Sunglasses, shorts, and taking in the sun on the piazza with an ice cream. It’s the perfect summer afternoon – until you recall that this is February.
Nobody can deny that the weather seen in the UK in February was a welcome change from the cold and snow faced across January. However, Monday 25th February 2019 was the hottest February day on record, with temperatures reaching a high of 20.3 degrees Celsius in Wales, and has raised concerns about how global warming is shifting weather patterns across the globe, and if this shift is causing more frequent and more extreme weather events.
Extreme weather events are usually defined as statistically rare events in a particular location and time of year. ‘Extreme’ is a subjective word, but is usually defined by the danger posed by an event, and its impact on infrastructure and human populations. As this type of events is by definition rare, it is difficult to establish whether they are due to our changing climate or simply natural occurrences that have been happening for centuries. The heatwave in February might not be considered an extreme event, but we can refer to events such as the ‘big freeze’ in the Northern Hemisphere in early 2018. This was contrasted by the record-breaking heat and wildfires across Europe over summer in the same year, followed by ‘national disaster’-level floods and landslides in Japan. The list goes on. Significant deviations of worldwide temperatures from historical averages, and the displacement of hundreds of thousands of people from their homes, are just two factors that have led many to draw the conclusion that our climate is changing for the worse. Yet historically, many civilisations are thought to have been wiped out by changing climates, centuries before electricity was even discovered. This includes the legendary Maya civilisation in Mexico’s Yucatán Peninsula, where severe drought is thought to be one of the driving factors in the abandoning of what was once a thriving city. This begs the question: how much of the extreme weather observed recently is down to climate change, and what is simply a more severe natural phenomenon?
The freezing weather in the Northern Hemisphere in 2019 was been reported throughout media outlets with click-baiting headlines warning of how the terrifying polar vortex was out to get us all. To some, it was proof that climate change had finally reached ‘Day After Tomorrow’ levels of hopelessness. To others, namely the President of the United States, it proved that global warming is a mere hoax, as surely higher global warming temperatures means everywhere should be warm all the time. Unfortunately, our climate is significantly more complex than Fox News would like to believe, and the truth behind the situation is more likely to lie between these two extremes.
The polar vortex is in fact a circulation of strong winds in the stratosphere around the pole of the Earth, that forms every year. This vortex can split apart in what is known as a ‘sudden stratospheric warming’, shifting the position of the jet stream, a fast moving stream of air separating freezing polar air from milder air at mid latitudes, further South. This lead to much colder temperatures than usual to be seen in the United States, for instance in Chicago. Studies in this area suggest that there is no link between the frequency of such sudden stratospheric warmings and climate change, however our data only extends back by 50 years, so we do not have pre-industrial data on the polar vortex to compare against. Theoretically, as the poles are warming at a faster rate than the rest of the Earth, the temperature difference between the poles and the rest of the Earth is decreasing. This results in a weaker polar vortex, which is more likely to split apart and cause the weather we have observed, so perhaps we will see an increase in such events in the following years. This would be something humans could prepare for, but could leave wildlife and fauna unable to adapt, likely leading to a large loss in biodiversity and a smaller crop yield. Given this is simply speculation, however, we should turn to the more universally accepted facts of our changing climate to observe their impact on our weather.
One such fact is that each of the last three decades has been successively warmer than any preceding decade since 1850. In the simplest of terms, higher temperatures increase the rate of evaporation of water from soil, plants, and bodies of water, increasing the risk of droughts and heatwaves. This leads to a higher water vapour content in the atmosphere, in turn increasing the risk of extreme rainfall events and floods in other locations. While total precipitation is not expected to grow significantly, where rain falls is changing. This is difficult to identify outright, as yearly there is natural variation in rainfall patterns, but we are already seeing long term effects on populations across the globe. Cape Town, South Africa is currently battling its worst drought in 100 years due to a severe lack of rainfall in the region. While increased water demand is partially responsible, it is also in part due to the El Niño Southern Oscillation, the naturally occurring weather phenomenon resulting from the warming of ocean water in the Pacific Ocean. This has a profound effect on weather patterns and can impact flooding, droughts, and crop yields globally. It has been observed for hundreds of years, and while climate change deniers may claim that this explains the recent extreme weather events and even the rise in global temperatures, a recent study finds a connection between increasing global surface temperatures and the strength of El Niño events. A stronger El Niño will increase the intensity of weather events, and lead to more severe droughts, tropical cyclones, and landslides, due to increased rainfall. The socioeconomic impact of these events will spread worldwide, so every person on Earth will feel the impact of the changing climate, whether it is through direct destruction by extreme weather, or decreased crop yields changing our lifestyles.
The overall effects of climate change may be mitigated by natural weather phenomena, but we cannot categorically state whether a certain event was ‘caused by global warming’ or not. The processes governing global weather are complex, difficult to model and to this day not entirely understood. While extreme weather alone does not prove the existence of global warming, we cannot deny that climate change exacerbates its effects. We must prepare for harsher weather and even a complete overhaul in life as we know it to survive, or work now to reduce our impact on the climate.