PICO
The Climate Litigation Network supports national organisations that are taking litigation action against their governments in respect of the adequacy and implementation of national climate policies and targets. This presentation will provide an overview of the role of science in climate cases that challenge governments’ overall emissions reductions (“framework cases”) – of which there are more than 100 globally.
In April 2024, the European Court of Human Rights (ECtHR) issued its first decision relating to climate change. Critically, the ECtHR found that the Swiss government had failed to put in place an adequate domestic regulatory framework to tackle climate change and, as such, was failing to uphold the right to private and family life under the European Convention of Human Rights. This decision will have immense implications for framework cases across Europe and beyond. In particular, in respect of how evidence and science will be used to assess the adequacy of governments’ actions in the context of human rights.
Specifically, one of the key issues with the Swiss government’s approach was that it failed to quantify national greenhouse emissions limitations through a carbon budget. The ECtHR’s assessment shows that states must set their emissions reductions targets in relation to the global remaining carbon budget, and must have regulatory frameworks in place to ensure such targets are met. Given that the global remaining carbon budget for 1.5C is almost exhausted, there will be a pressing need for scientific research to explore how government action can be tracked and verified to be compatible with the Paris Agreement and human rights obligations.
This presentation will highlight the current deployment of science in climate cases against governments and explore new frontiers in light of the ECtHR decision.
How to cite: Williamson, A.: Science and evidence for framework climate litigation , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3811, https://doi.org/10.5194/egusphere-egu25-3811, 2025.
Climate change attribution science describes with increasing precision how anthropogenic activities are affecting environments around the world. In legal disputes over corporations' and governments' responsibility for climate change, attribution science plays a key role in evaluating defendants' contribution to climate change impacts. This paper examines how attribution science is used to establish causal chains in climate litigation. While scientific methodologies are advancing rapidly, questions remain over how legal standards of proof should be applied to the evidence. If ongoing cases are successful in using attribution science to establish legal causation, they could set significant precedents for holding major greenhouse gas emitters to account.
How to cite: Walker-Crawford, N., Petkov, N., Reyes, J., and Stuart-Smith, R.: Attribution in action: Causal chains in climate litigation, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8468, https://doi.org/10.5194/egusphere-egu25-8468, 2025.
The interface between climate science and legal practice, particularly litigation, is of increasing relevance. Here we share our experiences from being involved in a number of legal cases over the past five years. Based on our experience, we discuss numerous challenges that are faced at this interface. These include presenting information in a way that a court can understand (and is typically very different from presenting information for scientific colleagues), the particular needs of litigation and their synergies and conflicts with scientific methods and uncertainty and the completely different timelines and pressure between the scientific and litigious environments. We outline various ways we have approached these challenges and highlight areas where we have not yet seen solutions. We conclude by laying out our view of the new research required to serve the science-litigation interface and some initial ideas of a research agenda to tackle this research.
How to cite: Nicholls, Z., Schleussner, C.-F., and Pelz, S.: Navigating the science-litigation interface, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5810, https://doi.org/10.5194/egusphere-egu25-5810, 2025.
The Paris Agreement’s fallback temperature goal, keeping global warming well below 2oC, is typically interpreted as staying below 2oC with a specified probability, with legal disputes over what the probability should be. Such framing is not futureproof because uncertainty decreases with time, systematically weakening the target towards allowing temperatures to approach 2C itself. We show the science and legal discussion available at the Paris Agreement’s signing guides an interpretation using a level of conserved median warming, with a minimum 66% chance of staying below 2oC translating to 1.8oC of expected median warming and a more defensible 83% chance giving 1.6oC.
How to cite: Lamboll, R. and Rogelj, J.: How below is well-below? Future-proofing interpretations of the Paris Agreement, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12279, https://doi.org/10.5194/egusphere-egu25-12279, 2025.
