The world needs "early, aggressive and sustained" government intervention to cut aviation emissions if Paris Agreement temperature goals are to be met, a think tank pointed out Thursday.

In a new report, the International Council on Clean Transportation (ICCT) emphasized that airlines must start to slash emissions before the end of the decade and by 2025 if possible.

The 2015 Paris climate treaty urges nations to limit global warming at "well below" two degrees Celsius, and 1.5 °C if possible.

Earth's average surface temperature has already risen 1.2°C above preindustrial levels.

To project aviation sector emissions, the ICCT ran three models assuming different levels of traffic, fuel efficiency, and other factors.

All of them improved on a baseline "business-as-usual" scenario, which would emit nearly 50 billion tonnes of CO2 by mid-century - more than annual emissions from all sources today.

The most optimistic model - which assumes "widespread investments in zero-carbon aircraft and fuels, peaking fossil fuel use in 2025, and zeroing it out by 2050" - would see a reduction of 22.5 billion tonnes of emissions by 2050. 

That would put aviation on course to cut greenhouse gas emissions by "an amount consistent with a 1.75C warming," highlighted the ICCT.

"But it would require aggressive policies to peak emissions by 2030 at the very latest," it noted.

These findings were more positive than anticipated but remain very ambitious, considered lead author Brandon Graver.

"The all-in strategy to deploy clean planes and fuels cuts emissions even deeper than we expected," he indicated.

The International Air Transport Association (IATA), which represents 290 airlines accounting for 83% of global air traffic, pledged last October to achieve net-zero carbon emissions by 2050.

It is noteworthy that the aviation industry is among the fastest-growing sources of greenhouse gases, and one of the most difficult sectors to decarbonize.