Summer only just started, but much of the world is already experiencing brutal heat. In the last two weeks, extreme heat waves have struck many parts of the US, Europe and China, threatening lives, increasing the risk of wildfires, and testing the limits of electric grids.
In Minnesota, temperatures climbing above 37 degrees Celsius causing some infrastructure damages, while in Kansas thousands of cattle perished. The extreme heat has affected also Western Europe from the Mediterranean to the North Sea unusually early, even before the summer solstice. And all that following the warmest May on record for France and hottest for Spain in at least 100 years.
"In some parts of Spain and France, temperatures are more than 10 degrees higher — that's huge — than the average for this time of year," Clare Nullis, a spokesperson for the World Meteorological Organization in Geneva, said. "Heat waves are starting earlier," said Nullis. "They're becoming more frequent and more severe because of concentrations of greenhouse gases in the atmosphere, which are at record level. What we're witnessing today is, unfortunately, a foretaste of the future." In the 1960s, there were an average of about two heat waves per year, whereas in the most recent decade there were an average of six, according to the US Environmental Protection Agency.
Meteorologists say the unusually early heat wave is a sign of what's to come as global warming continues, moving up in the calendar the temperatures that Europe would previously have seen only in July and August. The good news is that meteorologists can, to an extent, forecast extreme weather, and climate models are improving. While there is not much we can do to avoid them, some protective measures can help mitigate the effects.
The World Meteorological Organization, defines a heat wave as five or more consecutive days of prolonged heat in which the daily maximum temperature is higher than the average maximum temperature by 5 °C (9 °F) or more. Heat waves, typically, begin where there’s a buildup of high pressure in the atmosphere. That creates a sinking column of air that compresses, heats up, and oftentimes dries out. The high-pressure system also pushes out cooler, fast-moving air currents and squeezes clouds away, which gives the sun an unobstructed line of sight to the ground. The ground — soil, sand, concrete, and asphalt — then bakes in the sunlight, and in the long days and short nights of summer, heat energy quickly accumulates and temperatures rise. All that high pressure in the atmosphere acts like a lid on a pot, trapping heat so it can’t dissipate. That’s why these heat waves are often referred to as “heat domes” — the heat is trapped under a dome of pressure.
The effects of the heat waves are felt fore and foremost by the vulnerable parts of the population. Heat strokes are particularly dangerous for the elderly, with 250 people taken to the hospital in Tokyo during the latest heat wave. The homeless population is also particularly vulnerable, especially in developing countries. The less evident effect is the stress on the infrastructure, as more energy is required to run air conditioning units. Moreover, many areas that were traditionally considered “cold” are unprepared for the extreme heat. New air conditioning units need to be installed and powered by an already overloaded grid. This is especially dire given the current macro-environment of the energy crisis, as more fossil fuels are used to meet the increased power demands, further reinforcing climate change through their CO2 emissions.
The extreme heat wave on land unleashing a marine heat wave as well, meaning sea temperatures rise to extreme highs for five days or longer. These events alter the vertical circulation of water, which in turn affects the oceans’ capacity to absorb heat and carbon dioxide, as well as the circulation of nutrients key to marine wildlife.
Marine heat waves are relatively unknown to scientists, with research papers on these ocean temperatures starting to appear only in 2013. The phenomenon has since become a key signal of climate change — for decades oceans have absorbed most of the additional heat in the atmosphere, acting like sponges for global warming.
Scientists have known that oceans have absorbed 93% of heat captured by greenhouse gases since the 1970s. They also know that the ability to keep capturing and storing carbon dioxide stopped keeping pace with emissions in the 1990s. Figuring out how much they’re heating up and how much more heat the bodies of water can store is essential to understanding how fast the planet will warm in coming decades.
The trend is clear, heat waves are here to stay and their effects are tangible. The challenge remains: much of the world’s infrastructure, policies, and planning is based on historical averages — and it’s clear that the future won’t look like the past.
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