One of the most talked-about programmes of the past week – a primetime documentary on BBC1 – featured two people many seem to regard as living saints.

One was the presenter, Sir David Attenborough, the other Greta Thunberg, the Swedish teenage activist inspiring climate change 'school strikes' in several countries, including Britain.

The film's title was Climate Change: The Facts, and these, Sir David claimed, are now 'incontrovertible'. The film's message was so bleak it could have been made by Extinction Rebellion, the eco-anarchist protest group which has brought Central London to a standstill.

No one has done more to convey the marvels of the natural world than Attenborough, and his long career has rightly earned him public acclaim.

Sadly, on this occasion, I believe he has presented an alarmist argument derived from a questionable use of evidence, whose nuances he has ignored.

1: In the film an orangutan bounds along a felled tree trunk towards a digger bucket in a Borneo forest

According to Sir David, climate change, is the 'greatest threat' to humanity in thousands of years. 'We are facing the collapse of our societies,' he intoned, insisting we 'must all share responsibility… for the future of life on Earth.'

Attenborough is about to turn 93, while Thunberg is just 16, but they issued the same warning. 'It's our future and we can't just let it slip away from us,' she told viewers. Yet 'nothing is being done, no one is doing anything'.

The film rounded off a week which had already seen the BBC invite Extinction Rebellion extremists on to its news shows to expound the message – without serious challenge – that unless we cut greenhouse gas emissions to zero by 2025, 'our children will die'.

Last year, the BBC issued guidelines instructing editors that inviting comment from 'climate change deniers' was 'false balance'. In practice, this has meant that those who accept climate change is real, but less threatening than some such as Attenborough claim, have effectively been banished from the airwaves.

Now the Corporation has given acres of airtime to protesters demanding the overthrow of democratic governments and an almost immediate end to fossil fuel-derived power, heating and transport – in other words, the abrupt termination of civilisation as we know it.

Thunberg has become a global media darling, her pronouncements cherished as if they were holy writ.

'I want you all to panic,' she told the Davos economic forum in January: and Attenborough's film may well have persuaded viewers to do just that – and, perhaps, to join the Extinction Rebellion barricades.

2: After reaching the machine, the orangutan makes a desperate grab for it as a tree is about to be crushed

Watching it did fill me with horror, but not at the threat from global warming. It was at the way Sir David and the BBC presented a picture of the near future which was so much more frightening than is justified.

Climate science remains a field riven by deep uncertainties. The film largely glossed over these – and where faced with alternatives, it plumped unerringly for the most pessimistic version of the 'truth'.

Let me be clear: I am not a 'denier'. Global warming and climate change are real, in large measure caused by humans. According to the UN Intergovernmental Panel on Climate Change (IPCC), our emissions were responsible for more than half the 0.6C – 0.7C global average temperature rise recorded between 1951 and 2010.

But I am also convinced that the 'panic' Thunberg desires and Attenborough's film will encourage is not helpful when it comes to making policy designed to tackle it. Moreover, it is a grotesque travesty of the truth to claim that 'nothing' has been done: for example, since 1990, UK emissions have fallen by 43 per cent, according to the Government's Committee on Climate Change. Not only that, Government statistics say 53 per cent of our electricity came from low carbon sources in 2018, our last coal-fired power station will close in six years and the Government has pledged to reduce carbon emissions to below 100g/Kwhr by 2030.

Above all, the Climate Change Act requires Britain to reduce its 1990 carbon emissions by no less than 80 per cent by the year 2050, making us the first major economy to make such a dramatic commitment. To say that 'nothing' has been done is as risible as it is dishonest.

3: The digger arm is raised by the controller and the animal tumbles down on to the forest floor

One of the film's most questionable aspects was its claim that extreme weather events such as floods and storms have already got worse and more frequent, thanks to global warming, along with wildfires.

It did say that attributing reasons to any single event is difficult, and derived from probabilities. But in the words of interviewee Michael Mann, a US climate scientist, the effects of climate change are 'playing out in real time', and are 'no longer subtle'. Cue images of monster waves and hurricanes, accompanied by doomy music.

But is this true? The IPCC, regarded by mainstream scientists as the world's most authoritative source, says there have been some changes, such as higher rainfall. But its Fifth Assessment Report, published in 2013, stated there are 'no significant observed trends in global tropical cyclone frequency over the past century'. It added: 'No robust trends in annual numbers of tropical storms, hurricanes and major hurricane counts have been identified over the past 100 years in the North Atlantic basin.'

A separate IPCC report last year said that cyclones in the tropics would in future be less numerous, although some would be stronger.

In 2014, a group of IPCC experts published a paper about flooding. So far, they said, 'no gauge-based evidence has been found for a climate-driven, globally widespread change in the magnitude/frequency of floods.'

Another memorable segment of the film showed a father and son narrowly escaping from one of several devastating fires last year in California. These, too, were ascribed to global warming. Surprisingly, several recent scientific papers suggest that wildfires have been declining in recent years – even in California, where statistics gathered by the local agency, Calfires, says the number across the state has roughly halved since 1987, following a peak in the 1970s.

According to a study published by the Royal Society in 2016, 'many consider wildfire as an accelerating problem'. In reality, however, says the study: 'global area burned appears to have declined in past decades, and there is increasing evidence that there is less fire in the global landscape than centuries ago.'

