UK Climate Change Attribution (DARA)

2023, PI Dann Mitchell, funded by the Climate Change Committee (CCC)

Reviewing climate change attribution in UK natural hazards and their impacts (DARA)

Ahead of the Fourth UK Climate Change Risk Assessment (CCRA4), the Climate Change Committee (CCC) asked what we know about the impact of past and present climate change on natural and human systems here in the UK specifically. At the global level, the 2021 IPCC sixth assessment working group I (AR6 WGI) report concluded: “It is unequivocal that human influence has warmed the atmosphere, ocean and land.” This single sentence has been informed by decades of research by people at the cutting edge of climate science, and the evidence to support it has grown stronger in every IPCC report since they began. The report goes on to say: “Human-induced climate change is already affecting many weather and climate extremes in every region across the globe.” In last year’s follow-up AR6 WGII report on impacts, adaptation, and vulnerability, an extensive assessment of the science led to the conclusion that the magnitude and proliferation of extremes caused by human-induced climate change were having widespread, adverse impacts on both nature and people. Last summer’s heatwaves, and the concurrent dangers to health, homes, and the environment, were a graphic illustration of the nature of such human-induced impacts.

The study of impacts that informed this conclusion is the remit of climate scientists who specialise in “detection and attribution”. This is about looking at what is changing around us and being able to pinpoint the cause(s) – and particularly, whether human-induced climate change is at the root. To inform CCRA4, the CCC commissioned a joint Bristol and Exeter University team to conduct a comprehensive review of the detection and attribution of climate change in the UK. The first part covered the detection and attribution of weather and climate changes in the UK, relevant to specific “Climate Impact Drivers”. The second covered attribution of impacts on societal, infrastructural, economic, and biodiversity sectors. We looked into what studies have been done so far, where the gaps are, and whether they can be filled, or if they would require substantial new methodological or data advances. We identified variables which were key drivers of multiple impacts, and, importantly, where further attribution analysis is needed – especially when the impacts are critical for UK risk.

An attribution example for flood-related natural hazards (blue text) via associated CIDs (black), with some of the key impacts on human systems (red). Natural weather and climate variability can lead to natural hazards and impacts even under pre-industrial conditions (e.g., upper panel), including severe events and impacts, though these may be relatively rare.

Anthropogenic climate change alters many meteorological variables (CIDs) that may exacerbate such hazards and impacts (e.g., lower panel), increasing their frequency, intensity, and/or extent. The key task of attribution is to distinguish between the two in order to robustly quantify those changes in hazards and their impacts that are due to climate change.

Image copyright Science Graphic Design / Bristol Climate Dynamics Group.

Key findings and conclusions of the project are:

  • Overall, 67 Detection and Attribution (D&A) studies have been included and literature was found for 14 of the 29 hazards considered.
  • Heatwaves are the most studied hazard, with a unanimous consensus across all 33 studies of a strong attributable signal of human-induced climate change in their increased frequency and intensity over the last century.
  • For river and surface water flooding 19 studies are identified and the human contribution identified in large-scale precipitation trends, but not necessarily in regional studies.
  • Storms and related hazards such as extratropical cyclones, sting jets, storm surges, and coastal flooding are in general poorly studied within D&A. They can have significant impacts on infrastructure, but it is difficult to model them in general and attribution studies are thus rare.
  • The most notable gap identified by the review is the lack of impact attribution studies. This requires a multi-step approach that includes assessment of vulnerability and exposure.
  • The Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) is an initiative that investigates future impacts of climate change across affected sectors and spatial scales. Though typically projections-focused, this could provide a framework for impact attribution.

Final report

Mudhar, R., Mitchell, D. M., Stott, P. & Betts, R. 2023. Reviewing climate change attribution in UK natural hazards and their impacts. UK Climate Risk.