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The Earth’s jet streams play a fundamental role in the speed and direction of weather systems across the world.

This means that they are crucial for understanding extreme weather events and how they will change as the world warms.

Research suggests that upper-level jet-stream winds will accelerate on average as global temperatures rise, but little is known about how their fastest winds – known as “jet streaks” – will change.

In a first-ever study, published in Nature Climate Change, my co-author and I show that fast jet-stream winds will get faster and faster — by around 2% for every degree Celsius the world warms. This means that fast winds will speed up around 2.5 times more than average jet-stream winds. 

Furthermore, it means we should anticipate record-breaking jet-stream winds as warming continues.

Our research also reveals that this acceleration occurs because the difference between the density of the air in the tropics and the air at the poles will increase.

While further work will be needed to understand the full impact of our findings, we expect that they will include stronger severe storms and an increase in clear-air turbulence for aircraft passengers.

Fast flowing

The Earth’s jet streams are fast-flowing narrow bands of wind high up in the atmosphere. The fastest jet-stream winds blow from west to east and occur in the upper troposphere, around 10-12 km above the surface.

Jet streams are important because they shape Earth’s surface climate by steering weather systems, and so they can affect where severe weather occurs. For example, the regions around fast upper-level jet-stream winds – called “jet streaks” – have been linked to the occurrence of storms, tornadoes, hail and severe winds.

Jet streams are also key for air travel, providing an ideal tailwind for aircraft. Previous research has established that the average wind speed of the upper-level jet stream increases under climate change. This has the potential knock-on effect of causing more clear-air turbulence for aircraft passengers. 

Our research was inspired by reports in 2019 of transatlantic flights breaking speed records. As a result, we set out to find out how climate change will affect fast jet-stream winds.

Little is known about how fast upper-level jet-stream winds – classed as those above the 99th percentile – could change as the world warms. Furthermore, no mechanism has been proposed to explain why fast jet-stream winds would change.

Fast-get-faster response

We started by examining how physics-based climate models project fast jet-stream winds would change. We used models from the sixth Coupled Model Intercomparison Project (CMIP6), which were developed for the latest assessment by the Intergovernmental Panel on Climate Change (IPCC).

In these model projections, we compare daily jet-stream winds that exceed the 99th percentile at the end of the 20th (1980-2000) and 21st (2080-2100) centuries under a very high emissions scenario (SSP5-8.5). We also compare wind speeds for the near-term in an intermediate scenario (SSP2-4.5), which is broadly in line with the trajectory of global emissions today.

Our analysis finds that climate change makes the fastest upper-level jet-stream winds get faster and faster – by about 2% for every degree Celsius the world warms. This means that fast winds will speed up around 2.5 times more than average jet-stream winds.

We refer to this as the “fast-get-faster” response and we find the effect in all seasons of the year.

You can see this in the chart below, which shows the percentage change in the fastest winds at around 12km altitude per degree of warming across different latitudes (from 80 degrees south on the left-hand side to 80 degrees north on the right).

While the fast winds increase at all latitudes, those in the “extratropics” – that is, between around 20 to 60 degrees, where jet streams are found – are the fastest to begin with and thus get the largest boost under climate change.

Percentage changes in fast (>99th percentile) winds at 200 hectopascal (hPa), normalised by the global average change in surface air temperature for each climate model from 80 degrees south to 80 degrees north in latitude. Simulations use SSP5-8.5. The black line indicates the multi-model average and the shading indicates one standard deviation of the response across all the models. Source: Shaw & Miyawaki (2023)

Percentage changes in fast (>99th percentile) winds at 200 hectopascal (hPa), normalised by the global average change in surface air temperature for each climate model from 80 degrees south to 80 degrees north in latitude. Simulations use SSP5-8.5. The black line indicates the multi-model average and the shading indicates one standard deviation of the response across all the models. Source: Shaw & Miyawaki (2023)

Moist air

In addition to quantifying the “signal” of long-term change, we also provide a physical explanation for why it occurs.

Bridging the gap between simulating the response to climate change using models and understanding the causes helps us justify that this is a signal to take seriously.

The first step we take is to simplify the model to help isolate what physics underlies the signal. When the model is run without ocean currents and without land, we still find the signal.

This suggests that the fast-get-faster signal emerges in a world formed entirely of water. The result implies that the physics of a moist atmosphere is key to explaining the fast-get-faster response.

The second step we take is to use our physical understanding of the jet stream to quantify the connection between moisture and the signal.

