Evidence points to fundamental shift in climate

Changes will challenge our societal structures, and capitalism’s endless expansion in particular, writes PAUL GILLESPIE

TIPPING POINTS, paradigm shifts and critical junctures. These are some of the main concepts used by natural and social scientists to explain radical change. There is an interesting convergence between the different approaches, offering insights on current debates about climate change, global warming and extreme weather events.

All efforts to explain major change in big structures and large processes, by making huge comparisons, come up against the problem of how to interpret the relationship between particular events and longer-term trends.

Current discussions about the significance of the admittedly extreme drought in the United States corn belt and the persistently wet Irish summers focusing on the role of the transatlantic jet stream are a good example.

The jet stream flows between five and 10 kilometres above the E arth, determined by the border between cold Arctic and warm tropical air. Normally it moves north or south of Ireland, giving us a more varied summer, but for the last few years it has been locked in a position that gives us cool wet weather. The reverse is happening in the US.

Normality becomes an issue because climate scientists debate whether these events are more or less unusual. The US drought is the worst in 56 years and has had worldwide consequences for food supplies, while this summer has been one of the wettest in Ireland, although still within expected averages over 30 years.

But given the alarming news this week that the Arctic sea ice is about to reach its lowest recorded extent as a result of human-induced global warming, and knowing this will deeply affect climate patterns, it is perverse not to ask whether we are at a point that could trigger more radical change.

Climate change does not occur gradually but reaches tipping points fed by amplifying feedbacks that can hasten change and its consequences. Loss of the Arctic’s ice coverage in the summer decreases the Earth’s reflectivity, resulting in faster warming, with as yet unknown effects on weather systems.

Looking out on the Atlantic from Askillaun beyond Louisburgh in Co Mayo on a gloomy wet morning recently, it is hard not to take such warnings seriously. Michael and Ethna Viney add that another underestimated factor in these calculations is the North Atlantic Oscillation of the sea level pressure between Iceland and the Azores. Its barometric variation decides whether our winters are warm, wet and windy or cold and dry.

As they say in their fine book, Ireland’s Ocean, these issues are as yet poorly understood. Ireland is in a strong position to take the lead in researching them.