At Ratcliffe-on-Soar last year - when Climate Camp assailed the power station from all sides - I bumped into one well-known female activist who shrugged and said: "The problem is that, right now, I just don't care." She had done so much, been so out there over the previous year, that suddenly all the energy had gone out of her like an exhausted toddler.

Which is kind of the state that the climate change movement seems to be in right now. We're nearing the end of February and still the post-Copenhagen fog shows no sign of lifting. I speak to group after group, and they try to muster some enthusiasm for the year ahead. But really what's coming through is flat, flat, flat. No one quite knows what to do next. Do they carry on aiming for a global deal?

Do they concentrate on local issues and shelve climate change for a month or two? But it's too important! Flurries of activity, lots of letters and emails! But still, nothing much happens, in that tired, unfocused, February kind of way.

Burnout is a well-known problem for activists, and one that they are not afraid to admit to. I first heard about it from people who had been involved in Newbury and Twyford Down. You're working on a cause 24 hours a day, living on site, eating, drinking and sleeping it, and then something pops and you have to give up on the whole thing and leave the country for a bit, or at least stop handing out flyers.

More seriously, activists can go through some full-on experiences. Being walloped by a policeman is as horrible and disorientating as being walloped by a mugger, with the added complication that some people you know just won't believe you. Even after the brutal police raid on the Diaz school during the G8 summit in Genoa in 2001, there was no counselling for the activists who were beaten till bones broke and then imprisoned in conditions that public prosecutors described as torture.

“Firemen debrief after every operation," says the Activist Trauma Support group, which has been operating for five or so years. "A lot of people drop out, disappear, stop being active, feel excluded because of their fear or because they are suffering from post-traumatic stress disorders . . . We need to support each other."

So is the current calm just because the campaigners are taking a little breather and doling out back rubs? There is a graver possibility, unfortunately, which is that we are heading into one of the cyclical dips in the public's interest in the environment - or whichever cause was pushing buttons five minutes ago.

If we really have stopped caring about climate change for a while, the timing couldn't be worse. The sceptics, like zombies, are busting out of their dank corners, sensing a moment of weakness. The world's leaders are dithering. Any minute now, we'll see an outburst of consultations: always a bad sign. The scientists are getting even more defensive than usual, and that's saying something.

Up and up go the levels of carbon dioxide in the atmosphere. No amount of arguing and disputing seems to slow that. If I had any money to invest, it would be going into space rockets. Mars is looking more attractive by the hour.