In a second step, we project the exposure of European transport infrastructure to several climate extremes. The exposure analysis builds on a dataset of multiple hazards derived from the Inter-Sectoral Impact Model Intercomparison Project Phase 2b (ISIMIP2b) simulations. ISIMIP provides a set of consistent, global-scale, multi-sector climate change impact simulations, based on historical conditions and selected future scenarios. ISIMIP provides future projections at a global scale, at a spatial resolution of 0.5°×0.5° (approximately 55 km ×55 km at the equator) of variables of different impact sectors. analyzed an ensemble of climate and impact model simulations from ISIMIP project to quantify the change in frequency of droughts, heatwaves, river floods and wildfires under varying levels of future global warming. To this end, they developed a coherent dataset of yearly occurrence of these climate extremes considering historical and future climate conditions (1861–2099) following RCPs 2.6, 6.0, and 8.5. The climate extremes are obtained by forcing hydrological, vegetation, and heatwave, models with meteorological information generated by four Global Climate Models (GCMs; IPSL-CM5A-LR, HadGEM2-ES, MIROC5, and GFDL-ESM2M). Each GCM underwent trend-preserving bias adjustment against a reanalysis product . The definition of each extreme event is reported in Table . The employed extreme events definitions are commonly used in the scientific community and already used in analyses across multiple hazards e.g., . For heatwaves and droughts, the data is expressed as the occurrence or not for each year and each grid cell. For river floods and wildfires, the data is presented as the percentage of the grid cell exposed to the climate extreme.

We quantify the exposure of European transport infrastructure considering two future time horizons: 2024–2075 (hereafter referred to as the mid-century) and 2070–2099 (hereafter referred to as the end-of-century). The dataset provided by Lange et al. (2020) for heatwaves, river floods, wildfires, and droughts is clipped in the European bounding box, with coordinates: longitude min/max [35° W, 40° E] and latitude min/max [25° N, 72° N]. Heatwaves and droughts are recorded as affecting entire grid cells, while wildfires and floods are expressed as the fraction of grid cell area exposed. To ensure consistency, for these latter hazards we convert the fractional values into binary data using a threshold: grid cells are classified as affected when more than 3 % of their area is exposed. This relatively low threshold was selected based on a sensitivity analysis to ensure that enough events remain available for extracting spatial statistics across Europe. We tested several thresholds ranging from 1 % to 5 % of the cell area affected. Using the 5 % threshold, most flood events were not captured in the spatial statistics. At the 1 % threshold, however, exposure to hazards such as wildfires was overestimated, with large portions of the network appearing to be affected in nearly every case. The 3 % threshold provided a balance, capturing localized events like river floods without inflating exposure from more widespread hazards. It accounts for the highly localized nature of these hazards and avoids the exclusion of a substantial number of impactful events.

The three scenarios used in the analysis, RCP2.6, RCP6.0, RCP8.5, represent possible futures with varying degrees of climate action. RCP8.5 represents the most extreme, worst-case scenario with a roll-back of existing policies and a continued, strong growth in the use of fossil fuels. RCP2.6 represents a scenario with strongly enhanced ambition in terms of climate change mitigation compared to current policies. RCP6.0 is a scenario with a range of temperature outcomes that encompass the expected temperature range under current climate policies (which currently have a best-estimate outcome of around 3 °C by 2100) . In the main text, the results are presented for RCP6.0. Results for RCP2.6 and RCP8.5 are reported in the Appendix , and the comparisons with RCP6.0 projections are discussed in Sect. .

To analyse the exposure data, we use the Exposure Multiplication Factor (EMF), which describes the ratio of the number of future climate extremes across two time periods to the number of historical climate extremes. The EMF was proposed by and is defined as: 1EMF=EfutEhis The future exposure, Efut, is defined as the number of events occurring in mid-century (2040–2069) or end-of-century (2070–2099) future scenarios, respectively, while the historical exposure, Ehis, represents the number of events in the historical period (1980–2009). This metric provides a clear visualization of the regions of the network projected to experience an increase in extreme events compared to the historical period. It is conceptually related to the probability ratio metric widely used in attribution studies e.g.,, where the probability ratio is defined as the ratio of event probabilities, constrained within the range [0, 1]. However, the EMF differs in that since it is based on the ratio of event counts rather than probabilities. It explicitly incorporates exposure alongside hazard, advancing toward a more comprehensive risk definition . The use of the event count ratio as a metric makes it less dependent on the specific definitions of extreme events, which are often tied to return periods or other statistical thresholds (see Table ). This reduced dependence enables the analysis of different extreme events in a single unified framework, leading to a comprehensive analysis across multiple hazards. Its simplicity is particularly valuable, making it a powerful tool for communicating scientific findings to policymakers and stakeholders in an accessible manner.

