Seventy three years ago Tenzing Norgay stood on top of Everest, known as Chomolungma in Tibetan, which roughly translates as "Goddess Mother of the World".

A new biopic of Norgay's life and that first ascent, along with Edmund Hillary, of the highest mountain in the world portrays beautifully, and with compassion, his humility, and intimate bond with nature and the mountains. In some ways, however, the most spectacular star of the film is the majestic and awe-inspiring mountain landscapes captured so beautifully by the sweeping cinematography.

I am a mountaineer and glaciologist by profession and have an affinity for wild, open and vertiginous landscapes. The film made me wonder what Tenzing would think if he could return to the mountain today. How have things changed in the intervening years and what does that mean for the future of mountaineering and Alpine climbing?

Everest Base Camp (EBC) is a very different scene now. Instead of a single, admittedly gargantuan, expedition each year, the Nepalese government now issues many permits and, at peak season, base camp is a sea of tents, people and too often rubbish left behind by climbers.

A group of mountaineers at Mount Everest base camp, pictured in 2018. Jonathan Bamber, CC BY-NC-ND

That's quite sad and a far cry from what the 1953 expedition would have experienced, but so are the conditions and health of the Khumbu glacier which provides access to EBC and the start of the real climbing.

A recent study used declassified spy-satellite imagery to compare loss of ice mass across the Himalayas between the 1970s and the 2000s. They found that the rate of loss had doubled in the period 2000-2016 compared to the early epoch. They estimated the rate of thinning at the altitude of EBC was about 0.8 metres per year. The glacier is around 150 metres thick in the region below base camp. At the rate of thinning observed a decade ago it would lose about a third of its volume in 73 years exposing more and more loose and unstable rock.

However, my own work, with colleagues indicates that the acceleration in mass loss across the Himalaya has continued since 2016 to reach even higher rates. Google Earth imagery over the Khumbu glacier from 2021 shows extensive development of lakes on the ice surface: a sure sign of a glacier in decline. The lakes absorb more solar radiation than the surrounding ice and accelerate melt. There are, of course, no satellite images from 1953 but plenty of analogue photographs were taken and the changes are clear to see: now it's more chaotic, more broken and more covered in debris.

The cause of the recent catastrophic flood event close to the Nepal/Tibet border has been linked to increasing regional temperatures, weakening permafrost (frozen ground that thaws with warming) and greater glacier melt rates.

In the European Alps the situation feels even more dire. In just two years from 2022-2023 glaciers in the Swiss Alps lost 10% of their volume. If that rate was sustained, they would be gone in 20 years time.

This year, mountain huts closed and guides stopped taking clients up the "normal" routes on the Matterhorn and Mont Blanc because it was too dangerous due to the high temperatures and the consequent increased rockfall.

Many other routes were being avoided because of the dangerous rockfall conditions. The first six months of 2026 were the third warmest on record and it is no wonder that glaciers, and the frozen world is responding to this level global heating .

In August 1990 I climbed perhaps the most iconic and well known route in the Alps: the north face of the Eiger. The photo below shows me on a section called the second icefield, a crucial part of the original 1938 route that gains you access to the upper face and the ominously named Death Bivouc. The icefield no longer exists, and no one who wants a relatively safe passage climbs the route in summer. The recommended climbing season now is late winter or early spring to avoid the rotten rock and dangerous conditions that summer brings. Thus, in my short mountaineering career, I have seen unprecedented changes on famous Alpine routes and a transforming landscape in the high mountains.

The author on the second icefield, Eiger north face, in August 1990. Jonathan Bamber, CC BY-NC-ND

What does this mean for the future of mountaineering and glaciers? Based on current climate policies, the European Alps, western Canada and the US, Scandinavia and other regions are expected to lose about 90-100% of their mass by 2100.

That's just 74 years away, roughly the time between that first ascent of Everest and now. It will have a dramatic impact on the mountain landscape, ecosystems, tourism, beauty and natural hazard exposure of these, once pristine, mountain environments.

EBC has not been beautiful or pristine for many years, perhaps less because of global heating and more to do with the reckless attitude of some of the expeditions that visit. I wonder what Tenzing would have made of the changes to both the landscape and attitudes that have occurred since his historic and heroic first ascent of Everest, the sacred "Goddess Mother of the World"?

