Sub-zero Chicago colder than Antarctica

Extreme weather is back. A polar vortex has sent temperatures in the US plummeting below -40C. Halfway across the planet, baking Australia is set for the hottest January on record. A polar vortex has taken hold of the US. Over 200 million people are battling sub-zero temperatures, some of the coldest on record. Residents have been warned not to step outside due to the threat of instant frostbite. In parts of Illinois, Wisconsin and Minnesota, temperatures could plummet to -45C. Yesterday, Chicago was colder than the North Pole and parts of Antarctica. So far, six deaths have been blamed on the vortex, and cities are scrambling to shield the homeless from the deadly cold. On the other side of the world, wildfires are raging and roads are melting in Australia. In the city of Adelaide, temperatures have soared to 47C. Thousands of flying foxes have dropped from trees, killed by heat stroke. The freak heat is not a one-off event. Last month saw Australia's hottest December on record and January looks set to follow suit. Indeed, 2018 was the driest year ever for some parts of New South WalesThere were devastating floods around the city of Lismore earlier this year.. As the climate rises, scientists have warned that Australian cities could become uninhabitable in the very near future. Why, then, is the US so cold? President Donald Trump has been wondering the same thing. "What the hell is going on with Global Waming [sic]? Please come back fast, we need you!" he tweeted. In fact, the freezing temperatures battering the US midwest are consistent with climate change. The Arctic is encircled by a vortex of freezing air. As Arctic ice melts, the sea warms and heats up the air. This warming causes parts of the vortex to break off and spiral south, like the one currently affecting the US. According to the World Meteorological Organisation, 20 of the hottest years on record have come within the last 22 years. Climate change is making extreme weather more frequent and intense. Heat records were broken around the world from Norway to Oman last year. In November, the worst wildfires in California's history killed 85 people. With each weather event, "we need to think beyond what we have seen in the past and assume there's a high probability that it will be worse than anything we've ever seen," says associate professor Crystal A. Kolden from the University of Idaho. Ice and fire Scientists warn that extreme weather is the "new normal". Will we adapt? We could build floating homes that rise with the water, or underground cities to shelter us from storms or extreme heat. Or is prevention more important? Experts say we can avoid disaster if urgent action on greenhouse gas emissions is taken in the next 12 years. But will we even bother? As Trump's tweet shows, many people are still unwilling to face up to climate change. What would it take to make them believe? Is the situation hopeless? KeywordsNew South Wales - There were devastating floods around the city of Lismore earlier this year.