The EMF is calculated per hazard at the grid scale for each individual combination of emissions scenario, climate model, and impact model, after which the median value across each climate – impact model pair is computed per location and scenario. We consider a 30 years time windows, which provides a sufficiently large sample to account for the fact that the event counts are rare events. We use the multi-model ensemble median EMF as the primary indicator in our analysis to represent, for each pixel, the increase in exposure on which at least half of the climate-impact model simulations agreed. This is useful since there are some pixels for which zero extreme events occur in the historical period but a non-zero number in the future, so the EMF becomes infinite. Using the median as the metric for aggregating across simulations, the multi-model ensemble median EMF will be infinite if at least half of the simulations result in an infinite EMF. The count of pixels where the EMF tends to infinity is referred to as the “area newly exposed to extremes”, since EMF can also become infinite when changing from 0 to 1 extreme event. This metric describes the percentage of the network that was not exposed in the historical period but is projected to become exposed in the future. EMF statistics are provided for the historically exposed area of the network, where finite values of the multi-model ensemble median EMF are obtained.

The shapefile of the revised TEN-T network (see Sect. ) is superimposed on the 0.5×0.5° grid dataset to extract the exposure for each node and line of the vector network and for each extreme event. We consider the same extent of the TEN-T network for the historical period as for the future scenarios. From this, we extract the percentage of transport network for each mode that is exposed to a climate extreme. Each event is assumed to affect all transport modes within a grid cell, even though the exact location of the event within the cell is unknown. This assumption is reasonable if we consider the affected area as experiencing direct and indirect impacts, which extend to neighbouring elements. For example, a flood affecting a single road can cause disruptions, operational issues, or even a complete halt in circulation across the interconnected transport network within a grid cell.

Storms, windstorms, floods (pluvial, river and coastal), heatwaves and wildfires are climate extremes that affect European airport infrastructure the most . Their increasing impact on European airports is emerging as a growing problem in recent years (Table ). These events can cause both physical damage and operational disruptions. Examples of physical impacts include runway cracking, flooding, and melting, while operational issues can range from flight delays and suspensions to full airport closures . Additionally, these disruptions often lead to longer waiting times for passengers, an increase in refund requests, and the activation of emergency rescue services.

High temperatures, heatwaves, and wildfires are creating unprecedented challenges for airport infrastructure. Issues like melting runway pavement, cracking, and the deformation and melting of airport signage are emerging as problems that were not faced in the past . For example, in July 2023 subsequent wildfires hit Sicily, Dubrovnik, Rhodes, Gran Canaria, Lisbon and Cascais in Portugal . In Sicily, 55 separate wildfires broke out hitting Palermo and Catania airports . These wildfires caused direct airport infrastructure damage but also broader implications as the Palermo Borsellino airport closure, flight diversions generating impacts on tourism, and local economy, (see case study in Table  in Appendix ). Airport taxiways and runways built on expansive soils can be affected by prolonged drought, requiring soil stabilization methods to mitigate these issues. Although evidence from Europe is currently lacking, such impacts have been documented in the U.S. and should be taken into account for European airports built under similar conditions .

Flooding is also leading to increasing problems and economic losses due to physical damage, as well as the suspension and cancellation of airport operations . Over the past three years, the frequency of such events has risen, affecting both inland airports through river floods, and coastal airports due to the growing risk of coastal flooding. Sea level rise and associated coastal flooding present an especially significant threat to aviation. In the report “Climate Change Risks for European Aviation” the economic impact of a one-day closure due to full flooding is estimated at approximately EUR 3 million for medium-sized airports and EUR 18 million for large airports. For partial or short-term closures, these costs drop slightly to around EUR 2 million and EUR 15 million, respectively . However, actual financial losses can vary considerably depending on factors like the proximity of alternative airports and the extent of damage. Coastal flooding is receiving increasing attention due to the exposure of airports to the risks associated with sea level rise .

