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Investigation of chemistry-climate interactions, with a closer look at the U.S. warming hole. Loretta J. Mickley Eric Leibensperger , Xu Yue , Daniel Jacob , Jennifer Logan David Rind , GISS Jed Kaplan , U Geneva. 2009 wildfire in Southern California.

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slide1

Investigation of chemistry-climate interactions, with a closer look at the U.S. warming hole

Loretta J. Mickley

Eric Leibensperger, XuYue,

Daniel Jacob,Jennifer Logan

David Rind, GISS

JedKaplan, U Geneva

2009 wildfire in Southern California

slide2

Millions of people in US live in areas with unhealthy levels of ozone or particulate matter (PM2.5).

Number of people living in areas that exceed the national ambient air quality standards (NAAQS) in 2010.

Ozone

daily maximum 8-hour average

PM2.5

24-hour average or annual average

Bars on barplot will change with changing emissions.

Climate change could also change the size of these bars, by changing the day-to-day weather.

particles affect solar radiation directly and also indirectly by modifying cloud properties

Black carbon

California fire plumes

Pollution off U.S. east coast

Particles affect solar radiation directly…and also indirectly by modifying cloud properties.

Light-colored particles reflect sunlight and cool the earth’s surface.

Aircraft contrails and cirrus over Europe

cooler

life cycle of particulate matter pm aerosols

VOCs -- volatile organic compounds

NH3 -- ammonia

.

.

.

.

.

.

SO2 -- sulfur dioxide

NOx -- nitrogen oxides

Life cycle of particulate matter (PM, aerosols)

ultra-fine

(<0.01 mm)

fine

(0.01-1 mm)

cloud

(1-100 mm)

precursor gases

nucleation

cycling

coagulation

condensation

Soup of chemical reactions

coarse

(1-10 mm)

Organic carbon

scavenging

Black carbon

SO2

SO2

VOCs

NOx

NOx

VOCs

NOx

NH3

VOCs

NOx

VOCs

NOx

combustion

volcanoes

agriculture

biosphere

sea salt

wildfires

combustion

dust

slide5

Model frameworks

1. Standard

Assimilated meteorology

GEOS-4

GEOS-5

Atmospheric Chemistry

GEOS-Chem

2. Chemistry-climate

Chemical feedbacks

Meteorology from freely running climate model

Atmospheric Chemistry

GEOS-Chem

Land cover model

Fire prediction model

slide6

Climate change

Air Quality

  • Wildfire in the western United States in the mid-21st century
  • Consequences for air quality.

Rim fire, Yosemite Natl Park, 2013

slide7

Effects of wildfires on air quality in cities in Western US can be very dramatic.

  • Hayman fire, June 8-22, 2002
  • 56,000 ha burned
  • 30 miles from Denver and Colorado Springs

Unhealthy air quality in Denver

June 9, 2002

June 8, 2002

PM10 = 372 μg/m3

PM2.5 = 200 μg/m3

Standard = 35 µg/m3

PM10 = 40 μg/m3

PM2.5 = 10 μg/m3

Colorado Dept. of Public Health and Environment

Vedal et al., 2006

slide8

Fire activity had a big impact on California air quality in 2013.

Rim Fire

Timeseries of 3-hour average PM2.5 concentrations in Foothills Area

Hazardous levels > 250 mg m-3

PM2.5 (mg m-3)

Very unhealthy

Aug 28

August 31

August 20

Will fire change in the future climate?

Unhealthy air

Very unhealthy air

Aug 30

slide9

Observations suggest that fires are increasing in North America.

Area burned in Canada has increased since the 1960s, correlated with temperature increase.

obs temperature

area burned

Gillett et al., 2004

5 yr means

1960

2000

Increased fire frequency over the western U.S. since 1970,

related to warmer temperatures and earlier snow melt.

1970

2000

Westerling et al., 2007

slide10

IPCC AR4 models show increasing temperatures across North America by 2100 in A1B scenario.

D Temperature JJA, oC

D Precipitation JJA, %

Number of models showing increased precipitation.

most models

Models show increases of JJA temperatures of ~ 3K in Western US.

Results for precipitation changes are not so clear.

few models

IPCC, 2007

slide11
How do we predict fires in a future climate?We don’t have a good mechanistic approach for modeling wildfires.

Start with the past.

2 approaches

Use ensemble of climate models to gain confidence in prediction.

+

JJA Temperature increase by 2100

Relationship between observed meteorology + area burned

Future area burned

Future meteorology

slide12

Regression approach. Regress meteorological variables and fire indexes onto annual mean area burned in each of six ecoregions with a stepwise approach.

