Conversation took a turn for the worse at a dinner party I was at recently, when the guests began to boast about their environmental credentials, each claiming to be greener than the others.
One described how she diligently separates and recycles her rubbish. Another had volunteered to go planting trees on Lantau. A third related how he had spent a small fortune installing a solar water heater on the roof of his New Territories house.
In truth, none of the guests that evening could claim to be even remotely green. As well-heeled professionals with regional responsibilities and international backgrounds, they all spend much of their working lives flying around Asia, and each is happy to hop on a plane for a weekend away or for a longer vacation in Europe or the United States.
That penchant for air travel completely negates all their other efforts to go green. My own carbon footprint illustrates why. According to the emissions calculator at Climateers.org, at home and at work in Hong Kong, I'm responsible for pumping out about 10 tonnes of carbon dioxide a year. But factor in a couple of long-haul flights and a few trips around the region, and my emissions shoot up to 30 tonnes.
So if I or any of the other guests that night really wanted to go green, by far the most effective thing we could do would be to give up flying, or make sure that we offset the greenhouse gases emitted by our flights. In truth, we just talk about our concern for the environment, but we don't actually do anything to cut our emissions.
As with dinner party guests, so with governments around the world. It's only a few weeks since governments promised in Durban to devise a new treaty to reduce global emissions.
Now, the unholy row that's broken out over the European Union's attempt to force airlines flying into European airports to offset a portion of their greenhouse gas emissions has exposed the glaring insincerity of those promises.
The European scheme is not exactly onerous. Starting from last week, airlines flying to European destinations will be obliged to buy carbon credits to offset 15 per cent of the emissions from their flights.
According to the airline emissions calculator at atmosfair.de, an economy class flight from Hong Kong to London on a Boeing 747-400, the sort of aircraft that Cathay Pacific typically uses, emits 5.2 tonnes of carbon dioxide. Given that carbon credits are currently trading in Europe at Euro6.65 (HK$66) a tonne, the new rule will add HK$51.22 to the cost of an economy class ticket from Hong Kong to London.
With Cathay Pacific quoting economy fares to London for next month from HK$10,135 (including existing taxes and surcharges), that means the new scheme will push up the price of a ticket to Europe by just 0.5 per cent.
Even allowing for possible future increases in both the carbon price and the proportion of their emissions airlines are required to offset, that price rise hardly justifies the howls of outrage from airlines and governments around the world.
China's state-controlled airlines have been among the most vocal, swearing that they will not comply with the new rules. Meanwhile, Beijing has condemned Europe's action, while state media have talked of a trade war and hinted that Chinese airlines will be buying fewer European-made Airbus aircraft unless they are exempted.
Beijing is not alone. New Delhi is threatening not to co-operate, and there are mutterings from Washington about retaliation.
But despite the vehemence of these protests, complaints about the European legislation do not stand up well to examination.
Although the airlines will pass the extra costs on to their customers, they are naturally opposed to any increases in ticket fares which do not flow to their earnings. They are worried that the extra carbon charge on top of high fuel prices will deter people from flying, eating into their profits.
But in reality the airlines have had an easy ride so far over their emissions. Although a tonne of carbon dioxide emitted at altitude has the warming effect of almost three tonnes at sea level, unlike other industries, airlines have not been required to shoulder their share of environmental costs. Jet fuel isn't even taxed.
The official protests aren't convincing either. The new rules apply to all airlines flying to Europe, so no government can complain its airlines are being disadvantaged by unfair discrimination (if anything, European airlines fare worst).
Nor do complaints from Beijing that Europe has acted unilaterally rather than through established bodies like the United Nations ring true. The European Union has gone ahead with its measures precisely because years of multilateral negotiations have failed to achieve anything. In any case, the European rules make allowances for equivalent emission reduction measures should other governments introduce them.
Wherever they operate, firms are obliged to obey the local laws, and there is no reason why airlines should be any different. European law now requires airlines to offset a small portion of their emissions, so if they want to fly to Europe, airlines will have to comply.
Other governments can hardly say that's unfair, especially as they all claim they want to reduce greenhouse gas emissions.
After all, the benefits of any reductions will be shared globally, not confined to Europe.
So if they really want to be green, and not just talk about it like hypocritical dinner party guests, governments should shut up, and the airlines should pay up.