When Donald Rumsfeld, American Secretary of Defence pointed out that there are “known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don’t know we don’t know” he caused some hilarity.  I think that it is more significant that he missed out the “unknown knowns”. The things we know but choose to ignore. There are many issues which confront us personally and as a species which we choose to ignore or deny… such as climate change.

We’ve known about the basic chemistry of carbon pollution in the atmosphere and the greenhouse effect since the beginning of the last century. The scientific consensus is now that our burning of fossil fuels has a significant impact on average global temperatures and the consequent climate change.

David Cameron has recently linked the UK’s experience of abnormal weather events with climate change – as he said in the House of Commons last week: “We are seeing more abnormal weather events. Colleagues across the House can argue about whether that is linked to climate change or not. I very much suspect that it is.” Dr Peter Stott, Head of climate monitoring and attribution at the Hadley Centre, part of the Met Office, and Myles Allen of the University of Oxford’s climate dynamics group, have backed the PM’s judgment.

There was flooding in my hometown of Faversham over Christmas. Not as bad as in many other places in the UK, but close to home. Yet there are still people in Faversham in denial about climate change, incredibly still wanting to see housing built in flood risk areas. Humans are really good at denial.

Andrew Gilham of the UK’s Environment Agency responsible for flood defence is managing retreat, areas of land are being ceded to the sea. Gilham points out a patch where grass is being stripped off by the sea, exposing some of the earth beneath. He says the whole area will become a mixture of mudflat, grassland and marshlands.

As sea levels rise, Gilham says there’s a natural desire to keep building higher and higher defences. But he says the UK needs to move away from thinking it can hold every bit of coastline exactly where it is. “That’s a battle we won’t win,” Gilham says. “We are broadly looking at perhaps a metre of sea level rise over the next hundred years, and that would be very significant.” The problem with carbon pollution is that it hangs around the atmosphere for decades – out children’s children will live with the climate change to which we have contributed.