The report by the Intergovernmental Panel on Climate Change (IPCC) was, sceptics told us, going to confirm climate change itself was "on ice".

Lower atmospheric temperature rises than expected over the past 15 years would demonstrate problems caused by greenhouse gases had been exaggerated and prove the whole issue was an elaborate international hoax, it was predicted. We now know the report says no such thing.

Yes, the panel of UN-appointed experts confirmed a "pause" in the rate of temperature increase in recent years. However, while air temperatures may have plateaued over the past five years, other indicators show the rate of climate change has barely slowed at all.

The temperature of the atmosphere is still rising, as is that of the oceans. Polar snow and ice are retreating, sea levels are rising and the concentration of greenhouse gases in the air is also increasing.

This last statistic is telling. Climate change sceptics like to point to previous fluctuations in global temperature - such as the so-called medieval warm period - as examples which show climate change is natural. But the IPCC report points out that atmospheric concentrations of carbon dioxide, methane and nitrous oxide are now at levels "unprecedented in at least the last 800,000 years".

For this and other reasons, the conclusion that man is to blame for the changing climate is unequivocal, the scientists state.

That is not to say the scepticism has not been useful. We do not wish to return to the situation exposed at the University of East Anglia in 2009 where scientists appeared to be withholding data which complicated the picture on climate change. There are dangers in unchallenged consensus.

There is evidence of the impact of the sceptics in the new paper, which is conservative in almost all of its predictions, erring towards the lower end of the latest research on sea level rise, carbon dioxide levels and also the predictions of how sensitive the climate might be to atmospheric change.

This is a good thing. If estimates for climate change have been exaggerated by environmentalists, scientists or politicians, this should be addressed.

But it is equally wrong to exaggerate the arguments of the sceptics. Even with a more cautious approach, the IPCC's conclusions are stark. Climate change is real, we are not doing enough about it and a failure to curb greenhouse gas emissions will have an impact which lasts for centuries.

The report makes difficult demands of the international community. We have already emitted around 60% of the carbon necessary to raise temperatures 2C and cause potential climate catatrophe, it says. We cannot burn all the fossil fuel reserves we have - which may be hard for individual governments or businesses to face.

But face it we must, and in concert. This report says, very clearly, that humanity faces a profound challenge. It demands a global reponse.