The extra cost was outlined by council corporate policy team manager Nicola Johnston in a report to be considered at today's 2011-12 pre-draft annual plan hearing.
The council had planned to spend the next three years investigating how best to respond to the threats posed by climate change, in an exercise costing $67,500 each year.
The work would include a major study on the future of South Dunedin and four other city "hot spots", and was confirmed at a meeting of the council's finance, strategy and development committee in November.
However, council staff at the meeting were also asked to investigate ways of accelerating some of the work on hot spots by Cr Jinty MacTavish, the chairwoman of the council's new community resilience forum.
The decision prompted Ms Johnston's report, which said increasing the pace of the planning work would result in earlier action on climate change, but at extra cost - $371,000 if carried out over one year instead of three, or $181,000 if over two years.
The extra spending was not part of any council budget, meaning it would have to be rates-funded, she told the Otago Daily Times yesterday.
Instead, Ms Johnston's report recommended proceeding with the original proposal, but with the decision to be reviewed next year.
In the meantime, a sustainability adviser would be recruited, filling an existing vacancy within the council, to co-ordinate the council's "essential" climate change, peak oil and sustainability work, she said.
However, extra funding of up to $22,288 a year would be required to bridge the gap between the pay rate for the existing vacancy and that required for the more senior appointment needed, she said.
Once the position was filled and the work under way, staff would be in a better position to assess the merits of accelerating the work, she said.
Ms Johnston's report also outlined the timeline and resource requirements for the council's climate change, peak oil and sustainability work required over the next three years.
The recommendations would be considered by councillors today.
Cr MacTavish could not be reached for comment yesterday.