Campaign group Extinction Rebellion has accused Cornwall Council of failing to take enough action since declaring a "climate change emergency" at the start of 2019.
Protestors claimed the authority's response had been too "slow-paced" and described it at "three years of hot air".
Dozens demonstrated outside the council's headquarters in Truro.
The authority insisted it had made achievements in a number of areas.
A group of about 50 climate protestors gathered outside county hall while councillors attended a full meeting of the authority.
Demonstrator Tim Snell said: "Three years ago almost to the day Cornwall Council declared a climate change emergency, and we haven't nearly seen enough action within that time.
"We can't hold on for another three years of slow-paced action that doesn't quite go far enough," he said.
"The crisis is so severe, the future we face is absolutely dire," he added.
Mr Snell described it as "absolutely scandalous" that Cornwall Council was paying around £500,000 towards the Public Service Obligation (PSO) flight from Newquay to Gatwick, which is currently at 48% capacity.
The service has recently restarted after stopping due to the Covid-19 pandemic.
Martyn Alvey, portfolio holder for the environment and climate change, said it was "early days" for the service and the council was "convinced that it is important for the economy of Cornwall to have the connection to London by air".
Martyn Alvey said the council had made progress in a number of areas to help tackle climate change, including adding solar panels to 600 Cornwall Housing homes.
He added: "We've got the investment that we've made in geothermal, the floating offshore wind power investment that we're making - also Cornwall Council's brought online its first smart grid wind turbine," he said.
Mr Alvey also said another 150 electric vehicle charging points were due to come online in the authority's car parks, bringing the total number up to 360.