Download Air Quality and Climate overview for teachers

Air Quality 101
Rice Air Curriculum
Teacher Training
Leading Atmospheric Constituents
•
•
•
•
•
Nitrogen (N2)
Oxygen (O2)
Argon (Ar)
Water Vapor (H2O)
Carbon dioxide (CO2)
78%
21%
1%
0-3%
0.039%
Most air pollutants are in very small
quantities (parts per million or billion)
but affect our health and climate.
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Categories of Atmospheric Compounds
• Air pollutants: Substances that directly harm
health of humans, wildlife, or vegetation
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–
–
–
Air toxics: Carcinogens, mutagens, neurotoxins
Respiratory irritants
Substances that cause cardio-vascular impacts
Substances that damage crops, forests, ecosystems
• Particulate matter: Solid or liquid microscopic
particles suspended in air
• Ozone depleters: Substances that destroy
stratospheric ozone
• Climate-influencing compounds: Greenhouse
gases and particles that impact radiative budget
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Particulate Matter
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Particulate Matter
• Aerosol: Liquid or solid particles suspended in air
• Wide range of chemical composition
• Sizes range from <1nm to >10 μm
– Large particles settle out quickly
– Fine particles (<2.5 μm (PM2.5)) most damaging to
visibility & health (respiratory, cardio-vascular, mortality)
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Impacts of PM
• Health effects
– Fine particles go deep in lungs, to bloodstream
– Respiratory and cardiovascular disease
– Mortality
• Visibility/Haze
• Climate
• Regulatory concern
– Houston barely attains current standard
– EPA tightened 24-hr but not annual standard
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Ozone (O3)
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Stratospheric & Tropospheric Ozone:
“Good up high, Bad nearby”
• In stratosphere, ozone forms naturally when
Sun’s intense UV rays split oxygen:
–
–
–
–
O2 + hv  O + O
O + O 2  O3
This “good ozone” blocks UV rays
Stratospheric ozone can be destroyed by CFCs
• In troposphere, intense UV rays already blocked.
Ozone instead forms as a pollutant:
– Nitrogen oxides + Hydrocarbons + Sunlight  O3
– “Bad ozone”: air pollutant and greenhouse gas
Stratospheric Ozone Hole
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Montreal Protocol
drastically curtailed
ozone depleting
emissions
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WMO/UNEP Scientific Assessment of Ozone Depletion, 2010
Impacts of Montreal Protocol:
Halocarbon Concentrations
45 yr
lifetime
5 yr
lifetime
100 yr
lifetime
35 yr
lifetime
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NOAA
Ozone projected to recover as
halocarbon levels decline
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Ground-level Ozone “Smog”
Sunlight &
Heat
RO2
HO2
NO
VOC
OH
NO2
VOC
NOx
Hydrocarbons
Nitrogen
Oxides
O3
O3
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Tropospheric NOx Cycle
HO2 and CH3O2, other RO2
O3
CO, CH4,
VOCs
N2O
O(1D)
O
NO
hν
hν
Direct
emissions
*
NO2
ClO, BrO
ClONO2
BrONO2
*
hν
HNO3
NO3
O3
N2O5
Red: Ox destruction
Green: Ox production
Black: No change in Ox
Blue: Reservoir Species
*: Dominant pathway
during daytime
Sources of Ozone-forming Emissions
• Nitrogen Oxides
– Vehicles
– Power plants
– Other industry and equipment
• Hydrocarbons
– Natural vegetation
– Vehicles
– Refineries / Chemical plants
– Other sources
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Ozone Impacts
• Health effects
– Asthma and other respiratory illnesses
– Recently linked to mortality
• Regulatory concern
– Houston, Dallas, many other cities fail to
attain limits
• Atmospheric oxidant
– Oxidizes certain VOCs
– Contributes to formation of OH oxidant
• Greenhouse gas
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Emissions Trends
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Strong declines in ozone, but many
cities still exceed 75 ppb
Houston
http://www.tceq.state.tx.us/assets/public/implementation/air/
sip/hgb/hgb_sip_2009/09017SIP_Ch5_ado.pdf
US Cities
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Ozone Non-attainment: 75 ppb standard
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Map from US EPA
Climate Change Overview
• Is Earth warming?
• Natural or anthropogenic causes?
– Overview Earth’s radiative balance &
greenhouse effect
• Impacts
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Evidence of recent
climate change
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IPCC, 2007
Global
US
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National Geographic
Additional evidence of warming
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IPCC, Physical Basis Technical Summary, 2007
Past decade was warmest recorded
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Hansen et al 2010
This summer’s weather
Anomaly (°C) relative to 1951-1980 mean
http://www.columbia.edu/~mhs119/Temperature/
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In the news: Arctic sea ice reaches all
time minimum extent, August 26, 2012
Yellow line shows average minimum, 1979-2010
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NASA: http://climate.nasa.gov/news/index.cfm?FuseAction=ShowNews&NewsID=767
Climate Fundamentals: Earth’s Radiative
Balance and Greenhouse Effect
Yellow:
Solar UV
and Visible
Radiation
Beige:
Infrared
Radiation
Radiation
proportional to TK4
(Trenberth et al., BAMS, March 2009)
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Greenhouse gases absorb and re-radiate
infrared at atmosphere’s cooler temperature
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Earth’s Carbon Cycle
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(IPCC 2007, Physical Basis Chapter 7)
Rising Greenhouse Gas Levels
CO2
CH4
N2O
Total
Radiative
Forcing
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IPCC, 2007
Causes of Radiative Forcing, 1750-2005
Greenhouse gas
radiative forcing (W/m2)
well understood
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IPCC, 2007
Key Scientific Uncertainty: How much
warming per radiative forcing (°C/W-m2)
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Both anthropogenic and natural forcings
are needed to model temperature record
IPCC, 2007
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IPCC, 2007
Projected Impacts of Further Warming
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IPCC, Impacts SPM, 2007