Last December, climate scientist James Hansen and his wife Anniek wrote a letter to Barack and Michelle Obama, then just a few weeks away from taking up residence in the White House. It was billed as an open letter, so anybody who wanted to got to read it, but it was scripted in a very personal way - "Dear Michelle and Barack, we write to you as fellow parents concerned about the earth that will be inherited by our children" - as though this urgent appeal from the doyen of climate scientists, and his wife, would spur the Obamas into immediate action on climate change.

For people interested generally in the issue of climate change, it is a fascinating letter, summarising pithily and clearly all the issues that Hansen has been agitating about for the last few decades. But for those of us in Ireland, it has a more specific interest, because it addresses head-on the issue of a carbon tax, which is set to become one of the hot political issues of the next six months, one which will decide whether the Green Party will leave government with a signature achievement to take to the electorate.

It also makes clear that such a tax, unless it is introduced in the most careful way, has the potential to backfire in a manner that would wreck beyond repair the chances of the Greens ever becoming an electoral force in Ireland. It could also – if implemented carelessly and unfairly – set back the Green agenda by decades.

"A rising carbon price is essential to 'decarbonise' the economy, ie, move the nation toward the era beyond fossil fuels," the Hansens write. "The most effective way to achieve this is a carbon tax (on oil, gas and coal). The tax will appropriately affect all products and activities that use fossil fuels."

As prices go up because of the new tax, people's lifestyle choices will change, the letter says. But - and this will be the key issue for the Greens here – the Hansens believe the public would support such a tax because the money raised would be returned to them, divided equally between every taxpayer in America and deposited monthly into their bank accounts. "A person reducing his carbon footprint more than average makes money," they claim. "A person with large cars and a big house will pay a tax much higher than the dividend. Not one cent goes to Washington."

In Ireland, the Commission on Taxation is about to propose the introduction of a carbon tax, although we're still in the dark about the details, or whether it will ever be implemented. However, the Greens see such a tax as a core principle, so we must assume that one is on the way, and will soon take its place alongside the many other tariffs and taxes that have accompanied the economic downturn.

The Greens will have a battle persuading people to accept this extra tax, particularly when that very same downturn has ensured that Ireland's carbon emissions have decreased dramatically and that we will come close to meeting our Kyoto targets as a result. Convincing drivers that they will have to pay extra for petrol, persuading the new army of unemployed that they must pay higher electricity bills, expecting businesses to accept that their higher heating costs are good for the environment will not be an easy task.

The only way John Gormley and Eamon Ryan can achieve this is to ensure, to steal a phrase from the Hansens' letter, that not one cent goes to Dublin. If the public perceives that a new carbon tax is just another way to screw money out of them, they will turn on it, and on the people whose core principle it is.

Green senator Deirdre de Burca said recently that she expected that any money raised would go straight to the exchequer. It would be better for the Greens to have no carbon tax at all than to introduce something that would attack people's lifestyles in a way that they simply would not accept. In any case, such an innovation would not be a carbon tax, but just another way to fleece the population.

Anybody who tried to tell you otherwise would be lying. I'm sure the Greens wouldn't do such a thing.

Wedding address: Lisbon debate at corr nuptials

Informed political argument should be raging at Andrea Corr's wedding to Brett Desmond later this month. Andrea's brother Jim – a conspiracy theorist whose brain appears to have been addled by years of strumming for his sisters – believes that the Lisbon treaty is a plot by shady movers and shakers in the political and business establishment to impose what he calls a New World Order on us all. Meanwhile, sister Sharon (right) last week lent her support to the We Belong group, a potentially insufferable bunch of minor celebrities, business people and political activists which will be campaigning for a Yes vote to Lisbon. Unfortunately, my invitation got lost in the post, so I won't be able to report back whose views prevailed.

ddoyle@tribune.ie