Jonathan Bamber receives funding from the EC, the European Space Agency and Technical University Munich.

The potential collapse of Greenland's ice sheet is the most studied tipping point - by far. Goldilock Project / Shutterstock

Parts of the Earth's climate system can change abruptly once warming pushes them beyond critical thresholds. The Greenland and Antarctic ice sheets, the Amazon rainforest, coral reefs and major ocean currents are all among the systems containing potential climate tipping points.

These climate systems are known as tipping elements, and research into them has expanded rapidly. But it has not expanded evenly.

In a new study published in Proceedings of the National Academy of Sciences, colleagues and I examined 20,736 scientific publications on 14 climate tipping elements published between 2000 and 2025. We wanted to know where scientific attention has accumulated, and whether the systems with relatively low estimated warming thresholds tend to receive more of it.

An uneven research landscape

The Greenland Ice Sheet dominates the studies we analysed. It appeared in 4,141 publications - 20% of the entire dataset.

By contrast, abrupt thaw of permafrost in boreal forests just below the Arctic appeared in just 139 papers, or 0.7%. The North Atlantic subpolar gyre, a system of ocean circulation south of Greenland, accounted for 649 papers, or 3.1%. Other potential tipping elements, including Barents Sea winter ice and the East Antarctic subglacial basins, also had comparatively little research.

Denali National Park, Alaska. Permafrost in places like this could suddenly thaw. Ralf Broskvar / shutterstock

Unequal publication numbers are not, by themselves, surprising. Some parts of the climate system have been observed for longer, are easier to measure or model, or sit within larger and better-established scientific fields.

The more revealing comparison is with estimated warming thresholds.

In our study, we compared research attention with published estimates of the level of global warming at which each system might tip. Abrupt boreal permafrost thaw, for example, has a best-estimate threshold of about 1.5°C above pre-industrial temperatures. The estimate for the North Atlantic subpolar gyre is around 1.8°C. Greenland's is also around 1.5°C.

Yet we found no systematic tendency for tipping elements with lower estimated thresholds (that is, elements presumed to tip earlier) to attract more scientific attention. Some receive thousands of studies; others, with similarly low estimated thresholds, receive hundreds or fewer.

This result needs some care.

A warming threshold is not a timer counting down to a known date. Estimates come with substantial uncertainty, and scientists continue to debate the behaviour of several potential tipping elements. Nor does the number of publications tell us how strong the evidence for a particular tipping point is.

Our analysis measures scientific attention. It does not measure scientific certainty, the quality of individual studies or the importance of one tipping element relative to another.

There are also overlaps between research areas. The North Atlantic Subpolar Gyre, for instance, is closely connected with the Atlantic Meridional Overturning Circulation, or Amoc. Some relevant research may therefore appear in the much larger Amoc studies without treating the gyre as a separate tipping element.

We also looked beyond which systems scientists study to what they study about them.

What makes a tipping point unusual is not simply that a system changes. The change may happen abruptly. It may reinforce itself. The system may settle into a different state, or fail to return to its previous one even if the original pressure is reduced.

We therefore looked for studies that gave explicit attention to these kinds of tipping dynamics - abrupt change, self-perpetuation, persistence and irreversibility.

Only 8.1% of the publications we analysed explicitly examined one or more of these risk-relevant characteristics.

The gaps were particularly striking for some individual systems. Across 26 years of research, we identified just 22 peer reviewed scientific studies examining such dynamics in abrupt boreal permafrost thaw, low-latitude coral reefs and a mere 53 on the North Atlantic Subpolar Gyre.

Filling the gaps

None of this suggests that scientists studying Greenland or the Amoc should redirect their research elsewhere. There are good reasons why particular fields develop large research communities, with scientists able to monitor the real world and model it with computers.

But research priorities are also shaped collectively - by funding programmes, scientific institutions and decisions about where new monitoring and modelling capacity should be built.

