SETTING THE STAGE FOR: BIOSPHERE, CHEMISTRY, CLIMATE INTERACTIONS

transcript

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

fastOH HO2

Antarctic ozone depletion involves special case of ClOx catalyzed O3-destruction where (cold) PSCs return Cl from reservoir to catalyst

TROPOSPHERIC CHEMISTRY

OH HO2

h, H2ONO

CO, CH4, RH

h HNO3

OH, M VOC limited

NOx limited

CO, HC, NOx

Deposition

STRATOSPHERE

TROPOSPHERE8-18 km

PARTICULATE MATTER (PM, AEROSOLS) SOURCES AND PROCESSES

SO2H2SO4

RCO…

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

composition

TERRESTRIAL BIOSPHERE / ATMOSPHERE INTERFACE

Monson and Holland, 2001

OCEAN-ATMOSPHERE INTERFACE

Monson and Holland, 2001

TOPICS FOR TODAY

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

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

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

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

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

OH HO2

h, H2O

Deposition

CO, VOC

STRATOSPHERE

TROPOSPHERE

8-18 km

Troposphericozone

precursors

HOW WILL CLIMATE CHANGE AFFECT TROPOSPHERIC CHEMISTRY?

HOW WILL CLIMATE CHANGE AFFECT PM?

SO2H2SO4

RCO…

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

SETTING THE STAGE FOR: BIOSPHERE, CHEMISTRY, CLIMATE INTERACTIONS

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