''NOT all scientists are good scientists,'' Nobel laureate Harold Kroto says when asked what he thinks about the debate around global warming.

''We don't have a 100 per cent reliable assessment so we can only say - and I would say - that it doesn't look good.''

Nobel laureate Professor Harold Kroto is in Australia to promote science and the value of reason and evidence. Credit:Joe Armao

Professor Kroto ticks off the warning signs on his fingers, listing rising sea levels and temperatures, the shrinking Arctic and melting glaciers.

''I look at the evidence [and] the evidence is not good,'' he said. ''That's the situation. We're in a 100-year experiment and it will take another 100 years to decide and then it will be too late.''