Climate model simulations of the observed early-2000s hiatus of global warming

Abstract

Traditional free-running climate simulations that start in the mid-nineteenth century and proceed through the twentieth century with observed human-produced forcings, such as increasing greenhouse gases (GHGs), aerosols and ozone, along with natural forcings, such as aerosols from volcanic eruptions and solar variability, are designed to simulate the response of the climate system to those changes in external forcings. To do this, multiple realizations or ensemble members are run with each model. These are then averaged together to remove the effects of naturally occurring interannual and decadal timescale variability, leaving only the response to the external forcings. If the early-2000s hiatus is mostly a result of internally generated climate variability 2-5 , the average of all those simulations for the early 21st century would, and indeed does, lie above the actual plateau of warming that occurred in the observations 1,6 . Furthermore, the models could be overly sensitive to increasing GHGs (ref. 7), and there could have been contributions from a collection of moderate volcanic eruptions or other forcings [8][9][10]

Determining the likelihood of pauses and surges in global warming

“…Model simulations initialized with the observed ocean state match observations better than free-running simulations [Guemas et al, 2013], and Meehl et al [2014] found that the uninitialized CMIP5 simulations that simulated the hiatus (10 ensemble members out of a possible 262) showed a realization of internal variability very similar to that observed. Periods of reduced surface warming in simulations of historical and future periods tend to show increased storage of heat in the deep ocean [Meehl et al, 2011;Katsman and van Oldenborgh, 2011;Palmer et al, 2011], tentatively supported for the recent period by direct observation [Levitus et al, 2012] and ocean reanalysis [Balmaseda et al, 2013].…”

The rogue nature of hiatuses in a global warming climate

“…In this context, given the significant impact of the recent hiatus on the perception of climate change by the public and according to the Black Swan Theory (i.e., the destructive impact of the occurrence of outlier events on the development of theory for classical events [Taleb, 2007]), there is a risk of inappropriate mistrust of current numerical models instead of acknowledging the highly unlikely nature of the event, at the limit of climate variability [Taleb, 2001]. This mistrust would be especially counterproductive, since this past rogue event has been shown to be fully captured by current prediction systems [Guemas et al, 2013;Meehl et al, 2014], demonstrating the relevance of operational decadal predictions.…”

Análisis De Las Temperaturas Medias Y Sus Extremos a Partir De Diferentes Índices Durante El Período 1966-2015 en El Norte Grande Chileno

“…Algunos investigadores afirman que la sensibilidad del clima podría haberse sobreestimado (Otto et al 2013), otros apuntan a la incompleta cobertura a nivel global de las observaciones de temperatura y que este aumento de las mismas no está quedando registrado en aquellas regiones donde no hay una buena red de observatorios (Cowtan y Way 2014), o también debido a cambios en la actividad solar y en los aerosoles estratosféricos y troposféricos que hubieran provocado un estancamiento de las tendencias de temperatura en la última década (Solomon et al 2011;Santer et al 2014). En cualquier caso, la evidencia parece sugerir que el superávit de energía ha sido almacenado en los océanos (Meehl et al 2011;Guemas et al 2013), particularmente en el Pacífico ecuatorial (Kosaka y Xie 2013), en relación con la fase fría de la Oscilación Decadal del Pacífico (PDO) y el fortalecimiento de los trade winds (Trenberth y Fasullo 2013;England et al 2014;Meehl et al 2014).…”