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SCENIC

Storyline scenarios of extreme weather, climate, and environmental events along with their impacts in a warmer world

What would the 2019 and 2022 summer heatwaves in Germany have been like if they had taken place in a cooler climate without human-induced climate change? Would the numerous severe rainfall events in 2024, which led to the flooding of large areas in Europe, have been less severe without climate change? How would these and other extreme weather situations unfold in a globally 4 °C warmer world – and what would be the impacts on hydrology, agriculture, health, etc.? In the SCENIC project, all seven Helmholtz Earth & Environment Centres have collaborated to address such questions based on event-based storyline simulations with a hierarchy of global climate to regional impact models.

Maximum daily temperature on July 25, 2019 in Germany in today's climate (center), as well as in the pre-industrial (left) and globally 4 °C warmer climate according to AWI-CM1 storyline simulations corrected with observational data. Modified from [a] by Yves Novak, AWI

The well-established probabilistic method of attribution research reaches its limits when it comes to record-shattering extreme events that do not or hardly ever occur in simulations. In such cases, no robust statements can be made about changes in probability or intensity. The question also arises why the probability of an event changes: Is it simply due to the increased temperatures caused by greenhouse gases and how these directly affect other parameters thermodynamically, or do more complex changes in the wind systems play a role? For example, are blocking weather patterns becoming more frequent and/or more persistent, or is the opposite perhaps the case? In fact, such changes in atmospheric dynamics are subject to large uncertainty and usually differ from model to model. Event-based storylines circumvent these problems by asking: How would an observed extreme event have played out if the same wind patterns had occurred in a different climate state?

Main model domains used in SCENIC, see [f], figure by T. Klimiuk, KIT

A key element and innovation of SCENIC is a chain of storyline simulations from global to regional impacts. First, the large-scale atmospheric circulation patterns in global climate model simulations are prescribed by means of "nudging" using ERA5 or NCEP reanalysis data. Second, these simulations are dynamically downscaled with regional models. Third, these data are used to drive land-surface models focussing on, for example, hydrological and agricultural impacts.

Major achievements

  • Detailed analyses of continental as well as marine heatwaves and extreme precipitation events based on global storyline simulations [1,2,3,4]
  • Development of near-real-time global storyline simulations revealing the “climate change signal of the day” with just a few days delay, openly accessible through an online tool [3]
  • Analysis of impacts of a weakening Atlantic Meridional Overturning Circulation (AMOC) on global extremes [5], also in a storyline framework for Europe [6]
  • Analysis of the recent European droughts from a long-term perspective [7,8]
  • First air pollution storylines of future climate including vegetation response to abiotic stress and health impact on humans and ecosystems [9,10]
  • Dynamically downscaled regional storyline simulations with increased detail, including better representation of orographic and urban effects and diurnal cycles [11]
  • Spatio-temporal downscaling of rainfall fields based on machine learning models (conditional generative adversarial networks), with potential for application to storyline data [12,13]
  • Analysis of how agricultural heat stress evolves in Europe with climate warming, based on dynamically downscaled storyline data [14]
  • Hydrological storylines revealing how changes in precipitation and evaporative demand influence runoff across Europe, with societal implications related to river levels [15]
  • Estimates of the climate impact on mortality in Germany based on artificial intelligence (echo state network) and storyline simulation data [16]
  • Storylines of hydrological extreme events over South America and Europe such as droughts and extreme precipitation [17,18]
  • Preparation of a joint synthesis paper by all Helmholtz Earth and Environment Centres exploring the 2018–2022 European summer heat and drought period in a storyline framework from multiple angles [19]

Team