The problem with this belief is that, as far as I can make out, it is totally unsupported by any evidence whatsoever. It is not predicted by the climate models – they merely project that temperatures will increase steadily as carbon dioxide increases – and there is no evidence of tipping points occurring within what one might call the normal temperature range in the past.
But it hasn't stopped lots of people deluding the public with claimes that tipping points are real and dangerous. The most recent example is an interview with Bronwyn Hayward – an associate professor of political science and a member of an important IPCC committee – in a recent edition of the New Zealand Herald.
The interview is riddled with unsupported statements and she even claimed that Niue Island is at risk from climate change – presumably sea level rise. Obviously, she does not know that it is an uplifted Island 50 m above sea level and surrounded by cliffs. Sea level rise is the last thing Niue needs to worry about!
The interview was mostly about her belief that a temperature rise greater than 2° – or even 1.5° – above pre-industrial temperatures (the latter amounts to something like 0.5° above current temperatures) will trigger a “tipping point” that will have a disastrous effect on mankind.
This prompted me to do some research into the evidence supporting these “tipping points”. The Internet did not yield any hard information but I did discover that most of them discussed tipping points at 1.5° and 2° above current temperatures. So where Bronwyn Hayward and her IPCC committee got 1.5° above pre-industrial temperatures seems to be a total mystery.
I then contacted James Renwick of Victoria University who has spent a lifetime studying climate and working for the IPCC. All he was able to provide me with were two papers reporting on computer modelling of Antarctic sea levels that indicated that under certain circumstances, the sea level could rise by 1m by 2100. This, presumably, represented a global "tipping point” The mind boggles! He did not provide any evidence from the IPCC so I can only assume that no IPCC study has found evidence of any tipping points.
The interview gave no indication that Bronwyn is aware that the satellite temperature measurements – that NASA regards as the most accurate – show that there has been no significant global warming for the last 18 years even though carbon dioxide levels have increased or that sea level gauges around the world show a steady rise of 1.4 mm per year. This demonstrates that the climate models that predicted that the world would be 0.5° hotter than it is by now are worthless. It also confirms that man-made carbon dioxide does not cause dangerous global warming. If she had studied the IPCC technical reports carefully she would have realised that even the IPCC recognise that there are major uncertainties surrounding virtually every aspect of climate science.
I am sure that the public have an expectation that academics who speak publicly are careful to make statements that are backed up by solid scientific evidence and will explain where the uncertainties lie. There is no evidence that she has done either.
Why are taxpayers paying for her time and travelling expenses backwards and forwards to IPCC committee meetings in Brazil to study the effects of an unsupported urban myth?
The only things we can be absolutely sure of are that "tipping points" are no more than an urban myth and Bronwyn needs to do her homework.