Global Air Quality and Pollution By Hajime Akimoto Summary by Ricky Paredes Critique by Jesse Kantor EE563 Winter 2004

Summary IntroductionIntroduction Remote SensingRemote Sensing Tropospheric OzoneTropospheric Ozone Carbon Monoxide (CO)Carbon Monoxide (CO) AerosolsAerosols Intercontinental TransportIntercontinental Transport MegacitiesMegacities

Introduction The impact of global air pollution on climate and the environment is a new focus in atmospheric science Air pollution jeopardizes agricultural and natural ecosystems Air pollution has strong effect on climate change –Aerosols change global climate through their direct and indirect effects on radiative forcing. –Radiative forcing is the change in the balance between radiation coming into the atmosphere and radiation going out. A positive radiative forcing tends to warm the surface of the Earth, and negative forcing tends to cool the surface. In the 1990’s nitrogen oxide emissions from Asia surpassed those from North America and Europe and should continue to exceed them for decades.

Introduction Air pollution is international issue –First became clear when MAPS (1981) measured high levels of CO in Asia, Africa, and South America. –Major contributors: Fossil fuel combustion Biomass burning –Forest fires –Agricultural waste burning –Vegetable fuel combustion

Introduction

Remote Sensing MAPS (Measurement of Air Pollution from Satellite) –Launched in 1981 –Global distribution of CO –High concentrations of CO over: Tropical Asia Africa South America –Air pollution as an international issue

Remote Sensing TOMS (Total Ozone Mapping Spectrometer) –Tropospheric and Stratospheric Ozone measurements –On Nimbus 7 satellite –Measurements in Antarctica are shown below (notice the growing ozone hole)

Remote Sensing The TOMS is the first instrument to allow observation of aerosols as the particles cross the land/sea boundary. Using this data, it is possible to observe a wide range of phenomena such as desert dust storms, forest fires and biomass burning.

Remote Sensing

MOPITT (Measurement of Pollution in the Troposphere) –Measures carbon monoxide (CO) in the troposphere

Remote Sensing MOPITT in action

Remote Sensing GOME (Global Ozone Monitoring Experiment) –Measures nitrogen dioxide (NO 2 ) in the troposphere

Tropospheric Ozone Potent greenhouse gas that is toxic to –Humans May cause permanent damage to lungs Inhaling it triggers chest pains, coughing, nausea, throat irritation, and congestion. –Animals –Plant life

Tropospheric Ozone Lifetime of tropospheric ozone: –1 to 2 weeks in the summer –1 to 2 months in the winter Hemispherical transport –Characteristical timescale = 1 month –Occurs in all seasons except summer Therefore tropospheric ozone can be transported intercontinentally

Tropospheric Ozone Model-Calculated surface O 3 during the growing season in the Northern Hemisphere in 1860 and 1993

Tropospheric Ozone Spatial extent of global ozone pollution –The average concentration of ozone in remote areas of East Asia is already high enough to jeopardize agricultural and natural ecosystems there. Hence, long range transport of ozone can cause the addition of ozone produced locally or regionally to exceed critical levels. Small increments of ozone concentrations caused by contributions from other continents an issue of great concern

Carbon Monoxide (CO) Atmospheric lifetime of CO is also long enough to allow intercontinental transport and hemispherical air pollution Significant portion of CO pollution is from automobiles and biomass burning Global pollution by CO is worrisome because of its effect on the oxidizing capacity of the atmosphere

Aerosols Aerosols are tiny particles suspended in the air. Some occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels and the alteration of natural surface cover, also generate aerosols. Averaged over the globe, aerosols made by human activities currently account for about 10 percent of the total amount of aerosols in our atmosphere. Most of that 10 percent is concentrated in the Northern Hemisphere, especially downwind of industrial sites, slash-and-burn agricultural regions, and overgrazed grasslands.

Aerosols Lifetime of aerosol is about 1 to 2 weeks –Have a more uneven distribution than ozone –More concentrated near their source regions over continents and in the boundary layer The more uneven distribution of tropospheric aerosols causes highly heterogeneous radiative forcing, which can lead to climate effects occurring regionally and globally

Aerosols

Intercontinental Transport Studies of transboundary air pollution led –To the investigation of possible intercontinental transport and hemispheric air pollution Trans-Pacific transport of trace gases from Asia to North America has been reported most frequently This Asian outflow enhances the concentration of surface ozone in the US by a few ppbv

Intercontinental Transport Trans-Atlantic transport from North America to Europe has been investigated –North America pollution contributes an average of 5 ppbv to surface O 3 on the west coast of Ireland –And about 2 to 4 ppbv over Europe in the summer The influence of North American pollution on European air quality is seen most frequently in the free troposphere.

Intercontinental Transport Transport of European outflow across Eurasia to Asia has scarcely been studied Substantial amount of air travels from Europe to East Asia in winter and early Spring. Measurements of air pollutants over Eurasia made using commercial airlines have revealed high concentrations of O 3 in the upper troposphere Export of nitrogen oxides are the major sources over polluted continents and the clean ocean.

