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
FOR IMMEDIATE RELEASE
CCL volunteers and staff met with 47 Republican offices, including the office of Sen. Lindsay Graham (R-SC) on Capitol Hill last month.
Statement on Foreign Pollution Fee Act
April 8, 2025 – Citizens’ Climate Lobby (CCL) welcomes the reintroduction of the Foreign Pollution Fee Act by Senator Bill Cassidy (R-LA) and Senator Lindsey Graham (R-SC).
“Foreign polluters should be held accountable for the climate impacts of their exports to the U.S., and this bill takes a critical step in ensuring that imported goods reflect their true carbon cost,” said Jennifer Tyler, CCL Vice President of Government Affairs.
“By requiring robust emissions accounting for foreign imports, the legislation promotes transparency and fairness in global trade.”
The bill’s introduction comes just a few weeks after 50 right-of-center CCLers lobbied 47 Republican offices on Capitol Hill on foreign pollution fees and other policies to reduce emissions.
CCL is pleased to see this important bill reintroduced, and our grassroots volunteers nationwide will be working toward its passage in Congress.
CONTACT: Flannery Winchester, CCL Vice President of Communications, 615-337-3642, flannery@citizensclimate.org
###
Citizens’ Climate Lobby is a nonprofit, nonpartisan, grassroots advocacy organization focused on national policies to address climate change. Learn more at citizensclimatelobby.org.
The post Statement on Foreign Pollution Fee Act appeared first on Citizens' Climate Lobby.
Greenhouse Gases
Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015
Nearly 60 countries have drastically scaled back their plans for building coal-fired power plants since the Paris Agreement in 2015, according to figures released by Global Energy Monitor (GEM).
Among those making cuts of 98% or more to their coal-power pipeline are some of the world’s biggest coal users, including Turkey, Vietnam and Japan.
The data also shows that 35 nations eliminated coal from their plans entirely over the past decade, including South Korea and Germany.
Global coal-fired electricity generation has increased since 2015 as more power plants have come online.
But the data on plants in “pre-construction” phases in 2024 shows what GEM calls a “dramatic drop” in proposals for future coal plants.
The number of countries still planning new coal plants has roughly halved to just 33, with the proposed capacity – the maximum electricity output of those proposed plants – dropping by around two-thirds.
China and India, the world’s largest coal consumers, have also both reduced their planned coal capacity by more than 60% over the same timeframe, from a total of 801 gigawatts (GW) to 298GW.
However, both countries still have a large number of coal projects in the pipeline and, together, made up 92% of newly proposed coal capacity globally in 2024.
‘Dramatic drop’
The Paris Agreement in 2015 had major implications for the use of fossil fuels. As the fossil fuel that emits the most carbon dioxide (CO2) when burned, coal has long been viewed by many as requiring a rapid phaseout.
The Intergovernmental Panel on Climate Change (IPCC) and the International Energy Agency (IEA) both see steep declines in “unabated” coal use by 2030 as essential to limit global warming to 1.5C.
But coal power capacity has continued to grow, largely driven by China.
Global capacity hit 2,175GW in 2024, up 1% from the year before and 13% higher than in 2015, according to GEM’s global coal-plant tracker.
This growth disguises a collapse in plans for future coal projects.
GEM’s latest analysis charts a decade of developments since the Paris Agreement and the “dramatic drop” in the number of coal plant proposals.
In 2015, coal power capacity in pre-construction – meaning plants that had been announced, or reached either the pre-permit or permitted stage – stood at 1,179GW.
By 2024, this had fallen to 355GW – a 70% drop. This indicates that countries are increasingly turning away from their earlier plans for a continued reliance on coal.
In total, 23 nations reduced the size of their proposals over this period and another 35 completely eliminated coal power from their future energy plans. Together, these 58 countries account for 80% of global fossil fuel-related CO2 emissions.
The chart below shows these changes, with China and India shown on a different x-axis due to the scale of their proposals. (See section below for more information.)
2015 to 2024, gigawatts (GW), in all countries that saw declines over this period. Red arrows indicate countries that no longer have any plans to build coal power plants. Source: Global Energy Monitor.
According to GEM, of the coal plants that were either under pre-construction or construction in 2015, 55% ended up being cancelled, a third were completed and the remainder are still under development.
Many of the nations that have phased coal out of their electricity plans are either very small or only had modest ambitions for building coal power in the first place.
However, the list also includes countries such as Germany and South Korea. These nations are both in the top 10 of global coal consumers, but their governments have committed to significantly reducing or, in Germany’s case, phasing out coal use by the late 2030s.
Turkey, Vietnam and Japan are among the big coal-driven economies that are now approaching having zero new coal plants in the works. All have around 2% of the planned capacity they had a decade ago.
Other major coal consumers have also drastically reduced their coal pipelines. Indonesia, the fifth-biggest coal user, has reduced its coal proposals by 90% and South Africa – the seventh-biggest – has cut its planned capacity by 83%.
Of the 68 countries that were planning to build new coal plants in 2015, just nine have increased their planned capacity. Around 85% of the planned increase in capacity by these nations is in Russia and its central Asian neighbours.
