It never ceases to amaze me that people who say we can "save the planet" by wearing a jumper or growing our own veg are treated with the utmost seriousness, while those who argue that tackling climate change might require some larger-scale projects – such as geo-engineering the Earth – are treated as sci-fi freaks who should stick to reading Philip K Dick novels and stop polluting public debate with their insane ideas.

When it comes to climate change, the only acceptable debate, it seems, is how we can encourage ordinary people to do less, consume less and fly less. Bigger and more far-reaching ideas about how we might offset the impact of climate change are elbowed off the agenda.

This reveals something profound about environmentalism: it is not really a campaign to find solutions to the practical problem of climate change, but rather has become a semi-religious, almost medieval demonisation of human behaviour as dirty and destructive. This is really a priestly, ideological effort to lower people's horizons and expectations, rather than a focused attempt to create a less polluted planet.

Consider the events of yesterday. First, the 10:10 campaign – supported by the Guardian – was launched. Its aim is to encourage people and organisations to cut their carbon emissions by 10% in 2010.

Second, the Royal Society published a report on the need to invest in geo-engineering projects, such as putting a giant mirror on the moon to deflect the sun ray's from Earth or erecting enormous "CO2 scrubbers" to clean the air. (In keeping with orthodoxy, however, the Royal Society also said that such projects should not detract from their efforts to reduce carbon emissions.)

Needless to say, the 10:10 campaign – with its exhortations to "turn off the lights" or "grow veg on the balcony" – was treated more seriously than the Royal Society report. Indeed, Greenpeace rubbished any talk of geo-engineering, claiming that "intervening in our planet's systems carries huge risks" and will "undermine" the need to continue pursuing "emissions reductions". In short, large-scale solutions to climate change only divert attention from the myopic, mean-spirited focus on changing people's behaviour and outlook.

Unfortunately, the 10:10 campaign highlights the petty moralism behind environmentalism. At the launch at the Tate Modern last night, the artist Bob and Roberta Smith suggested that people who own a 4x4 should spend a "night in the cells". Another attendee said "it's immoral to be wasteful".

Other 10:10 supporters promise to eat less "junk food" and to take fewer flights. It's hard to know what is more galling about these pledges to live a cleaner life: the fact that they implicitly demonise certain forms of leisurely behaviour – especially the kind enjoyed by the 4x4-driving, junk-food-eating nouveau riche – or the idea that making these minor changes will "save the planet".

There is a glaring disconnect between the scaremongering employed by environmentalists and their proposed solutions. In one breath they tell us we face the worst crisis in human history, one which will make "genocide and ethnic cleansing look like sideshows at the circus of human suffering", and in the next they tell us we can avoid this disaster by wearing thermal underwear instead of turning on the heat and going to Leon instead of McDonald's.

No wonder "ordinary people" aren't enthusiastically signing up to the environmentalist ethos. They know it simply doesn't make sense to say that we face an enviro-holocaust and then to claim we can prevent it by not taking a cheap flight to Majorca. Yesterday Ian Katz said that only "a small, saintly portion of the population" is taking climate change seriously; that is because the larger, presumably un-saintly portion of the population instinctively recognises that changing their lightbulbs will not prevent the alleged End of Days.

The moralistic nature of environmentalism was revealed in the reports of the 10:10 launch. It took place in the Tate Modern, a "cathedral to the concept of cutting emissions", the Guardian said; individuals held up pledge cards and promised to wear the 10:10 necklace, like a modern-day crucifix marking them out as Good. It reminded me more than anything else of those youthful members of the religious right in the US who take pledges to be decent people, only where they "just say no" to sex and alcohol, the 10:10 supporters "just say no" to junk food and flights.

Franny Armstrong flatteringly compares the 10:10 campaign to the Suffragette movement. Yet Sylvia Pankhurst said: "Socialism means plenty for all. We do not preach a gospel of want and scarcity, but of abundance … We do not call for limitation of births, for penurious thrift, and self-denial. We call for a great production that will supply all, and more than all the people can consume." The 10:10 campaign, I'm afraid, is the very opposite of that.