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Science | History | Geography

Polar vortex puts world into deep freeze

Will there be another ice age? Many believe the answer is yes – but scientists say that global warming caused by human activity may have delayed it by over 50,000 years. The north wind howls and the mercury plummets. An arctic winter is sweeping across Europe and North America, bringing sub-zero temperatures to every state in the US and blizzards to the east of England. The heat waves of last summer are a distant memory. But this bitter weather really started a month ago as dramatically warming air, high up in the arctic atmosphere. This high-altitude polar vortex normally keeps a lid on the frozen weather at the north pole. But when it warms, the wind weakens and changes direction, pushing cold air southward. This is called sudden stratospheric warming and is a fairly common weather pattern, occurring on average six times every decade. In 2018, it created a hurricane-strength storm dubbed the beast from the east. In 2019, Lake Michigan froze and temperatures in Minnesota dropped to -48°C, colder than the south pole. But there is more to our extreme weather than the polar vortex. The Earth’s climate is affected by many cycles, some changing slowly over millennia, others more quickly. Every 11 years, the sun’s activity drops to a low called the solar minimum, leading to colder winters. And our star has just entered the quietest period in a century. Occasionally, these minimums can last decades. Between 1672 and 1699 fewer than 50 sunspots were recorded, compared to over 40,000 in modern times. This was the Maunder Minimum and it happened at the same time as exceptionally cold weather known as the Little Ice Age. Historians link its harsh winters and failed harvests with major events from the Thirty Years’ War to the collapse of the Chinese Ming Dynasty. However, geologists say the Little Ice Age is a misnomer. There have only been five major ice ages in the Earth’s 4.5 billion year history. The last one, the Quaternary Period, began three million years ago – and we are still in it. Over this stretch of geological time, the glaciers have expanded and retreated as the climate has repeatedly cooled and warmed. The last glacial period ended 11,700 years ago, and it is this that is known as the last ice age. Since then, Earth has enjoyed a milder climate. And humanity has taken advantage of the fine weather, discovering agriculture around 10,000 years ago and building civilisation as we know it. But these interglacial periods can’t last forever. The Earth is due another ice age. Except there is no sign of one anytime soon. Glaciers are shrinking instead of growing. Twenty-eight trillion tons of ice has melted since 1994. And the world is not cooling. It is heating up by over 1.5°C per century, faster than at any point in the last two thousand years. Scientists warn that global warming caused by human activity may have delayed the next ice age by over 50,000 years. Others suggest we have stopped the glacial cycles altogether. This would mark a new period in the Earth’s history, the Anthropocene, in which humans and not glaciers are the biggest factor determining our weather and climate. Will there be another ice age? The big freeze Some say yes, it is just a matter of time. Humans are fixated on dramatic changes in weather, but the ice ages are about gradual shifts in climate over thousands of years. Sunspots, volcanic activity, the polar ice caps and the earth’s orbit all contribute to the complex cycle of rising and falling temperatures. At some point in the future, ice sheets will again extend across the globe. Others say no, we have changed the planet’s climate too much. In the short term, the warming arctic will lead to more cold winters further south. But the bigger picture is of runaway climate change. Throughout the history of its existence, the Earth has cycled through ice ages and greenhouse periods – when the atmosphere was too warm for ice to form. Now, we are in danger of creating a greenhouse planet that cannot be reversed. KeywordsMisnomer - When something is named inaccurately.

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