Carbon emissions:Responsibility for most carbon emissions lies with governments and not with airlines, Ryanair chief executive Michael O'Leary told the Dublin Economic Workshop in Kenmare.

Air travel, which accounts for 2 per cent of global carbon emissions and is on track to reach 4 per cent, should not be targeted by policymakers simply because it is a fast-growing sector, he said.

"Taxing something that is 2-4 per cent of emissions is not going to alter climate change. The big cause of carbon emissions is governments. In Ireland, it is the ESB, but no one goes after the ESB because it is government-owned."

ESRI economist Colm McCarthy backed Mr O'Leary's assertion that the targeting of airlines through proposed "green taxes" is arbitrary and unfair. The concentration of "environmental angst" on the aviation sector is intriguing, he said. "There are roughly 40,000 freighters chugging around the world's oceans. Does environmental angst extend to aeroplanes but not to ocean freighters?"

But Mr McCarthy said airlines should be in favour of a universal carbon tax because it would prove "less troublesome" than a special aviation tax such as the green tax on flights announced by the British government.

A carbon tax would also be a more attractive option than being forced to join the EU Emissions Trading System, which would favour older, slower-growing airlines by giving a free allocation of permits based on historical emissions. A carbon tax of €20 per tonne would add about 3 per cent to ticket prices, Mr McCarthy estimated.