In light of seeing temperatures now closely approach the international targets set by the 2015 Paris Agreement for limiting global warming, in particular the 1.5 °C target, an accurate and reliable tracking of changes in the global surface temperature is critical. We introduce a comprehensive benchmark time series for global surface air temperature (GSAT) extending from 1850 to 2024, complemented by a projection up to 2034 and scenarios through to 2050. Building on and advanced from widely recognized global mean surface temperature (GMST) records used by the IPCC, we established a detailed and traceable GSAT annual and 20-year-mean time record in this form, referenced to the conventional preindustrial level (mean 1850-1900). Our record indicates an increase of the 20-year-mean GSAT change to 1.40 [1.30-1.49] °C by 2024 and a subsequent exceedance of the 1.5 °C threshold by 2028 [2025-2032] (uncertainty ranges denote a 90% confidence interval). Given this imminence of 1.5 °C, we propose a new classification system to gauge, with regular updates, the compliance with the Paris goals (1.5 °C goal, well-below-2 °C goal; or exceedance up to 2 °C or even beyond). These improvements in compliance/exceedance quantification may help policymakers, the judiciary and the general public to obtain standardized and thus more reliable assessments of the degree of compliance with the Paris climate targets over the coming years and decades.
How to cite: Kirchengast, G. and Pichler, M.: Clearer metrics for the Paris climate targets: A new compliance quantification approach, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8486, https://doi.org/10.5194/egusphere-egu25-8486, 2025.
Parties to the Paris Agreement are committed to submit five-yearly climate pledges, known as Nationally Determined Contribution (NDCs), that describe their intended climate change mitigation actions for the next 5 to 10 years. The Paris Agreement mandates that subsequent NDCs represent a progression compared to earlier NDCs, be a country’s highest possible ambition, and reflect a country’s common but differentiated responsibilities and respective capabilities in the light of different national circumstances. While there is a rich literature on interpreting and operationalising equity and fairness in international climate policy, scholarship on interpreting and operationalising the norms of progression and highest possible ambition is largely absent. In addition, recent literature indicates that because of insufficient past action, several countries find themselves in a position where even their deepest possible emissions reductions do not result in equitable contribution when considered in an appropriate historical context. Here, we will present a framework for the operationalisation of highest possible ambition in NDCs. While this framework is applicable to all countries, it is also presented as a way to inform minimum requirements for the level of ambition of climate change mitigation action under the Paris Agreement by historically high emitters.
How to cite: Rogelj, J. and Schönfeld, J. K.: Highest possible ambition as a minimum requirement for historical high emitters under the Paris Agreement, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21225, https://doi.org/10.5194/egusphere-egu25-21225, 2025.
Current assessments of "fair shares" of global mitigation efforts have tended to focus on the responsibility of States. However, recent climate litigation has started to focus on the responsibility of non-state actors, which should ideally be informed by quantitative fair share assessments. Here, we explore a case study of large investor-owned carbon majors, which were responsible for 24% of global fossil CO2 emissions between 1990 and 2018. Drawing on commonly invoked principles of climate justice, we suggest that large investor-owned “carbon majors” should be assigned Direct Air Carbon Capture and Storage (DACCS) investment responsibilities. This responsibility is in addition to their primary responsibility to adopt a stringent decarbonisation trajectory consistent with the Paris Agreement objectives. DACCS is a potentially important component of mitigation portfolios consistent with global climate objectives and has a low land footprint relative to other carbon dioxide removal options. However, DACCS is in its formative phase, the early and expensive stage of technology deployment. Significant near-term investments are necessary to buy-down the cost of the technology so that it can play a cost-efficient role in future mitigation. We assess the level of investments necessary to move DACCS out of its niche phase (32 billion USD central estimate, with interquartile range 6 – 92 billion USD). Beyond that, about 250 billion USD in investments (central estimate, interquartile range 135 – 313 billion USD) may be required to buy-down the costs to 100 USD / tonne of CO2 captured. We assign responsibilities for this deployment to investor-owned carbon majors, finding that the ten highest emitting carbon majors should bear responsibility for around 17 billion USD (central estimate) in investments to contribute to moving DACCS out of its formative phase. When we also account for the buy-down cost to achieve the 100 USD/tonne goal, the scale of this responsibility may double if these company emissions grow at the same rate as global stated policies. Adopting a decarbonisation trajectory in line with a net zero emissions scenario significantly reduces this ongoing responsibility, reiterating the importance of robust company-level strategies aligned with the 1.5°C warming limit of the Paris Agreement.
