Signals of anthropogenic influence on European warming as seen in the trend patterns of daily temperature variance

Abstract

Signals of anthropogenic warming over Europe are searched for in the spatial trend patterns for the variance and skewness (expressed by the 10th and 90th percentiles) of the distribution of daily mean temperature. Comparisons are made between these patterns in the station records of the European Climate Assessment dataset for the 1976-99 period, the patterns associated with natural variability in the observations (which were empirically derived from the observations in the 1946-75 period), and the patterns of future warming and natural variability as simulated by the National Center for Atmospheric Research Community Climate System Model in the Challenge ensemble experiment.The results indicate that, on the basis of the patterns for the variance, a distinction can be made between temperature change due to natural variability and temperature change due to changes in external forcing. The observed variance trend patterns for the spring (March-May) and summer (June-August) warming 1976-99 are clearly different from the patterns for the change in variance associated with a warming due to natural variability in the observations. This led us to conclude that a change in an external forcing has to be invoked to explain the observed spring and summer warming. From the evaluation of the greenhouse and natural variability patterns in the climate model simulations, we infer that the observed spring and summer variance trend patterns contain imprints consistent with anthropogenic warming. The analysis of the variance trend patterns for the winter (December-February) season is inconclusive about identifying causes of the observed warming for that season. Unlike the other three seasons, the autumn (September-November) is for Europe a period of cooling in recent decades. The observed variance trend pattern for this season closely resembles the estimated pattern for the change in variance associated with a cooling due to natural variability, indicating that the observed autumn cooling can be ascribed to random weather variations in the period under consideration.

Recent severe heat waves in central Europe: how to view them in a long‐term prospect?

“…Variance of daily temperatures and the first-order autocorrelation coefficients are kept unchanged in experiments A, B and C. However, since global warming is expected to be supplemented by a rise in interannual variability of summer temperatures over large parts of Europe Klein Tank et al, 2005;Scherrer et al, 2005;Della-Marta et al, 2007b), which is driven by a decline in spring and summer precipitation and a strong land-atmosphere coupling (Seneviratne et al, 2006;Fischer et al, 2007), a variance increase of 2.5%/decade is assumed over 2007-2100 together with the mid-scenario of warming of 0.5°C/decade in another experiment A-var. The variance increase is achieved by adding a seasonal temperature anomaly, drawn from a normal distribution with rising variance over time (on the interannual scale), to all values in the particular realization of a given year [generated by the AR(1) model].…”

“…Since the AMO may weaken in the next 50 years (Knight et al, 2005), the AMO-related summer cooling may partially offset the rise in the severity of heat waves expected from anthropogenic influences, and the lower bound scenario of future summer warming may be the more realistic one over the next few decades. Other studies attribute a substantial part of the warming over the first half of the 20th century to solar and volcanic forcings while the increase in temperatures during the second half of the 20th century is largely attributable to anthropogenic influences (Stott et al, 2004;Klein Tank et al, 2005;IPCC, 2007b). The extent to which the AMO sharpens summer heat wave severity over Europe (as well as the possible physical mechanisms of the link) remains unclear.…”

Spatial analysis of mean temperature trends in Spain over the period 1961–2006

“…Several authors have carried out temperature trend analysis at different spatial scales, for instance: Schönwiese and Rapp (1997), Parry (2000), Klein Tank et al (2002), Klein Tank and Können (2003), Klein Tank et al (2005), Luterbacher et al (2004), and Moberg et al (2006) for all Europe or Brunetti et al (2000Brunetti et al ( , 2004Brunetti et al ( , 2006, Toreti and Desiato (2008), and Toreti et al (2010) in Italy; Degirmendžić et al (2004) in Poland; Rebetez and Reinhard (2008) in Switzerland; Wulfmeyer and Henning-Müller (2006) in Germany; Chaouche et al (2010) in France;and Feidas et al (2004) in Greece. Although there are local and regional differences most of Europe has experienced rising temperatures of about 0.8°C during the 20th century (IPCC, 2001) showing similar patterns to the global or a hemispheric scale.…”

Changes in Climate Extremes and Catastrophic Events in the Mongolian Plateau from 1951 to 2012

“…RClimDex calculates 16 temperature and 11 precipitation indices that are defined by the World Meteorological Organization Working Group on Climate Change Detection. This suite of indices was used to examine changes in extremes in five areas of the world where regional climate change workshops were held (Aguilar et al 2005;Haylock et al 2006;Klein Tank et al 2005;New et al 2006;Vincent et al 2005;Zhang et al 2005), and one global analysis incorporated the indices calculated at the regional workshops (Alexander et al 2006). In this study, indices mostly relevant to this study area were examined and a final selection of 11 temperature and 10 precipitation indices was selected (Table 1).…”