Air Traffic Flow Management (ATFM) involves regulating air traffic to prevent exceeding the capacity of airports or air traffic control systems. Storms are historically responsible for up to 7.5 % of total en route ATFM delays at the network level. In 2019 alone, storms caused an estimated EUR 2.2 billion in en route delays for the aviation industry. The bulk of these costs originated from en route ATFM delays (61.6 %), followed by the cost of lost passenger time (28.8 %) . On average, each flight affected by a storm experienced an en route ATFM delay of 17 to 18 min. Attempts to avoid severe storms often result in longer flight distances. For instance, in 2019, over 1 million additional kilometers were flown in efforts to circumvent major storms .

Port disruptions due to climate extremes can be multifaced, leading to a decrease in the volume of goods processed for a period of time, delays, goods depreciation, and, if cargo is rerouted, increased transportation costs . River floods, flash floods and high temperature can be particularly damaging to river ports, while seaports are also more exposed to high winds and coastal flooding . The impacts also extend to maritime operations, posing risks to infrastructure, cargo, and personnel .

High winds create problems in seaport navigation and bething, endanger crane operators, destabilize containers, and reduce vessel maneuverability, increasing the likelihood of accidents in ports and at sea (; ; ). Extreme high temperatures damage infrastructure, equipment, and cargo, may limit operations, cause pavement and track damages leading to asset lifetime reduction, and also increases in the staff health risk . They threaten perishable cargo by accelerating spoilage and increasing condensation inside shipping containers . Drought impacts ship and port operations by reducing water levels, causing severe disruption to supply chains (Table ). Flooding from intensifying heavy rainfall, as well as other associated extreme events (e.g. landslides), increase the disruptions and delays in rail and road transportation, affecting also connections/access to seaports . Additionally, storms can generate high waves causing structural damage, cargo loss, and navigation hazards, and the rain can create visibility issues, impacting cargo transfer and worker safety . Maritime ports are located in vulnerable areas to climate change impacts: on coasts exposed to storms and sea-level rise or at river estuaries susceptible to flooding .

assessed the risk to global port infrastructure at the asset level, considering multiple hazards. Their risk framework includes both operational disruptions to ports (that do not cause damages), which typically occur due to extreme wind, temperature, wave heights and overtopping, as well as the physical damages to port infrastructure as a result of natural hazards from earthquakes, river flooding, pluvial flooding and coastal flooding. They quantified the potential impacts on both physical asset damage and the disruption of logistical services (i.e., port-specific risks), as well as the risk posed to maritime trade flows (i.e., trade-related risks). Port-specific risk is defined as the sum of three type of impacts affecting the actors who own, operate and use ports: (i) the physical damages to port infrastructure such as terminals, cranes and industrial facilities, (ii) the physical damages to critical infrastructure in the surrounding area (electricity, road, rail and power plants) on which the port relies and (iii) additional logistical losses incurred by port operators, carriers, and shippers due to downtime that exceeds operational limits or during asset reconstruction . Logistics losses are significant for ports that handle large quantities of cargo, especially those exposed to maritime extremes. Even without major damage to infrastructure, these high-traffic ports can face severe disruptions if forced to shut down.

Of the 1340 ports analyzed, 94.8 % are exposed to more than one natural hazard, with 50 % facing the impact of four to five hazards . Ports located in Northern and Eastern Europe are exposed to one or two hazards, whereas ports located in Western Europe – for instance, along the Spanish coast and the North-West region of France – are exposed to multiple hazards such as pluvial flooding, river flooding, cyclones, and coastal flooding (Table ). This suggests that the vast majority of maritime ports need to consider multiple hazards in the design and operations of infrastructure .

