Global warming is happening so fast that it may become impossible to predict its full effects in the future, one of the world's most influential climate scientists has warned.
Dr Martin Manning said the inability of scientists to predict something as fundamental as the worst-case scenario for rising sea levels was "worrying the hell" out of him.
Dr Manning is a director of the UN's Intergovernmental Panel on Climate Change (IPCC), which is charged with monitoring the science behind global warming and predicting its possible effects.
He said that this year alone the extent to which Arctic sea ice had melted was outside all the computer modelling that scientists worldwide had done.
He said it was even more worrying that the extent of the melting, which was 20 per cent greater than the previous record in 2005, suggested that global warming may be accelerating because of "positive feedback".
Positive feedback occurs when the Arctic sea ice melts because of rising temperatures. Increased sunlight warms the oceans further, which in turn melts more ice, accelerating the melting of the polar ice cap and leading to both higher temperatures and rising sea levels.
"It is suggesting that some of these positive feedbacks are quite hard to get right in our modelling and you only have to have an anomalous year like this year and it leads to a domino effect in succeeding years, and that's a worry.
"It's hard to tune a model for climate change based on the past. We are seeing phenomena with a warmer world that we have had no experience of before.
"In 2001 when we reported on potential sea level rises, we gave upper and lower bounds. In 2007, six years on, you'd think we'd know more, but actually we're saying we don't know what the upper boundary is anymore."
Dr Manning was a speaker at the first of two lectures on climate change organised by the Environmental Protection Agency in Dublin last night.
He was one of the authors of the IPCC's fourth assessment report on climate change, released in February. It concluded that the effects of climate change were unequivocal and that the certainty was growing that it was man-made.
Dr Manning said more global warming was inevitable even if emission targets set by the EU to keep global temperatures at two degrees above pre-industrial levels were achieved.
