Ian McLean Spokesperson for the Green Party

A shift to a healthy lifestyle that uses fewer resources will benefit all of us as individuals –and as a society. Even if the doctor is wrong, or the cure is found, we have little to lose and everything to gain.

A man I once knew was diagnosed with diabetes mellitus. His doctor exhorted him: 'Unless you make some radical lifestyle changes, you will be dead in 20 years. You must give up smoking and drinking alcohol, completely change your diet and increase your level of exercise”.

The man argued: 'All of those changes are too extreme. The doctor has a hidden agenda and is just trying to scare me. Anyway, medical science will find a cure within the next 20 years”.

So he continued to live his accustomed lifestyle, enjoying every minute and ignoring the increasingly evident consequences because they were too costly to respond to.

The man was still alive 20 years later. But his lower legs were amputated, he was legally blind and he suffered from advanced kidney failure. Between sucks on his bottled oxygen, he cursed medical science for its failure to find a cure and his doctor for not giving stronger warnings.

His only comfort was in knowing he only had a short time left to endure the pain.

It is hard to change an established lifestyle. We enjoy the way we live, we don't want dramatic change; and we hope and expect that technology will emerge to deal with unexpected challenges. Even in the face of evidence that things are going seriously wrong, we are remarkably good at adjusting the facts to suit our preferences. Warnings are, after all, just projections, and we can always put faith in the hope that they are wrong.