For tipping elements with relatively low estimated warming thresholds but comparatively little research, additional studies may help establish what is known, what remains uncertain and which uncertainties are most consequential. The same applies to the processes that make tipping different from gradual environmental change: whether transitions can become abrupt, self-perpetuating or irreversible.

As global warming continues, decision-makers should ask a straightforward question: which potentially consequential climate risks remain difficult to assess because comparatively little scientific attention has reached them?

Finding those gaps before the climate system tests them for us would be a useful place to start.

Asaf Tzachor does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Videnskab.dk/Lærke Slot

Traffic, trains, nightlife - in cities everywhere, there is a near constant background hum that most people simply get used to.

But research shows that this background noise can affect your sleep, stress levels and even increase your risk of heart disease and high blood pressure.

Indeed, noise is now considered the second biggest environmental health risk in Europe after air pollution. Around one in five people living in European cities are exposed to harmful levels of environmental noise.

I study how sound shapes cities, including how environmental noise affects health and everyday life. This makes Denmark and England an interesting comparison because, despite facing similar challenges, each country has made different choices about how much noise is accepted as part of urban life.

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Health Gap / Sundhedskløften is a collaborative series from The Conversation UK and Denmark's Videnskab.dk exploring what the two countries can learn from each other when it comes to health and wellbeing.

From cycling and alcohol to inequality, healthcare and everyday habits, the series looks beyond hospitals and medical treatment to explore how culture, politics and society shape the way people live - and how healthy they are.

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Take both capital cities, for example. At roughly 13 times the size of Copenhagen, London is a much busier and louder city, so you might expect it to have a much bigger noise problem. But the reality is more nuanced.

As the largest cities in their respective countries, both London and Copenhagen experience substantial noise from busy roads, railways and airports.

But while from the outside, Copenhagen can look like a quieter city characterised by cycling and low-rise neighbourhoods, it would be wrong to romanticise it as quiet.

Around 16% of the population in Denmark is exposed to transport noise above recommended thresholds. Vladimira Pufflerova/Shutterstock

Indeed, across Denmark, the Danish Environmental Protection Agency has found that almost one in three homes are exposed to road traffic noise above the national guideline of 58 decibels (dB).

A noise level of 58dB is roughly comparable to a normal conversation or the background noise in a quiet office. While it's not loud enough to damage hearing, long-term exposure, especially in the home, can disturb sleep and increase the risk of certain health problems, which is why it's used as a planning guideline.

Overall, around 16% of the population in Denmark - roughly 918,000 people - are exposed to transport noise above recommended levels, most of it from road traffic.

England uses a different threshold, making direct comparisons difficult. Even so, around 40% of adults in England are exposed to long-term road traffic noise of above 50 decibels.

Managing noise

The biggest difference between Denmark and England, however, is not simply how noisy cities are, but how it's decided what level of noise is acceptable.

Denmark treats noise as both a planning issue and a public health concern, with responsibility shared across government and society. Noise limits are used to decide where homes can be built.

In England, there is no equivalent national threshold that acts as a cut-off for further development. Instead, planning decisions are made on a case-by-case basis, balancing noise against housing need and economic growth.

Noise is now considered the second biggest environmental health risk in Europe after air pollution. starlings_images/shutterstock

This approach gives local authorities more flexibility, but can also mean people end up living in areas that would be considered too noisy under Danish guidelines.

And it means that whether people can sleep with their windows open, whether children have quiet places to play, or whether green spaces actually feel restorative, can vary a lot area to area.

Can cities ever be quiet?

Both Denmark and England map traffic noise and identify the worst-affected neighbourhoods.

Denmark's approach, however, places greater emphasis on reducing exposure through measures such as lower speed limits, noise barriers and better insulation. While England gives local planners more flexibility to balance noise against competing priorities like housing and economic growth.

But should noise really be treated just as an unavoidable consequence of modern cities, or more as a public health risk that can be designed around?

Most urban noise comes from traffic and transport. Marcus E Jones/Shutterstock

Indeed, as the comparison between England and Denmark shows, urban noise is not simply an unavoidable feature of modern life. City planners can choose how they design streets, buildings and neighbourhoods around sound.

As populations grow and cities become denser, such choice will become increasingly important. The question then is not whether cities will be noisy - they will - but how much noise people should be expected to have to live with.

