For those who distrust the motives of radical environmentalists — the various “crises” being but a pretext for government intrusion in our lives — here are two examples that will either make you cringe or laugh darkly.

First, Lord Stern (great name, eh?) wants the world to cut out meat.

People will need to consider turning vegetarian if the world is to conquer climate change, according to a leading authority on global warming.

In an interview with The Times, Lord Stern of Brentford said: “Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world’s resources. A vegetarian diet is better.”

Direct emissions of methane from cows and pigs is a significant source of greenhouse gases. Methane is 23 times more powerful than carbon dioxide as a global warming gas.

Lord Stern, the author of the influential 2006 Stern Review on the cost of tackling global warming, said that a successful deal at the Climate Change Conference in Copenhagen in December would lead to soaring costs for meat and other foods that generate large quantities of greenhouse gases.

That’s mild compared with Alex Renton, writing in the UK Guardian, who wants the west to reduce babies.

The worst thing that you or I can do for the planet is to have children. If they behave as the average person in the rich world does now, they will emit some 11 tonnes of CO_² every year of their lives. In their turn, they are likely to have more carbon-emitting children who will make an even bigger mess. If Britain is to meet the government’s target of an 80% reduction in our emissions by 2050, we need to start reversing our rising rate of population growth immediately.

And if that makes sense, why not start cutting population everywhere? Are condoms not the greenest technology of all?

World population is forecast to peak at 9.2bn by 2050. According to a report by the LSE for the Optimum Population Trust, the lobbying body currently asking parents to “Stop at Two”, it would cost $220m to provide the family planning that would reduce the 2050 population by half a billion, preventing the emission of 34 gigatonnes of carbon. Introducing low-carbon technology for the same result would cost more than $1 trillion.

So why does population control hardly feature on the agendas of the UN bodies or of the governments now committed to tackling climate change? And why do the development and environmental groups shy away from it? The Guardian’s George Monbiot dismisses the topic as a distraction, the obsession largely of “post-reproductive, middle-class white men… a group more responsible for environmental destruction than any other class in history”. David King, the government’s former chief scientific adviser, argues: “The only way to tackle climate change is to change the way energy is used by those of us that have already been born.”

Guilt, self-loathing, righteous piety — can the return of the hairshirt be far off?