital ingredient for success: private investment.
With governments facing fiscal and political pressures, attracting private capital will be crucial for accelerating climate action in the coming years.
Yet many Nationally Determined Contributions (NDCs) still do not have the sector-specific plans, economic incentives, policy certainty, infrastructure investment and ongoing dialogue needed to break silos between the public and private sectors and bring more businesses on board.
“If you just have the high-level (NDC) target from the government in a vacuum, it’s not going to spur much business action,” said Greg Briner, senior manager for policy at the We Mean Business Coalition, which works with companies pushing for stronger climate action.
“But that target combined with … more specific policies and measures that get put in place as a result of that target-implementing process, or as a result of the NDCs, is where the magic starts happening,” he explained.
NDCs: late and inadequate
NDCs are voluntary climate action plans created by countries under the Paris Agreement. They include commitments such as expanding renewable energy, reducing fossil fuels, halting deforestation and other measures to cut greenhouse gas emissions and limit global warming.
First submitted in 2015 for the Paris Agreement, NDCs should be updated with more ambitious targets every five years, although some governments have not stuck to this timetable.
Last year, most countries missed an initial February deadline to finalise the latest round of plans, known as “NDCs 3.0” – and at least 50 countries, mainly developing nations, have still not done so.
Paris Agreement committee snubbed over missing NDC climate plans
Although these national plans have helped drive emissions reductions in some sectors – including falling deforestation rates and greater investments in renewables – climate experts say progress remains far too slow to meet the Paris goals and urgent action is now needed.
Last November, the UN climate body projected that global emissions would fall by around 12% from 2019 levels by 2035, based on a preliminary assessment of new NDCs announced by countries that produce nearly 70% of the world’s greenhouse gases.
The Intergovernmental Panel on Climate Change has said countries should cut emissions far more rapidly, with a 60% drop by 2035 needed to limit global warming to 1.5C.
But for developing economies especially, the multi-billion-dollar costs associated with transitioning to greener energy systems and curbing their emissions are still a major barrier. Climate experts say governments and businesses need to move in step if NDC targets are to be achieved.
“There are positive actions going on but we need a significant ramping up. It’s not happening quickly enough,” said Briner. “It’s (about) building on these foundations that are being put in place.”
Nurturing the conditions for private investment
Last September, consumer goods giant Unilever published a report, entitled Bold Plans, Real Impact, examining how corporate climate transition plans and NDCs can support each other.
Among its recommendations, the report called for governments to provide clearer roadmaps for private-sector engagement. It also highlighted the need for stronger regulatory frameworks, market incentives, sector-specific transition pathways and integrated, economy-wide planning.
For businesses, the report recommended aligning their transition plans with national climate priorities, collaborating more closely with industry peers, strengthening monitoring and verification systems, and unlocking finance through public-private partnerships.
Comment: The missing piece in COP climate talks – market signals for adaptation
A year earlier, the We Mean Business Coalition published a similar report, Time to Deliver: Business Call to Action for Ambitious and Investible NDCs.
This report urged governments – particularly in the G20 economies – to unlock private investment through sectoral targets, clean energy expansion, energy efficiency measures, fossil fuel phase-outs and commitments to halt deforestation.
It also stressed the importance of translating climate targets into concrete policies, backed by national implementation strategies and coordination across ministries.
Another key recommendation was the need for more transparent and inclusive dialogue with businesses throughout the NDC process. Early consultation with companies, the report said, should be embedded into the development and implementation of NDCs to ensure that climate plans reflect commercial realities.
Briner of We Mean Business said the economics of decarbonisation have changed dramatically over the past two decades.
“Ten to 20 years ago, decarbonising and investing in clean energy and electrification was seen as nice-to-have and a more expensive option, but these days, it simply makes business sense,” he said, referring to recent geopolitical events in the Middle East that have roiled oil and gas markets, pushing up fossil fuel prices.
However, upfront costs for clean energy infrastructure remain a major hurdle. Governments therefore need to complement climate policies with investments, concessional loans, grants, subsidies and tax incentives to help reduce risks, Briner added.
“Globally, there are still significant subsidies going to fossil fuels in different forms,” he said. “If we could redirect some of those current incentives away from fossil fuels and into clean electrification and clean energy, then that would certainly help.”
Brazil’s sector-specific climate planning
Brazil’s NDC targets include expanding renewable energy – which already accounts for nearly 45% of its energy mix – ending illegal deforestation and reaching net-zero emissions by 2050.
According to Briner, Brazil’s climate strategy – known as Plano Clima – offers an example of how governments can provide businesses with clearer implementation guidance.
Years in development, the initiative sets out how Brazil intends to meet its climate goals through a series of sectoral plans covering areas such as energy, transport and land use.
“They’ve put together some pretty detailed, impressive plans,” Briner said. “Those are the types of things that will influence business models and business decisions. It’s this more detailed second layer of setting out national plans which is of interest to business.”


Last year, a transport coalition of more than 50 associations, companies and academia put forward a plan to help reduce the sector’s emissions and attract more than $600 billion in green investments in Brazil.
The previous year, 55 companies operating in Brazil, including Natura, Nestle, Itau and Unilever, called for more ambitious NDCs and clearer implementation policies, as well as encouraging climate-friendly investment and private-sector involvement.
Unilever, for example, has a global goal to create a deforestation-free supply chain and is partnering with a leading supplier in Brazil to ensure that soybean oil used at its factory there is not linked to forest loss.