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This series was commissioned as part of a partnership between Videnskab.dk and The Conversation, where articles are published in English and Danish.

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Francesco Aletta does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

AP Tolang / Shutterstock

On August 26, a rock and ice avalanche triggered a huge flood that swept through a steep valley in Nepal, leaving thousands dead and missing. It was an extreme example of a growing problem across the Himalayas. As glaciers melt, glacial lakes expand, and mountain permafrost thaws, the risks from floods, landslides and other high-mountain hazards are increasing. At the same time, more people and infrastructure are moving into the valleys where these hazards are most likely to strike.

Our new study shows how quickly this exposure is growing. We focused on Nepal, and the catchment areas of rivers that drain into Nepal. In that region, between 2016 and 2023, the built-up areas potentially exposed to flooding increased by 46%. Across the Nepalese Himalayas, we estimate almost 300,000 people live in these flood-prone areas, including more than 100,000 downstream of glacial lakes.

Those lakes, formed in depressions carved out by retreating glaciers, are a particular risk because they can suddenly breach, sending flood waters crashing down steep valleys. So far, scientists have largely focused on what's causing these hazards: the melting glaciers, landslides, torrential monsoon rains and so on. Far less attention has been paid to exposure: the people, buildings, and infrastructure potentially at risk.

Our results reveal a concerning trend of continued urbanisation in areas susceptible to flooding. This is partly due to the geography. In the Himalayas, valley floors are some of the only flat and accessible places to build roads, settlements and other infrastructure. Rivers also provide natural routes through the mountains - the recent disaster struck Nepal's primary trade route to China running along the Bhotekoshi-Trishuli rivers, for instance.

Humans are expanding further into the Himalayas. Rei Imagine / shutterstock

Yet as trade and tourism grow, these corridors attract new roads, tracks, lodges, hydropower projects and more. And once a road connects a valley, other development often follows, including homes, schools and healthcare facilities.

But these same valleys are also the natural pathways for floods, debris flows and landslides.

Measuring flood exposure

We measured exposure to potential flooding using a metric called "height above nearest drainage", or Hand, which estimates how high a building sits above the nearest river channel. In steep mountain valleys, two locations may be only a short distance apart horizontally, but separated by tens of metres vertically, resulting in very different flood exposure.

In a flood like this one in Kathmandu Valley in 2024, some parts of town can be entirely destroyed, while slightly higher streets and buildings are left untouched. Pratisha Manandhar / shutterstock

This makes it particularly difficult to produce flood hazard models in steep Himalayan valleys, which often lack detailed topographic data. Height above nearest drainage does not replace the critical need for this detailed flood hazard mapping, but offers a simple screening metric to identify exposure hotspots. We combined it with satellite-derived building data to track changes in flood exposure between 2016 and 2023.

Preparing for the future

Our study does not suggest that floods are inevitable everywhere or that all development near rivers should stop. Exposure to the flood waters themselves is only one component of risk, and other factors such as building type, early warning systems, preparedness and evacuation planning all influence whether a hazardous event becomes a disaster. Nonetheless, our findings reveal a clear trend, that exposure to potential flooding is rising and that development decisions being made today will shape disaster risk for the coming decades.

Climate change is making some Himalayan hazards more dangerous. But disaster risk is also being shaped by where people live and work. Identifying the places where exposure is already high, and incorporating that information into land and infrastructure planning, could help prevent today's new developments turning into disaster zones of the future.

C. Scott Watson receives funding from a UKRI Future Leaders Fellowship (grant number MR/Y016564/1).

Milan Shrestha received funding from the National Science Foundation of the USA (CNH Grant # 1516912 between 2015-2019) to study a research project "Science-Driven, Community-Based Approach to Reducing Glacier Lake Outburst Flood Risks in Nepal"

fogcatcher / shutterstock

Wildlife populations around the world have declined by an average of 73% since 1970. That's according to the WWF's new 2026 Living Planet Index - a major estimate, updated every two years, of the changing state of nature. This does not mean that 73% of the world's animals have disappeared. Rather, it is the average decline in the size of wildlife populations that is being monitored.

