Hundreds of people joined a rally on College Green on Saturday to oppose the expansion of Bristol Airport, in what campaigners describe as a 'code red for humanity'.
It comes as the campaign group, Bristol Airport Action Network (BAAN), vowed to appeal last week's High Court ruling which will allow the airport to increase annual passenger capacity to 12 million and see up to 10,000 extra flights a year.
Protesters argue that the expansion will see a huge rise in the amount of carbon being emitted in the region, despite local leaders committing to net zero targets by 2030.
Jackie Head, from BAAN, said: “The decision is devastating and will take a while to process. I know we will regroup and fight on. Bristol Airport needs to know that we are playing the long game and will not stop until justice and fairness in aviation are achieved.”
ITV News understands the campaign group has written to the High Court judge asking to appeal the decision.
Steven Clarke, also from BAAN, said: "This case shows that no one is taking responsibility for the extra carbon emissions from the 2 million additional passengers because they will not have been taken into account at any stage of the process either locally or nationally.
"The Planning Inspectors who presided over the Inquiry stated that the responsibility lay with national Government however the Secretary of State has chosen not to consider the impact of the additional carbon; either at Bristol or other regional airport."
Bristol Airport has pledged to make its operations net zero by 2030, but this does not include its flights.
Simon Earles, from Bristol Airport, said: "We acknowledge what a significant issue climate change is and that's been built into our plans from day one. We've set an ambitious target to work with the industry to deliver a net zero flight by 2050. There is some superb innovation in the South West to make that happen as soon as possible."