Impacts of a global 2 degrees C

climate change upon European

air quality

Lacressonnière Gwendoline(1,2)

Our common future under climate change, 8 July 2015

and Watson, L., Engardt, M., Gauss, M., Andersson, C., Beekmann, M., Colette, A., Foret, G.,

Josse, B., Marécal, V., Nyiri, A., Siour, G. and Vautard, R.

1- Aria Technologies

2- IPSL/CNRS

Context and objectives

• IMPACT2C is a European Commission 7th Framework funded project that assesses a wide variety of impacts of a 2-degree rise in global temperatures.

• This study aims to evaluate how a future 2-degree increase in temperature may be expected to affect the production, deposition, and distribution of air pollutants over Europe.

• To do so, we provided long-term pan-European gridded simulations of recent climate air quality pollutants (ozone (O3), particulate matter (PM10 and PM2.5) ) over the past 20 years (hindcast and climate run), their projections under a “2°C climate” given a few compatible air pollutant emission scenarios, and the associated uncertainties.

1. Methodology

• Intercomparisons of 4 chemistry and transport models (CTMs): CHIMERE [IPSL],

EMEP [MET.NBO], MATCH [SMHI] and MOCAGE [Météo-France]

Institute CTM Driving GCM RCM used for

downscaling

Chemical boundary

conditions

CNRS-IPSL CHIMERE IPSL-CM5A-MR WRF LMDz-INCA

MET.NO EMEP NorESM WRF LMDz-INCA

SMHI MATCH EC-EARTH RCA4 LMDz-INCA

Météo-France MOCAGE ARPEGE ARPEGE MOCAGE

Participating models

Description of the model chains used

Anthropogenic emissions

• All models used the same 2005 and 2050 anthropogenic emission data from the ECLIPSE project (http://eclipse.nilu.no/).

2. Future scenario

Name Climate Boundary conditions Emissions

HISTORICAL 1971-2000 2005 ECLIPSE v4a 2005

S1 +2°C RCP4.5 2050 ECLIPSE v4a 2050 CLE

S2 1971-2000 2050 ECLIPSE v4a 2050 CLE

S3 +2°C RCP4.5 2050 ECLIPSE v4a 2050 MFR**

* Current Legislation Emissions , ** Maximum Feasible Reduction

2.1 Combined impacts of climate and emission changes

The impact of a +2ºC climate and of associated emission changes is demonstrated

when S1 is compared to the control (HISTORICAL) scenario.

• 3 CTMs simulate a large decrease of

PM2.5 in the future scenario

-> All the secondary aerosols

decrease in the future as a result of

decreasing anthropogenic emission

of precursors

PM2.5 differences for S1-HISTORICAL (Watson et al., in prep)

O3 differences for S1-HISTORICAL (Watson et al., in prep)

• The CTMs simulate a large decrease in summer O3

-> Increase in O3 production due to regional climate change is offset due to the

reduction of anthropogenic emissions

• Winter levels of O3 increase due to less titration by NOx

2.2 Effects of two mitigation scenarios

The difference between S3 (MFR) and S1 (CLE) shows that surface PM2.5

could be reduced by up to 3 µg.m-3 under the MFR scenario.

PM2.5 differences for S3-S1 (Watson et al., in prep)

O3 differences for S3-S1 (Watson et al., in prep)

JJA O3 [S3 – S1] DJF O3 [S3 – S1]

ppbv

ppbv

• The MFR scenario shows a larger reduction in future ozone in the summertime

(up to 3 ppbv)

• Reduction in NOx in the MFR scenario lead to less removal of O3

2.3 Regional climate change effects and uncertainties

• Differences between S1 and S2 shows how the +2ºC climate affects surface

PM in the absence of emission changes, under the regional climate change only.

PM2.5 differences for S1-S2 (Watson et al., in prep)

• Projected change of PM2.5 concentrations vary greatly between the model under regional climate change

• Small effects for a 2°C global warming over continental Europe

• Robustness and uncertainty of model predictions ?

• Evaluate uncertainties associated to future projections, using an ensemble of 3

CTMs (CHIMERE, EMEP and MATCH)

• PM2.5 levels slightly affected by regional climate change: ensemble average range from -0.5

µg.m-3 to 1.1 µg.m-3

• Beyond the model uncertainty, decrease of PM2.5 simulated over southwestern Russia can be

stated with confidence, as well as the increase of PM2.5 over south of Spain

• According to the analysis of PM components, the changes in PM2.5 are mainly due to natural

emissions, such as desert dust, sea salt and biogenic emissions, affected by changes in

meteorology

a) Ensemble mean of PM2.5 differences between S1 and S2, b) ensemble spread (|Max-Min|) and c) ratio

between the ensemble mean and the ensemble spread. From Lacressonnière et al., 2015

JJA DJF

O3 differences for S1-S2 (Watson et al., in prep)

• Changes in O3 greatly vary depending on the season

• Increases in temperature appear as a predominant parameter that enhance levels

of summer Ozone

• The processes involved in winter changes are titration, deposition and transport

a) Ensemble mean of SOMO35 differences between S1 and S2, b) ensemble spread (|Max-Min|) and c)

ratio between the ensemble mean and the ensemble spread. From Lacressonnière et al., 2015

• The ensemble average of SOMO35 range from -171 ppbv to 322 ppbv

• An agreement is simulated over most central and southern Europe where SOMO35 increases

in the future scenario of S1

• Changes of SOMO35 can’t be stated with confidence over any large part of Europe (ensemble

mean/ensemble spread <1)

• Uncertainty analysis of future projections, using an ensemble of CTMs

Conclusions

• The future scenarios highlight:

- Decrease of annual PM2.5 mainly induced by the decreases of emissions, while the

changes induced by regional climate change are comparatively small

- Maximum technically feasible reduction would further improve air quality

- Summer levels of O3 decrease with the decrease of emissions, while a climate

penalty is simulated over most of the domain in a 2° warming world

- Ozone levels can be significantly reduced with the MFR scenario

• Uncertainty analysis of regional climate change projections :

- Beyond the model uncertainty, climate penalties or benefits have been made evident

- The model uncertainty is mainly due differences in regional climate projections,

affecting several meteorological parameters that are crucial for air quality, such as

precipitation and wind direction

- Changes in PM2.5 are mainly related to natural and biogenic emissions that can’t be

controlled by policy measures

- Changes in SOMO35 and ozone can be large, depending on the season, area and

model considered

- The variability between the models is higher than the ensemble climate change

signal

- We can’t state a clear conclusion about changes of SOMO35 in the future climate

The fate of European air pollution in the coming decades is primarily controlled

by emission reductions

A +2°C global warming will not hinder beneficial effects of air quality legislation,

despite small changes in particulate matter and ozone levels.

Thank you