The use of climate change information by public and commercial managers in the wider community is a topical and sometimes controversial issue for many communities around the world. Here we describe a specific case study in which climate science information has been used in major multi-million dollar decisions affecting over 1 million people living in Perth, Western Australia.

The demand from Perth residents for information from climate scientists has primarily been driven by an observed halving of water flow into Perth’s dams since the mid-1970s. This unprecedented decline has severely challenged water managers. The decline has been accompanied by the emergence of climate change scenarios since the 1980s. The scenarios suggest that global warming will lower rainfall over southern Australia including Perth. Water managers in Western Australia recognize the uncertainties associated with the scenarios but the information has, nevertheless, had an impact on their decision-making. Here we outline why water managers make use of uncertain climate change information in their decision-making, what the managers think of the information, how they use the information, and how climate scientists can contribute to more widespread and prudent use of the information they produce. We will pay particular attention to the influence and design of a research program called the Indian Ocean Climate Initiative (IOCI).