The jet stream exists because of the contrast of density between air at the equator, which is warm and light, and air at the pole, which is cold and dense. We connect this contrast to the response of moisture under climate change.

In particular, in today’s climate, tropical air holds more moisture than air at the poles because it is warmer. Climate change exacerbates this contrast because hotter air can hold much more moisture than colder air. 

While the air at the poles is warming more rapidly than in the tropics, hotter air can hold so much more moisture than cold air that the overall density difference still increases.

This effect increases the density contrast under climate change, accelerating the jet-stream winds. Importantly, the effect is multiplicative – namely, fast jet-stream winds today that involve a steep density contrast would be boosted much more in the future than slower jet-stream winds that involve a shallower density contrast.

Thus, our results project record-breaking jet-stream winds.

Emerging signal

When we look at the recent past (1980–2022) using reanalysis data – which combines physical observations with model simulations – we do not find that the fast-get-faster signal has yet emerged from the noise of natural variability.

However, all the climate models in our study suggest that a statistically significant fast-get-faster signal will emerge for the extratropics in both the southern and northern hemispheres by the middle of this century.

Specifically, under SSP2-4.5, all climate models project the signal in the southern and northern hemispheres extratropics by 2038 and 2048, respectively. Under SSP5-8.5, this is slightly earlier – by 2035 and 2045, respectively.

This is shown in the figures below, which show the percentage change in fast jet-stream winds, relative to 1980-2000, from 1980 to 2050 in the southern (top) and northern (bottom) hemispheres, excluding the tropics. The lines indicate reanalysis data (black) and climate models projections under SSP2-4.5 (green) and SSP5-8.5 (orange).

The charts on the right-hand side show the trend, per degree of warming, for each model (green and orange) and the reanalysis data (black). Closed and open circles indicate results that are and are not statistically significant, respectively.

Timeseries of percentage changes (relative to 1980-2000) in fast 200hPa jet-stream winds in reanalysis and climate models for different emission scenarios for the southern (top) and northern (bottom) hemisphere extratropics from 1980 to 2050. Data are presented as multi-model average (thick line) with one standard deviation of the response across the models (shading). Right-hand charts show the linear trends of these changes per degree of global warming, where statistically significant trends are indicated by closed circles. Source: Shaw & Miyawaki (2023)

Timeseries of percentage changes (relative to 1980-2000) in fast 200hPa jet-stream winds in reanalysis and climate models for different emission scenarios for the southern (top) and northern (bottom) hemisphere extratropics from 1980 to 2050. Data are presented as multi-model average (thick line) with one standard deviation of the response across the models (shading). Right-hand charts show the linear trends of these changes per degree of global warming, where statistically significant trends are indicated by closed circles. Source: Shaw & Miyawaki (2023)

We are now working to better understand the knock-on impacts of these changes in the jet stream for severe weather.

New climate models are allowing scientists to look in greater detail at how extreme weather is – and will – change. Ultimately, unravelling the impacts of climate change on winds at regional scales will help society better prepare for the implications of a warming world.

The post Guest post: Why ‘jet-streak’ winds will get faster as the climate warms appeared first on Carbon Brief.

Guest post: Why ‘jet-streak’ winds will get faster as the climate warms

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COP17 must settle who decides how Cali Fund money is disbursed

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June Rubis is a steering group committee member for the Cali Fund, from Sarawak in Malaysian Borneo.

At COP16 in Cali, governments made a significant commitment: at least half of the funding from the new Cali Fund should support the self-identified needs of Indigenous Peoples and local communities, including women and youth. It was a watershed moment for multilateral benefit-sharing.

The challenge now is to translate that commitment into access arrangements that recognise the different institutions, priorities and decision-making processes of Indigenous Peoples and local communities.

For generations, biodiversity and traditional Indigenous knowledge have provided significant value to companies who depend on nature’s genetic diversity to discover new drugs that fight diseases, create products that improve health, and grow crops resilient to extreme heat and flooding events. While some compounds are sampled directly from the source country, increasingly the digital blueprints are held in online public databases which are freely accessible to use for innovation and research.

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The Cali Fund was established at COP16 to encourage commercial users of Digital Sequence Information, or DSI, to share benefits arising from its use. Estimates suggest it could generate over $3.5 billion a year – a stark contrast to the modest $10,656 currently committed to the fund from just five SMEs, underlining how much progress must be made at COP17 over the next two weeks.

The COP16 decision that set up the fund offers two routes for money to reach Indigenous Peoples and local communities: through government authorities, and through direct payments to institutions identified by Indigenous Peoples and local communities themselves.