The index is one of the metrics used to track progress towards the UN's biodiversity goals and shapes narratives of biodiversity loss across the world. But the data behind that 73% headline, one of the most comprehensive available, is still far from complete.

Very few, outside of those of us working at the coalface of handling biodiversity data, understand just how poorly wild animal populations are monitored. Though the world faces the joint crises of climate change and biodiversity loss, we can track climate change through thousands of weather stations or measures of atmospheric CO₂. Biodiversity is far harder to measure. Counting wildlife is highly resource intensive, generally can't be done from space, and systematic monitoring is extremely patchy.

What this means is that, relative to the data we do possess, there are far, far more wildlife populations that no one is counting.

Though initiatives are seeking to address this, it will be years before they will produce outcomes. And we still have the issue of historic data gaps, that is, we cannot travel back in time to count populations of the past. This means the Living Planet Index and similar efforts to track how wildlife is changing must rely on whatever data is available. These come from ad hoc academic studies, patchy monitoring programmes, and management data for harvested species.

Some critiques of the index have focused on the fact that when these records are taken at face value, roughly the same number of populations are increasing as decreasing. Similar patterns are observed in one of the other biggest collections of population change data, BioTIME.

So why does the Living Planet Index show such a strong overall decline? One reason is that the populations we have data for are not necessarily representative of wildlife populations as a whole.

The wildlife we count is not a random sample

For example, the Living Planet Index is biased towards counts from protected areas, and preliminary analysis from our team indicates both it and BioTIME contain a disproportionate number of counts in areas of mostly undisturbed habitat - such as remote wilderness or national parks.

A stork-billed kingfisher in Tanjung Puting National Park, Indonesia. Hari Gopalakrishnen / shutterstock

In other words, most of the information we possess about wildlife change worldwide could be from areas where we would hope biodiversity is doing okay. This might explain the balance of declining and increasing populations in the raw data. If we don't account for this, we risk making major underestimates of how much biodiversity is declining.

Though there do tend to be "winners" from habitat loss or change, such as farmland birds that thrive after a forest is converted to agriculture, many instances of habitat loss result in far more populations declining than increasing, like conversions of tropical forest to monoculture plantations, or grasslands to towns or cities.

But the bias could also work in the other direction. The Living Planet Index might be more likely to have data on threatened species, or on species harvested by humans (such as fish). These are all species we might expect to be declining. The truth is, we don't fully understand all the ways in which the wildlife counts we have could be biased, or how this could affect what we know.

How scientists are trying to fill the gaps

The Living Planet Index takes steps to address bias by giving greater importance to counts from under-sampled regions such as Africa and South America.

There, the loss of undisturbed habitat is greater and there are far more species, so giving their population counts greater relative importance is a coarse way to balance some bias. It also includes data collected over very short periods - sometimes just two time points.

This sparseness comes with uncertainty about population trends, but excluding these populations would leave the index with even less data and make its underlying biases worse.

More sophisticated methods to understand bias in biodiversity science are in their infancy, and scientists are working hard to develop tools and make indicators more accurate. In the meantime, anyone interpreting the Living Planet Index must remember that the task presented to teams developing biodiversity indicators is twofold: not only to analyse existing data in rigorous ways but also to make adjustments so that the data itself is as representative as possible of the real world.

Getting this right is a phenomenally difficult task, especially for global indicators like the Living Planet Index, which have to produce a single narrative that summarises the great diversity of wildlife changes happening across the planet. As new methods emerge, scientists will work to ensure that the story told of global biodiversity loss is as accurate as possible.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

Vinokurov Yury/Shutterstock

The timing of a hospital appointment does more than tell you when to see a doctor. It can also shape how you get there. For some older patients, an early appointment can fall before their concessionary bus pass, which provides free bus travel, becomes valid. An unreliable bus service can mean having to leave much earlier than necessary. And an appointment at a specialist hospital rather than the one closest to home can turn a straightforward journey into one that involves several connections.

For someone who is already unwell, these are not minor inconveniences. A short appointment can involve hours of travelling and waiting, followed by the challenge of getting home again.

