Global Warming presents an enormous challenge to the Steel Industry, which is both carbonintensive and energy efficient. Lean production can provide some short-term emission mitigation, at the level of the Kyoto requirements. In the middle term, more use of scrap will also help alleviate emissions. But to reach much larger reductions in GHG emissions, on a par with the likely targets that will be set after the Kyoto period, the Steel Industry will have to imagine new production paradigms, which constitutes its most formidable challenge for the years to come. Carbon capture and sequestration, processes leaner in carbon use, electricity and hydrogen from green sources will have to be added together in a patchwork of process routes, which will have to be developed at great risk in the next decade, hopefully through broad international cooperation. Introduction Steel is one of the pillars of the well being of our modern societies in developed countries and it will definitely continue to play this role long into the 21st century, both in post-modern economies and in the developing world. Steel is also a mature basic material, which has incorporated accumulated knowledge to the point where its production technology has reached very high levels of efficiency, in terms of usage of raw materials and of energy. This dichotomy sets the stage for the challenge that Global Warming poses to the Steel Industry in terms of managing the short term, where strong reduction of greenhouse gases (GHG) and more particularly of CO2 emissions are out of reach as most of what is achievable has already been achieved by the most efficient producers, and the long term, where the development of process routes, which would drastically reduce emissions, raises questions that are very open on possible technologies and their expected cost of production. But challenges, formidable as they may seem, do turn out to be a strong driver for change and progress. This is indeed what is expected, in a more general way, of the adoption of Sustainable Development policies by the Steel Business. Short-term GHG emission mitigation The concept of sustainability was first introduced by Ms Brundtland, in her famous 1987 report (1), but Industries and the Steel Industry more particularly -have been practicing the concept, nolens volens, since the 1960's at least. 0 500 10 00 15 00 20 00 25 00 30 00 35 00 40 00 19 6