MAIN MESSAGES ON OZONE TRENDS Dick Derwent rdscientific, Newbury, United Kingdom 16th TFMM Meeting, Crakow, Poland 8th May 2015

Much more needs to be done European Environment Agency

UNDERSTANDING EUROPEAN OZONE TRENDS European ozone has two main components Hemispheric scale baseline ozone European regional scale ozone WE NEED TO UNDERSTAND THE TRENDS IN BOTH COMPONENTS

ACKNOWLEDGEMENTS – BASELINE OZONE TRENDS D. Parrish K. Law J. Staehelin O. Cooper H. Tanimoto Volz-Thomas S. Glige H.-E. Scheel M. Steinbrecher E. Chan Atmos. Chem. Phys. 12, 1-20, (2012)

LONG-TERM OZONE TRENDS - 1957-ONWARDS DE0009R Zingst

LONG-TERM OZONE TRENDS – 1980s ONWARDS DE0057G

AIR MASS ORIGINS AT MACE HEAD, IRELAND – EMEP SITE IE0031R Baseline air masses

LONG-TERM OZONE TRENDS – 1990s ONWARDS Baseline ozone has increased, levelled out and started to decline IE0031R

LONG-TERM OZONE TRENDS – 1990s ONWARDS MACE HEAD, IRELAND Data courtesy of Peter Simmonds

BASELINE OZONE - SUMMARY Baseline ozone has: increased levelled off started to decrease Why is this ? Because of intercontinental transport. Intercontinental attribution can be provided for all EMEP sites. Atmos Environ 112, 216-224

INTERCONTINENTAL SOURCE ATTRIBUTION FOR OZONE FORMATION AT MACE HEAD, IRELAND IE0031R Tagged ozone labelling

LONG-TERM OZONE TRENDS – 1990s ONWARDS Mace Head, Ireland Summertime elevations have been reduced

REGIONAL OZONE TRENDS Health effects assessment based on World Health Organisation 2005 guidelines Daily maximum 8-hour ozone mean concentrations below 50 ppb Acknowledgements Anne-Gunn Hjellbrekke CCC for reformulating EMEP ozone database using annual maximum 8-hour means Handbook on Environmental Chemistry 132 (2012)

TRENDS IN MAXIMUM 8-HOUR MEAN FOR 1980 - 2009 most important period because it covers the entire period over which trends are expected 5 sites meet tight data capture criteria DE0003R Schauinsland DE0002R Langenbrugge DE0001R Westerland GB0039R Sibton -1.4 ± 0.9 ppb per year GB0036R Harwell -1.2 ± 0.7 ppb per year

MAXIMUM 8-HOUR MEAN OZONE TRENDS – GB0039R Sibton -1.4 ± 0.9 ppb per year

MAXIMUM 8-HOUR MEAN OZONE TRENDS – GB0036R Harwell -1.2 ± 0.7 ppb per year

TRENDS IN MAXIMUM 8-HOUR MEAN FOR 1990 - 2009 40 stations have complete records over this period 16 stations show highly significant downwards trends α < 0.1 19 stations show significant downwards trends α > 0.1 5 stations showed no trends

MAXIMUM 8-HOUR MEAN OZONE TRENDS – NL0009R Kollumerwaard -0.9 ± 0.7 ppb per year

MAXIMUM 8-HOUR MEAN OZONE TRENDS – IT0004R Ispra -2.3 ± 1.1 ppb per year

GB0038R Highest 8-hour running mean in ppb at Lullington Heath -1.7 ± 1.1 ppb per year

DOWNWARDS TRENDS AT LONG-RUNNING RURAL MONITORING STATIONS BETWEEN 1990 AND 2010 WHO AQG

WHY SHOULD DOWNWARDS TRENDS BE STRONGEST FOR STATIONS WITH HIGHEST OZONE IN 1990s ? It is likely that downwards trends at stations with highest ozone levels have been driven by European regional pollution emission reductions it is likely that the trends due to European regional pollution emission reductions at stations with lowest ozone levels have been offset by another trend what is the offsetting trend at the stations with lowest ozone levels ? presumably the growth in hemispheric baseline levels is the offsetting trend

INTERCONTINENTAL SOURCE ATTRIBUTION FOR OZONE FORMATION AT MACE HEAD, IRELAND IE0031R Tagged ozone labelling European regional pollution event

SUMMARY OF EUROPEAN REGIONAL OZONE TRENDS Health effects assessment based on maximum 8-hour mean ozone concentrations episodic peak levels have declined significantly since EMEP measurements began at long-running stations downwards trends have been greatest at stations where ozone levels are highest downwards trends driven by controls on VOC and NOx emissions downwards trends at lowest ozone sites have been offset by increasing hemispheric ozone baselines hemispheric baseline ozone has started to decrease and this will pull down ozone across all sites in 2010s

KEY MESSAGES 1980s – formulate CLRTAP VOC and NOx protocols Parties based aspirations on motor vehicle controls 1990s – EU implement motor vehicle emission directives 1990 - 2010s – see decline in peak 8-hour mean ozone levels 1990 - 2010s – see decline in observed VOCs and NOx 1990 - 2010s – direct relationship between precursor emission reductions and decline in episodic peak ozone