Varied ways of organising

Indigenous Peoples and local communities organise through a wide range of institutions. Some have national or regional organisations experienced in managing international grants. Others work through territorial organisations, customary institutions, community associations, cooperatives or networks. Some have professional finance teams and audited accounts; others have extensive experience governing territories, collective resources or conservation work without having been organised around international funding requirements.

For direct access, some questions are already apparent. Which institutions should be able to receive funds? How should they be identified? What fiduciary standards should apply? How should safeguards and accountability work where institutional capacities differ? What support may be needed where institutions have strong community mandates but less experience with international finance?

Comment: Protecting nature is a public duty, not a Wall Street profit opportunity

If access is designed mainly around institutions that already meet the expectations of large international finance mechanisms, early funding will tend to favour those already familiar to funders. They will gain further experience and become better positioned for future funding, while institutions with less administrative capacity may remain outside the system despite strong community mandates and long histories of stewardship.

These first decisions matter most, because they set the terms for everyone who follows.

The role of intermediaries requires care. Some Indigenous organisations may want a fiscal host to hold and manage funds on their behalf. Communities may choose to work through an NGO they trust. Government-facilitated arrangements may work well in particular national contexts.

What matters is the function an intermediary performs and the authority that comes with it. Providing administrative support is different from deciding which Indigenous organisations qualify, which priorities can receive support, or how success will be assessed. Direct access means communities keep that decision-making authority.

Decision-making power

The COP16 decision refers to institutions that Indigenous Peoples and local communities identify. But authority among Indigenous Peoples does not sit in one kind of body. It may sit with territorial organisations, customary institutions, community associations or combinations of these. Legal recognition and customary authority do not always align neatly.

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An important feature of the Cali Fund’s governance is that Indigenous Peoples and local communities participate as full members of the Steering Committee, rather than as observers. Seven Indigenous Peoples and local community representatives, one from each of the seven socio-cultural regions, participate in consensus-based decision-making alongside representatives of governments and UN entities. Six additional representatives from civil society, scientific institutions and the private sector participate as observers.

That representation carries responsibility. Institutional legitimacy, access and representation take different forms across the seven socio-cultural regions. Indigenous Peoples and local communities members therefore have an important role in bringing those differences into the Fund’s governance and in ensuring that arrangements developed for one context do not become the assumed model for everyone else. 

Safeguards and clear responsibilities

COP17 can establish the core principles and direction, while allowing operational pathways to develop in ways that respond to different regional contexts. The decisions countries take in Yerevan will shape how that flexibility is realised in practice. 

The choices made around access will influence which institutions are able to participate, which routes become established and which forms of authority are recognised within the funding architecture. The aim should be an architecture with enough structure to maintain confidence while allowing for different forms of Indigenous and community governance.

A credible direct-access pathway will need safeguards, financial oversight and clear responsibilities. This would give the 50% commitment a stronger institutional foundation.

The Cali Fund’s importance will ultimately depend not only on how much funding reaches Indigenous Peoples and local communities, but on whether they are able to determine how the money is accessed, governed and used. This requires access pathways that recognise their institutions, priorities and decision-making processes, rather than requiring them to conform to a single predetermined model.

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COP17 must settle who decides how Cali Fund money is disbursed

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UK approves gas drilling despite admitting blow to “climate leadership” status

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The UK government has approved extraction at the Jackdaw gas field in the North Sea, despite acknowledging that this decision could make it harder for Britain to convince other countries to move away from fossil fuel production.

UK energy secretary Miatta Fahnbulleh approved the drilling on Wednesday after months of high-profile debate, fuelled in part by interventions from US President Donald Trump. She argued that the project would boost energy security in the wake of the Middle East fossil fuel crisis, protect hundreds of jobs and add £2.9 billion ($3.88bn) to the UK economy.

She said Jackdaw’s gas would be cleaner than imported gas and would not prevent the UK from meeting its legally-binding carbon targets and its goal of net zero by 2050. As the field is already licensed, she said extraction was consistent with the Labour Party’s 2024 manifesto promise not to issue any new oil and gas licenses.

The same morning, the government announced a new Energy Wealth Fund to reinvest oil and gas revenues in the climate transition. It will start with £2 billion ($2.67bn) from the government and be topped up over time with tax revenues from offshore oil and gas production.

