Although the IPCC is not perfect - it famously predicted that all Himalayan glaciers would be gone in 2035, when the more likely year is 2350 - its many experts generally give us the best information on the fractious issue of global warming.

Because of extensive leaks, the report's contents are mostly known. And, because we have done this four times already, how the report will play out politically is also mostly known. But because 20 years of efforts to address climate change have not amounted to anything serious, it might be worth exploring a different strategy this time.

The new report's fundamental conclusion will be that global warming is real and mostly our own doing. Much will be said and written about the fact that the IPCC is now even more certain (95 per cent, up from 90 per cent in 2007) that humans have caused more than half of the global rise in temperature since 1950. But this merely confirms what we have known for a long time - that burning fossil fuels emits carbon dioxide, which tends to warm the planet. As climate scientist Andrew Dessler of Texas A&M University tweeted: "Summary of upcoming IPCC report: 'Exactly what we told you in 2007, 2001, 1995, 1990 reports' "

More specifically, the report's June draft shows "similar" temperature rises to the earlier reports, about 1C-3.7C by the end of the century. For sea-level rise, the IPCC now includes modelling of glacier responses of 3cm-20cm, leading to a higher total estimate of 40cm-62cm by century's end - much lower than the exaggerated and scary figure of 1m-2m of sea-level rise that many environmental activists, and even some media outlets, bandy about.

Similarly, the IPCC has allowed for lower temperature rises by reducing the lower end of its estimate of so-called climate sensitivity. It is also less certain that humans have caused hurricane and drought events since 1950. The 2007 report was more than 50 per cent certain that they have; now it is less than 21 per cent certain. Yet these sensible and moderate findings will be met with a predictable wall of alarmism. Many will mimic the blogger Joe Romm, who has declared that "this ultra-conservative and instantly obsolete report ignores the latest science", and continues to claim 5C temperature rises and six-foot (1.83m) sea-level rises.

Romm and many others made similar arguments following the release of the 2007 IPCC report, claiming that the latest, much more alarming, research had been left out. The bigger problem for the IPCC is that global temperature has risen little or not at all in the past 10-20 years. To be clear, this slowdown does not mean that there is no global warming - there is; but it does call into question how much.

To its credit, the IPCC admits that "models do not generally reproduce the observed reduction in the surface warming trend over the last 10-15 years". This matters, because if the models overshoot for recent decades, the century-long forecasts are open to doubt.

Compared with the actual temperature rise since 1980, the average of 32 top climate models (the so-called CMIP5) overestimates it by 71-159 per cent. A new Nature Climate Change study shows the prevailing climate models produced estimates that overshot the temperature rise over the past 15 years by more than 300 per cent.

Several studies from this year show that the slowdown could be caused by a natural cycle in the Atlantic or Pacific that caused temperatures to rise more in the 1980s and 1990s but that has slowed or stopped global warming now. Global warming is real, but it has probably been exaggerated in the past, just as it is being underestimated now.

This highlights the fact that the IPCC has always claimed only that more than half of the temperature rise is due to humans, although in public discussion it has usually been interpreted as all. As the IPCC emphasises, climate change is a problem. But the report contains none of the media's typical apocalyptic scenarios, no alarmism, and no demands from natural scientists to cut emissions by X per cent or to lavish subsidies on solar panels. All of this is almost certain to be lost in the hullabaloo from lobbyists clamouring for action and media hungry for bad news. Indeed, though the IPCC, according to its own principles, is a policy-neutral organisation, its head, Rajendra Pachauri, will feed the frenzy by insisting that "humanity has pushed the world's climate system to the brink", and that we need to complete a "transition away from fossil fuels", maybe with some kind of "price of carbon".

As a result, the likely outcome of the report's release will be more of the same: a welter of scary scenarios, followed by politicians promising huge carbon cuts and expensive policies that have virtually no impact on climate change. Maybe we should try to alter this scenario. We should accept that there is global warming. But we should also accept that current policies are costly and have little upside. The European Union will pay $250 billion for its current climate policies each and every year for 87 years. For almost $20 trillion, temperatures by the end of the century will be reduced by a negligible 0.05C.

The current green-energy technologies still cost far too much and produce far too little to replace existing energy sources. To insist on buying these expensive non-solutions is to put the cart before the horse. What we need is investment in R&D to reduce green energy's cost and boost its scale. When solar and other green technologies can take over cheaply, we will have addressed global warming - without the angst.