The claim was made on the back of carbon offsets the airport had purchased, which it says more than compensate for the planet-heating gases from the airport's operations.
But a complaint to the Advertising Standards Authority said this was misleading because the tally did not include carbon emissions from flights in and out of the airport, which make up more than 90 percent of the airport's total climate impact.
Last year, the airport's own reporting showed that these flights created almost 700,000 tonnes of carbon dioxide - about 1 percent of New Zealand's emissions, or half as much as what pumps out of the Glenbrook Steel Mill annually.
The complainant cited a UN expert report recommending companies disclose their full climate impacts (including from third parties using their products, such as airlines, in this case) and focus on reducing those, rather than offsetting them.
The airport responded that it was reducing its direct emissions and was "working with airline partners" to get their flying emissions down. According to one study, aviation is about 12 percent of New Zealand's emissions, and has been growing.
The complaint was settled when the airport told the ASA it had stopped using the phrase "climate positive" since late 2023.
However, the airport denied the phrase was wrong, saying an independent certifier had backed up its claim that climate projects the airport paid for had offset 120 percent of its "controllable" emissions (not including flights by airlines enabled by using its airport).
"We don't want use of the phrase relating to airport operations to detract from our extensive emissions reduction actions, nor what we are doing to reduce our own emissions and influence decarbonisation of the broader aviation sector," the airport said in an email statement, when asked why it had stopped using the words.
Lobby group Stop Central Otago Airport, which is campaigning against the company building a new airport at Tarras, said it believed the airport was still greenwashing, because the phrase 'climate positive' still appeared in the company's marketing.
RNZ confirmed the phrase is still in sustainability materials on the airport's website.