Published

2 years ago

December 19, 2023

Alice Rush

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)

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)

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

Climate Change

Greenpeace urges governments to defend international law, as evidence suggests breaches by deep sea mining contractors

Published

8 hours ago

March 9, 2026

Alice Rush

SYDNEY/FIJI, Monday 9 March 2026 — As the International Seabed Authority (ISA) opens its 31st Session today, Greenpeace International is calling on member states to take firm and swift action if breaches by subsidiaries and subcontractors of The Metals Company (TMC) are established. Evidence compiled and submitted to the ISA’s Secretary General suggests that violations of exploration contracts may have occurred.

Louisa Casson, Campaigner, Greenpeace International, said: “In July, governments at the ISA sent a clear message: rogue companies trying to sidestep international law will face consequences. Turning that promise into action at this meeting is far more important than rushing through a Mining Code designed to appease corporate interests rather than protect the common good. As delegations from around the world gather today, they must unite and confront the US and TMC’s neo-colonial resource grab and make clear that deep sea mining is a reckless gamble humanity cannot afford.”

The ISA launched an inquiry at its last Council meeting in July 2025, in response to TMC USA seeking unilateral deep sea mining licences from the Trump administration. If the US administration unilaterally allows mining of the international seabed, it would be considered in violation of international law.

Greenpeace International has compiled and submitted evidence to the ISA Secretary-General, Leticia Carvalho, to support the ongoing inquiry into deep sea mining contractors. This evidence shows that those supporting these unprecedented rogue efforts to start deep sea mining unilaterally via President Trump could be in breach of their obligations with the ISA.

The analysis focuses on TMC’s subsidiaries — Nauru Ocean Resources Inc (NORI) and Tonga Offshore Mining Ltd (TOML) — as well as Blue Minerals Jamaica (BMJ), a company linked to Dutch-Swiss offshore engineering firm Allseas, one of TMC’s subcontractors and largest shareholders. The information compiled indicates that their activities may violate core contractual obligations under the United Nations Convention on the Law of the Sea (UNCLOS). If these breaches are confirmed, NORI and TOML’s exploration contracts, which expire in July 2026 and January 2027 respectively, the ISA should take action, including considering not renewing the contract.

Letícia Carvalho has recently publicly advocated for governments to finalise a streamlined deep sea mining code this year and has expressed her own concerns with the calls from 40 governments for a moratorium. At a time when rogue actors are attempting to bypass or weaken the international system, establishing rules and regulations that will allow mining to start could mean falling into the trap of international bullies. A Mining Code would legitimise and drive investment into a flagging industry, supporting rogue actor companies like TMC and weakening deterrence against unilateral mining outside the ISA framework.

Casson added: “Rushing to finalise a Mining Code serves the interests of multinational corporations, not the principles of multilateralism. With what we know now, rules to mine the deep sea cannot coexist with ocean protection. Governments are legally obliged to only authorise deep sea mining if it can demonstrably benefit humanity – and that is non-negotiable. As the long list of scientific, environmental and social concerns with this industry keeps growing, what is needed is a clear political signal that the world will not be intimidated into rushing a mining code by unilateral threats and will instead keep moving towards a moratorium on deep sea mining.”

—ENDS—

Key findings from the full briefing:

Following TMC USA’s application to mine the international seabed unilaterally, NORI and TOML have amended their agreements to provide payments to Nauru and Tonga, respectively, if US-authorised commercial mining goes ahead. This sets up their participation in a financial mechanism predicated on mining in contradiction to UNCLOS.
NORI and TOML have signed intercompany intellectual property and data-sharing agreements with TMC USA, and the data obtained by NORI and TOML under the ISA exploration contracts has been key to facilitating TMC USA’s application under US national regulations.
Just a few individuals hold key decision-making roles across the TMC and all relevant subsidiaries, making claims of independent management ungrounded. NORI, TOML, and TMC USA, while legally distinct, are managed as an integrated corporate group with a single, coordinated strategy under the direct control and strategic direction of TMC.

Greenpeace urges governments to defend international law, as evidence suggests breaches by deep sea mining contractors

Climate Change

After a Decade of Missteps, a Texas City Careens Toward a Water-Shortage Catastrophe

Published

17 hours ago

March 9, 2026

Alice Rush

Officials in Corpus Christi expect a “water emergency” within months and fully run out of water next year. That would halt jet fuel supplies to Texas airports, fuel a surge in gasoline prices and trigger an “economic disaster” without precedent, former officials said.

By Dylan Baddour

CORPUS CHRISTI, Texas—The imminent depletion of water supplies in Corpus Christi threatens to cut off the flow of jet fuel to Texas airports and other oil exports from one of the nation’s largest petroleum ports, triggering potential shockwaves through energy markets in Texas and beyond.

After a Decade of Missteps, a Texas City Careens Toward a Water-Shortage Catastrophe

Climate Change

Is the FBI Investigating Environmental Activists?

Published

18 hours ago

March 9, 2026

Alice Rush

A recent visit by an FBI agent to a climate activist hints at a broadening Trump administration effort to target political opponents.

By Nicholas Kusnetz

NEW YORK CITY—The group in the Brooklyn studio seemed harmless. There was a graduate student, a Yiddish teacher, a hairdresser. Fifteen people had gathered on a Wednesday night for a training offered by Extinction Rebellion NYC and Climate Defiance, two climate activist groups that engage in nonviolent civil disobedience and theatrical protest.