China and India
China is by far the world’s largest coal consumer, with India the second largest.
There was 44GW of coal power added to the global fleet last year. China was responsible for 30.5GW of this while retiring just 2.5GW, and India added 5.8GW while retiring 0.2GW.
Between them, these nations contributed 70% of the global coal-plant construction in 2024.
Nevertheless, there were signs of change as newly operating coal capacity around the world reached its lowest level in 20 years.
China and India have also seen significant drops in their pre-construction coal capacity over the past decade.
In 2015, China had 560GW of coal power in its pipeline and India had 241GW. Both nations have seen their proposed capacity drop by more than 60% to reach 217GW and 81GW, respectively.
While this is a significant reduction, both nations still have more coal capacity planned now than any other nation did in 2015. China’s current 217GW is roughly four times more than the 57GW Turkey was planning at that time.
GEM attributes the “slowdown” in China’s new proposals to the nation’s record-breaking solar and wind growth, which saw more electricity generation capacity installed in 2023 and 2024 than in the rest of the world combined.
As for India, GEM says the “notable declines” in coal proposals and commissions came after a “coal-plant investment bubble that went bust in the early 2010s”.
It notes that India is now “encouraging and fast-tracking the development of large coal plants”. The government has cited the need to meet the large nation’s growing electricity demand, especially due to the increased need for cooling technologies during heatwaves.
As other nations move away from the fossil fuel, coal capacity is likely to become increasingly concentrated in these two nations. Together, they made up 92% of the 116GW in newly proposed capacity last year.
The post Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015 appeared first on Carbon Brief.
Analysis: Nearly 60 countries have ‘dramatically’ cut plans to build coal plants since 2015
Greenhouse Gases
Power-sector CO2 hits ‘all-time high’ in 2024 despite record growth for clean energy
Global power-sector emissions hit an “all-time high” in 2024, despite solar and wind power continuing to grow at record speed, according to analysis from thinktank Ember.
Emissions from the sector increased by 1.6% year-on-year, to reach a record high of 14.6bn tonnes of carbon dioxide (tCO2).
This increase was predominantly due to a 4% growth in electricity demand worldwide, leading coal generation to increase by 1.4% and gas by 1.6%.
Embers’ analysis finds that the increase in fossil-fuel generation was, in particular, due to hotter temperatures in 2024, which drove up electricity demand in key regions such as India.
Clean electricity generation grew by a record 927 terawatt house (TWh), which would have been sufficient to cover 96% of electricity demand growth not caused by higher temperatures.
Despite the increase in emissions in the short-term, this “should not be mistaken for failure of the energy transition”, notes Ember, but a sign we’re nearing a “tipping point” wherein changes in weather and demand hold a particularly strong sway.
Clean-power growth
Low-carbon energy sources – renewables and nuclear – provided 40.9% of the world’s electricity in 2024, according to Ember.
This is the first time they have passed the 40% mark since the 1940s, when hydropower contributed around that percentage and coal made up 55%.
Renewable power sources collectively added a record 858TWh of generation last year – a 49% increase on the previous record set in 2022 of 577TWh.
Solar dominated electricity generation growth for the third year in a row in 2024, adding 474TWh of generation, as shown on the chart below. This was up 29% on 2023.
This allowed solar, which hit a total global capacity of 2,131TWh, to meet 40% of global electricity demand growth in 2024 alone.
Solar generation “avoided” an estimated 1,658MtCO2 in 2024 – equivalent to the power-sector emissions of the US, according to Ember.
The technology’s significant growth in 2024 – with more solar capacity installed last year than annual capacity installations of all fuels combined in any year before 2023 – continues a trend seen over recent years.
Across 99 countries, the electricity they produce from solar power has doubled in the past five years.
In 2024, non-OECD economies accounted for 58% of global solar generation, with China accounting for 39% alone. A decade ago the 38 Organisation for Economic Co-operation and Development (OECD) countries – a group founded in 1961 to stimulate economic growth and global trade – made up 81% of global solar generation.
This shift follows the cost of solar falling more than 90% between 2010 and 2023, according to the International Renewable Energy Agency (IRENA). The low cost of the technology has been a key factor in deployment rising sharply worldwide.
It has also enabled new markets to emerge, with Saudi Arabia and Pakistan among the top importers of Chinese solar panels in 2024, according to a recent guest post on Carbon Brief.
In a statement, Phil MacDonald, Ember’s managing director said:
“Solar power has become the engine of the global energy transition. Paired with battery storage, solar is set to be an unstoppable force. As the fastest-growing and largest source of new electricity, it is critical in meeting the world’s ever-increasing demand for electricity.”
Wind generation also grew in 2024, although at a more moderate pace than solar power. Globally, an additional 182TW of wind capacity was added, or an increase of 7.9%.
Despite continued capacity additions, some geographies saw their lowest increase in wind generation in four years due to reduced wind speeds, notes Ember.
Hydro generation rebounded as drought conditions eased in 2023. This was particularly true in China, where capacity increased 130TWh, it adds.
Coal generation grew to 10,602TWh and gas generation to 6,788TWh, an increase of 149TWh and 104TWh, respectively.
