||The key challenge for environmental scientists and policy-makers today is to quantify the present state of the global environment and forecast its future evolution. Meeting this challenge requires taking an integrated view, whereby the atmosphere, ocean, cryosphere and biosphere are considered to be part of a fully coupled integrated Earth System. Data Assimilation (DA) techniques play a vital role in this endeavour as they enable one to produce the most complete and dynamic picture of the Earth System by integrating all available knowledge on the system, including observations (in-situ and space-borne data) and physical principles (state-of-the-art models). Recent advances in observation technology, numerical models and Data Assimilation have led to the development of a variety of Earth System Information services generating enormous benefits for our society. ESA has set up a long-term summer school training programme to promote the exploitation of Earth Observation (EO) data across disciplines, with a particular focus on the use of numerical models and Data Assimilation techniques to maximise the scientific and economic benefits of satellite data. The 1st ENVISAT summer school focussing on the "Atmosphere" was held last year in ESRIN (Frascati, Italy). Some 57 young scientists from 17 countries enjoyed taking part in the school (including keynote lectures, computing exercises and workshops) and social/sport activities. The 2nd ENVISAT summer school will focus on the Earth System paradigm and target multi-disciplinary topics and end-to-end applications. The 2004 school will aim to train young scientists in taking an integrated end-to-end perspective from measurement techniques to end-user applications and thereby help them appreciate how their own specialised field fits into a broader context.