Markku Kulmala

Jaana Bäck, Timo Vesala, Veli-Matti Kerminen, Tuukka Petäjä

INAR

Faculty of Science and Faculty of Agriculture and Forestry / University of Helsinki

Finland

The multiple effect of increasing carbon sink (re-forestingand afforesting) on climate

18/02/2019 1

Acknowledgements

• ERC

• The Academy of Finland

• PEEX

• The Atmospheric Radiation Measurement (ARM) Climate Research Facility is a U.S. Department of Energy

• St1 Ltd

• INAR science community - particularly Ksenia Tabakova

Clear and ambitious vision / from deep

understanding to practical solutions

Empirical measurements and modelling /

from observations to new theories

From research to innovations /

economic growth and human wellbeing

MULTIDIMENSIONAL, MULTIDISCIPLINARY, MULTISCALE

APPROACH TO ANSWER GRAND CHALLENGES

CURRENT STATE

• Initial Conditions• Assimilation

Provides

context

Complete

the picture

Satellite data

Provides

details

Multiscale Models

Ground-based data

Nature Comment (2018), Nature 553, 21–23 Nature Comment (2018), Nature 554, 25-27

Academician, Academy Professor Markku KulmalaUniversity of Helsinki, Faculty of ScienceInstitute for Atmospheric and Earth System Research markku.kulmala@helsinki.fi

Academician, Professor Guo HuadongChair of DBAR The Institute of Remote Sensing and Digital EarthChinese Academy of Sciencesguohd@radi.ac.cn

Sharing big data from satellite imagery and other Earth observations

Global SMEAR and Digital Belt & Road - DBAR

INTEGRATED APPROACH:

THE GLOBAL EARTH OBSERVATORY / GLOBAL SMEAR

Current observations (see IPCC 2013) arefragmented:

1) Greenhouse gases

2) Aerosols

3) Air quality

4) Ecosystems

5) Climate

6) …

Future aspiration: Integrated approach

• To understand feedbacks

• To reduce uncertainties

• To mitigate and adapt effectively

SMEAR II-station (boreal forest, country side)

Continuous, comprehensive observations

Lakes Peatlands

Site for ICOS, ACTRIS, INGOS, EXPEER, ANAEE, LTEER, LifeWatch, WMO, EMEP, CARBOEUROPE,

NITROEUROPE, EUCAARI, PEGASOS

Forest

Over 1200different variables Urban

SMEAR II Hyytiälä

CARBON: partitioningNeedle respiration

300 g C m-2

Needle photosynthesis

1100 g C m-2

Root respiration Decomposition of

soil organic matter

Wood respiration

100 g C m-2

The net carbon

sequestration 200-250

g C m-2 a-1

Soil carbon efflux

600 g C m-2

Litter production

100 g C m-2

Respiration

~75 g C m-2

Photosynthesis

100 g C m-2

Courtesy: Pasi Kolari

CO2

Processes

Root exudates

100-200 g C m-2

Photosyntesis,

GPP VOCs

GR

CCN, CS, Accumulation

mode, AOD

Diffuse radiation

Global radiation

CO2+

+

+

+

+

+

Carbon sink

Aerosol effects

8% 6%

6%

6%1.5%

0.7%

+ 10 ppm

SMEAR II: 1996-2009

Kulmala et al., 2014, BER

FROM CARBON SINK TO AEROSOL SORCE AND BACK

What do forests do?

• Carbon sink (sometimes source)

• Decreasing albedo

• BUT THIS IS NOT EVERYTHING

• VOC source

• Aerosol particle source

• CCN source

• Makes its own clouds and precipitation

• How big forest is needed?

• What is the role of newly formed particles in the cloud activation in-situ?

• Do they alter the cloud properties / precipitation?

Petäjä, T. (2013) Science Plan Biogenic Aerosols – Effects on Clouds and

Climate (BAECC), US Department of Energy, Office of Science, DOE/SC-ARM-

13-024.

1. From gas phase

Emissions to

Aerosol particles

2. From Aerosol

particles to Cloud

droplets / Cloudss

3. From Clouds to

Precipitation

4. Feedbacks and

Interactions

2019/2/18 13

The key scientific questions:

• What is the minimum spatial scale of boreal forest that can produce its own clouds and thereby

produce its own precipitation and modify the regional water cycle and sustain forest growth?

• Under which conditions is the water cycle self-sustained on the regional scale?

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2019/2/18 15

Aerosol size

distribution

and mass

2019/2/18 16

Aerosol

chemistry

2019/2/18 17

In-situ measured CCN concentrations

increase as a function of time-over-land

2019/2/18 18

Backscattering

In-situ and ground-based remote sensing agree!

Ground-based remote sensingIn-situ

2019/2/18 19

Liquid water path

2019/2/18 20

Cloud droplet concentration

Sogacheva et al., 2005, BER

CO2

+ 8 %+ 10 ppm

THE POTENTIAL OF SMEAR CONCEPT:

GLOBAL COMPREHENSIVE FEEDBACK ANALYSIS

Kulmala et al., 2014, BER

20 largest

metropolitan areas

Arctic-Boreal PEEX area

Eastern Asian PEEX area

Amazonas

Sahara + EMME region

Africa

Cloudsaerosol effects

+ 6 %

Diffuse radiation

Global Radiation

+ 1.5 %

PhotosynthesisCarbon sink

Volatile organic compounds

+ 6 %

+ 0.7 %

How big forest is enough to make its ownprecipitation?• Time over land: ca 70-80 h

• Distance: ca 700 – 1000 km

• Needed area: 1000 km x 1000 km = 1 000 000 km²

• Sahara: 9 200 000 km²

• Siberia: 13 100 000 km²

• An excellent way to mitigate climate: re-foresting and afforesting• Carbon sink

• Aerosol source

• Makes its own clouds (-> albedo effect good for climatenor minor albedoeffect)

• Makes its own precipitation