What is climate change impact attribution all about?
This image gives a sense of what climate change impact attribution is about by showing how climate and land cover can influence river flow and dam levels. It is not based on observed or modelled data and is not an accurate representation of a specific catchment, but is AI-generated conceptual illustration.
Addressing climate change requires adequate knowledge of its impacts on both nature and people. This is especially important in Africa and across the Global South, where people are often more vulnerable to these impacts, and adaptation needs are more urgent.
A new paper on climate change impact attribution has been published by Nature Reviews Earth & Environment, with contributions from People in Nature and Climate Lab (PiNC) at the African Climate and Development Initiative (ACDI) at the University of Cape Town (UCT) lead Dr Petra Holden and lab researcher, Professor Mark New.
In this paper, led by Sabine Undorf from the Potsdam Institute for Climate Impact Research (PIK), researchers review current approaches to climate change impact attribution, and societal uses of the results. They also highlight the main challenges and knowledge gaps that need to be addressed for these results to be most effective in informing climate policy.
According to holden, methodological choices really affect the results of impact attribution, so it’s important for researchers to be clear on the differences and limitations of the various approaches.
“We can use attribution to give us numbers to help communicate the impacts of climate change and assess adaptation options. But choices about framing, methods, counterfactuals and so on influence the results,” she says.
“Not all social and ecological impacts can be measured on a common scale, because values are embedded. Impact attribution can be helpful to inform policy but only alongside other forms of evidence.”
Approaches to impact attribution include a diversity of choices
The researchers describe impact attribution as the process of evaluating the contribution of one or more causal factors (which must include climate change or its drivers) to observed changes or events in a human or natural system.
This process involves a series of steps. Firstly, researchers choose the specific research question to address, for example reduced river flow during a drought, or acres of land burned by wildfires. They then identify potential causal pathways, including climate change but also human impact factors such as population density, land use, and infrastructure.
Models are then run using factual and counterfactual input data to generate a ‘real-world’ scenario and an imaginary scenario simulated without human-caused climate change. The comparison of these factual and counterfactual scenarios reveals the attribution of climate change impacts.
Non-climate counterfactuals, such as land-use changes, can also be used to investigate how adaptation measures could have moderated climate change impacts. This is an important use case for disaster risk-reduction research, however these non-climate counterfactuals can be challenging to define as climatic and socioeconomic factors interact in complex ways.
The researchers find that focusing on a limited number of causal pathways could help to reduce complexity and therefore uncertainty, and could be used to derive useful results that might be missed by an approach that considers more pathways.
The case of Cape Town’s ‘Day Zero’ drought
Climate change impact attribution was used to analyse Cape Town’s 2015-2017 drought. The analysis showed that climate change reduced streamflow by 12-29% relative to a counterfactual with anthropogenic emissions removed.
Furthermore, by modelling adaptation counterfactuals, the researchers found that the impact could have been ameliorated by up to 16% if they had applied nature-based solutions (specifically, clearing invasive trees and restoring the natural vegetation in the river catchment).
Improvements needed in data coverage and quality
For impact attribution science to improve, there needs to be better access to data held by national meteorological services, academic, public and corporate actors (including global re-insurance companies). Long-term (ideally continuous) datasets are essential for trend attribution, which requires enduring, continued investment.
The researchers also note that citizen science and remote-sensing data can help to fill coverage gaps and increase the accuracy of observations. In addition, qualitative data and local, Indigenous knowledge is another information source that could be used in impact attribution.
Greater collaboration required for effective application
Climate change impact attribution is an emerging and rapidly advancing field of research with considerable potential to inform international climate negotiations, disaster response and recovery efforts, legal and accountability processes, and climate adaptation planning.
Given the increasing public attention to this work, the researchers emphasise the scientific community’s responsibility to clarify the differences between approaches, develop unifying concepts and terminology, and communicate the methodological and general limitations.
Unlocking the full potential of the field will require significant improvements in data availability, especially across the Global South. Equally important is deeper collaboration among climate attribution scientists, impact modellers, policy specialists, related academic disciplines, and stakeholders beyond the research community.
Citation
Undorf, S., Dimitrova, A., Harrington, L.J. et al. (2026) Approaches, challenges and applications of climate change impact attribution. Nat Rev Earth Environ. https://doi.org/10.1038/s43017-026-00798-8