aerosol impacts on arctic climate during the 20th century: a giss climate model study

Aerosol Impacts on Arctic Climate Aerosol Impacts on Arctic Climate During the 20th Century: A GISS During the 20th Century: A GISS

Climate Model StudyClimate Model Study

Dorothy Koch Columbia University/ Goddard Institute for Space Studies

Surabi Menon, Stephen Warren, Igor Alienov, Reto Ruedy, Tami Bond

SPAC Workshop Oslo, Norway November 5, 2007

Aerosol effects in the Arctic1. Direct Effect, warming or cooling?: Sulfates cool, BC

may cool the surface but warm column

2. Indirect Effect, warming or cooling?: Increased CDNC may cause cooling (SW) or warming (LW)

3. BC-albedo Effect, warming: black carbon darkens snow, enhances melting, exposes darker surfaces causing more melting

Which Effects warm/cool?

What are their seasonalities?

How do changing LL GHG influence the aerosol effects?

ModelGISS ModelE GCM (Schmidt et al., 2006) 4x5x20 levelsAtmosphere-ocean equilibrium climate simulations using q-flux ocean for 1995

and 1890 simulationsAerosol species (mass, externally mixed) interact with climate: Black and organic carbon (BC, OC) , sulfate (SO4), sea saltAerosols coupled to GCM: transport, cloud processing, boundary layer, dry

deposition, radiationRemoval: Sulfate and sea-salt are soluble

Non-biomass burning BC and OM become soluble with timeBiomass burning OM and BC and dust have fixed solubility

Aerosol emissions: Sulfate fossil fuel: 1995 EDGAR v3.2; 1890 Van Aardenne et al. (2001) Carbonaceous fossil and bio- fuels:

1996 Bond et al. (2004); 1890 Bond et al. (2007) Biomass burning: GFED v1, average of 1997-2001; for 1890 reduce tropical

burning by 0.5 Natural OM: Terpene emissions Natural sulfate: DMS oceanic biogenic, volcanoes Sea salt source model wind-speed parameterization

Can the model simulate Arctic haze?Model aerosol concentrations compared with surface

measurements

Model

Observed

Is aerosol column amount (AOD), absorption (AAOD) OK?

Model AOD, AAOD compared to AERONET

Model

Observed

Model

AERONET observed

Tests for model BC Tests for model BC deposition, removal:deposition, removal:

Model deposition compared to BC deposition compiled in Flanner et al. (2007).

Percent dry deposition from Davidson et al (1985)

Scavenging ratio from Davidson et al (1985) and Noone and Clarke (1988)

These are sensitive to removal assumptions. Here we assume 12% removal by ice phase (compared to liquid phase)

Major aerosol source regions for the Arctic

N. America

Europe

S.E. Asia

North Asia

At the surface most Arctic aerosol is from Europe and biomass burning Koch and Hansen, JGR (2005); Koch et al., JGR (2007)

Surface Arctic BC is mostly from residential and transport sources

Koch et al., J. Geophys. Res., (2007)

Residential Transport Industry Power

Most Arctic sulfate comes from the industry and power sectors Koch et al., J. Geophys. Res., (2007)

AOD

Emission trends during the past century

Emission histories

We model Arctic pollution in 1890 and 1996.

SulfurVan Aardenne et al., 2001

Black carbonBond et al., 2007

Total

Total

Europe

EuropeN. Am.

N. Am.

S.E. Asia

S.E. Asia

Europe+SE_Asia+N_Am+Russia

Europe+SE_Asia+N_Am+Russia

Arctic Surface BC: was larger in 1920, with more from Europe, N. America, and Northern Asia

McConnell et al. (2007): BC and sulfate in Greenland ice core.

Fires?