How to cite: Kellou, D., Pratama, Y., Zuniga, C., Riany, F., Gidden, M. J., Heede, R., Ganti, G., and Schleussner, C.-F.: Evaluating the responsibility of investor-owned carbon majors to invest in direct air carbon capture and storage, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18077, https://doi.org/10.5194/egusphere-egu25-18077, 2025.
Under current scenario projections of global climate ambition, we expect to exceed a 1.5°C consistent remaining carbon budget this decade. At the same time, many countries have already accrued ‘carbon debt’, reflecting historical emissions exceeding their ‘fair share’ of the remaining carbon budget. The ‘carbon debt’ concept can be extended to forward-looking scenario-based assessments, by comparing expected future emissions trajectories with current remaining budget allocations (or debts) for a given temperature target. At the year of net-zero carbon emissions, we term this the ‘net-zero carbon debt’. This measure can be used to assign responsibilities for expected temperature exceedance and related domestic climate impacts, capturing both intra- and inter-generational inequities. Such an approach ensures that ‘fair share’ considerations persist even if a remaining carbon budget is initially exhausted, linking expected emissions pathways with corresponding carbon drawdown obligations and responsibilities for realised impacts. We apply this approach to examine recent downscaled scenario projections for European Union member countries, quantifying the expected carbon drawdown obligations and responsibility for climate impacts that they imply. We then discuss the value and limitations of such assessments in informing domestic considerations of fairness thus far reliant on a rapidly dwindling remaining carbon budget. In summary, this work examines a new forward-looking domestic application of ‘fair share’ considerations in a manner robust to exhaustion of a 1.5°C consistent remaining carbon budget.
How to cite: Pelz, S., Ganti, G., and Schluessner, C.-F.: Towards forward-looking carbon debt assessments to comprehensively capture state responsibility for climate change, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13353, https://doi.org/10.5194/egusphere-egu25-13353, 2025.
While the field of event impact attribution is still relatively nascent, diverse methodologies and datasets are starting to be used to put numbers on the share of additional impacts that occur due to climate change during extreme weather events. The growth of this body of evidence has implications for climate litigation as these studies can be starting points for legal cases centred around specific climate change impacts, such as heat-related mortality or economic costs of extreme weather.
As we work towards operationalising a tracker that will provide timely estimates of losses and damages from extreme weather events globally, we aim to present results from our initial rapid studies conducted over the past year. We will reflect on the potential implications of the increasing availability of loss and damage information and the broader need for communication and awareness raising around these issues. We also plan to highlight prevailing methodological challenges and areas of research to be advanced in the near future that are relevant for legal efforts.
How to cite: Theokritoff, E., Sparks, N., Otto, F., Rogelj, J., and Toumi, R.: Tracking losses and damages from extreme weather events, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6900, https://doi.org/10.5194/egusphere-egu25-6900, 2025.
Typically, responsibility for impacts from aggregate global GHG emissions is attributed proportional to an actor's share of emissions. This way, individual actors are only attributed comparatively small shares of any caused harm and can point to the aggregated responsibility of others far exceeding their own when pressed to take action. This fragmentation of responsibility leads to profound challenges in establishing climate accountability based on principles of international environmental law.
The EUCHR ruling in the Verein KlimaSeniorinnen Schweiz v. Switzerland case states that "each State has its own responsibilities within its own territorial jurisdiction in respect of climate change." Following this argument, we propose an analysis framework to take states' heightened mandate of care towards their own citizens and territories into account, introducing an alternative line of differentiation by experienced impacts.
Using the fast climate impact emulator RIME-X for impact attribution, we quantify national shares of global climate impacts exploring different impact allocation regimes (e.g. area, population, or GDP). We introduce the responsibility-to-harm ratio as the ratio of the share in historic emissions vs. the share in experienced impacts on a national basis. This identifies the percentage of self-inflicted harm vs. harm caused by the conduct of others.
This weighting of national emissions by impacts enables a prioritisation of a state's accountability for domestic impacts. It, thus, partially counteracts the fragmentation of responsibility, making principles of international environmental law more easily actionable. It also provides a simple metric for the inequitable distribution between responsibility for climate change and the impacts it causes, contributing to the quantification of international climate injustice.
