The 10:10 campaign supported by the Guardian resonates because of its simplicity. It suggests that wealthy western consumers who make modest, personal commitments to the fight against climate change are making a real difference. We're saving the world, one insulated loft at a time. That, very unfortunately, is misleading and the numbers tell us why.

Here in the developed world, we produce an average of 12 tonnes of CO 2 per person per year. Though that figure has risen in the last three decades, it has done so fairly slowly. Meanwhile, the number of us actually living in the developed world is also hovering at a fairly static level.

Where that stasis gets interesting is when we look at the developing world by comparison. For "developing world" I am taking the most frequently used definition: all nations in Africa, Latin America and the Caribbean, Asia (except Japan) and Melanesia, Micronesia and Polynesia.

Since 1996, the average per-person emissions across that vast section of the planet has ballooned from two tonnes per person per year to a whisker shy of four tonnes. So, while the UK's contribution has shrunk by 1% and that of the US has increased by only (only!) 7%, China's has more than doubled. India's has grown by 55%.

Where those numbers get scary, if they weren't already, is when you put them next to the population projections. In 2000, 42% of the population of the least developed nations on earth was aged under 15 – more than twice the proportion of kids in developed nations. That's why it only took us 12 years to get from a global population of 5bn to one of 6bn. In fact, the LSE's survey of population growth in the developing world forecasts the 8bn mark will be hit around 2040.

Those 2bn newcomers will not be living in Canada or New Zealand or Norway. Already 80% of the world's population lives in the developing world and, of the 78m newcomers to the world last year, 97% were from those regions.

It's when we look at those numbers – the spiralling emissions and ballooning populations – then set them against Britain, with our tiny (2%) contribution to the world's emissions, that those hours spent up a ladder pulling insulation splinters out of my thumbs seem suddenly a little more pointless.

This isn't new news. Environmentalists, Jonathan Porritt among them, have long drawn a link between population growth and climate change. Unfortunately (because I'm able to change my lightbulbs but I'm less able to influence average family size in Mumbai) the green debate has largely averted its gaze from that over which it has no influence.

So, emissions cuts in the developing world must be the answer. This surely requires, if only to demonstrate that we're making sacrifices too, western output to be cut even more sharply. That, somehow, is the easy bit, because unless the developing world comes with us on that journey, it will be a painful, expensive walk into climate oblivion.

Except (and here's the tricky bit) forcing them to cut emissions throws up some questions we really don't want to ask.

In a generation, in China alone, 500 million people have been dragged out of severe poverty. They have been given access to food, clean water, shelter, medicine. The basic infrastructure of modern life. To them, those two dirty coal-fired power plants opening every week isn't a disaster, it's an opportunity for a better life. It means schools and hospitals and roads. To them, like it or not, climate change saves lives.

The choice seems bleak. A cut in developing world emissions would mean the slashing of the already fragile safety-net of development being placed underneath an enormous number of people. But failure to act would be to abandon the climate, perhaps irreversibly.

It's not an easy choice. To encourage those nations to cut their emissions, we can pump money and expertise into the developing world on an unparalleled scale. We can give those nations preferential trade agreements to prop up their economies without them having to resort to the pile-em-high-and-sell-em-cheap model which demands quick and dirty industrialisation. We will need to. Ultimately, though, we cannot afford to accept "no" as the answer.

10:10 will fail if it becomes little more than a hobby for those on the wealthy, western left. If, though, it can provide real momentum behind the call for governments to engage seriously with the true issues at the heart of climate change, the population time-bomb chief among them, then perhaps my buying an energy-saving boiler wasn't quite such an empty gesture after all.

• To sign up to 10:10 go to www.1010uk.org