Column SO4

Column SO41995: Europe, SE Asia, Russia1920: Europe, N. America

6 pairs of Equilibrium Climate Experiments

Aerosols (LL) GHG Aerosol Effects

1995/1880 1995 Direct

1995/1880 1995 Direct+Indirect

1995/1880 1995 Direct+Indirect+BC-albedo

1995/1880 1995/1880 Direct

1995/1880 1995/1880 Direct+Indirect

1995/1880 1995/1880 Direct+Indirect+BC-albedo

1. Distinguish relative aerosol impacts on climate2. How are aerosol effects modified by GHG changes

Parameterization of black carbon effect on snow albedo

1. Model albedo depends upon model BC snow concentration as in Warren and Wiscombe (1985)

2. Snow grain size as a function of snow age and surface air temperature is calculated from Marshall (1989)

New: grains = 0.1 mm

Old: grains = 1 mm

Parameterization of aerosol indirect effects

Model cloud droplet number concentration depends upon aerosol number concentration as in Menon and Rotstayn (2006) for warm clouds only.

Surface Air Temperature Changes: 1995-1880

C

Direct Also Indirect also BC-albedo Indirect only BC-albedo only

G

HG

N

o G

HG


C


G

HG

N

o G

HG

b) - a)


C


G

HG

N

o G

HG

b) - a) c) - b)


C


G

HG

N

o G

HG

Arctic [Global]

Surface Air Temperature Changes:

1995-1880Seasonality

C

GHG

No GHG

Direct

+Indirect

+BC-albedo

BC-albedo

Indirect



GHG

No GHG

Direct

BC-albedo

IndirectEffect Peak season

Direct - spring/fall

Indirect - winter

BC-albedo + spring/fall

Indirect effectSeasonality

GHG

No GHG

Direct

BC-albedo

IndirectEffect Peak season

Indirect - winter

Low Cloud Changes: 1995-1880

%


G

HG

N

o G

HG

GISS model: cool more low level cloudswarm fewer low level clouds

High Cloud Changes: 1995-1880

%


G

HG

N

o G

HG

GISS model: cool more low level clouds, less high cloudswarm fewer low level clouds, more high clouds

Cloud Changes: 1995-1880 Seasonality

GHG

No GHGIndirect

Indirect effect: More low clouds, fewer high clouds during summer

Indirect

Indirect

Indirect

Radiative forcing changes: 1995-1880 Seasonality

GHG

No GHG

IndirectIndirect

Indirect

Indirect effect: LW forcing is maximum and negative in winter

Snow/Ice Changes: 1995-1880

%


G

HG

N

o G

HG

Indirect effect: Colder temperatures, increased snow cover, brighter surfaces reduce LW radiation especially during winter when cloud cover is less. INDIRECT INDIRECT EFFECT!INDIRECT INDIRECT EFFECT!

BC-albedo effectSurface Air Temperature Changes: 1995-1880

C


G

HG

N

o G

HG

Arctic [Global]

Snow/Ice Changes: 1995-1880

%


G

HG

N

o G

HG

BC-albedo effect: Is larger when GHG is fixed, since increasing GHG already reduces snow/ice cover. (Also, BC deposition increase is smaller…)

BC-albedo effect: Spatial correlation between change in surface air temperature and snow/ice

Change in temperature snow/ice

G

HG

N

o G

HG

warmer temperature less snow/ice

BC-albedo effect: Cloud changes also correlate.

Change in high clouds temperature snow/ice

GH

G

No

GH

G

More high clouds, warmer temperature less snow/ice



GHG

No GHG

Direct

BC-albedo

Effect Peak season

Direct - spring/fall

Indirect - winter

BC-albedo + spring/fall

Snow/Ice Changes: 1995-1880 Seasonality

No GHG

Direct

BC-albedo

GHG

BC-albedo

%


G

HG

N

o G

HG

Western Arctic sea-ice changes: Arctic Climate Impact Assessment (2004)

According to the model, either an increase BC-albedo effect, or recent decreases in (sulfate) indirect effect might explain loss of sea ice in western Arctic

During the past decade:1. Most Arctic pollution aerosol is

sulfate. Most sulfate pollution is from Europe. European sulfate is decreasing. Therefore the indirect effect should be decreasing warming

2. Surface BC is also mostly from Europe is probably also decreasing, especially to the north of Europe.

3. Black carbon pollution from Asia and boreal fires may be increasing (large sources of surface and high level BC in western Arctic) and may be contributing to melting in those regions.

