26th July 2023
The scorching summer heat is breaking records worldwide, with devastating heat waves roasting regions from the southwest United States to China and Southern Europe. The news is dominated with reports of out-of-control wildfires and the evacuation of tourists from Greek islands. Temperatures have soared to unprecedented levels, and the relentless heat shows no signs of letting up. But what's behind these extreme heat events, and why are they becoming more frequent and severe?
One of the key factors driving these extreme heat waves is climate change. Human activities, such as the burning of fossil fuels, have been pumping greenhouse gases into the atmosphere for decades. These gases trap heat, leading to a warmer planet overall. Scientists have conducted attribution studies that simulate the world with and without climate change to understand its influence on extreme weather events. The results consistently show that climate change has made extreme heat waves more likely and more intense.
As well as becoming more common, heat waves are also getting hotter. Climate change is pushing the temperature envelope, with heat waves breaking records year after year. The most extreme events that used to occur once every thousand years are now happening every couple of decades. This increase in frequency and intensity is making extreme heat a noticeable part of our daily lives.
While climate change plays a significant role, there's more to the story. The Earth's weather is heavily influenced by powerful ribbons of wind called jet streams. These high-velocity winds control the movement of high and low-pressure systems and can influence the formation and intensity of extreme weather events.
Normally, jet streams flow westward at high altitudes, but they can meander and get stuck in certain patterns. When jet streams develop broad waves and undulations, they create bulges of hot air that linger over specific areas for days or weeks. This phenomenon results in heat domes, which are responsible for prolonged periods of scorching temperatures.
Scientists have noted that the jet streams seem to be meandering more frequently and becoming stuck in place a lot more. This shift could be linked to climate change altering the dynamics of these winds - researchers are still investigating the exact mechanisms involved.
Another contributing factor to this year's extreme heat is the return of the El Niño-Southern Oscillation (ENSO). This natural climate cycle influences sea surface temperatures in the central and eastern tropical Pacific Ocean. El Niño events can temporarily heat the planet, leading to warmer global temperatures.
As the planet is already experiencing warmer oceans due to climate change, the influence of El Niño exacerbates the heat waves. The warm waters in the Pacific Ocean release heat into the atmosphere, trapping it with greenhouse gases and contributing to the record-breaking temperatures.
While El Niño can play a significant role in driving extreme heat, climate change remains the underlying cause of the warming planet. The combination of human-caused climate change and natural climate phenomena like El Niño is pushing the boundaries of extreme heat and making it a more frequent and dangerous occurrence.
One thing is for certain... we are moving inexorably closer to a tipping point - the crucial threshold of 1.5 degrees Celsius above pre industrial levels. This is the point beyond which, scientists have warned, we will face dire, irreversible consequences.