I started working at Friends of the Earth (FoE) Scotland 20 years ago this month.

In many ways life back then was easy if frustrating.

Scotland was run by Tory Ministers who spent most of their time at Westminster. They announced initiatives on, say, big roads plans or fish farming and we put out a press release saying it was rubbish. We didn't have much chance of changing policy as there was hardly any UK parliamentary time for Scottish stuff and all the action was 400 miles away.

FoE Scotland was the only environment group to actively campaign for a Scottish Parliament. When this came into being the people making many of the decisions were just down the road and actually had time to speak to you. Since 1999 there have been frustrations, but good results have included excellent laws on climate change, flooding and managing the seas.

But still someone else was making big decisions on issues such as whom we go to war with, nuclear weapons, what banks are allowed to do and energy policy. To me it makes sense to control environment, social and financial policies together so that we have at least the potential to do great things.

Concentrating the levers of power in one place is likely to produce a sensible compromise most of the time. Whether an independent Scotland or a devolved Scotland with greater powers would do better on the environment and climate change mostly depends on who is in charge.

The key extra offer from the independence camp is a written constitution that binds us to get rid of Trident and to protect the environment. This is an additional safeguard which means that, however stupidly we vote in the future, there are just some bad things that our elected members won't be able to do.

A previous environment minister suggested to me that the powers to meet Scotland's climate targets lay one-third in Scotland's hands, one-third in the UK's and one-third in Europe's. The UK Government, supposed to be the "greenest ever", is rapidly moving backwards on key areas like renewables and home insulation, while selling a dream of cheap shale gas and rigging the whole electricity market to pay tens of billions of pounds for new nuclear plants that will probably never be built.

An independent Scotland could concentrate on developing our huge renewable energy resources and dealing once and for all with fuel poverty. An independent Scotland would have more power to meet our climate targets and there would be no-one else to blame if we did not.

I've seen Scottish ministers at work at the annual United Nations' Climate Change meetings. They have done a good job of telling the story about Scotland's climate change targets and about the impressive growth of renewable energy in our country. But they have had to do this in side meetings and by seeking out environment ministers from other countries.

Although Scotland has an official place as part of the UK delegation at these meetings, the reality is that Scotland has no official voice to tell its mostly very positive story. An independent Scotland would have that voice, not only in the UN but also in Europe.

I was complaining to three senior officials recently that the Scottish Government had not reacted more strongly to a weak position from Europe on future climate and energy targets. I was able to say to them that I expect better because, in the event of a Yes vote, Scotland would one day have its turn at the six-month presidency of the EU and it could be key in using that time to push forward on the climate agenda.

I am in my second stint with FoE Scotland, and this time around the organisation is neutral on the constitutional issue, while asking questions of both sides and highlighting good and bad ideas. Personally, I'm completely convinced that independence is the only way for Scotland to deliver on its environmental potential, at home and abroad.