Forcings Dr William H. Davies, Monitoring and the CAMS 74 team CAMS 4th General Assembly, Budapest, 17-18 September 2019 CAMS Climate F o r c i n g s

Atmosphere Monitoring • We are a climate-focused service based on the CAMS Reanalysis of Atmospheric Composition.

• We provide estimates and uncertainties of exerted by changes in atmospheric composition caused by human activities.

• Our users are involved in the scientific and policy aspects of . Radiative forcing

Atmosphere Monitoring Radiative forcing quantifies energy budget imbalances

Positive radiative forcing means a gain in energy in the system. Negative means a loss of energy.

Current estimates come from a variety of methods depending on the forcing Figure 8.15 of IPCC AR5, 2013 agent. CAMS Climate Forcing brings consistency. Version 1 products

Atmosphere Monitoring 2003—2016

Carbon dioxide +20% per decade Methane +3% per decade Version 1 product evaluation

Atmosphere Monitoring Comparison to IPCC AR5 (Chris Smith, Leeds)

Time series and envelope: CAMS version 1, uncertainties from a Perturbed Parameter Ensemble Error bars: IPCC AR5 ranges (for methane, dashed bar accounts for Etminan’s correction)

Ozone will be evaluated in the Autumn 2019. Additional products

Atmosphere Monitoring • In the process of estimating radiative forcing, we derive useful distributions out of the CAMS Reanalysis, like anthropogenic aerosol optical thickness or profiles of cloud condensation nuclei.

Cloud condensation nuclei concentrations at 200 hPa [CCN, cm−3]

150 100 50 0 Current work and challenges

Atmosphere Monitoring • Current work covers: – Use of carbon dioxide and methane concentrations from CAMS73. • Accounts for the first time for daily/horizontal/vertical variations. • Challenge: Find the best way to obtain a preindustrial state compatible with those distributions.

– Revision of aerosol optical properties, with CAMS43 • Improvements to carbonaceous aerosol optical properties.

– Estimates of preindustrial ozone distributions, with CAMS42 • Again, need to find the best way to obtain a preindustrial state compatible with present-day distributions simulated in the CAMS Reanalysis. • Challenge: Pushing the ECMWF C-IFS into new territory. Preindustrial ozone

Atmosphere Monitoring First attempts were based on Cariolle simulations (left), which have important discrepancies compared to CMIP6 modelling (right): • Much larger industrial-era increases in tropospheric concentrations • Lack of an ozone hole

Thankfully, progress made by CAMS42 with BASCOE are very promising and will allow us to be fully CAMS-based for our ozone radiative forcing estimates. Where to find our products?

Atmosphere Monitoring

Products will be updated to latest version in the coming months.

http://apps.ecmwf.int/datasets/data/cams-climate-forcings/ CAMS Climate F o r c i n g s

Atmosphere Monitoring • We are a climate-focused • CAMS Climate Forcing is: service based on the CAMS – University of Reading • Nicolas Bellouin, Will Reanalysis of Atmospheric Davies, Keith Shine Composition. – University of Leipzig • Johannes Quaas, Johannes Muelmenstaedt • We provide estimates and – University of Leeds uncertainties of radiative • , Chris Smith forcing exerted by changes in – MPI-Meteorologie Hamburg atmospheric composition • Guy Brasseur, Natalia Sudarchikova caused by human activities. – LMD, UPMC, Paris • Olivier Boucher • Our users are involved in the – CICERO Oslo scientific and policy aspects of • Gunnar Myhre climate change.