A motion agreed earlier this week calls on its cabinet to commission a full assessment to allow the council to 'accurately' measure its progress towards the 2030 net-zero goal.
Its proposer, councillor Judith Smyth, said there needed to be 'a scientific and comprehensive approach' to be able to prioritise the most effective schemes.
'Portsmouth has achieved a lot in reducing carbon emissions but we need to move to a more urgent approach where we can distinguish the success of putting a beehive on public land from the much more significant work needed,' she said.
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Councillor Charlotte Gerada said: 'It's not possible to manage what you can't measure. An important starting point for adequately responding to the climate crisis will be to better understand the sources of carbon emissions and then strategise about how to reduce them.'
The council declared a climate emergency in 2019, setting its target to reduce carbon emissions but the motion said 'far too little' had been done, particularly in the production of detailed plans, and called for this work to be completed by July.
Cabinet member for climate change, councillor Kimberly Barrett said this was already under way with a strategy on track to be completed ahead of that deadline.
'We recognise that we need to act faster than the government's own target and we want to be collaborating with the community and agreeing those further consensus for the solutions that benefit everybody,' she said.
'The work we're doing is not for the benefit of ourselves on this chamber is for my kids and yours and future generations. We need to make sure what we do is high quality and not rushed. We only get one chance to do this.'
She added that the council had halved its emissions since 2011.
Council leader Gerald Vernon-Jackson said this would continue to fall, partly due to a planned 'huge' extension to solar power generation and that a carbon budget will be produced alongside the usual financial budget at the start of next year.
'There will be tough decisions ahead,' he said. 'We have made most of the decisions where action by the council will save both carbon but also money. In the future we'll need to decide what the priorities are and some will be difficult.'
He said the council was not considering commissioning a carbon audit and would instead rely on publicly-accessible data to inform its decisions. He said this would save the council an estimated £50,000.