Intercontinental Transport Study of the intercontinental transport and chemical transformation of O 3 between North America, Europe, and Asia using a global chemical transport model

Intercontinental Transport

Intercontinental transport of O 3 from East Asia (to North America and Europe) occurs mostly in the middle and upper troposphere. Intercontinental Transport of O 3 from Europe affects mainly near-surface O 3 concentrations in East Asia. The O 3 from the US affects Europe in the boundary layer and middle and upper troposphere.

Intercontinental Transport NO x emissions from North America and Europe have been nearly equal since 1980 Stringent emission control in western European countries after 1990 Asian emissions have increased rapidly and are expected to continue for at least the next couple of decades

Intercontinental Transport Future increases of emissions from Africa and South America, because of the economic growth there, would make global air quality more of an issue in the Southern Hemisphere Southern Hemisphere is a region where only biomass burning has been considered important so far.

Megacities Important source of regional and global pollution Defined as a metropolitan area with over 10 million inhabitants 17 megacities in 2001 With rapid growth in developing countries, megacities become major contributors of pollution

Megacities Megacities that have three or more pollutants that exceed the WHO (World Health Organization) health protection guidelines: –Beijing (China) –Sao Palo (Brazil) –Moscow (Russia) –Los Angeles (USA) –Cairo (Egypt) –Jakarta (Indonesia) –Mexico City (Mexico) Mexico City was classified as having serious problems for sulfur dioxide, carbon monoxide, and ozone in addition to heavy pollution for lead and nitrogen dioxide. Mexico City suffers in particular due to its high altitude and climate which results in poor ventilation, in addition to the large number of old and poorly maintained vehicles.

Megacities

Author’s Conclusion Local, regional, and global air-quality issues, and regional and global environmental impacts, including climate change, should be viewed in an integrated manner.

Critique By Jesse Kantor

CRITIQUE Why should we believe his conclusions about the increasing global pollution? Does he have enough data to support his conclusions?

Many Satellites Air Pollution Measuring Satellites –MAPS(Measurement of Air Pollution from Satellite) –MOPITT(Measurement of pollution in Troposphere) –SCHIAMACHY(Scanning Imaging Absorption Spectro-meter for Atmospheric Cartography) Ozone Measuring Satellites –TOMS(Total Ozone Mapping Spectrometer) –GOME(Global Ozone Monitoring Experiments) Aerosol Measuring Satellites –SEAWIFS(Sea Viewing Wide-Field-of-View Sensor Data) –AVHRR(Advanced Very High Resolution Radiometers) –MODIS(Moderate Resolution Imaging Spectrometer on Terra Satellite) –SAGE(Stratospheric Aerosol and Gas Experiment on Nimbus 7 satellite) Total –9 Satellites (A large amount of information sources)

References 48 sources(A large amount) Only 3 written by Akimoto –This is 6.25 percent Many of sources were written in the past 10 years The large amount of references gives credibility to the paper

No Old Sources Is it good to have only recent sources? –J. Lelieveld, F. Dentener wrote “high-latitude Eurasian and North American continents was 15 to 25 parts per billion by volume (ppbv) in 1860 but has increased to ppbv even in relatively remote areas” (2000) –Brings into doubt their estimation of historical information since satellite sensor technology is relatively new –It is excellent to have current sources which show that experts currently believe we have greatly increasing global pollution –It is difficult to believe they are entirely correct about how fast it is increasing –They may also not know all the causes Many factors contribute to pollution such as biomass pollution (forest fires, agricultural waste burning)

Critique of Major Argument His major claim is that small concentrations of ozone from other continents can push endangered regions to a “critical mass” His arguments are very convincing that we have pollution problems It was not as believable that one continents pollution is having a great effect on other countries Akimoto writes “One example of the special extent of global ozone pollution is that the average concentration of ozone in remote areas of East Asia is already high enough to jeopardize agriculture and natural ecosystems there” He assumes that these remote areas are polluted by other continents It is more likely that pollution in rural Asia comes from urban Asia

Good Point The lifetime of these pollutants last long enough to spread (1 week-2 months) globally –We need to be concerned with this possibility Some pollutants have more effect globally than others –Tropospheric ozone and CO are more harmful globally because their lifetimes are 1-2 months –Aerosol is not as global Its lifetime is 1-2 weeks Any global effects are episodic It mainly affects local and regional areas

Same Old Argument It is just difficult to prove how much 1 continent is affected by another It is difficult to see the effects of pollution. –This makes it difficult to motivate people to do something about it

Final Argument: Intercontinental Pollution He has 11 sources showing some evidence of intercontinental transport of gases –Note: These were not harmful gases they tracked –They have not observed ozone transport, only measured increases of ozone in certain areas –On the other hand, just because we haven’t observed it, it doesn’t mean it is not there –If it is true for other gases, we should be concerned about ozone

Counter Arguments to Intercontinental Pollution Trans Atlantic transport of O 3 and CO from North America to Europe were studied for 6 years but few episodes of intercontinental pollution were identified Transport of European outflow across Eurasia has scarcely been studied Most of evidence presented by Akimoto that supports global pollution more clearly was done through modeling Hard evidence is more concrete than modeling Last page showed more proof of the large amount of pollution rather than the intercontinental effects of pollution

Conclusion This was a good article It may not completely prove all its points but it does show we need to be concerned and do more studies of intercontinental pollution

The End Questions? Comments?