Energy Secretary Miatta Fahnbulleh and Chancellor of the Exchequer John Healey leave 10 Downing Street following Prime Minister Andy Burnham’s first cabinet meeting, on July 21, 2026 in London, England. (Photo by Ben Montgomery/Getty Images)

Climate campaigners in the UK and abroad were quick to condemn the decision, while a leading legal expert told Climate Home News it goes against the advice of the International Court of Justice. Meanwhile, the government’s own documents reveal that it recognises the drilling could damage the UK’s reputation and its ability to push forward the global transition away from fossil fuels.

“Climate leadership” blow

The 92-page decision document says Fahnbulleh “acknowledges that international standing on climate is important and accepts that a decision to grant consent may not further the UK’s international climate leadership.”

It adds: “She acknowledges concerns about the potential implications for the UK’s credibility and influence – including the difficulty inherent in encouraging other states to move away from fossil fuel production while the UK continues, in a limited and transitional way, to draw on its own domestic resources.”

While noting that Jackdaw has not been issued with a new license – just permission to extract gas – the document says Fahnbulleh “accepts this does not fully resolve the underlying tension in the UK’s position” but “considers this alongside the substance of the UK’s wider record [on emissions reduction], which remains significant”.

It continues that she accepts these concerns are “legitimate” and weigh against approving gas extraction, but only gives this argument a “moderate negative weight” set against the benefits of gas production.

“Huge” wrong signal

In international climate talks, the UK has long supported the transition away from fossil fuels and is one of very few major oil and gas producers to ban new licenses. Across the North Sea, the Norwegian government continues to make offshore areas available for oil and gas exploration through annual licensing rounds.

Climate experts and campaigners shared the concern, acknowledged in the decision document, that approving Jackdaw could set a precedent for fossil fuel production elsewhere. Sam Fankhauser, professor of climate change economics at Oxford University, said the direct climate impact of Jackdaw is “much smaller than the debate around it would suggest” but the “wrong signal it sends, however, is huge”.

    Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change, said that while Jackdaw’s output will be very small, “it will signal to other fossil fuel producers that they too should carry on with business as usual, less than a month before the COP31”.

    Kenyan campaigner Mohamed Adow, director of Power Shift Africa, called the decision “a serious blow to Britain’s international climate credibility” as “the UK cannot expect developing countries to move away from fossil fuels while giving the green light to new drilling in its own backyard”.

    International Court of Justice

    In July 2025, the International Court of Justice (ICJ) advised that government failure to take appropriate climate action “including through fossil fuel production” may amount to an internationally wrongful act.

    The UK voted in favour of a United Nations resolution welcoming the advisory opinion. Yet, in its Jackdaw decision document, it notes that the ICJ opinion is not legally binding and says the UK does not accept the court’s opinion that the customary international law duty to prevent significant harm to the environment applies to climate change.

    Fahnbulleh concludes that, although it will have “significant effect on the environment”, gas drilling in Jackdaw “would not lead to significant harm to the environment” – and so does not breach any duty to prevent such harm. Instead, the government document says the duty should be considered “as a matter of policy rather than legal obligation”.

    Margaretha Wewerinke-Singh, who led Vanuatu’s legal team pushing for the ICJ’s advisory opinion, told Climate Home News that treating the duty as a matter of policy rather than legal obligation is “not how international law works”. “An advisory opinion is not a judgement,” she said, “but it states the law as it stands, and that law binds the UK whether or not it accepts it.”

    “Even as a matter of policy,” she added, “the decision asks the wrong question: whether Jackdaw on its own would cause significant harm. The Court found that accumulated emissions are already causing significant harm. What matters is whether approving new production is consistent with the stringent due diligence the duty requires.”

    Public support for decision

    While the decision was criticised by climate campaigners and the opposition Green party, polling reported by Politico suggests that 55% of British adults support drilling at Jackdaw, with just 14% opposed. Even supporters of the UK’s net zero target back new drilling by more than two to one, the polling found.

    Jackdaw is one of two North Sea oil and gas fields the government has been debating whether to extract more from for months. While Jackdaw is a small gas field, the other, Rosebank, is a much larger field that holds mostly oil.

    Rosebank’s emissions are estimated to be around seven times higher than Jackdaw’s. Fahnbulleh told Sky News that Rosebank is “different” to Jackdaw because its oil would be exported, whereas Jackdaw’s gas will be used in the UK, adding that she will consider it “in its own right”.

    The Guardian reported on Wednesday that UK officials say Fahnbulleh is minded to refuse approval for Rosebank. She has not yet taken a final decision on Rosebank, the newspaper said, but a ruling is expected later this year.

    The post UK approves gas drilling despite admitting blow to “climate leadership” status appeared first on Climate Home News.

    UK approves gas drilling despite admitting blow to “climate leadership” status

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