Fluvial (22.6 %) and coastal flood (23.7 %) are the leading hazards for Western and Northern Europe . The spatial footprints of port-specific risks contributed by flooding depend on the location of rivers and occurrence of extreme coastal water levels. Furthermore, the local presence or absence of flood protection standards and the freeboard of the terminals also contribute. The high exposure of ports in northwestern Europe to coastal flooding aligns with the findings of , who also identified this region as being highly vulnerable to current extreme water levels.

The three different risk factors (port infrastructure damages, critical infrastructure damages, and logistics losses) contribute to port-specific risk to varying extents. Globally, physical damages to port infrastructure account for 58.6 % of port-specific risk, followed by logistics losses (22.2 %) and critical infrastructure damages (19.2 %) . Damage to port infrastructure also emerges as the primary driver of port-specific risk across most ports in Europe. However, impacts on critical infrastructure are highly relevant as well, since flood-related disruptions to surrounding networks can hinder port functionality. Critical infrastructures are often more exposed to fluvial and coastal flooding, given that port terminals are typically built at higher elevations. Therefore, managing flood risks to critical infrastructure near ports should be a key component of overall risk management and the development of adaptive strategies, as emphasized in prior research .

Inland waterways (IWWs) in Europe are a network of almost 40 000 km of navigable waterways with the majority of these concentrated around relatively few river systems – for instance the Rhine, the Danube, the Elbe, the Rhone, the Seine, and the Po . Over the past four decades, IWWs have seen a substantial growth in traffic and tonnage in Europe, becoming a reliable mode for transporting various goods, including raw materials . IWWs are vulnerable to climate change as river navigation depends on water levels.

The droughts of 2018 and 2022 illustrate the significant consequences that low water level extremes can have on transport navigation . In 2018, Europe experienced an extended period of high-pressure systems, causing extreme temperatures across the continent. Germany, in particular, saw a devastating combination of extremely high temperatures and minimal precipitation, amplifying the damage to its transport infrastructure . This event, unprecedented in both heat and dryness, caused major disruptions, especially to river shipping . On the Rhine River, ships could only travel partially loaded due to the low water levels, resulting in interruptions in the logistics chain and an economic loss of EUR 2.7 billion in Germany and the Netherlands (Table  in Appendix ). In 2022, Europe once again experienced a similar drought and its consequences due to low water levels .

These events led to severe disruptions in commercial navigation across multiple European waterways, temporarily hindering the delivery of bulk and container goods . The sectors and companies dependent on IWWs are those most likely to suffer economically from low-flow events . This comprises a variety of critical industries, since it does not only affect transportation of industrial goods but also of raw materials such as coal, metal ores and refined petroleum products. Moreover, interrupting the supply chain for these goods can substantially disrupt industrial production and indirectly affect economic sectors and segments of society well beyond the geographical extent of the river areas. The average annual amount of transported goods across Western, Central and Eastern Europe has been lowered as a consequence of droughts .

The European Drought Risk Atlas presents the risk analysis outcomes under present climate conditions in terms of both average annual loss, and the anticipated loss occurring on average once every 50 years. Loss is measured as the relative decrease in transported goods, indicating the percentage reduction compared to the expected amount of goods transported annually for each country . Average annual loss of transported goods in relation to expected transportation is quite homogeneous in the countries considered: less than 2.5 % except for Poland and Croatia which experience an average annual loss of 2.5 %–5 %. However, as countries are interlinked through the river network, bottlenecks in individual countries may affect riparian countries. When considering only a rare drought event, which is expected to occur only once every 50 years, losses increase to substantial fractions, especially in Eastern European countries .

Floods, often caused by heavy rainfall or snowmelt, can lead to suspended navigation, delays, vessel damage from driftwood (e.g., to propulsion devices), and changes in river and bank morphology . The impact on infrastructure and protected areas is generally more severe than on waterway transport itself, damaging or clogging navigation signs, gauges, ramps, and port areas, and flooding protected zones. Navigation suspension usually lasts only a few days per year but can extend longer, depending on the waterway . Generally, wind does not constitute a significant obstacle to inland waterway transport. Most inland vessels are sufficiently wide and stable in order to cope with strong winds. Nevertheless, locally wind speeds may attain high values hindering navigation . Heatwaves can lower water levels and affect the structural integrity of the infrastructure, affecting inland waterway navigation. Wildfires, can damage infrastructure, and create safety risks for vessels and crews, especially near ports and riverbanks. Droughts can severely disrupt inland navigation services by reducing water levels either to completely non-navigable ones or to levels that oblige operators to reduce vessel load. This results in a temporary interruption of the supply chain of industries dependent on IWWs.