Research shows that transport can affect access to healthcare. A 2024 review of research into repeated missed appointments found that transport problems, distance and access to services were among the reasons people struggled to attend. It also highlighted the value of more flexible, patient-centred appointment systems.

There are implications for the climate too. Patient and visitor journeys account for more than 40% of transport emissions from England's NHS. The most recent figures from the Department for Transport's now-discontinued journey-time statistics, which cover 2019, show that around two-thirds of households in England could not reach their nearest hospital within 30 minutes by public transport or walking.

More recent research illustrates how healthcare itself generates substantial travel. A 2025 study of 6,599 NHS patients in Greater Glasgow found that annual hospital travel varied considerably according to health condition and peaked around the year of diagnosis. Among the conditions examined, people with cancer travelled the furthest.

It is tempting to treat this as a question of persuading patients to drive less. But decisions about when and where healthcare is provided can make public transport practical or make travelling by car or taxi almost unavoidable.

Our research in Southampton and the Isle of Wight shows how some of these difficulties play out locally. The Community responsive digital twins for inequality alleviation and low-carbon mobility (Cordial) project explored connections between access to healthcare, transport disadvantage and carbon emissions. The Extreme temperature and health outcomes (Ethos) project examines how extreme heat and cold affect people who may be particularly vulnerable, including those living with several long-term health conditions.

Across this work, members of the public contributed their experiences of travelling to healthcare. Many were living with long-term conditions and regularly attending appointments. They described indirect and unreliable buses, long walks to bus stops and journeys involving several connections. Others spoke about the cost of repeated hospital visits when household budgets were already tight.

These experiences echo findings elsewhere. A study of cancer patients in north-east Scotland found that travelling for treatment could take up much of a day and create extra financial and physical strain. Some participants described fuel costs becoming difficult to manage, while others said transport problems affected when they sought help.

Repeated tests, treatment and follow-up appointments can make these difficulties particularly burdensome. Timing can make them harder still. Some contributors to our work said early appointments meant travelling before their concessionary passes became valid, so they had to pay for journeys that would otherwise have been free. Others caught an earlier bus to allow for delays. One person described spending around an hour travelling to hospital despite living in the same city. Another allowed as much as two hours to be confident of arriving on time.

Making healthcare travel greener also means making public transport practical and accessible for patients with different mobility needs. Pixe1Power/Shutterstock

Bus stops that are far away or provide little shelter or shade can add further difficulties during periods of extreme heat or cold. A 2026 review of research found that people who are more vulnerable to extreme temperatures can face practical difficulties protecting themselves, showing why the design of environments and services also needs to be considered.

Getting home can be harder

The journey home may create different problems. People attending chemotherapy, blood tests, eye procedures and other appointments in our work described feeling tired or light-headed afterwards. One contributor said they would prefer to cycle because it was quicker but used the bus because they were worried about becoming light-headed on the journey home. People undergoing cancer treatment also raised concerns about crowded public transport while their immune systems were weakened.

Reducing healthcare travel emissions cannot depend principally on patients choosing a lower-carbon form of transport. Changes to healthcare itself can reduce the number or difficulty of journeys.

Remote consultations are one example. A review of 48 studies covering more than 68 million consultations found substantial reductions in travel and related carbon emissions when remote consultations replaced in-person appointments. However, many of the studies focused mainly on emissions saved through avoided travel rather than the full environmental impact of providing care remotely.

Where clinically appropriate, several appointments could also be coordinated for the same day. Appointment times could take account of local public transport and concessionary travel arrangements. Providing some services closer to patients could shorten journeys.

Transport support can help too. A review of research found that measures such as bus and taxi vouchers, shared transport and dedicated van services were linked with fewer missed appointments, although there was less evidence about whether they reduced costs or improved health.

Volunteer-led car services can provide another option for people who cannot readily use public transport. Contributors to our research noted that some were unavailable at weekends and bank holidays, could not accommodate wheelchair users and relied on an ageing pool of volunteers.

Reducing emissions from healthcare travel does not simply depend on persuading more patients to catch the bus. By considering where and when care is provided, and whether every appointment needs to happen in person, healthcare providers can reduce unnecessary travel while ensuring that patients still have workable ways of reaching care.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.