RCM Mean Bias Correction

Electronic supplementary material

RCM mean bias correction

Rainfall and temperature have been mean-bias corrected for each individual RCM with respect to the 1990-2009climatology. Namely for each year:

For temperature:

For rainfall:

i and j denote a specific grid point per latitude / longitude, and m denotes a specific month. The correction is applied for each month within the season. The reference climatology is based on the 1990-2009 time period.

Overwintering criterion

Figure S1a shows the suitable regions for A. albopictus to survive European winters based on mean observed climatic variables for the 1960-1989 period. The western and southern coasts of England, Wales, western France, part of Belgium and Netherlands, the north-western coasts of Spain (Galicia region), Portugal, northern and the south-western coasts of Italy, the western coasts of the Balkans and Greece appears to be suitable areas for the overwintering of A. albopictus (for Rain_ann>700mm and T_jan > 2°C). The delineation of overwintering areas with T_jan > 0°C and Rain_ann > 500m has been generally accepted in former published studies (Burgess, 1995; Mitchell, 1995; Knudsen et al., 1996; Rodhain, 1996; Fisher et al., 2011). The regions that do not fit this criterion (unsuitable) are depicted by the light grey shading on Figure S1. Considering these standard climatic thresholds, most of western Europe including France, northern and the eastern coast of Spain, Portugal, most of the UK excepting the highland regions of Scotland, the Benelux, most of Italy and the coast of the Adriatic appear to be possible overwintering areas for A. albopictus over the period 1960-1989 while most of eastern Europe and the Scandinavian countries are of low or no suitability as the winters are too extreme or the conditions are too dry for the mosquito to survive. Within the context of climate change, annual rainfall has generally increased over northern Europe (more marked during the winter season) whereas this has decreased over southern Europe and the Mediterranean basin especially (more pronounced in summer) during the last two decades. A significant decrease in the number of frost days in winter has also been observed. Figure S1b shows the regions for the overwintering of A. albopictus over the last 20 years (1990-2009), for which temperature and the rainfall amounts have significantly changed.Aedes albopictus suitable areas (white shading) have spread across the Benelux, the western coasts of Denmark, and western Germany. In Spain, conditions have become more unsuitable for the mosquito. Considering the standard overwintering criterion (light gray shading), it is notable that unsuitable areas have moved eastward over north-western central Europe (Germany), and that part of Croatia, Slovenia and Bosnia-Herzegovina have become more suitable for the overwintering mosquito during the last two decades. As the vector has been introduced recently into these countries through importation, recent climate change conditions might have favoured its survival in the winter conditions.

The future scenario based on regional climate model projections highlight similar overwintering trends for the period 2030-2050 (FigS2). Regions become more suitable over north-western central Europe (Benelux, western Germany and western Denmark), as the unsuitable zones retreat eastward with respect to the recent climatic context. This is related to both an increase in simulated temperatures and increased moister conditions over northern Europe (especially in winter, not shown). Future climate projections highlight that A. albopictus overwintering is also favoured over the Balkans. A larger area of Spain becomes more unsuitable as simulated drier conditions (occurring especially in summer) could limit the southward expansion of the vector. There are no significant future changes over the UK and France with respect to the recent climatic context (1990-2009). However, these results are based on the multi-model ensemble mean. There are significant differences across the different model projections (FigS3). Some RCMs projections are close to the ensemble mean pattern (SMHIRCA, KNMI-RACMO2 models). Some models (C4IRCA4, ETHZ-CLM) simulate a large eastward retreat of the unsuitable areas over north-western and central Europe (including most of Germany and Denmark), while for others (MPI-M-REMO, OURANOSMRRCC) the simulated future overwintering pattern is relatively close to the one which is based on recent climate observations.

Multimedia

An animated movie depicting the climate suitability of A.albopictusbased on Model 1(Kobayashi et al., 2002) has been createdby the authors and is available on youtube at this address:

The present period (1950-2009) is based on gridded observation data (EOBS), while the future projections (2010-2050) are based on the regional climate model ensemble mean carried out within the ENSEMBLES project (SRESA1B) scenario. Trends are depicted as a 5 year running average is applied to the data. The RCMs outputs are mean bias corrected with respect to the observations.

Figure S1: Overwintering capacity of A. albopictus to survive based on mean observed January temperatures and annual rainfall. This is carried out for the period 1960-1989 (a) and 1990-2009 (b) based on the EOBS dataset. White areas depict regions for which climate is suitable for the mosquito. The different grey and black shadings depict regions of unsuitability according to different climatic thresholds. The light gray shading depicts strictly unsuitable areas.