Climate extremes can lead to severe infrastructure damage to railways and roads, causing disruptions and delays in transportation services . Interruptions and damages due to heatwaves, floods and wildfires became more frequent in recent years for these two transport modes (Table ).

Extreme heat can impact roads and railways causing, for instance, cable melting and pavement and track deformities due to heat-induced expansion, leading to issues such as asphalt rutting and rail track buckling . Heat stress can thus lead to structural damages, reducing the lifespan of roads and railways and necessitating more frequent maintenance and repairs . Drought can have serious impacts on the functionality of the soils since by causing strong structural destabilization and associated geotechnical problems . When soils become desiccated due to low moisture, they contract, compromising the frictional bond. As soils swell and shrink, they can stress and damage buildings and other structures that they support, such as roads , bridges, and railways . A direct effect is the warping and cracking of highways' pavement. Railway tracks built on expansive soils, such as clay, can be particularly affected by prolonged drought, lack of precipitation, and soil moisture variations. These conditions may lead to reduced permeability, desiccation, desiccation cracking, and swell-shrink behavior. Consequently, the track structure can experience instability, and settlement problems . Moreover, landslides triggered by flash floods can be intensified if a drought precedes the event, as it weakens vegetation and reduces soil cohesion . Prolonged dry conditions also reduce soil moisture, lowering pore-fluid pressure and creating infiltration pathways that accelerate water percolation, ultimately destabilizing the slope .

Under dry and hot conditions, the risk of forest fires and roadside fires increases . When a fire occurs near railway lines, train traffic can be disrupted or even temporarily interrupted. found that in the vicinity of an electrified railway line there is more than 4 times higher chance that a vegetation fire occurs than near a non-electrified line. The risk is also higher for sections of the rail network located within railway station perimeters or intensively used by freight traffic. The occurrence of vegetation fires near railway lines is exacerbated by warming weather conditions, with a 1 °C increase in the 10 d average air temperature raising the probability of a vegetation fire by 26 % .

Changing precipitation patterns contribute to soil instability, threatening the foundations of roads and railway tracks. Increased heavy precipitation can trigger landslides and erosion, further compromising the integrity of transportation infrastructure . Flooding also poses a substantial threat by eroding road foundations and railway tracks and causing landslides that obstruct both modes of transportation . Extreme precipitation and consecutive floods can cause extensive road and rail infrastructure damage. For example, in July 2021 a flood event affected Germany and the Benelux countries. In Germany, road and railway infrastructure suffered severe damage, with over 130 km of motorway closed, and an overall cost estimated between EUR 700 million and EUR 2 billion . In Belgium, 10 km of railway tracks and 3000 sleepers required replacement, with costs estimated at EUR 30–50 million. In the Netherlands, damages included highway closures and railway infrastructure damage due to lower flow velocities .

According to the DRMKC database, between 2010 and 2022, EUR 8.44 billion losses were reported for railways and roads due to river floods, coastal floods, and flash floods. Italy, France, and Spain have experienced the highest number of events, while Germany has reported the highest economic losses reported. Most of the losses have been attributed to river floods (74.4 %) followed by flash floods (22.3 %) (Fig. ).

In addition to infrastructure damage and service interruptions, extreme events are causing severe health impacts for passengers and other users . High temperatures can lead to technical and electrical issues that halt trains, as well as stoppages due to wildfires on the tracks . In recent years, cases of passengers stranded on trains for hours have become increasingly common. In many cases, health impacts are exacerbated by the failure of air conditioning systems, often requiring the involvement of emergency services, the distribution of water, and, in severe instances, hospitalizations due to heat exhaustion .