ERM

RMF

PNW

NMS

Identify the meteorological variables and fire indexes that best predict area burned.

Include lagged met variables.

CCS

DSW

Ecoregions are aggregates of those in Bailey et al. (1994)

For example,

Area burned in Nevada/ semi-desert = f ( + T summer max that year + RH and rainfall previous years)

Best predictors: Temp, RH, precip, Build-up Index, Drought code, Duff moisture code.

predicted fires match observed area burned reasonably well least best fit is in southern california
Predicted fires match observed area burned reasonably well. Least best fit is in Southern California.

Obs

Fit

RMF

ERM

PNW

NMS

CCS

DSW

Area burned in many ecoregions depends on previous year’s relative humidity, rainfall, or temp.

Yue et al., 2013

slide14

Start with the past.

+

Relationship between observed meteorology + area burned

Future area burned

Future meteorology

use of an ensemble of 15 climate models improves confidence in the results
Use of an ensemble of 15 climate models improves confidence in the results.
  • Changes in 2050s climate in the West.
  • Temperature increases 2-2.5 K.
  • Changes in precip and relative humidity are small and not always robust.
  • Next step: apply meteorology from climate models to the two fire prediction schemes.

Yue et al., 2013

slide16

Wildfire area burned increases across the western United States by the 2050s timeframe.

Results from regressions approach.

Shown are median results.

Yue et al., 2013

+

Relationship between observed meteorology + area burned

Future area burned

Future meteorology

slide17

Predicted area burned shows large increases in 2050s during peak months.

Units = 104 hectares

future

present-day

X2 increase

X4 increase

Yue et al., 2013

slide18

How will changing area burned affect air quality?

Ensemble of climate models

Median area burned

Emissions = area burned x fuel consumption x emission factors

Future meteorology

GEOS-CHEM Global chemistry model

Future air quality

slide19

Organic particles increase in future atmosphere over the western U.S. in summer, especially during extreme events.

Cumulative probability of daily mean concentrations of OC, Rocky Mountains

D Organic Carbon, OC

May-Oct

Ma

2050s

doubling

Present-day

JJA

Change in summertime mean organic PM2.5 in ~2050s, relative to present-day.

Wildfires may swamp efforts to regulate air quality in future.

Yue et al., 2013

slide20

What do these increases in wildfire aerosol mean for human health?

% area burned

% OC particles

Ongoing project with Yale will look at health impacts of these increases.

Yue et al., 2013

slide21

How will wildfire change in a changing climate in Canada?

Ratio of 2050s area burned to present-day

Alaska Boreal Cordillera

  • Area burned increases in the West due to:
  • Higher temperatures
  • More frequent blocking high pressure systems.
  • Increased rainfall in Central and eastern Canada blunt these effects.

Ratio of 2050s area burned to present-day

Ecoregions West to East

Yue, in progress

slide22

Aerosols

Climate change

  • Regional climate effects of 1950-2050 trends in US anthropogenic aerosols.

Pittsburgh, 1973

observed us surface temperature trend

What caused the U.S. warming hole of the 20th century?

Observed US surface temperature trend

1

No trend between 1930 and 1980.

Warming trend after 1980

0

-1

Contiguous US

Observed spatial trend in temperatures, 1930-1990

o C

GISTEMP 2010

-1

1

slide24

1950

1960

1970

1980

1990

2001

Clearing trend in particles over United States since 1980s suggests possible recent warming.

Calculated trend in surface sulfate concentrations

Increasing sulfate from 1950-1990s.

Decreasing sulfate by 2001.

Circles show observations.

Leibensperger et al., 2012a

slide25

We first perform a pilot study:

Constant aerosols vs. zeroed US aerosols

Constant aerosols everywhere

Spin-up

GISS climate model

A1B scenario of greenhouse gases

Zeroed US aerosols, constant elsewhere

2010

2050

Forcing due to aerosol removal over US

Model setup causes large warming over East.

By comparison, global DF from CO2 is +1.8 Wm-2.

slide26
Results from pilot study: Removal of aerosol sources over US increases annual mean surface temperatures by 0.5 o C.

Additional warming due to zeroing of US aerosols

Warming due to 2010-2050 trend in greenhouse gases.

Summertime temperatures increase as much as 1.5 oC.

Only direct aerosol effect included.

white areas = insignificant differences

Mickley et al., 2012

slide27

Warming begins immediately and persists through the decades.

