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SETTING THE STAGE FOR:
BIOSPHERE, CHEMISTRY, CLIMATE INTERACTIONS
TOPICS FOR TODAY
1.
Intro to atmospheric chemistry concepts
2.
Atmosphere-biosphere connections
3.
Climate change observed & predicted
4.
How chemistry may amplify/dampen climate change
5.
How climate change may change atmospheric
composition
STRATOSPHERIC CHEMISTRY…BASIC MECHANISM
Chapman Mechanism:
Source of ozone (O2 + hv)
Sink of ozone (O+O3)
 predicts too much ozone!
Other ozone sinks: catalytic loss cycles:
1. HOx: from H2O
2. NOx: from N2O / lightning
3. ClOx: from CFCs
H2O
slow
OH
fast
HO2
slow
Antarctic ozone depletion involves special case of ClOx catalyzed O3-destruction
where (cold) PSCs return Cl from reservoir to catalyst
TROPOSPHERIC CHEMISTRY
O2
hn
O3
STRATOSPHERE
8-18 km
TROPOSPHERE
hn
O3
OH, M VOC limited
NO2
NO
hn, H2O
NOx limited
OH
Deposition
HNO3
HO2
CO, CH4, RH
CO, HC, NOx
H2O2
PARTICULATE MATTER (PM, AEROSOLS) SOURCES AND PROCESSES
ultra-fine
(<0.01 mm)
precursor gases
oxidation
SO2
nucleation
H2SO4
fine
(0.01-1 mm)
. . coagulation
.
. . .
cloud
(1-100 mm)
cycling
condensation
VOCs
NOx
RCO…
coarse
scavenging
(1-10 mm)
HNO3
NH3
combustion
biosphere
volcanoes
agriculture
biosphere
carbonaceous
combustion
particles
soil dust
sea salt
TOPICS FOR TODAY
1.
Intro to atmospheric chemistry concepts
2.
Atmosphere-biosphere connections
3.
Climate change observed & predicted
4.
How chemistry may amplify/dampen climate change
5.
How climate change may change atmospheric
composition
TERRESTRIAL BIOSPHERE / ATMOSPHERE INTERFACE
Monson and Holland, 2001
OCEAN-ATMOSPHERE INTERFACE
Monson and Holland, 2001
TOPICS FOR TODAY
1.
Intro to atmospheric chemistry concepts
2.
Atmosphere-biosphere connections
3.
Climate change observed & predicted
4.
How chemistry may amplify/dampen climate change
5.
How climate change may change atmospheric
composition
OBSERVED TEMPERATURE TREND
100-year trend
(1906–2005):
0.74°C ± 0.18°C
rate of warming doubled
in later half of century
Land warming faster than
ocean
IPCC, 2007
OBSERVED TREND IN WATER VAPOUR
Total column water vapour
has increased over the global
oceans by 1.2 ± 0.3%
per decade (1988 to 2004)
 UT water vapour also increasing,
where of radiative importance
ocean
global UT
IPCC, 2007
OBSERVED TREND IN PRECIPITATION
Long-term trends in precipitation
amounts from 1900 to 2005 have been
observed in many large regions:
↑ eastern North and South America,
northern Europe and northern and central
Asia
↓ Sahel, the Mediterranean,
southern Africa and parts of southern
Asia
Also evidence for an increase of
intense tropical cyclone activity in the N
Atlantic since about 1970, correlated
with increases in tropical SSTs.
