Storylines of UK drought based on the 2010–2012 event

Abstract

Abstract. Spatially extensive multi-year hydrological droughts cause significant environmental stress. Given the impacts of climate change, the UK is expected to remain vulnerable to future multi-year droughts. Existing approaches to quantify hydrological impacts of climate change are often scenario-driven and may miss out plausible outcomes with significant impacts. Event-based storyline approaches aim to quantify storylines of how observed events could hypothetically have unfolded in alternative ways. This study uses the 2010–2012 drought, the most recent period of severe hydrological drought in the UK, as a basis, and analyses counterfactual storylines based on changes to 1) precondition severity, 2) temporal drought sequence, and 3) climate change. Evidence from multiple storylines shows that maximum intensity, mean deficit and duration of the 2010–2012 drought were highly conditioned by its meteorological preconditions, particularly for northern catchments at shorter time scales. Recovery time from progressively drier preconditions reflect both spatial variation in drought conditions and the role of physical catchment characteristics, particularly hydrogeology in the propagation of multi-year droughts. Two plausible storylines of an additional dry year with dry winter conditions repeated either before the observed drought or replacing the observed dramatic drought termination confirm the vulnerability of UK catchments to a three dry winter scenario. Applying the UKCP18 climate projections, we find that drought conditions worsen with global warming with a mitigation of drought conditions by wetter winters in northern catchments at high warming levels. Comparison of the storylines with a benchmark drought (1975–76) and a protracted multi-year drought (1989–93) shows that for each storyline, drought conditions could have matched and exceeded those experienced during the past droughts at catchments across the UK, particularly for southern catchments. The construction of storylines based on observed events can complement existing methods to stress test UK catchments against plausible unrealized droughts.

Vulnerability of European ecosystems to two compound dry and hot summers in 2018 and 2019

“…We do this in two steps: first by fitting a linear regression model for mean EVI anom in each cluster and then, for more detailed insights, by fitting a random forest model at pixel scale, in which we include potential seasonal legacy effects. In both cases, the training period includes other DH events (Ciais et al, 2005;Orth et al, 2016), with similar climate anomalies, particularly 2003, thereby reducing the risk of attempting to predict EVI anom based on "unseen" climatic conditions.…”

“…In Europe, DH events usually have strong negative impacts on ecosystems, such as reduced ecosystem productivity (Ciais et al, 2005;Bastos et al, 2020b). After severe drought and heat stress, plant recovery can be lagged, for example due to reduced growth or non-reversible losses in hydraulic conductance or carbon reserve depletion (Ruehr et al, 2019).…”

Tracking the methodological evolution of climate change projections for UK river flows

“…what if the northerly jet stream persisted longer than observed). Similarly, Chan et al (2021) created counterfactual event storylines to quantify how much worse the 2010-12 UK drought could have been if it was preceded by drier preconditions or followed by a plausible third dry winter. These approaches make use of traditional “top-down” scenarios in novel ways and could be particularly useful to satisfy requirements in water resources planning such as assessing resilience to one in 500-years droughts for which there are no historical observations.…”