D Temperature, 2050s

A1B

Daily max T

Daily mean T

Change in surface temperatures due to aerosol removal, Northeast US

Warming due to aerosol removal is strongest in late summer / early fall

Heatwaves show 1-2 K increase.

Mickley et al., 2012

slide28

D

D

Climate response of Northeast to aerosol removal

Increased diurnal temperature range, higher Tmax

Daily max T

Daily mean T

Warming, especially in late summer, early fall.

D

D

Shift from increased latent flux to increased sensible and LW flux in late summer.

Sensible heat

Increased solar flux in July-October

Latent heat

LW

D

D

Reduced cloud cover and relative humidity

Low cloud cover

Increased sunlight depletes soil moisture by late summer.

Rel humidity

slide29

Feedbacks involving soil moisture and low cloud cover amplify local temperature response in Aug-Oct period.

D

Soil moisture depletes through summer.

Cloud cover diminishes in response.

Shift from increased latent flux to increased sensible and LW flux in late summer.

Sensible heat

Latent heat

LW

Diffuse warming

Local warming

slide30

1950

1960

1970

1980

1990

2001

Next, we perform a more realistic set of simulations, with changing emissions, 1950-2050.

Calculated trend in surface sulfate concentrations

Increasing sulfate from 1950-1990s.

Decreasing sulfate beginning in 1990s.

We applied decadal trends in anthropogenic aerosol to the GISS climate model.

Circles show observations.

Leibensperger et al., 2012a

slide31

Forcing from US anthropogenic aerosols peaks in 1980 -1990s.

Direct radiative forcing

Forcings over Eastern US

Peak forcings -2 W m-2, mainly from sulfate.

Warming from black carbon offsets the cooling early in the record.

Results suggest little climate benefit to reducing black carbon sources in US.

Indirect radiative forcing from clouds is about the same magnitude as direct effect.

Net DF

Indirect radiative forcing

Leibensperger et al., 2012a.

slide32

Cooling from U.S. anthropogenic aerosols during 1970-1990.

Results are from two 5-member ensembles, with and without US anthropogenic aerosols.

Indirect + direct effects included.

Cooling is greatest over the Eastern US and North Atlantic.

1 oC cooling at surface over East

C

Leibensperger et al., 2012b

slide33

D Model Temperature 1970-1990

Cooling over U.S. is not co-located with aerosol burden.

Local changes in cloud cover and soil moisture amplify the cooling effect.

Cooling over North Atlantic strengthens Bermuda High, increasing onshore flow of moisture from Gulf of Mexico.

Results are controversial.

C

D Cloud Cover

D Soil moisture availability

%

%

slide34

Observations show intensification of the Bermuda High during the 1980s and early 1990s, apparently consistent with aerosol loading.

1948-1977

1978-2007

Variation of western edge of Bermuda High during JJA, 1948-2007.

Edge = 1560-gpm contour line at 850 hPa.

Shift westward

Westward extent of Bermuda High

ERA

East

NCEP

Reference longitude

What about effect of Pacific Decadal Oscillation?

West

Period of greatest aerosol loading

1950

2000

1980

Li et al., 2011

slide35
Inclusion of US anthropogenic aerosols improves match with observed trends in surface temperatures over the East.

Eastern US

  • Results suggest that US anthropogenic aerosols can explain the “warming hole.”
  • Warming since 1990s can be attributed to reductions in aerosol sources.

Model without US aerosols

Standard model

Observations

Most of the warming from reducing aerosol sources has already been realized.

Leibensperger et al., 2012b

slide36

How have competing trends in BC and SO2 over 20th century affected regional climate across mid-latitudes?

Timeseries of US emissions

BC

U.S. SO2 emissions (Tg S)

U.S. BC emissions (Tg C)

  • Ongoing work.
  • BC aerosol
  • warms mid- to upper troposphere
  • cools surface
  • stabilizes atmosphere
  • Sulfate cools surface, may augment stabilization.
  • We will compare model BC with lake core sediments from Adirondacks (Husain et al., 2008) and with ice cores from J. McConnell.

SO2

1850

1950

2000

1900

Deposition in Adirondacks

obst

observations

BC deposition (g m-2 a-1)

model

1860

1940

Leibensperger, Cusworth, and Mickley

slide37

Take home messages.

  • Area burned by wildfires may increase significantly across western North America by 2050s, depending on the ecosystem.
  • Increased smoke from wildfires may thwart efforts to regulate air quality in coming decades. This is a climate penalty.
  • Decreases in aerosol loading may have unintended consequences for regional climate, leading to warming.

Wildfires in Quebec the same day.

Haze over Boston on May 31, 2010