Opinion: many recent extreme weather events couldn't have occurred without our influence in the global warming process
The atmosphere is a key component of the climate system. Its natural greenhouse gases are essential to make our home, the planet Earth, inhabitable. However, human activity, mainly due to the combustion of fossil fuels, has already altered the composition of the atmosphere and its natural dynamic equilibrium which is in charge of the transport and distribution of energy and water around the globe. Unfortunately, what happens in the atmosphere doesn’t stay in the atmosphere.
Despite some discordant voices, global warming cannot be fully explained without taking the human influence into consideration. Natural factors such as changes in solar radiation or volcanic eruptions are not enough to justify the warming that we are experiencing. Human activity is the missing piece of the puzzle.
The human emissions of greenhouse gases don’t just apply to slow onset events like the increase of the global mean temperature or the sea level rise, but also to extreme events. A warmer atmosphere is able to contain a greater amount of water vapour and the water cycle is altered as a consequence, changing the patterns of distribution and the intensity of the precipitation. In fact, the episodes of heavy precipitation in Europe have already increased in magnitude and frequency, giving rise to the risk of flooding.
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From RTÉ Radio 1's News at One, reporter Aisling Kenny speaks to some of the School pupils "on strike" outside Leinster House over climate change
Events like floods, heatwaves, droughts and wildfires happen in the lifetime of a person. We all remember Storm Ophelia or the heatwave last summer. Searching for human influence in these more sporadic events has been always challenging. But we know that they have been changing since the 1950s, just when the anthropogenic emission of greenhouse gases started to increase the mean global temperature.
Since we have already inevitably changed the natural evolution of our planet’s climate, it doesn’t make any sense to ask if we have influenced a heatwave or an episode of heavy precipitation. Of course we have, no doubt about it. The important question is: how much are we responsible for having more frequent heatwaves or heavier precipitation?
The first time that these questions were asked was around 2003. At that time, Professor Myles Allen from the University of Oxford devised a new methodology that was applied for the first time to the heatwave that swept Europe that summer. The results showed that a similar deadly heatwave is now more than twice probable due to the anthropogenic climate change.
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From RTÉ The Week In Politics, Ailbhe Conneely reports on proposed government policy to cut carbon emissions
Since 2012, the Bulletin of the American Meteorological Society has published an annual report about the influence of anthropogenic climate change in specific extreme events. Last year’s report left no doubt that humans have threefold the probability of a heatwave like the one that affected Southern Europe in the summer of 2017.
Still fresh in our memory is the heatwave of summer 2018. According to the attribution study of the World Weather Attribution project (WWA), the probability of this happening in Ireland is double under the current climate. The list continues on and so. Some of the extreme weather events analysed to date couldn’t have occurred without our influence in the global warming process.
Nowadays, this kind of study constitutes a new subfield of the climate science in its own right: climate attribution. That is, attribute the changes detected in extreme weather and climate events to a probable cause, namely the human emissions of greenhouse gases.
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From RTÉ Radio 1's Drivetime, Dr Gerard McCarthy from Maynooth University on a new study on climate change and rising sea levels in Ireland
The climate extremes are unrepeatable, rare at any point and any time. They are the result of a unique combination of ingredients. Currently, the improvement of the computational capabilities and the simulation models have made it possible to replicate the evolution of the climate under different conditions (various concentrations of greenhouse gases, volcanic eruptions, the NAO, the ENSO, etc). Switching on and off the ingredients in the models allows researchers to get to know how the climate extremes are affected by those conditions.
The changes observed in the occurrence or intensity of a climate extreme can be attributed to the human influence in terms of probabilities by simulating two different versions of our world: with and without anthropogenic emission of greenhouse gases. The result indicates how much more probable is an event to happen due to human influence, the so-called risk ratio. A similar approach can be applied to two different periods of time in our current or factual world: a less human influence period and a more recent one.
Since climate attribution is a relatively new area of research, there is still room for new approaches and a long way ahead to explore future applications. The methodology of climate attribution can be applied to analyse the economic pressure of anthropogenic emissions on the health system as result of an increase in the frequency of heatwaves, for example, or due to the change in the distribution of diseases and their vectors.
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From RTÉ Radio 1's Drivetime, Maeve Higgins, host of the Mothers of Invention podcast and contributing writer to the New York Times, talks about the legal action taken by Friends of the Irish Environment against the Government over climate change
We can also get to know how much more probable is the human influence in ecosystems such as the great barrier reef, peatlands or wetlands. Similarly, it can indicate the changes in the distribution and phenology of plant and animal species due to human-related climate change, from crops or phytoplankton to bees and fishes.
Moreover, the science of attribution opens the door to court cases about climate change. In order for a defendant to be held liable for their contribution to the greenhouse gas emissions, or their inaction to defend people’s rights, there has to be proof that they disregarded the evidences available. This is the case of the oil industry that had documentation about the potential climate warming back in 1957, and decided to turn a blind eye.
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From UCC's Plain Speaking podcast, former President of Ireland Mary Robinson discusses climate change
Don’t be caught off-guard: global warming is not a future problem. It’s happening right now and we are experiencing it first hand through rapidly evolving extreme events.
The views expressed here are those of the author and do not represent or reflect the views of RTÉ