IPCC, 2007
OBSERVED CHANGES IN SNOW COVER, SEA ICE
AND SEA LEVEL
1961 to 2003 global mean sea level rise:
1.8 ± 0.5 mm yr–1
 thermal expansion contribution: 0.42 ±
0.12 mm yr–1
 melting of glaciers, ice caps and ice
sheets: 0.7 ± 0.5 mm yr–1
IPCC, 2007
EXTREME WEATHER AND CLIMATE: TRENDS AND
PREDICTIONS
IPCC, 2007
PREDICTED TEMPERATURE TREND
IPCC, 2007
PREDICTED PRECIPITATION TREND
Increases in the
amount of
precipitation are
very likely at high
latitudes
while decreases are
likely in most
subtropical land
regions
IPCC, 2007
UNCERTAINTY IN CLIMATE SENSITIVITY
Climate Sensitivity: the warming to be expected if CO2 concentrations were
sustained at double PI (~ 550ppm)
“equilibrium climate sensitivity is likely to be in the range 2°C to 4.5°C,
with a best estimate value of about 3°C.”
IPCC, 2007
TOPICS FOR TODAY
1.
Intro to atmospheric chemistry concepts
2.
Atmosphere-biosphere connections
3.
Climate change observed & predicted
4.
How chemistry may amplify/dampen climate change
5.
How climate change may change atmospheric
composition
DIRECT RADIATIVE FORCING AGENTS
IPCC, 2007
AEROSOL “INDIRECT EFFECT” FROM CLOUD CHANGES
Clouds form by condensation on pre-existing aerosol particles (“cloud
condensation nuclei”) when RH>100%
clean cloud (few particles):
large cloud droplets
• low albedo
• efficient precipitation
polluted cloud (many particles):
small cloud droplets
• high albedo (1st indirect)
• suppressed precipitation (2nd indirect)
SCATTERING vs. ABSORBING AEROSOLS
Scattering sulfate and organic aerosol
over Massachusetts
Partly absorbing dust aerosol
downwind of Sahara
Absorbing aerosols (black carbon, dust) warm the climate by absorbing solar
radiation
AEROSOL RADIATIVE FORCING: UNCERTAINTIES
Forward calculations: models of aerosol physics and chemistry
Inverse calculations: forcing to match model simulations with observed T changes
IGAC, 2006
TOPICS FOR TODAY
1.
Intro to atmospheric chemistry concepts
2.
Atmosphere-biosphere connections
3.
Climate change observed & predicted
4.
How chemistry may amplify/dampen climate change
5.
How climate change may change atmospheric
composition
HOW WILL CLIMATE CHANGE AFFECT STRATOSPHERIC
CHEMISTRY?
Chapman Mechanism:
Source of ozone (O2 + hv)
Sink of ozone (O+O3)
 predicts too much ozone!
Other ozone sinks: catalytic loss cycles:
1. HOx: from H2O
2. NOx: from N2O / lightning
3. ClOx: from CFCs
H2O
slow
OH
fast
HO2
slow
Antarctic ozone depletion involves special case of ClOx catalyzed O3-destruction
where (cold) PSCs return Cl from reservoir to catalyst
O2
hn
STRATOSPHERE
8-18 km
O3
HOW WILL CLIMATE CHANGE AFFECT
TROPOSPHERIC CHEMISTRY?
TROPOSPHERE
hn
O3
NO2
NO
OH
HO2
hn, H2O
Deposition
CO, VOC
Nitrogen oxide radicals; NOx = NO + NO2
combustion, soils, lightning
Tropospheric
ozone
precursors
Methane
wetlands, livestock, natural gas
Nonmethane volatile organic compounds (NMVOCs)
vegetation, combustion, industry
CO (carbon monoxide)
combustion, VOC oxidation
H2O2
HOW WILL CLIMATE CHANGE AFFECT PM?
ultra-fine
(<0.01 mm)
precursor gases
oxidation
SO2
nucleation
H2SO4
fine
(0.01-1 mm)
. . coagulation
.
. . .
cloud
(1-100 mm)
cycling
condensation
VOCs
NOx
RCO…
coarse
scavenging
(1-10 mm)
HNO3
NH3
combustion
biosphere
volcanoes
agriculture
biosphere
carbonaceous
combustion
particles
soil dust
sea salt
EFFECTS OF CLIMATE CHANGE ON BIOSPHEREATMOSPHERE SYSTEM
Zepp et al., 2003