Who wants to offset their flight? Or, for that matter, say they plan to go carbon neutral, joining the likes of Costa Rica, Norway, Google and Yahoo?

Voluntary carbon offsetting involves paying someone to cut their emissions of greenhouse gases, so that you can go ahead and take that flight, car journey or whatever, but not add to mankinds contribution to global warming. Going carbon neutral involves offsetting all your emissions.

Offsetting is a small but growing slice of the global carbon market. Carbon trading is viewed by the European Union and United Nations as a key policy plank in the worlds fight against climate change.

Voluntary offsetting is becoming big news. British media have this month continued their blitz of critical coverage, exposing dodgy practices, and especially examples of project developers earning carbon credits for emissions cuts that were planned anyway.

A group of British parliamentarians weighed into the debate on Monday, relaying some uncomfortable facts. They said that HSBCs emissions rose the year it said it went carbon neutral suggesting that offsetting may not change behaviour. Illustrating the need for standards, it said mangos planted to offset Coldplay rock concerts died from lack of water. And it poured scorn on British Airways service to help customers offset their flights, saying the profile of the service had been non existent and achievements risible. The implication was that BA had no desire to flag up the problem of climate change to its customers.

Does any of this matter?

Yes, according to some of the worlds biggest banks, who are investing billions of dollars in the much bigger, regulated carbon market under the Kyoto Protocol. Banks are buying carbon credits from developing countries to sell to rich countries struggling to meet their Kyoto targets. This is a kind of posh offsetting very transparent, highly regulated and based on mandatory emissions limits.

The banks are worried if voluntary offsetting implodes itll take down the entire $30 billion global carbon market with it.

The British government also thinks the reputation of the voluntary market matters. London accounted for half of global carbon trades under Kyoto last year, worth $5 billion. The UK wants the voluntary market to adopt Kyoto-style standards.

But Mondays report pointed out that offsetting under Kyoto had its own reputation issues. Indeed it does. Some have alleged fraud in India. And the majority of Kyoto offset deals have centred on a handful of projects to destroy greenhouse gas emissions from chemical plants in China, making a tiny elite of brokers rich.

Reputation problems for carbon trading dont stop there. Europes carbon market is perversely handing windfall profits which could top 10 billion euros to electricity generators, the continents biggest polluters.

So voluntary offsetting matters quite a lot if its troubles mirror problems across all carbon trading, and our response to climate change.

Carbon trading is new and we should give it time. Much attention is now focused on 2013, when both Kyoto and the European carbon market are set for a re-vamp. What role carbon trading plays then will depend on whether it can be shown to work.