The green campaigner and journalist Mark Lynas is well-known for his books on global climate change. In High Tides, which came out in 2004, he travelled around the world documenting how climate change was already affecting the planet. In Six Degrees, published earlier this year, he posits what might happen as the earth gets warmer, taking it degree by degree.

Many of us don't want to read about things over which we have no control - both books are disturbing and the more extreme forecasts are very scary - so that is why his third book, also published this year, is a welcome addition to the Lynas canon. Carbon Calculator helps give you a sense of control. It is a short book, packed with advice on simple changes you can make to reduce your own personal carbon footprint; including how to reduce your electricity emissions to zero by switching to a 100 per cent renewable supplier.

It doesn't quite get away from unpalatable facts - the first section explains about greenhouse gases and global warming, summarising very quickly what the effects of increased warming would be. He also addresses the issue of whether global warming is a hoax. After that, he gets stuck into the nitty gritty of how to calculate your own emissions and reduce them.

Covering household and transport emissions, consumption and the workplace, the book includes inspiring ideas and excellent contact details. So why did Mark decide to write it? "I wanted to write a book which answers the question which people always come to me with, which is 'What can I do?'". He went through the book himself and calculated that his lifestyle, without flying, emits 2.5 tonnes of carbon. So what steps has he taken to reduce his own emissions?

"We already have cavity-wall insulation, but we've insulated the loft. I switched to a green energy tariff called Good Energy. We keep the central heating off most of the time and our space heating comes from the wood-burning stove, with locally-supplied wood," he said. "We don't own a car, so get around by bicycle, trains and occasional car hire, and we don't fly for personal holidays."

Does he ever feel that he's missing out on anything? "No, I feel my life is richer and more fulfilled that ever before, actually. We don't ever shop in supermarkets; we get pretty much everything from local shops and the farmers' market, which is actually a very sociable experience," he said. He argues that even if people don't make all the changes he has, some change is better than none.

His path to environmental campaigning began as a youngster when he was a self-confessed anorak about the weather and learned about climate through mountains and glaciers. His family were already quite green-minded. "My dad used to grow organic veg when I was a kid, long before it was fashionable," he said. However, Mark says that it wasn't a cross-generational thing. "It was a shared family journey, a few years ago, when we were all discovering these things," he said. "We certainly cross-fertilised and my mum and brothers and sisters too, but we've become aware of it as the rest of the world has become aware of it." As for making a career out of it, he feels he didn't have any choice. "Once you understand that unless we solve this problem, all other problems become irrelevant, it seemed to me to be something that I spend my life on."

He is keen to stress that much of Six Degrees encompasses 'what if' scenarios, projections of what might happen. "Some of the early changes are actual predictions, because they're already pretty much in the system," he said. "From 3 degC upwards, there's still everything to play for." He adds: "It's only scaremongering if you only tell people about the worst-case scenarios and don't tell people about all of it, from the best-case to the worst-case scenarios."

Oxford is a melting-pot of green activists, thinkers and campaigners. He says many people linked to the university are doing interesting things on climate-related issues, and Six Degrees was researched in the Radcliffe Science library. "There are so many practical things going on in Oxford, too," he said. "This weekend, for example, 18 eco-renovated houses in Oxfordshire are opening their doors to share their experiences. It's being organised by the Climate Outreach Information Network and Climate Xchange, both Oxford-based organisations."

He argues that we have little time to avert climate change. "We've got so far to go and the inertia of the system is huge," he said. It makes him more determined, though. "Think of an analogy of 1941; did you rush off to learn German, or did you decide that you were going to fight against all odds?"

Carbon Calculator is published by Collins Gem at £4.99. For details of the open houses, see www.ecovation.org.uk.