The North Atlantic Climate System Integrated Study

Major changes are occurring across the North Atlantic climate system: in ocean and atmosphere temperatures and circulation, in sea ice thickness and extent, and in key atmospheric constituents such as ozone, methane and particles known as aerosols. Many observed changes are unprecedented in instrumental records. Changes in the North Atlantic directly affect the UK's climate, weather and air quality, with major economic impacts on agriculture, fisheries, water, energy, transport and health. The North Atlantic also has global importance, since changes here drive changes in climate, hazardous weather and air quality further afield, such as in North America, Africa and Asia.

ACSIS is a 5 year strategic research programme that brings together and exploits a wide range of capabilities and expertise in the UK environmental science community. It's goal is to enhance the UK's capability to detect, attribute (i.e. explain the causes of) and predict changes in the North Atlantic Climate System. ACSIS will deliver new understanding of the NA climate system by integrating new and old observations of atmospheric physics and chemistry, of the ocean state and of Arctic Ice. The observations will be complemented by detailed data analysis and numerical simulations.

Observations will come from existing networks, from NERC's own observational sites in the North Atlantic, and from space. Seasonal surveys using the NCAS FAAM aeroplane will further enhance our observational strategy. A key dimension of the observational opportunity is that data records of sufficient length, for multiple variables, are becoming available for the first time. The modelling component will involve core numerical simulations with cutting-edge atmosphere, ocean, sea ice, chemistry and aerosol models using the latest parameterizations and unprecedented spatial detail, as well as bespoke experiments to investigate specific time periods or to explore and explain particular observations.

ACSIS will provide advances in understanding and predicting changes in the NA climate system that can be exploited to assess the impact of these changes on the UK and other countries - for example in terms of the consequences for hazardous weather risk, the environment and businesses. ACSIS outputs will also inform policy on climate change adaptation and air quality.

Policy makers: Advances in understanding the role of natural and anthropogenic drivers in North Atlantic climate change delivered by ACSIS will contribute to the next Intergovernmental Panel on Climate Change Assessment Report (AR6) and to national and international policy-making on climate change adaptation and mitigation. Improved understanding of the impact of stratospheric ozone change on tropospheric composition and climate will inform assessments for the Montreal Protocol. Advances in understanding the role of emissions, relative to other factors, in shaping UK air quality will benefit policy formulation in Defra. Representatives of relevant government departments will be invited to the Community Meetings that are a planned part of the programme. These meetings will include specific sessions on stakeholder needs. The Met Office and its customers will benefit from the process-based evaluation of their models and forecast systems. Improvements in modelling and understanding will be exploited to improve the accuracy and reliability of climate forecasts and projections. This will happen efficiently through the co-delivery of ACSIS by Met Office and NERC scientists. The EU Copernicus Climate Change Service will benefit from advances in observations, models, understanding and predictions of changes in the regional climate of the North Atlantic/European region. ACSIS partners are already directly engaged in the development of relevant services and this engagement will increase through the programme. Businesses concerned with changing weather and weather-related risks will benefit from advances in understanding the drivers of changing risk. ACSIS partners have established collaborations with the insurance and energy industries in particular, and these collaborations will provide an important pathway for communication of ACSIS findings. These interactions will be enhanced internationally through related work in the EU PRIMAVERA programme, as well as through the Community Meetings mentioned above.

General public and the media. The observations of declining Arctic sea-ice have become an iconic symbol of our changing climate system for the media and the general public. The ACSIS Essential Climate Variables, presented in accessible form and updated regularly on the ACSIS website, will provide a similar but broader based snap-shot of how the climate system is changing in the UK's backyard. The presentation of multiple variables in a consistent format will provide an important regular opportunity for ACSIS scientists to discuss and explain the complex nature of changes in a way that is accessible and engaging. We anticipate a high level of media interest in this dimension of the programme.

ACSIS is specifically designed to enable as well as deliver research and as such there is a wide community of academic beneficiaries (see separate summary), who will themselves contribute to enhancing the overall impacts of the programme.