Reductions in NO2 Driven by Policy and Recession

Patricia Castellanos1 & K. Folkert Boersma1,2

AGU

1Royal Netherlands Meteorological Institute (KNMI) 2Eindhoven University of Technology, Fluid Dynamics Lab

Why do we care about NO2 over Europe?

2008 NO2 Annual Mean [μg/m3]• Ozone precursor• Aerosol formation• Eutrophication of soil

and water• Acid deposition• Toxic at high

concentrations

• Limits were supposed to be reached by 2010

• Timeline will be extended by 5 years without penalty

• Poorly quantified high biases• Lack spatial representativity• Reporting issues• Need an independent assessment

of changing NO2 concentrations

Bad air quality costs the UK 8.5-20 billion pounds per year, and can cut life expectancy by years – UK Environmental Audit Committee

Satellite Observations

NO2 Trends From Space

• Satellites provide – Global coverage– Independent & self-consistent time series

• Monitor effectiveness of pollution abatement strategies

Trend [% per year] Time Period

Richter et al. [2005] -3% to -4% 1996-2004

van der A et al. [2008] -2% to -5% (mostly insignificant)

1996-2006

Konovalov et al. [2008] -2% to -5% 1996-2005

Space-based European NO2 column trends in the literature

A Few % Per Year

NO2 Column Trends

Amsterdam

• Different summer and winter NO2 lifetimes• Large seasonal fluctuations

– Normally only look at one season

• Transport effects in winter but not in summer– Cannot always assume some regular seasonal variability

Separate the slow-moving trend from other variability

Frequency Separation – KZ Filter

# of Iterations

Transfer Function

Trends based on low-pass filtered data

K-iterations of a moving average

NO2 Column Trends: August

2008/2005 2009/2005 2010/2005

2005 2006/2005 2007/2005

NO2 Trends Relate to Economic Indicators

Fitting the NO2 Trend

• Differentiate between policy (pre-recession) and recession related NO2 changes

European Averagecontinuous

continuous + recession

Recession Change

European Average

2004-2010 Continuous Change [Ccontinuousx 6 years] [Crecession]

One year of economic recession outweighed ~4-years of policy improvements

Recession period reductions were the same or greater than pre-recession reductions

2004-2007 Reported NOx Emissions trend ÷ Ccontinuous trend

UK reports reduced emissions but NO2 has increased

Report increased emissions but NO2 has decreased

Uncontrolled shipping emissions may be reducing air quality in the countries bordering the English channel

Final Remarks• High resolution daily OMI observations allow us to analyze

spatially AND temporally heterogeneous trends

• NO2 concentrations over Europe are 10-50% lower than in 2004

• Fast declines in NOx emissions during the economic recession led to 15-30% NO2 reductions in 2008-09

Trend [% per year] Time Period

Richter et al. [2005] -3% to -4% 1996-2004

van der A et al. [2008] -2% to -5% (mostly insignificant)

1996-2006

Konovalov et al. [2008] -2% to -5% 1996-2005

Castellanos & Boersma [2011] -2% to -5%-15 to -30%

2004-20082008-2009

European NO2 column trends in the literature