London’s Daily Mail reports that global warming is an underperformer:

A leaked copy of the world’s most authoritative climate study reveals scientific forecasts of imminent doom were drastically wrong.

The Mail on Sunday has obtained the final draft of a report to be published later this month by the UN Intergovernmental Panel on Climate Change (IPCC), the ultimate watchdog whose massive, six-yearly ‘assessments’ are accepted by environmentalists, politicians and experts as the gospel of climate science.

They are cited worldwide to justify swingeing fossil fuel taxes and subsidies for ‘renewable’ energy.

Yet the leaked report makes the extraordinary concession that the world has been warming at only just over half the rate claimed by the IPCC in its last assessment,  published in 2007.

Back then, it said that the planet was warming at a rate of 0.2C every decade – a figure it claimed was in line with the forecasts made by computer climate models.

But the new report says the true figure since 1951 has been only 0.12C per decade – a rate far below even the lowest computer prediction.

The 31-page ‘summary for policymakers’ is based on a more technical 2,000-page analysis which will be issued at the same time. It also surprisingly reveals: IPCC scientists accept their forecast computers may have exaggerated the effect of increased carbon emissions on world temperatures  – and not taken enough notice of natural variability.

• They recognise the global warming ‘pause’ first reported by The Mail on Sunday last year is real – and concede that their computer models did not predict it. But they cannot explain why world average temperatures have not shown any statistically significant increase since 1997.
• They admit large parts of the world were as warm as they are now for decades at a time between 950 and 1250 AD – centuries before the Industrial Revolution, and when the population and CO2 levels were both much lower.
• The IPCC admits that while computer models forecast a decline in Antarctic sea ice, it has actually grown to a new record high. Again, the IPCC cannot say why.
• A forecast in the 2007 report that hurricanes would become more intense has simply been dropped, without mention.

This year has been one of the quietest hurricane seasons in history and the US is currently enjoying its longest-ever period – almost eight years – without a single hurricane of Category 3 or above making landfall.

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One of the report’s own authors, Professor Myles Allen, the director of Oxford University’s Climate Research Network, last night said this should be the last IPCC assessment – accusing its cumbersome production process of ‘misrepresenting how science works.

Despite the many scientific uncertainties disclosed by the leaked report, it nonetheless draws familiar, apocalyptic conclusions – insisting that the IPCC is more confident than ever that global warming is mainly humans’ fault.

It says the world will continue to warm catastrophically unless there is drastic action to curb greenhouse gases – with big rises in sea level, floods, droughts and the disappearance of the Arctic icecap.

Last night Professor Judith Curry, head of climate science at Georgia Institute of Technology in Atlanta, said the leaked summary showed that ‘the science is clearly not settled, and  is in a state of flux’.

She said  it therefore made no sense that the IPCC was claiming that its confidence in its forecasts and conclusions has increased.

For example, in the new report, the IPCC says it is ‘extremely likely’ – 95 per cent certain – that human  influence caused more than half  the temperature rises from 1951 to 2010, up from ‘very confident’ –  90 per cent certain – in 2007.

Prof Curry said: ‘This is incomprehensible to me’ – adding that the IPCC projections are ‘overconfident’, especially given the report’s admitted areas of doubt. …

Dr Benny Peiser, of the Global Warming Policy Foundation, described the leaked report as a ‘staggering concoction of confusion, speculation and sheer ignorance’.

As for the pause, he said ‘it would appear that the IPCC is running out of answers .  .  . to explain why there is a widening gap between predictions and reality’.

The Mail on Sunday has also seen an earlier draft of the report, dated October last year. There are many striking differences between it and the current, ‘final’ version.

The 2012 draft makes no mention of the pause and, far from admitting that the  Middle Ages were unusually warm, it states that today’s temperatures are the highest for at least 1,300 years, as it did in 2007. Prof Allen said the change ‘reflects greater uncertainty about what was happening around the last millennium but one’.

A further change in the new version is the first-ever scaling down of a crucial yardstick, the ‘equilibrium climate sensitivity’ – the extent to which the world is meant to warm each time CO2 levels double.

As things stand, the atmosphere is expected to have twice as much CO2 as in pre-industrial times by about 2050. In 2007, the IPCC said the ‘likeliest’ figure was 3C, with up to 4.5C still ‘likely’.

Now it does not give a ‘likeliest’ value and admits it is ‘likely’ it may be as little as 1.5C – so giving the world many more decades to work out how to reduce carbon emissions before temperatures rise to dangerous levels.

That part about “misrepresenting how science works” is amusing given that “climate scientists” have misrepresented how science works ever since they predicted the next Ice Age in the 1970s. It should be obvious to anyone that scientists and others who sign on to this manure are motivated by something other than science.