Equally questionable was the film's claim that global warming is triggering a wave of extinctions, with eight per cent of species under threat solely because of it.

This also appears to oversimplify the findings of the IPCC, which said in 2014: 'There is low confidence that rates of species extinctions have increased over the last several decades. Most extinctions over the last several centuries have been attributed to habitat loss, over-exploitation, pollution, or invasive species.

'Of the more than 800 extinctions documented by the International Union for Conservation of Nature, only 20 have been tenuously linked to recent climate change. It says: 'Overall, there is very low confidence that observed species extinctions can be attributed to recent climate warming.'

The IPCC is clear that further warming will make things worse, but has found 'low agreement' over which species are at risk, and when extinctions might occur.

Attenborough made yet another contentious claim about corals, claiming that one third of the world's reefs have perished due to 'heat stress' in the past three years.

But why are Borneo's forests being cut down? The reason, as Attenborough said, is palm oil, a lucrative crop used in products ranging from soap to biscuits. Unfortunately, he left out the final stage of the argument

It is true that the record high temperatures recorded during the powerful 'El Nino' event of 2015/16 – which saw the central Pacific warm by several degrees and drove warmer weather elsewhere – damaged corals badly.

But many have begun to recover, including those of the supposedly moribund Great Barrier Reef.

I suppose it could be argued that this film merely jumped the gun a little, by portraying climate impacts which, while not discernible yet, soon will be.

But here we must turn to its most provocative claim of all – that IPCC computer model projections show that, by the end of this century, world average temperatures will be between three and six degrees higher than now. Needless to say, this would be devastating.

In fact, the IPCC issues not one but four such projections, each one showing what would happen with differing levels of future greenhouse gas emissions.

The most pessimistic – known in the trade as 'RCP 8.5' – suggests that by 2100, the world would indeed be much hotter: according to the 2013 IPCC report, between 2.6 and 4.8 degrees above the average between 1986 and 2005.

This, of course, is lower than the 3-6 degree range predicted by Attenborough.

Meanwhile, there is evidence that RCP 8.5 is almost certain not to take place. First, it posits population increases far higher than those now thought likely by many demographers.

UN forecasts claim the global population will reach 11 billion by 2100, but several expert teams now say falling birthrates mean it will peak much earlier.

'It will never reach nine billion,' says the eminent futurologist Jorgen Randers. 'It will peak at eight billion in 2040 and then decline.'

For the RCP 8.5 prediction to become a reality would also require a massive increase in the use of coal, and the reversal of the emissions cuts which many countries have already achieved.

All of which means the world is more likely to conform to what are known as RCP 4.5 or RCP 6. Under RCP 4.5, the IPCC says, the 'likely' range of warming by 2100 would be between 1.1C and 2.6C; under RCP 6, between 1.4C and 3.1C.

A BBC spokesperson said yesterday that the film said the 3-6 degrees of warming was a reasonable estimate given the current emissions trajectory, and said emissions 'have been following the RCP 8.5 curve rather than the alternatives.' Under this, an upper limit of 6C was possible.

She added: 'The film sought to make clear that scientists don't know exactly what may happen.'

I'm not trying to argue that climate change is trivial, nor that the world doesn't need 'action' to deal with it. On the other hand, we have already seen what can happen when 'panic' determines policy: the introduction of measures conceived by a need to be seen to be doing something under pressure from groups such as Extinction Rebellion.

Without making this clear, the film revealed one of the worst examples of this unfortunate effect. A powerful sequence showed an orangutan, fleeing loggers who have been eradicating Borneo's rainforest.

This is disastrous for both wildlife and the climate because, as the film pointed out, a third of global emissions are down to deforestation, because giant trees lock up a lot of carbon.

But why are Borneo's forests being cut down? The reason, as Attenborough said, is palm oil, a lucrative crop used in products ranging from soap to biscuits. Unfortunately, he left out the final stage of the argument.

Half of all the millions of tons of palm oil sent to Europe is used to make 'biofuel', thanks to an EU directive stating that, by 2020, ten per cent of forecourt fuel must come from 'renewable' biological sources. Malaysia says this has 'created an unprecedented demand'.

To put it another way: misguided 'action' designed to save the planet is actually helping to damage it – although the EU has pledged to phase out palm oil biofuel by 2030.

Another example of a misconceived effort to save the planet is Drax power plant in Yorkshire which is fed, thanks to £700 million of annual subsidy, by 'renewable' wood pellets made from chopped-down American trees – while pumping more CO2 into the atmosphere than when it burnt only coal.

In theory, the trees it burns will be replaced – but a large part of its supply comes from hardwood forests that take 100 years to mature.

There are times when climate propaganda – for this is what this was – calls to mind the apocalyptic prophets of the Middle Ages, who led popular movements by preaching that the sins of human beings were so great that they could only be redeemed by suffering, in order to create a paradise on earth.

Perhaps this is how Attenborough, nature journalism's Methuselah, sees himself. But climate change is too important to be handled in this manner. It needs rational, well-informed debate. Too often, cheered on by the eco-zealots of Extinction Rebellion, the BBC is intent on encouraging quite the opposite.

'An earlier version of this article said 56 per cent of our electricity came from low carbon sources in 2018. This figure related to one quarter of the year and the total for UK-generated electricity in the full year was 53 per cent.'