Climate change is already here, but still we do little to stop it
GENERATIONS of Irish pupils have been brought up in the belief that Ireland has one of the most equable climates in the world due to our oceanic location. This is demonstrably true. The difference between the mean winter and mean summer temperature at Valentia is a measly 7.3C, a seasonal range more typical of the hot tropics than a mid-latitude location like Ireland.
Yet, in common with many mid-latitude locations, Ireland has this summer been experiencing extremes of heat and drought unparalleled for decades, and this following a cold and exceptionally long winter and an autumn when the first near intact Atlantic hurricane for half a century approached our shores.
The frequency of extreme weather events changes more rapidly than does the average conditions during a period of climate change. The accompanying graph, with its bell-shaped curves, indicates that for most of the time our temperatures fall within a relatively small range. Infrequently, extremes of cold and warmth occur as indicated on the right and left ‘tails’ of the curve.
But if we shift the curve to the right, much more dramatic changes in extreme heat occur than the small shift in temperature would suggest. We have now shifted the curve and are in the process of shifting it even more as ongoing climate change occurs. Everywhere in Ireland is on average 0.5C warmer over the past 30 years.
Another 0.5C warming is a near certainty over the coming two decades. Our all-time temperature record of 33.3C, measured in Co Kilkenny in 1887, is coming increasingly under threat.
The main feature of the present summer has been the extent to which these phenomena have occurred in much more northerly locations than normal.
Forest fires, many north of the Arctic Circle, have ravaged Sweden, where it has been the hottest July in 250 years. In Japan, where temperatures exceeded 40C in metropolitan Tokyo, there were 65 deaths and 22,000 people were hospitalised. A similar death toll was recorded in Canada’s July heatwave. Wildfires in Siberia, where temperatures above 30C occurred for several consecutive days, were so extensive that their smoke eventually reached the eastern seaboard of the US.
This is all symptomatic of a jetstream locked in position much nearer the North Pole than its more customary mid-latitude location.
Perhaps the most bizarre statistic of the summer thus far, however, came from the North Cape of Norway, just a couple of thousand kilometres from the pole itself, where the overnight minimum temperature on July 19 was 25.2C.
The question on everyone’s lips is of course: were these events caused by climate change? But this is not the question we should be asking.
All extreme events of this nature have probably occurred sometime in the past, long before we added carbon dioxide and methane from industry and agriculture to the atmosphere. We can’t therefore say that individual events in 2018 were caused by climate change alone.
A more nuanced question is: to what extent has climate change made these events more likely to occur? This is the basis of a rapidly emerging strand of climate research called ‘attribution’.
It has been facilitated by the rapid growth in computing power which has enabled climate models to be run hundreds of times rather than once.
The probability of individual extreme events can thus be calculated by gauging how often they occur in the outputs. The new ingredient, though, is that the models can now be run hundreds of times with an atmosphere with pre-industrial levels of greenhouse gases and questions posed to their outputs, eg how often would a heatwave like 2018 occur? Then they are run with the current greenhouse gas concentrations and the same question posed, and comparisons drawn. So how much more likely is an individual event with today’s greenhouse gas loadings of the atmosphere as opposed to that which would have occurred ‘naturally’?
Such an attribution study has very recently been published and made use of meteorological observations from Ireland. The conclusion for Ireland was that the probability of the 2018 heatwave was doubled by the current greenhouse gas loading in the atmosphere.
One can debate the merits and methods employed, but the message is clear: we face more frequent and more severe climate shocks as we continue to load the atmosphere with our waste gases.
The link was even more explicitly expressed by the deputy secretarygeneral of the World Meteorological Organisation, Elena Manaenkova, when she said: “2018 is shaping up to be one of the hottest years on record, with new temperature records in many countries. This is no surprise. The heatwaves and extreme heat we are experiencing are consistent with what we expect as a result of climate change caused by greenhouse gas emissions. This is not a future scenario. It is happening now.”
As someone who was responsible for some of the earliest future climate projections for Ireland, over a decade-and-a-half ago, it is a strange feeling seeing the predictions made then now being realised. On the one hand, as a climate scientist, it is reassuring that the science was sound and that climate change is playing out as projected.
As an Irish citizen, however, it is profoundly painful to witness the lack of courage and actions in tackling climate change which has characterised the past decade and led us to be witnesses to what will be increasing vulnerability to climate extremes for the coming generation.