To extend the development of cumulative theory on the enduring themes of Information Systems (IS), we take an historical perspective of a core topic within the field, namely Decision Support Systems (DSS). Motivated by the complexity of strategic decision-making within the Climate Change Working Group of the State Government of New South Wales, we conducted a content analysis of IT strategy documentation from 1989 to the present. In our analysis of the resulting concept maps we observe the increasing dynamism and complexity of DSS over this period and suggest that we are now entering a critical era for IS in dealing with such dynamism and complexity. Crucial issues such as climate change now require planning over much longer time frames (up to 100 years) than are currently considered by either government or business. The decision-making of the Working Group calls for the integration of very large data sets and the sharing of information from many different government agencies and external sources. In a pattern of distributed leadership there is an increase in participation from citizens in decision-making for local climate change initiatives often through social media. We re-evaluate DSS not as IS but as a broad 'information infrastructure' which can flexibly and rapidly adapt to the needs of specific projects.