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Pray he’s wrong

Hansen believes we are looking at multi-metre sea-level rises in the coming decades, not centuries.

Former NASA chief climatologist, Jim Hansen has a prejudicial knack of being right a lot more often than he’s wrong. And when it comes to projecting the future path of climate change, he has an equally unfortunate habit of being well ahead of the scientific posse.

Back in the sweltering summer of 1988 Hansen testified to the US Congress on climate change, a phenomenon that was, until his electrifying presentation, seen as something of a scientific curio, an issue that distant future generations would, eventually, have to confront. Hansen confirmed that not only was it real, it was already happening. Calculations Hansen published in the late 1980s of likely future climate change track what has actually occurred with uncanny accuracy.

Fast forward to 2015, a year in which global temperatures were smashed by record margins to make it, by some distance, the hottest ever recorded. And temperatures recorded in the first two months of 2016 have been described by climate scientists as “off the charts”.

The February 2016 global temperature anomaly is +1.35C above average. It took from the beginning of the industrial revolution until October 2015 to record a +1C global temperature rise. To add another 0.35C within less than six months has left the scientific community running out of superlatives.

cityAnd now Hansen is back. He and 19 colleagues have just published a blockbuster paper in the journal Atmospheric Chemistry & Physics. While the IPCC’s assessment reports represent the conservative mainstream view of climate science, Hansen and his colleagues can be said to be at the bleeding edge.

What their research has concluded is profoundly disturbing, throwing into question almost everything we think we know about how climate change is likely to play out in the 21st century. While the IPCC plumped for a likely maximum sea level increase this century of around 1 metre, Hansen argues this may be a hopeless underestimate.

“The models that were run for the IPCC report did not include ice melt, and we also conclude that most models, ours included, have excessive small-scale mixing, and that tends to limit the effect of this freshwater lens on the ocean surface from melting of Greenland and Antarctica”, Hansen told a press conference marking the launch of his paper last month.

How Hansen sees this playing out in the real world reads like apocalyptic science fiction. Instead of a slow, incremental increase in sea levels, he believes we are looking at multi-metre sea-level rises in the coming decades, not centuries.

Nor will this be a gentle process: he predicts devastating superstorms quite unlike anything since the last Ice Age, and the near-shutdown of major ocean currents such as the Atlantic Meridional Overturning Circulation (AMOC), or the Gulf stream, that vast current of warm tropical water that keeps northwest Europe, including Ireland, from not being frozen solid for several months a year.

If this is beginning to sound familiar, you’re probably thinking of the movie ‘The Day After Tomorrow’, where abrupt climate change triggered a massive freeze in the northern hemisphere. That, of course, is purely speculative; there is already far too much excess heat in the system for the return of widespread Ice Age conditions anytime in the next hundred millennia.

What is truly alarming, according to Hansen, is that as the heat differential between the equator and the northern hemisphere increases, this is likely to fuel powerful mid-latitude storms, on a scale not endured in thousands of years.

Such storms could be powerful enough indeed to pick up massive boulders weighting thousands of tonnes and toss them hundreds of metres inland. We have clear evidence that this has happened before – and he believes it can happen again.

With severe storms battering the world’s coastal regions, compounded by rapid sea-level rise, the nightmare scenario of most of the world’s great cities being lost to coastal inundation moves from being some distant spectre far beyond the year 2100 and bang smack into the middle of this century. Cork, Dublin, Galway, Belfast, Limerick, Wexford… the list goes on, and that’s just on this tiny island.

Apart from the unimaginable human misery and forced migration of millions, the economic impact is almost incalculable Most of our critical infrastructure, including all the world’s great ports and trading hubs would be lost.

Not everyone agrees. Professor Peter Thorne of NUIM was among those who reviewed Hansen’s paper, and while not ruling out worst-case scenarios, believes publicising them may be counterproductive.

“Does this actually confuse, does it cause despair, does it help or hinder? I don’t know whether communicating something like this actually elicits a response that says: let’s do something”, he cautions.

By John Gibbons