Evaluation of trends in high temperature extremes in north-western Europe in regional climate models

Abstract

Projections of future changes in weather extremes on the regional and local scale depend on a realistic representation of trends in extremes in regional climate models (RCMs). We have tested this assumption for moderate high temperature extremes (the annual maximum of the daily maximum 2 m temperature, T ann.max ). Linear trends in T ann.max from historical runs of 14 RCMs driven by atmospheric reanalysis data are compared with trends in gridded station data. The ensemble of RCMs significantly underestimates the observed trends over most of the north-western European land surface. Individual models do not fare much better, with even the best performing models underestimating observed trends over large areas. We argue that the inability of RCMs to reproduce observed trends is probably not due to errors in large-scale circulation. There is also no significant correlation between the RCM T ann.max trends and trends in radiation or Bowen ratio. We conclude that care should be taken when using RCM data for adaptation decisions.

Extreme heat in India and anthropogenic climate change

“…They show that over Switzerland the frequency of very hot days exceeding the 99th percentile of daily maximum temperature has more than tripled. Also, TXx in north-western Europe has a strong trend, as shown by Min et al (2013). However, these studies also show that in many regions, such as eastern North America and western Europe, there are large discrepancies between modelled and observed trends in heat waves.…”

“…Those directly exposed to the heat including outdoor workers, the homeless and those with pre-existing medical conditions (e.g. the elderly) constitute the majority of negative heat-related outcomes in India (Tran et al, 2013;Nag et al, 2009). Naturally, the question was raised whether human-induced climate change played a role in this record-breaking heat.…”

The Role of Anthropogenic Warming in 2015 Central European Heat Waves

“…These estimates are thus lower than those estimated from the observations but can be largely explained by method-and datarelated differences. For instance, the statistical method assumes that the trend is caused fully by anthropogenic factors, while the model analysis is based on a "real counterfactual" scenario but tends to underestimate warming trends in temperature extremes in Europe (Min et al 2013). The mean observed change across all locations between 2015 and 1901 of 3.1°C (Tair 3d, max ) and 2.2°C (WBTX 3d, max ) is much larger than the original (+1.1°C in Tair 3d, max and +0.5°C in WBTX 3d, max ) and bias corrected (+0.9°C in Tair 3d, max and +0.5°C in WBTX 3d, max ) model simulations.…”

Evaluation of the performance of CORDEX regional climate models in simulating present climate conditions of Tanzania

“…These are atmospheric models run on a limited geographical area using boundary conditions from GCMs (Danis et al 2002, Min et al 2013. Their finer spatial resolution allows simulation of local climate conditions in greater detail by incorporation of impacts of orography (mountains, coastlines, water bodies, vegetation) and land-use, and small scale dynamical and boundary layer processes.…”

“…These simulations, however, are subject to a number of uncertainties that come from boundary conditions, size of the integration domain, natural variability within the RCMs and RCM formulation (Min et al 2013). Meier et al (2011) assessed the impact of boundary conditions from three global climate models (HadCM3, ECHAM4 and ECHAM5) on the Rossby Centre Atmosphere model version 3 (RCA3) RCM in simulating surface meteorological variables over the Baltic Sea.…”