McConnell et al. (2007) Greenland data

Black Carbon (BC) Measurements at Alert.

-Measurements conducted by Environment Canada since 1989.

-Higher BC in winter due to “Arctic Haze”.

-Decline in trends of BC measurements since 1989 by 55% (Sharma et al., 2004).

Environment Environnement Canada Canada

-Change in BC measurementsare proportional to changes in emissions and Atmospheric transport to the Arctic.

Alert Measurement Station – 82oN, 62.5oW

Year

0.0

0.5

1.0

1.5

2.0

1988 1993 1998 2003 2008

Date

light absorption (Mm

-1)

0.00

0.05

0.10

0.15

0.20

estimated black carbon (ug/m

3)Barrow light absorption

(Ogren)

Alert BC(Sharma)

Alert Measurement Station – 82oN, 62.5oW

Year

Black Carbon (BC) Measurements at Alert.

-Measurements conducted by Environment Canada since 1989.

-Higher BC in winter due to “Arctic Haze”.

-Decline in trends of BC measurements since 1989 by 55% (Sharma et al., 2004).

Environment Environnement Canada Canada

-Change in BC measurementsare proportional to changes in emissions and Atmospheric transport to the Arctic.

0.0

0.5

1.0

1.5

2.0

1988 1993 1998 2003 2008

Date

light absorption (Mm

-1)

0.00

0.05

0.10

0.15

0.20

estimated black carbon (ug/m

3)Barrow light absorption

(Ogren)

Alert BC(Sharma)

SE Asia

Europe Russia

N. America

Biomass burning

Model surface BC from regions

Arctic haze captured by Calipso retrieval, typically seen in discrete pollution plumes

Courtesy of David Winker

Northeast coast of Greenland

WE

…Seems to originate in Northern Russia

Northeast coast of Greenland

WE

From David Winker

CALIOP (CALIPSO) 16-day orbit pattern

(from Dave Winker)

Caveats

1. Analysis is preliminary. Significance?

2. Indirect effect: warm clouds only

3. Indirect effect: very uncertain

4. BC albedo effect: how to validate?

5. Equilibrium (not transient) experiments

Next steps1. Perform 20th century transient experiments

2. Indirect effect: include ice phase parameterization, treatment of Arctic clouds

3. Perform ongoing comparison of model clouds/aerosols with CALIPSO, IPY campaign measurements

Conclusions1.1. Direct effect cools Arctic surface Direct effect cools Arctic surface

temperaturestemperatures

2.2. Indirect effect has powerful effect Indirect effect has powerful effect cooler temperatures cooler temperatures increased increased snow/ice and albedosnow/ice and albedo

3.3. BC-albedo effect slight warming BC-albedo effect slight warming (about same amount as direct effect (about same amount as direct effect cooling). Note cooling). Note BC in Arctic from BC in Arctic from 1890 to 1990 not very large. But 1890 to 1990 not very large. But there are regional differences.there are regional differences.

4.4. GHG reduces aerosol effects (due GHG reduces aerosol effects (due to GHG large effects on cryosphere).to GHG large effects on cryosphere).

5.5. Eastern Arctic sea ice loss may be Eastern Arctic sea ice loss may be from a) increased BC-albedo effect in from a) increased BC-albedo effect in that region and/or b) decrease in that region and/or b) decrease in indirect effectindirect effect

Effect SAT snow/ice

GHG +2.3 -1.6

Direct -0.3 +0.2

Indirect

+ GHG

-2.2 +3.8

-1.5 +1.6

BC-alb

+GHG

+0.5 -1.2

+0.2 -0.2

Effect SAT snow/ice

GHG +2.3 -1.6

Direct -0.3 +0.2

Indirect

+ GHG

-2.2 +3.8

-1.5 +1.6

BC-alb

+GHG

+0.5 -1.2

+0.2 -0.2

1. Biggest uncertainties:

Cloud effects in the Arctic

Indirect effect (positive or negative)

BC-albedo effect

Transport to the Arctic

CALIPSO, CloudSat, IPY campaigns will help!

