Leading article: When the ice melts, it is too late

On the day-to-day timescale that humans normally deal with, climate change appears to be a slow process that takes place over decades and centuries. This generates a common misconception: if things get really bad, we can quickly change our behaviour and set it all right again.

This is a fallacy, rather like the idea that we can alter the course of a supertanker minutes before it collides with an iceberg. The climate responds slowly because it has an in-built resistance to change – which is why 200 years of vast fossil-fuel emissions have taken so long to produce an effect, and why any delay now in curbing carbon dioxide emissions will only store up bigger problems for the future.

Since the last report of the Intergovernmental Panel on Climate Change (IPCC) two years ago, it has become evident that sea levels are likely to rise faster than predicted, reaching a metre or more higher than had been estimated for 2100. This would have devastating consequences for the hundreds of millions of people living in the vulnerable coastal areas that lie within a metre or two of sea level.

When they were writing their report, the IPCC scientists did not have the latest studies on melting ice sheets and how they would contribute to a rise in the sea level. It has since become clear that, in addition to the thermal expansion of the oceans caused by warmer seas and the melting of mountain glaciers, there will probably be an even bigger contribution to sea-level rise from melting ice sheets in Greenland and Antarctica as they begin to break up and disintegrate in a warmer world.

Scientists know that even if we stop emitting carbon dioxide today, the planet will continue to warm and sea levels will continue to rise for many years to come because of the in-built inertia of the global climate system. But they also know that the longer we continue to emit carbon dioxide, the longer it will take to alter the course of the climate supertanker – and the worse it will be for our children and grandchildren.

This is why the global conference on climate change due to take place in Copenhagen in December cannot be allowed to fail.