Irish heatwave reveals vulnerabilities we should not ignore

This year has been a year to remember weather wise, and we are only just past the halfway mark. Recent weeks have brought extreme temperatures and drought. Long-standing weather records have been threatened, while others have been broken. The hot and dry conditions are set to continue for at least the next 10 days. The next few weeks will tell if 2018 becomes synonymous with the perfect storm for water resources and agriculture. The question on many people’s minds include: “how rare are these conditions?” and “is this climate change?”

In Ireland, we have a rich history of weather observing that stretches back to the mid-1800s for many locations. At Maynooth University, together with colleagues at Met Éireann and Loughborough University in the United Kingdom, we have been working to stitch together and quality-assure those records. That work allows us to put this recent spell in context and it has indeed been remarkable to this point.

In the last two weeks the highest temperature recorded for Ireland, 33.3 degrees in Kilkenny during June 1887, has been challenged but not broken. So far the summer 2018 peak has reached 32 degrees at Shannon – close but no cigar. However, it is worth bearing in mind that temperature observations in 1887 would not have been compliant with modern measurement standards. Therefore, the 1887 record should be treated with caution until more rigorously assessed.

The highest temperature of the 20th century, when observing standards were more reliable, is 32.5 degrees, recorded at Boora, Co Offaly in 1976 – another drought year. Droughts and heatwaves often go hand in hand as compound events.

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Greenhouse gases

In our long temperature records summer 1995 stands out as the hottest. It is too early to say if summer 2018 will challenge this. However, since 1900 we have seen the likelihood of a summer as hot as 1995 increase 50-fold. We have also observed increases in the number of hot summer days and in average temperatures across all seasons.

While the “Beast from the East” is fresh in the memory, there has actually been a large reduction in the number of annual frost days over recent decades, as winter minimum temperatures increase.

Human-driven climate change is likely to amplify these warming trends over the coming decades – by how much depends on how effective we are at reducing greenhouse gases. We expect more, hotter and longer heatwaves. In fact, by the end of the century our warmest summer on record up to now could plausibly by then be a cool summer. We estimate that by the 2080s only one in seven summers may be as cool as 1995.

Heat extremes are one of the more concerning aspects of future climate change. Research by the UK Met Office has shown that the 2003 European heatwave, which caused thousands of excess deaths across Europe together with major economic impacts, could be an average summer by 2050 and even a cool summer by the end of the century.

Climate scientists have shown repeatedly that the fingerprint of human-emitted greenhouse gases can be found in numerous recent extreme heat events. Moreover, even if we are successful at limiting global temperatures to the optimistic target of 1.5 degrees above pre-industrial levels, heat extremes are likely to be a far more common feature of our future.

The remarkable recent weather is revealing some important vulnerabilities that should not be ignored

Turning to rainfall (or the lack thereof) June 2018 was the driest in our records at Phoenix Park since at least 1850 – coming in at a paltry 3.8mm. The cumulative rainfall total over both May and June 2018 is the driest in at least 168 years at both Phoenix Park and Dublin Airport. Rainfall over consecutive months is important for water resources. For those of us born after 1976 Irish drought may appear to be somewhat of a contradiction.

However, the long records we have been working on reveal a much greater propensity for droughts throughout much of the 19th and 20th centuries than in recent decades.

Major implications

Those same long records show a tendency towards drier summers. This trend is consistent with expected reductions in summer rainfall with climate change over the coming century. However, the magnitude of reductions in summer rainfall with climate change are hard to pin down. Climate models suggest modest changes to large reductions of more than 60 percent by end of century. Obviously, the latter would have major implications across many sectors.

While many, probably most, are enjoying the remarkable recent weather, it is revealing some important vulnerabilities that should not be ignored. Not least it shows how sensitive our water systems are to what is still, in the context of our historical records, a relatively short, though intense drought event. This vulnerability is manifest from decades of little to no investment in critical water infrastructure.

Our new development framework, Project Ireland 2040, sets a vision for Ireland as a climate-resilient island. Climate-water connections extend beyond water supply to broader concerns about food and energy security, economic development, agricultural intensification, water quality, biodiversity loss, invasive species, and even civil unrest.

Realising a climate-resilient Ireland will require huge capital investment in upgrading water infrastructure and rethinking our relationship with water to reduce demand on our most precious of resources.

It is vital that those investments are stress tested against historical climate variability and the full range of plausible future climate change. We as a nation depend upon it.

Dr Conor Murphy is a member of the Irish Climate Analysis and Research Unit (ICARUS), Department of Geography, Maynooth University.