"There's been a very strong campaign by those who want to continue fossil fuel 'business as usual', and the scientific story has not been powerful enough to offset that push."
Part of the problem was the climate sceptic lobby used communications professionals, whereas "scientists are barely competent at communicating with the public".
The result was in recent years "a gap has opened between what is understood about global warming by the relevant scientific community and what's known by the people who need to know - and that's the public. However there's nothing that has happened to reduce our scientific conclusion that we are pushing the system into very dangerous territory, in fact that conclusion has become stronger over that same time period."
Hansen said significant climatic extreme events were now occurring over 10 per cent to 15 per cent of the planet annually, whereas between 1950 to 1980 they occurred over less than 1 per cent.
He added: "So in places like Texas this year, Moscow last year, and Europe in 2003, the climate change is so big that they are undeniable. Within 10 to 15 years they're going to occur over 15 to 20 per cent of the planet, so people have to notice that the climate is changing."
BURNING ISSUE
Texas: The American state has just had its driest summer since record-keeping began in 1895, with 75 per cent of the state classified as "exceptional drought", the worst level.
Moscow: Russia experienced its hottest-ever summer last year - for weeks, a large portion of European Russia was more than 7C warmer than normal and a new national record was set of 44C. Forest fires filled Moscow with smoke.
Northern Europe, 2003: A heatwave led to health crises in several countries and more than 40,000 people are thought to have died.
- Independent