However, due to the increases in renewable generation – despite coal and gas generation increasing in absolute terms – their share of generation has fallen.
Coal generation has dropped from 40.8% in 2007 to 34.4% in 2024, according to Ember. The share of gas generation has fallen for four consecutive years now since its peak in 2020 at 23.9%, with 22% of the world’s electricity generation from gas in 2024.
The increase in fossil-fuel generation was virtually identical in 2024 as it was in 2023, despite electricity demand growing (245TWh vs 246TWh, respectively).
Increased demand in short-term
Emissions in the power sector grew by 223mtCO2, despite the increase in renewables due to fossil fuels being relied on to meet increased demand, according to Ember.
Electricity demand increased by 4% over 2024 to meet 30,856TWh globally – crossing the 30,000TWh point for the first time ever. This is up from a 2.6% increase seen in 2023.
Fossil-fuel generation rose to meet the additional demand increase of 208TWh that was specifically driven by higher temperatures, according to Ember.
This dynamic was particularly pronounced in countries that experienced strong heatwaves.
For example, heatwaves in India led to the country experiencing its hottest day on record, with the western Rajasthan state’s Churu city hitting 50.5C on 28 May.
Coal-generation growth met 64% of India’s electricity demand growth in 2024, according to Ember, including that created by air conditioning.
However, this is still less than 91% of electricity demand growth in 2023, highlighting India’s continued transition away from coal, despite short-term trends.
On a global basis, if 2024 had the same temperatures as 2023, fossil generation would have increased by just 0.2%, Ember notes.
As it was, renewables met three-quarters of demand increases, with coal and gas meeting the majority of the rest.
Alongside heatwaves, emerging sectors such as data centres and electric vehicles (EVs), had a modest impact on increased electricity demand.
Demand from data centres and cryptocurrency mining increased by 20% in 2024, adding 0.4% to global electricity demand.
EV electricity demand increased by 38% in 2024, adding 0.2% to global electricity demand.
Despite increasing electricity demand, the growth of fossil fuels is still expected to be nearing the end.
According to Ember, assuming typical capacity factors, solar generation is expected to grow at an average rate of 21% per year between 2024 and 2030. Similarly, wind is expected to grow 13% per year.
Together with modest hydro and nuclear power growth, clean generation is expected to increase by an average of 9% per year to the end of the decade, adding 8,399TWh of annual generation by 2030.
This increase would be sufficient to keep pace with an increase in demand of 4.1% per year to 2030, exceeding the International Energy Agency’s (IEA) “stated policies scenario” scenario forecast of 3.3%, as shown in the chart below.
As such, over the next few years, while “changes in fossil generation in the short-term may be noisy, the direction and ultimate destination are unmistakable”, notes the Ember report, adding: “The global energy transition is no longer a question of if, but how fast.”
Many of the changes are expected to be partially determined by weather condition fluctuations from year to year.
Temperature effects impacted generation as well as demand. For example, if global weather conditions in 2024 had been in line with the five-year average, wind generation would have been 2TWh higher and hydro would have been 86TWh higher.
China and India
The world’s largest emerging economies are “on a path of clean electricity expansion that is set to reverse their power-sector fossil growth trends, tipping the global balance on fossil generation”, according to Ember.
China’s clean electricity additions met 81% of demand growth in 2024, due to record wind and solar capacity installations. This is the highest share since 2015 when the country saw its demand fall.
Its 623TWh increase in electricity demand was largely met by wind and solar, which collectively added 356TWh and a rebound in hydro generation which added 130TWh.
Fossil-fuel generation increased by 116TWh in 2024, a third of that seen in 2023, as shown in the chart below.
According to Ember, without the impact of hotter weather, clean generation would have met 97% of China’s rise in electricity demand in 2024.
The country’s renewables surge kept CO2 emissions below those for 2023 over the last 10 months of 2024, according to analysis for Carbon Brief.
Ember’s report suggests that India is likely to surpass China to become the country with the largest fossil-fuel generation growth in the coming years. Its fossil-fuel generation increase was the second-largest of any country in 2024 at 67TWh.
However, the cost of solar has fallen by 90% globally between 2010 and 2023. This has led to capacity increasing by 24 gigawatts of alternating current (GWac) in 2024 in India.
Currently, there are 143 gigawatts (GW) of wind and solar capacity under construction in the country, made up of 82GW of solar, 25GW of wind and 36GW of hybrid capacity.
Utility-scale projects already under construction as of January 2025 will nearly double India’s wind and solar capacity, notes Ember.
Elsewhere, wind and solar together generated 17% of the US’s electricity in 2024. The share of coal in the electricity mix fell below 15% – an all-time low – but gas generation rose, with the US accounting for more than half of the global gas generation increase in 2024.
Solar overtook coal generation in the EU for the first time in 2024 with the block seeing the largest fall in coal generation globally.
The post Power-sector CO2 hits ‘all-time high’ in 2024 despite record growth for clean energy appeared first on Carbon Brief.
Power-sector CO2 hits ‘all-time high’ in 2024 despite record growth for clean energy
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