Cheaper capital, high-quality projects
Although Brazil has relatively sophisticated capital markets, high interest rates still make long-term, low-carbon investments difficult, said Natalie Unterstell, president of the Talanoa Institute, a Brazilian environmental think-tank.
To address this challenge, Brazil is scaling up Fundo Clima – its National Climate Change Fund – as a central part of its implementation strategy by offering cheaper financing at scale.
But Unterstell said the private sector also needs to demonstrate that it can develop and deliver high-quality, low-carbon projects.
“Making Brazil’s policies investable is about making sure cheaper capital meets a pipeline of real, high-quality projects,” she said by email.
Brazilian firm behind SAF plan found growing oil palm on deforested Amazon land
While many companies have announced climate commitments, investment decisions have not always followed, she added.
“What companies can do better is move from targets to investment: adopt robust transition plans, and integrate carbon risk into core financial decisions,” Unterstell said.
On the government side, the priority is to “fix the signals”, she added. That means ensuring Brazil’s regulated carbon market – which is due to start in 2027 for sectors including iron and steel, cement, and oil and gas – operates with clear rules, credible enforcement and no delays, while aligning public finance with climate goals and providing long-term policy certainty.
“At the moment, both sides are waiting for stronger signals from the other, hence breaking that co-ordination problem is key,” she said.
Indonesia’s challenge: bridging the finance gap
Like Brazil, Indonesia is home to large areas of rainforest, but its energy mix relies far more heavily on fossil fuels, with coal providing about a third of supply. In its NDCs, Indonesia has pledged to reduce emissions by 31.9% by 2030 compared with business-as-usual levels, or by 43.2% with international support, on the way to reaching net zero by 2060.
Yet despite being promised more than $20 billion in international financial support from donor governments and investors under its Just Energy Transition Partnership, Jakarta has decided to row back on a plan to close a key coal power station early, saying it will focus on shuttering older and dirtier plants first.
To attract private investment to help achieve its emissions goals, Indonesia must provide policy clarity and long-term certainty, said Fabby Tumiwa, executive director of the Institute for Essential Services Reform, an Indonesian think-tank.
Comment: Indonesia’s failing Just Energy Transition Partnership is a cautionary tale
“Any investor wants to understand the long-term risks of the country so that they can assess the risks properly and come up with a risk mitigation strategy. Uncertain policies basically make investors unable to mitigate the risks,” Tumiwa told Climate Home News.
“To make Indonesia’s climate policies investable for the private sector, the core task is to convert climate ambition into bankable, enforceable, risk-adjusted projects,” he said. “Investors do not only need targets; they need predictable revenue, credible off-takers, permits, grid access, currency-risk management and policy durability.”
Indonesia has estimated the investment needed to meet its NDC goals at more than $400 billion but has yet to clearly outline how businesses can directly contribute, said Egi Suarga, senior manager for climate at World Resources Institute Indonesia, a research organisation.
He said climate action should be framed as an investment opportunity rather than an economic burden.
Evolving policies and regulations
Over 100 Indonesian companies have adopted net-zero and are ready to ramp up decarbonisation given clear national guidance, according to the We Mean Business Coalition.
Indonesia’s Indika Energy is making heavy investments in renewable energy such as solar, while cement company Solusi Bangun Indonesia is also investing in cleaner energy, fuel efficiency and pushing better biodiversity management.
Meanwhile, Unilever’s climate transition plan states that the company is working with local government and environmental NGOs in Indonesia to protect and restore forests in Aceh and North Sumatra. It is also switching from natural gas to biomethane at its Indonesian sites.


One positive development, Suarga noted, is the creation of carbon pricing regulations aimed at attracting private finance, with an initial focus on the forestry sector.
“It can create a good climate for investors,” he said. “It doesn’t directly mention that this is for achieving the NDCs but there is no trade-off between development financing with environmental protections – so that’s a good start.”
Indonesia also needs stronger incentives and regulations for renewable energy, he added.
“We also have to think about other sectors now – like the energy sector and renewables,” Suarga said. “How can the government provide more incentives or facilitating regulations that can be more profitable to create a level playing field for renewables and fossil fuels?”
Ambition loop to drive action
Like Tumiwa, Suarga stressed the need for greater dialogue between the government and businesses so companies can understand better how they can contribute to Indonesia’s emissions targets.
“They know about sustainability because of the market and demands of the market… [but] I’m not sure whether [they] really understand about Indonesia’s target to achieve a certain amount of emissions reductions in the NDCs,” he said.
Currently, the government and private sector are largely working separately, Suarga added. The challenge lies in bringing them together to set targets, plan implementation and monitor emissions reductions. “It will need two to tango. The government should engage more with the private sector,” he emphasised.
Big banks’ lending to coal backers undermines Indonesia’s green plans
For the We Mean Business Coalition’s Briner, what is ultimately needed is an “ambition loop” in which businesses lead on emissions reductions while governments create policies that accelerate private-sector action.
“It really helps governments when they have a strong voice from business calling for policy action. It helps move things forward,” he said.
Without stronger policies and incentives, achieving NDC goals will become increasingly difficult to achieve and costly, experts say.
“It’s really a case of all hands-on deck right now,” Briner said. “We need all sides of this equation working together and trying to get this done because there isn’t an alternative.”
The post Two to tango: How governments can unlock private investment for national climate goals appeared first on Climate Home News.
Two to tango: How governments can unlock private investment for national climate goals
Climate Change
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