Global Warming

New Research Links Extreme Weather to Global Warming

A new study has been published by a team of climatologists possibly linking global warming to these extreme weather events.

The key to this is what’s called a “blocking pattern”, where a high-pressure system becomes immobile, squatting over a specific spot. Under the high-pressure spot, this can bring long, gruelling heat waves that don’t go away for days or weeks. On the edges it can bring a deluge of rain, as moist air from the south is brought up to meet colder air coming down from the north. That’s what Detroit and New York just went through.

These blocking patterns are themselves associated with the jet stream, the constant flow of air about 10 kilometres above sea level at latitudes between 30° and 60°. Sometimes the flow weakens, and the winds can dip down into more southern latitudes. These meanders (sometimes mistakenly called the “polar vortex”) depend on a lot of factors, but the new research just published indicates they may be due to the Arctic warming up. The physics is complicated — fluid dynamics is amazingly subtle and complex — but the research indicates a warming Arctic can create and amplify the conditions that lead to jet stream excursions, and therefore blocking patterns.

It was a blocking pattern that led to a phenomenal heat wave in Alaska in 2013, to the floods in the Northeast, and to the unbelievable rain we saw in Boulder, Colorado last year; they got over 30 cm in just a day.