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As global temperatures rise, vast swathes of the global population are experiencing heat extremes that they have never faced before.

In some parts of the world, exposure to extreme heat is breaching survival limits for even the healthiest people. Heat-related deaths have increased rapidly in recent decades.

But the risks of extreme heat are even more acute for certain groups of people. Those most vulnerable include newborns, infants and children, those with preexisting medical conditions, including certain disabilities, the over 65s and workers who work outside or in a high heat indoor setting.

Despite these risks, our new research – published in the International Journal of Biometeorology – shows that vulnerable groups are being overlooked in studies of heat stress.

For early warning systems to be effective during heat extremes, it is crucial that appropriate thresholds are established for those most at risk.

Heat stress metrics

Heat stress is the build-up of body heat generated either internally by muscle use or externally by the environment. Research shows that the risks and impacts of heat stress are rising as the global climate warms.

Certain groups are typically more vulnerable to heat stress either because they are more exposed to heat – such as outdoor workers – or they have a physical limit in their ability to thermoregulate – that is, cool their body down – such as the elderly and young children.

A key metric to quantify heat stress is “wet-bulb globe temperature”. It has a long history as an international standard – originally developed by the US navy in the 1950s to indicate safe heat levels for military training.

Wet-bulb globe temperature has three components:

  1. Wet-bulb temperature, a measure of temperature that takes humidity and wind into account.
  2. Globe temperature, a measure of heat stress from direct sunlight.
  3. Air temperature.

Together, these components indicate a likelihood of an individual experiencing heat stress when specific thresholds are met.

Vulnerable groups overlooked

In our paper, we assess 931 peer-reviewed studies that use wet-bulb globe temperature to investigate heat stress thresholds for different population groups.

We find that the body of literature on wet-bulb globe temperature has grown substantially since the first study was published in December 1957.

The charts below show how those studies are divided by decade and sex (left) and by age group (right).

The number of studies on heat vulnerability, displayed by sex and decade of publication (left) and age groups/categories (right)
The number of studies on heat vulnerability, displayed by sex and decade of publication (left) and age groups/categories (right). In the latter, groups are defined as many (mixed age groups), adult (25 to 55), young adult (18 to 25), child (1 to 12), adolescent (12 to 18), older adult (55 to 65), elderly (65+), neonatal: up to 1 month. Source: Brimicombe et al. (2024)

Of those 931 papers, 257 explored the differences due to sex and the majority focused on males (154).

This highlights a sex-related bias; however, this can somewhat be explained by the split in occupations where, traditionally, males end up in jobs that have clearer links to extreme heat exposure.

Only three of the 257 papers studied pregnant women and only one assessed other aspects of female health.

This is despite pregnant and postpartum women being a particularly vulnerable group. Experts in medicine, human thermal physiology and climate science have found a strong connection between extreme heat exposure and a range of negative birth outcomes, including preterm birth, low birth weight, cognitive deficits and even stillbirth.

Where the effects of age were considered (in 556 papers), most studies were conducted on adults (443) of 25-55 years of age and younger adults of 18-25 (48).

Very few studies focused on children, with five considering children of between one and five years old, just one focused on newborns up to 28 days old, and no studies of babies between one month and one year old.

For older adults, only three studies considered those 55-65 years old and four of those 65 and above. No studies placed an exclusive focus on elderly and/or older females, although women have a longer life expectancy than men.

Appropriate thresholds

In order to build a successful early warning system for extreme heat, it is necessary to identify appropriate thresholds for when people are at risk. Timely warnings can then help protect vulnerable groups by giving them time to take action.

In 2022, several UN agencies launched an “early warnings for all” initiative. This included a target to ensure that everyone in the world is protected by early warning systems for four types of extreme weather event – including heatwaves – by 2027.

However, there are many barriers to making sure that such a system is effective and properly supported by other policy measures.

One is that the wet-bulb globe temperature threshold proposed by the international standard organisation (specifically, ISO 7243:2017) only allows for different thresholds based on acclimatisation – that is, how much a person is used to their environment.

It takes a healthy individual around two weeks to acclimatise to a new thermal environment and those who are athletic often have a higher heat tolerance. (Although limits do exist, in a similar way to low oxygen at high altitudes.)

As we have described above, there has been a lot of research into appropriate thresholds for different groups of people. However, much of this understanding comes from studies on athletics.

In addition, as we have shown above, vulnerable groups are chronically underrepresented across these studies.

This is illustrated by the charts below, which show the heat thresholds estimated by the studies we have reviewed according to sex (top-left), age (top-right), clothing (bottom-left) and acclimatisation (bottom-right). Each dot represents a heat threshold estimate and the boxes and whiskers indicate the range across all the results.

The charts highlight how more research into thresholds is needed for vulnerable groups, particularly children, the elderly and older adults. For example, research in Europe has shown that elderly women are more likely to die during a heatwave.

The thresholds for heat stress used in studies on the outdoor wet-bulb globe temperature for different categories, namely threshold groups by a) sex, b) age, focusing on different age groups, with multiple age categories, defined by years of age.
The thresholds for heat stress used in studies on the outdoor wet-bulb globe temperature for different categories, namely threshold groups by a) sex, b) age, focusing on different age groups, with multiple age categories, defined by years of age – many (mixed age groups), adult (25 to 55), young adult (18 to 25), child (1 to 12), adolescent (12 to 18), older adult (55 to 65), elderly (65+), (c) type of clothing, and (d) level of acclimatisation. The box and whiskers show the range of heat warning thresholds considered by studies. (The maximum value considered by a study was 47.1 and the minimum value considered by a study was 12.6. The maximum threshold in the ISO is 33C). Source: Brimicombe et al. (2024)

When assessing the reception and response to extreme heat warnings, the perceived threat of danger is the strongest factor in why people do or do not heed them. This means it is even more important to fully understand which groups are most at risk.

By tailoring early warning systems to individuals needs and requirements, effective warnings can promote societal resilience by protecting the most exposed and vulnerable. And targeted heat thresholds are fundamental to this.

The post Guest post: Heat stress thresholds are not designed for vulnerable groups appeared first on Carbon Brief.

Guest post: Heat stress thresholds are not designed for vulnerable groups

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Germany election 2025: What the manifestos say on energy and climate change

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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.

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Guest post: How atmospheric rivers are bringing rain to West Antarctica 

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“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.

Amundsen sea, map.
A map of the Amundsen Sea embayment region in West Antarctica. Source: Produced by the British Antarctic Survey’s Mapping and Geographic Information Centre, 2025.

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.

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Colombia’s COP16 presidency in suspense as minister resigns

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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.

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)

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