How to cite: Högner, A., Nauels, A., Nicholls, Z., Schwind, N., and Schleussner, C.-F.: Establishing climate accountability through attribution of climate impacts to GHG emissions within territorial jurisdictions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9647, https://doi.org/10.5194/egusphere-egu25-9647, 2025.
Introduction
Global temperatures are rising due to anthropogenic greenhouse gas emissions. Record-breaking temperatures observed in Europe during the summer of 2022 were associated with more than 60,000 heat-related deaths, with countries near the Mediterranean Sea, particularly Greece, being most affected. This study explores the death toll of prolonged heat periods in Greece, its spatial disparities, and how these patterns have changed over time.
Methods
We retrieved individual-level data on cause-specific mortality in Greece during 2000-2019 from the Hellenic Statistical Authority. The data included information on age, sex, cause of death, region of residence (Nomenclature of Units for Territorial Statistics, level 3; NUTS3), and date of death. Daily maximum temperatures during 2000–2019 at 0.25° x 0.25° resolution were retrieved from ERA-5 reanalysis data. We considered six heatwave definitions, combining two durations (>2 and >3 days) and three temperature thresholds (90th, 95th, and 99th percentiles). A Bayesian hierarchical Poisson model was developed, accounting for spatiotemporal variation in heatwave effects using Gaussian priors. We also controlled for national holidays and population-weighted relative humidity.
Results
We observed 177,112 cardiovascular deaths and 39,646 respiratory deaths in individuals aged 65 and older in Greece during 2000–2019. A strong association was found between heatwaves and cardiovascular and respiratory mortality under all definitions. Evidence of spatial variation in heatwave effects was weak, as was evidence of temporal adaptation. However, for the most extreme heatwave definition, we observed an increasing trend in the effect of heat over the study period. Over 20 years, 6,926 (95% CI: 6,260–7,587) cardiorespiratory deaths were attributed to heatwaves, equating to approximately 350 deaths per year.
Conclusion
Heatwaves impose a significant mortality toll in Greece. While the effect of heatwaves on mortality has not changed over time in most heatwave definitions, the increasing trend of the effect of extreme heatwaves calls for immediate action to mitigate future risks.
Funding:
EUREST-RISE
How to cite: Konstantinoudis, G., Evangelopoulos, D., and Filippidis, F.: Estimating the temporal adaptation and spatial vulnerabilities of the heatwave mortality risk in Greece, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3573, https://doi.org/10.5194/egusphere-egu25-3573, 2025.
Climate change is already causing widespread negative impacts across the world, including by increasing the frequency and intensity of extreme events such as heatwaves, droughts and wildfires. With further warming, children and young people will be exposed to an ever-greater number of risks from anthropogenic climate change. Building on previous research quantifying lifetime exposure to climate extremes [1,2], we present a flexible framework, demographics4climate, that can be applied on any climate dataset to quantify lifetime exposure to climate risks in a spatially explicit and age-specific way. We present the application of the framework on a case study by estimating the lifetime exposure to high and very high fire weather conditions in Portugal for different generations and under different demographic and warming scenarios. We discuss the relevance of this analysis for the climate lawsuit Duarte Agostinho and others v. Portugal and others (recently dismissed from the European Court of Human Rights), as well as the relevance of the framework for child and youth-led climate lawsuits more broadly. We propose that this framework, including possible extensions upstream towards emission sources and downstream towards impacts, could provide meaningful science-based contributions to the evidentiary base of child and youth-led climate lawsuits.
[1] Thiery, W. et al. Intergenerational inequities in exposure to climate extremes. Science 374, 158–160 (2021).
[2] Grant, L. et al. Global emergence of unprecedented lifetime exposure to climate extremes. Nature, accepted.
How to cite: Pietroiusti, R., Savaresi, A., Adelman, S., and Thiery, W.: Quantifying intergenerational inequity in lifetime climate risk as evidence in child and youth-led lawsuits , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16281, https://doi.org/10.5194/egusphere-egu25-16281, 2025.
