Post on 21-Dec-2015
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 H2O2. NOx: from N2O / lightning3. ClOx: from CFCs
H2Oslow
slow
fastOH HO2
Antarctic ozone depletion involves special case of ClOx catalyzed O3-destruction where (cold) PSCs return Cl from reservoir to catalyst
TROPOSPHERIC CHEMISTRY
O3
OH HO2
h, H2ONO
H2O2
CO, CH4, RH
NO2
h HNO3
OH, M VOC limited
NOx limited
CO, HC, NOx
O3
O2 h
Deposition
STRATOSPHERE
TROPOSPHERE8-18 km
PARTICULATE MATTER (PM, AEROSOLS) SOURCES AND PROCESSES
SO2H2SO4
NH3
VOCs
NOx
RCO…
HNO3
nucleation coagulation
condensation
carbonaceouscombustion
particlessoil dustsea salt
..
...
.oxidation cycling
ultra-fine(<0.01 m)
fine(0.01-1 m)
cloud(1-100 m)
combustionbiospherevolcanoes
agriculturebiosphere
coarse(1-10m) scavenging
precursor gases
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 centuryLand warming faster than ocean
IPCC, 2007
OBSERVED TREND IN WATER VAPOUR
IPCC, 2007
ocean
global UT
Total column water vapourhas increased over the global
oceans by 1.2 ± 0.3%per decade (1988 to 2004)
UT water vapour also increasing, where of radiative importance
OBSERVED TREND IN PRECIPITATION
IPCC, 2007
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 ofintense tropical cyclone activity in the N
Atlantic since about 1970, correlated with increases in tropical SSTs.
OBSERVED CHANGES IN SNOW COVER, SEA ICE AND SEA LEVEL
IPCC, 2007
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
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
latitudeswhile decreases are
likely in most subtropical land
regions
IPCC, 2007
UNCERTAINTY IN CLIMATE SENSITIVITY
“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.”
Climate Sensitivity: the warming to be expected if CO2 concentrations were sustained at double PI (~ 550ppm)
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 aerosolover Massachusetts
Partly absorbing dust aerosoldownwind of Sahara
Absorbing aerosols (black carbon, dust) warm the climate by absorbing solarradiation
AEROSOL RADIATIVE FORCING: UNCERTAINTIES
IGAC, 2006
Forward calculations: models of aerosol physics and chemistryInverse calculations: forcing to match model simulations with observed T changes
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 H2O2. NOx: from N2O / lightning3. ClOx: from CFCs
H2Oslow
slow
fastOH HO2
Antarctic ozone depletion involves special case of ClOx catalyzed O3-destruction where (cold) PSCs return Cl from reservoir to catalyst
Nitrogen oxide radicals; NOx = NO + NO2
combustion, soils, lightningMethanewetlands, livestock, natural gasNonmethane volatile organic compounds (NMVOCs)vegetation, combustion, industryCO (carbon monoxide)combustion, VOC oxidation
O3
O2h
O3
OH HO2
h, H2O
Deposition
NO
H2O2
CO, VOC
NO2
h
STRATOSPHERE
TROPOSPHERE
8-18 km
Troposphericozone
precursors
HOW WILL CLIMATE CHANGE AFFECT TROPOSPHERIC CHEMISTRY?
HOW WILL CLIMATE CHANGE AFFECT PM?
SO2H2SO4
NH3
VOCs
NOx
RCO…
HNO3
nucleation coagulation
condensation
carbonaceouscombustion
particlessoil dustsea salt
..
...
.oxidation cycling
ultra-fine(<0.01 m)
fine(0.01-1 m)
cloud(1-100 m)
combustionbiospherevolcanoes
agriculturebiosphere
coarse(1-10m) scavenging
precursor gases
EFFECTS OF CLIMATE CHANGE ON BIOSPHERE-ATMOSPHERE SYSTEM
Zepp et al., 2003