Human activities primarily affect the Earth system and climate through emissions of gases and aerosol into the atmosphere. Changes in atmospheric composition entail changes in radiation budgets and in microphysics including cloud and rain processes and are thus key drivers of climate change. Rising CO2 levels are a major concern, but this is only part of the story. Other greenhouse gases, such as CH4 and N2O, reactive species such as ozone, and different aerosol types also play a role and require monitoring to understand our changing climate.

Thankfully, a range of data on atmospheric composition are available today from remote-sensing (space and from the ground) or in-situ monitoring. Building on decades of experience with numerical weather prediction, modern numerical models can turn these data into meaningful information on the spatial distribution of many of these species and their variability over time. The models can also be used to evaluate surface sources and sinks of certain species.

Information services have emerged recently, in particular in Europe in the context of the EU-funded Copernicus programme, to monitor and characterise changes in atmospheric composition by processing observations using numerical models and producing so-called reanalyses. Accurate information obtained from such systems helps us to understand why and how the current climate is changing, and it can help to evaluate Earth system models used to make climate predictions and projections. Atmospheric composition models can also be used to explore the effects of reducing emissions of different species on air quality on the one hand and climate change on the other and to develop win-win strategies. Such services bring value to observations and provide facts for evidence-based policy making on atmospheric emissions by human activities, with climate and air quality aspects being considered together.

This event will focus on the ways in which these new information services on atmospheric composition can contribute to our understanding of climate change and support most effective decision-making on anthropogenic emissions. Experts from policy-making, science and the media communities will discuss how these services can help governments meet their obligations under a possible global treaty at COP 21 in Paris.

This event will be held in the conference room of the �Balloon of Paris�, a tethered balloon that is a landmark tourist attraction of the city and, since 2008, a flying lab dedicated to Paris air quality monitoring. After the debate, you will have an opportunity to fly aboard the balloon, 150 meters over Paris.
Related link: http://www.ballondeparis.com/fr/infopratique/infos-pratiques

The role of ECMWF in the Copernicus Services
ECMWF is operating two services on behalf of the European Union: the Copernicus Atmosphere Monitoring Service and the Copernicus Climate Change Service.
From the start, ECMWF has been strongly involved in the development of Copernicus information services. Currently, in addition to being the coordinator of the pilot atmosphere service (MACC-II) and of a precursor of the climate change service (ERA-CLIM2), ECMWF is also involved in the marine and emergency services, by running in particular the computational centre and hosting the information system platform of the European Flood Awareness System (EFAS). These services operate and are developed in a way complementary to the established range of meteorological and environmental services that are operated nationally. The strong involvement of current service providers as well as of key representatives from the relevant academic communities ensures that the Copernicus services can benefit most fully from existing infrastructure and knowledge, and that the Copernicus services are implemented in a manner consistent with the EU principles of complementarity and subsidiarity.
Related links:�
http://www.ecmwf.int/en/about/what-we-do/copernicus/copernicus-atmosphere-monitoring-service
http://www.copernicus.eu/


Contact: The Desk � Najette Chaib : +33 1 40 54 19 62 -� [email protected]