Figure S2: Futureoverwintering capacity of A. albopictus to survive based on mean observed January temperatures and annual rainfall. This is carried out for the period 2030-2050 based on the SimA1B scenario experiment (ensemble mean of all RCM experiments). White areas depicts regions for which climate is suitable for the mosquito. The different grey and black shadings depict regions of unsuitability according to different climatic thresholds. The light gray shading depicts strict unsuitability areas (lower scenario).

Figure S3:Overwintering capacity of A. albopictus to survive based on mean simulated January temperatures and annual rainfall. This is carried out for the period 2030-2050 for each Regional Climate Model projections. The RCMs data are mean bias corrected with the mean reference climate based on the EOBS data for the period 1990-2009 (the delta estimated from the models is added to the mean observed climate).
Figure S4: Climatic parameters employed to drive the different methods. Observed annual rainfall climatology for the period a) 1960-89 and b) 1990-2009. Mean observed January temperatures for the period c) 1960-89 and d) 1990-2009. Observed annual temperature climatology for the period e) 1960-89 and f) 1990-2009. Mean observed summer (June-July-August) temperatures for the period g) 1960-89 and h) 1990-2009.
Figure S5:Aedes albopictussuitability based on the standard overwintering criterion and annual mean temperatures (Model 1). This is carried out for the period 2030-2050 for each Regional Climate Model projections. The RCMs data are mean bias corrected with the mean reference climate based on the EOBS data for the period 1990-2009 (the delta estimated from the models is added to the mean observed climate).
Figure S6:Aedes albopictussuitability based on the MCDA method developed in ECDC, 2009 (Model 2). This is carried out for the period 2030-2050 for each Regional Climate Model projections. The RCMs data are mean bias corrected with the mean reference climate based on the EOBS data for the period 1990-2009 (the delta estimated from the models is added to the mean observed climate).
Figure S7:Weeks of adult mosquito activity based on Medlock et al, 2006 (Model 3). This is carried out for the period 2030-2050 for each regional climate model projections. The RCMs data are mean bias corrected with the mean reference climate based on the EOBS data for the period 1990-2009 (the delta estimated from the models is added to the mean observed climate).
a)Model 1 / b)Model 2 / c)Model 3
/ /
Figure S8:Receiver Operating Characteristic (ROC) curves of the different modelperformances employed in the study (driven by observed climate data for 1990-2009). The analysis is carried out for the grid points where absence and presence of the mosquito has been reported (ECDC/VBORNET dataset).All model outputs have been rescaled between 0 and 1, and all data have been interpolated to the common 0.25° grid.
Country / Year of detection / Reference
USA / 1985 / Hawley et al., 1987
Brazil / 1986 / Forattini, 1986
Mexico / 1988 / Anonymous, 1989
Barbados / 1993 / Reiter, 1998
Dominican republic / 1993 / Peña, 1993
Cuba / 1995 / Broche Borja, 1999
Honduras / 1995 / Anonymous, 1996
Guatemala / 1995 / Ogata Amayoa, 1996
El Salvador / 1996 / Anonymous, 1996
Bolivia / 1997 / Anonymous, 1997
Argentina / 1998 / Rossi et al., 1999
Colombia / 1998 / Velez et al., 1998
Paraguay / 1999 / Anonymous, 1999
Panama / 2002 / Anonymous, 2002
Uruguay / 2003 / Anonymous, 2003
Nicaragua / 2003 / Lugo et al., 2005
South Africa / 1990 / Cornel Hunt, 1991
Nigeria / 1991 / Savage et al., 1992
Cameroon / 2000 / Fontenille Toto, 2001
Equatorial Guinea / 2001 / Toto et al., 2003
Gabon / 2006 / Krueger Hagen, 2007
Lebanon / 2003 / Anonymous, 2003
Israel / 2003 / Pener et al., 2003
Syria / 2005 / Anonymous, 2006
Albania / 1979 / Adhami Reiter, 1998
Italy / 1990 / Dalla Pozza et al., 1994
France / 1999 / Schaffner Karch, 2000
Belgium / 2000 / Schaffner et al., 2004
Montenegro / 2001 / Petric et al., 2001
Switzerland / 2003 / Flacio et al., 2004
Greece / 2003 / Samanidou-Voyadjoglouet al., 2005
Spain / 2004 / Aranda et al., 2006
Croatia / 2004 / Klobucaret al., 2006
Netherlands / 2005 / Sholte et al., 2007
Bosnia and Herzegovina / 2005 / ECDC, 2006
Slovenia / 2005 / Petric et al., 2006
Germany / 2007 / Pluskotaet al., 2008
Malta / 2009 / Gatt et al., 2009
Table 1: Countries where A. albopictus was detected from 1979 to 2011.
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