It is important to note that the increasing occurrence of individual climate extremes raises the probability of: (i) experiencing multiple climate extremes simultaneously (ii) a single extreme covering multiple areas, (iii) a single extreme occurring consecutively over time, and (iv) different extremes affecting various parts simultaneously.

Examples of each type of compounding have already been observed or modelled in Europe: (i) The increasing frequency of heatwaves and droughts could make concurrent hot and dry conditions more common , as recently demonstrated in Germany (Table ). (ii) The potential increase of simultaneous wildfires in multiple locations could intensify the impact due to the limited capacity of rescue services to respond across affected areas (Table ). (iii) Consecutive floods could further extend recovery times from one year to the next, reducing the system's overall resilience (Table ). (iv) The potential failure of different parts of the network due to simultaneous and different hazards could increase the need to consider alternative routes (Table ).

These types of connected events, referred to in the literature as compound events, have been extensively studied in literature e.g., yet there is still limited focus on their specific implications for the transport sector. Based on the results of this analysis, it is evident that future research should investigate the potential consequences of interconnected climate extremes. Their direct effects on the overall functioning of the transport system should be integrated into transport risk analysis .

Climate change also influences other extremes that will have an impact on transport infrastructure and are not considered in this study. For example, coastal flooding and windstorms were identified in the literature review as particularly relevant. Existing studies provide insights into the potential future risks associated with these hazards:

Coastal floods. Coastal floods is one of the climate extremes that is projected to drastically increase the risk for the whole transport infrastructure. According to RCP8.5 projections, by 2100 more than 200 million additional tonnes of cargo will be handled annually in ports exposed to extreme sea levels exceeding 4.5 m, compared to 2010 . Northern European ports such as Rotterdam, Antwerp, and Hamburg are projected to be among the most vulnerable . Countries on the the North Sea, such as Germany, the Netherlands, and Belgium, have the highest number of airports that could potentially be fully flooded due to the high concentration of aerodromes in their coastal regions . By 2090, under a lower intermediate emissions pathway (RCP4.5 for the study conducted by ), the number of airports likely to face severe flooding (more than 50 % of the runway) or be fully flooded increases by 14 % and 16 %, respectively, compared to the year 2000. This indicates an escalating risk, even under a relatively optimistic socioeconomic scenario. Sea level rise will increase flooding risk for all transport elements close to the coast, having impacts also on coastal railways and roads . The most extreme condition is not only the sea level rise alone, but its combination with high tide, and episodic water level fluctuations due to climate extremes, such as wave or storm surge . A storm surge caused by storms, strong winds, or cyclones, occurring on top of an already elevated sea level, will lead to unprecedented water height in the flooded areas . Airports, ports, and transport infrastructure along the coast of Northen sea, parts of Ireland and Baltic sea are projected to face highest risk, also in 2050 under a lower intermediate emissions pathway (RCP4.5 in this case) .

This study also does not analyse hazards such as landslides and flash floods. Assessing the influence of climate change on these hazards remains challenging due to limitations in process representation and data availability . Nevertheless, a growing body of evidence suggests that their frequency and intensity may increase in parts of Europe under climate change, for example in some Alpine areas , with potentially severe consequences for transport infrastructure (as exemplified by the recent disruption of the Fréjus Tunnel; see ). Landslide occurrence is highly location-specific and is controlled by a variety of physical mechanisms (e.g., heavy rainfall, snow melting, flash floods, deforestation, wildfires, earthquakes) . Despite climate change affects precipitation, increasing the frequency of extreme events that drive the risk of landslides , modelling these processes and isolating the direct impact of climate change on individual events remains highly challenging . Flash floods are acute localised hazards for which the main weather driving mechanism is an intense and short precipitation event. While models generally agree on the increasing trends in heavy precipitation , a driver of both landslides and flash floods, there are currently limited data sets available that allow for a systematic comparison landslides and flash floods to the other hazard categories considered in this study.

Other extremes that could be considered are extreme cold events. However, previous analyses show that the occurrence and severity of cold extremes have consistently diminished in line with global warming trends . The frequency and intensity of these events are further projected to decrease in future . The number of days with extreme cold temperatures has decreased by a factor of 2–3, with temperatures rising by more than 3 °C regionally, substantially more than the winter mean temperatures .