PLASIM-ENTSem: a spatio-temporal emulator of future climate change for impacts assessment

Abstract

Many applications in the evaluation of climate impacts and environmental policy require detailed spatio-temporal projections of future climate. To capture feedbacks from impacted natural or socio-economic systems requires interactive two-way coupling but this is generally computationally infeasible with even moderately complex general circulation models (GCMs). Dimension reduction using emulation is one solution to this problem, demonstrated here with the GCM PLASIM-ENTS. Our approach generates temporally evolving spatial patterns of climate variables, considering multiple modes of variability in order to capture non-linear feedbacks. The emulator provides a 188-member ensemble of decadally and spatially resolved (~ 5° resolution) seasonal climate data in response to an arbitrary future CO₂ concentration and radiative forcing scenario. We present the PLASIM-ENTS coupled model, the construction of its emulator from an ensemble of transient future simulations, an application of the emulator methodology to produce heating and cooling degree-day projections, and the validation of the results against empirical data and higher-complexity models. We also demonstrate the application to estimates of sea-level rise and associated uncertainty

Worldwide impacts of climate change on energy for heating and cooling

“…The slab sea ice was held fixed in the simulations used to build the version of the emulator used here, which predates the configuration described in (Holden et al, 2013). Warming patterns in response to RCP6.0 are illustrated in Figure 2.…”

“…The validations of both PLASIM-ENTS and PLASIM-ENTSem are described in detail in (Holden et al, 2013).…”

“…This avoids the potential neglect of densely populated coastal regions, but comes at the expense of ascribing an oceanic climate to some populated regions, likely understating seasonal variability and future warming. The validation of seasonally and regionally resolved population-weighted degree-days is described in (Holden et al, 2013).…”

“…The climate model emulator used here is PLASIM-ENTSem (Holden et al, 2013), an emulation of PLASIM-ENTS, Fraedrich et al (2005) coupled to the ENTS vegetation and land surface model (Williamson et al, 2006), here run at T21 resolution (approximately 5 degree).…”

Compressing an Ensemble With Statistical Models: An Algorithm for Global 3D Spatio-Temporal Temperature

“…In this regard, the statistical model can be regarded as an emulator of an initial condition ensemble, under the assumption that runs are independent for different initial conditions. This is, to our knowledge, the first time an emulator is used in this context, as it is traditionally used for calibration and sensitivity analysis (Sansó et al, 2008;Sansó and Forest, 2009;Bhat et al, 2012;Drignei et al, 2008;Chang et al, 2015) or scenario extrapolation (Holden and Edwards, 2010;Castruccio and Stein, 2013;Holden et al, 2013;Castruccio et al, 2014). The key difference with traditional emulators is that we do not assume correlation among inputs, as different initial conditions sensibly sampled from the spin-up run generate effectively independent runs.…”