Institute for Climate & Atmospheric Science
SCHOOL OF EARTH AND ENVIRONMENT
Status and plans of the CLOUD experiment
CLOUD’s contribution to understanding
global aerosols and climate
Ken Carslaw
Jasper Kirkby, Hamish Gordon, Eimear Dunne,
Kamalika Sengupta, Cat Scott
The CLOUD Consortium
CERN SPSC June 2017
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
CLOUD-ITN
CLOUD-TRAIN
BACCHUS
CRESCENDO
Aerosol particles and climate
Scattering and absorption of
solar radiation
Intergovernmental Panel on Climate Change
Changes in the properties of
clouds
2KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Climate prediction needs
mechanistic models
CO2 concentration
Climate
warming
Sulphate (aerosol)
concentration
Climate
cooling
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
• Ice cores record
greenhouse gas
concentrations
• They also record
sulphate (aerosol)
mass concentration
• No information on the
number of aerosol
particles
• We need climate
models that include
the physical
processes
Aerosol particles in the atmosphere
About half of climaterelevant particles
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
The CLOUD experiment
A unique chamber simulating near-atmospheric conditions with
~40 instruments measuring gases, ions, molecular clusters,
particles and cloud droplets
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
CLOUD breakthroughs 2016-17
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Understanding aerosol particle
concentrations in the atmosphere
Prior to 2015
H2SO4-H2O
nucleation
Primary
particles
Nucleation schemes based on
theory and crude ambient
observations
Now (from CLOUD)
Other
nucleation
Total particle concentration / cm-3
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Mechanistic nucleation rates
based on laboratory
measurements
(This has been the case for gas
phase chemistry for 30 years!)
Towards a mechanistic understanding
Climate model simulations over many decades
requires a mechanistic understanding of
nucleation:
• Which species other than H2SO4?
• How important are ions?
• What is the role of the biosphere?
• What happens at low temperature?
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Biogenic control of particle
concentration seasonal cycle
Under-prediction of summertime particle concentrations is solved
using CLOUD mechanism from Riccobono et al., Science, 2014
Pearson
correlation
coeff (R)
Observations
Old H2SO4-H2O “mechanism”
Riccobono et al., Oxidation Products of Biogenic Emissions
Contribute to Nucleation of Atmospheric Particles, Science (2014)
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Discovery of “pure biogenic” nucleation
A new nucleation mechanism involving ions and highly
oxidised multi-functional organic molecules (HOMs)
Ion
effect
Kirkby et al., Ion-induced nucleation of pure biogenic particles, Nature (2016)
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Pure biogenic nucleation and climate
% change in particles caused by “pure biogenic nucleation”
Pre-industrial
Gordon et al. Reduced anthropogenic aerosol
radiative forcing caused by biogenic new
particle formation, Proc. Nat. Acad. (2016)
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Present day
• Forcing reduced by 23%
• Implies a reduction in climate
sensitivity
Importance of preindustrial aerosol
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Carslaw et al. Large contribution of natural
aerosols to uncertainty in indirect forcing,
Nature (2013)
What about nucleation in the rest of the atmosphere?
Total particle concentration / cm-3
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Global model based on experimental
nucleation rates
The most extensive measurements of nucleation rates
covering atmospheric conditions (T, ions, trace gases)
Ions
Ammonia
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Dunne et al. Global atmospheric particle formation
from CERN CLOUD measurements, Science (2016)
Global model based on experimental
nucleation rates
350 nucleation rate measurements from CLOUD campaigns
3, 5 and 7 to build global model mechanisms
208 K
278 K
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
223 K
248 K
292 K
Dunne et al. Global atmospheric particle formation
from CERN CLOUD measurements, Science (2016)
Global model based on experimental
nucleation rates
Nucleation rates separated into different pathways for the first time
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Dunne et al. Global atmospheric particle formation
from CERN CLOUD measurements, Science (2016)
Global model based on experimental
nucleation rates
“Nearly all nucleation throughout the present-day atmosphere involves
ammonia or biogenic organic compounds, in addition to sulfuric acid”
Observations
New model
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Neutral H2SO4 only
Dunne et al. Global atmospheric particle formation
from CERN CLOUD measurements, Science (2016)
Global importance of nucleation
65% of climate-relevant aerosol particles in the preindustrial
atmosphere come from nucleation, and 55% today
H2SO4/NH3 + H2SO4/Biogenic + Pure biogenic
Pre-industrial nucleation frac.
Present day nucleation frac.
Gordon et al. Causes and importance of new particle formation in the present-day and
pre-industrial atmospheres, submitted to Journal of Geophysical Research
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Importance of ions for nucleation
H2SO4/NH3 + H2SO4/Biogenic + Pure biogenic
Global mean
Gordon et al. Causes and importance of new particle formation in the presentdayCERN
and SPSC
pre-industrial
KEN CARSLAW, CLOUD project,
June 2017 atmospheres, submitted to JGR
Collaboration Issues
•
•
CERN CLOUD team:
‣ CLOUD thanks CERN EP for providing an Applied Fellow for
CLOUD Run Coordinator (starting 1 Jan 2017)
‣ CLOUD also joined by open-choice Research Fellow who is
focussing her research on global modelling (1 Jan 2017)
CLOUD-MOTION:
‣ CLOUD has been awarded an unprecedented third Marie
Curie Innovative Training Grant (3.9M€) within EC Horizon
2020 framework
‣ 15 ESRs for 10 CLOUD partners (coordinator: Goethe
University Frankfurt)
‣ 2 ESRs will join CERN team
‣ Project expected to run from 1 Sep 2017 until 30 Aug 2021
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
CLOUD12 Beam Request
•
18 Sep - 27 Nov 217 (9 wk, inc. 1 wk GCR at end)
•
Aims:
– Coastal/Arctic marine nucleation and growth involving iodine
compounds (2 wk):
– Growth rates of pure sulphuric acid particles at small sizes (3 d):
– Multi-component aerosol particle nucleation and growth (4 wk):
– Anthropogenic aerosol particle nucleation and growth (2 wk):
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
CLOUD requests
•
•
Dedicated CLOUD meeting room/open office:
‣
CLOUD has no offices for collaboration members
‣
CLOUD has on average 30 researchers at CERN during
experimental runs - and up to 50 at certain times
‣
CLOUD needs CERN’s support to find a permanent solution for a 50
m2 meeting room near the T11 zone to use as a daily
meeting/planning room and office working space for visiting
experimenters
CLOUD operation during LS2 East Area Renovation, 2019-2020:
‣
CLOUD requests to run with cosmics during the fall 2018 and fall
2019 periods when CERN accelerators are off:
✦ Importance/urgency of CLOUD scientific results for climate
assessments
✦ CLOUD-MOTION ESRs (15 PhD students) will rely on CLOUD
data in 2018-2020 runs
‣
In close discussions with East Area Renovation team (project leader
Sebastian Evrard/EN-EA-AC) to explore how essential CLOUD
services can be maintained to allow operation in fall 2019 and fall
2020, without impacting East Area Renovation schedule
KEN CARSLAW, CLOUD project, CERN SPSC June 2017
Summary
• CLOUD is the pre-eminent aerosol experiment
in the world
• CLOUD has transformed how aerosols are
represented in global climate models
• Gone from theoretical/empirical models to
mechanistic models based on laboratory data
• An ambitious research programme ahead:
marine/Arctic environments, more complex
multi-component systems, polluted urban
environments
KEN CARSLAW, CLOUD project, CERN SPSC June 2017