SOURCE: Politico

DATE: August 16, 2018

SNIP: We’ve all become increasingly used to reports of extreme weather over the past few years. But this summer’s raft of dramatic weather events is significant: Not only does it show what warming can do, it points to the potential large-scale trouble that lurks in the disruption of the planet’s winds and ocean currents.

That global warming leads to more heat extremes is not rocket science and has been confirmed by global data analysis. We’re seeing five times more monthly heat records — such as “hottest July on record in California” — now than we would in a stable climate.

It’s not just that the weather is doing what it always does, except at a higher temperature level. Rather, there is growing evidence that the dynamics of weather itself are changing.

This is currently one of the hottest topics in climate research. The basic idea is that the jet stream — a band of high winds around the Northern Hemisphere that significantly influences our weather in the mid-latitudes — is changing.

This phenomenon has been confirmed by data: Researchers showed in 2015 that the jet stream has actually slowed down significantly in recent decades and undulates more. The cause is probably the strong warming of the Arctic, as the jet stream is driven by the temperature contrast between the tropics and the Arctic. Because this temperature difference is getting smaller and smaller, the jet stream is weakening and becoming less stable.

The weaker summer circulation means fewer weather changes, so the weather is becoming more persistent.

But the atmosphere is not the only player that can change its flow patterns. The ocean circulation may also have played a role, in particular the Gulf Stream System.

Climate change does not just mean that everything is gradually getting warmer: It is also changing the major circulations of our atmosphere and ocean. This is making the weather increasingly weird and unpredictable.