2. Usefulness of “forcing” in the Arctic???

Maybe a matrix of SAT, snow/ice, sea level pressure

3. Local vs extrapolar forcing:

GHG, warm-cloud indirect effect: both important

BC-albedo, ice-cloud indirect effect: local

4. Delay the onset of spring melt?

Analyze an ice core in Siberia to determine whether Asia is a big source, this is where BC is increasing

Answers to Questions

Support from Clean Air Task Force, NASA RS and MAP

Indirect Effect

SW, LW cloud forcing: -0.4, -0.2 W/m2, no GHG

SW, LW cloud forcing: -0.04, -0.4 W/m2, GHG

SW, LW forcing: -2.1, -1.9 W/m2 > cloud forcing due to surface albedo increase

reff = -1.1m warm stratiform (no GHG)

reff = -0.01 warm stratiform (GHG; LWC, LWP increase)

CDNC = 30 cm-3

Direct Effect

SW clear sky forcing (no GHG) = -0.7 W/m2

SW all-sky forcing (no GHG) = -0.4 W/m2

SW absorption (TOA-surface) about 0.8 W/m2 (no GHG)

or about 1.5 W/m2 (GHG; due to loss of clouds?)

Instantaneous SW forcing from tracer run: -0.2 W/m2

Instantaneous SW absorption from tracer run: 1.3 W/m2

BC-albedo Effect

Radiative forcing (no GHG):

0.3 W/m2 SW

0.2 W/m2 LW

These would be larger than ‘instantaneous’ due to increased clouds.

With GHG little effect: albedo is already decreasing

Flanner et al (2007): 0.1 W/m2

albedo (no GHG)

-0.12 %

SW forcing Changes: 1995-1880


G

HG

N

o G

HG

W/m2

LW forcing Changes: 1995-1880


G

HG

N

o G

HG

W/m2

Radiative forcing changes: 1995-1880 Seasonality

GHG

No GHG

Direct

Indirect

BC-albedo

Indirect

BC-albedo

Sea level pressure Changes: 1995-1880

mb


G

HG

N

o G

HG

Sea level pressure changes: 1995-1880


G

HG

N

o G

HG

mb

Sea level pressure changes: 1995-1880 Seasonality

GHG

No GHG

Indirect

BC-albedo

Sulfur trend check: model vs sulfur in Greenland ice core (Fischer et al., 1998)

Core observations

Model S in snow

Model x 6

Change in aerosol optical depths between 1880 and 1995


GHG

No GHG

Direct+Indirect

+BC-albedo

BC-albedo

Indirect

Low Cloud Changes: 1995-1880

%


G

HG

N

o G

HG

High Cloud Changes: 1995-1880

%


G

HG

N

o G

HG

Snow/ice Changes: 1995-1880

%


G

HG

N

o G

HG

SW forcing Changes: 1995-1880

%


G

HG

N

o G

HG

W/m2

LW forcing Changes: 1995-1880

W/m2


G

HG

N

o G

HG


GHG

No GHG

Direct

+BC-albedo

BC-albedo

Indirect

Effect SAT low cloud high cloud

Direct - spring/fall warm summer (w/o GHG) Cool spring/fall

Indirect - winter Cool summer (w/o GHG) Cool summer

BC-alb + spring/fall Warm spring/fall (w/o GHG) ?

In the column (AOD) most Arctic aerosol (sulfate) is from Europe, most absorbing aerosol (BC) is from SE Asia

Koch et al., J. Geophys. Res. (2007); Koch and Hansen, J. Geophys. Res. (2005)

AODx10

BC in Column (AOD)

Column BC: More BC from Europe and N. America

Evolution of Arctic BC:1920 - 1996 Pollution transport (from SE Asia) is shifted to higher altitudes. Implications for stability, cloud heights..

aerosol impacts on arctic climate during the 20th century: a giss climate model study

Documents

arctic aerosol

model bc deposition

surface arctic bc

model deposition

aerosol effects

model aerosol concentrations

arctic sulfate

arctic climate