If you have ever looked at a weather map, you’ve a seen picture of the jet stream, that wavy west to east line linking areas experiencing relatively similar weather. In the three dimensional world, jet streams are high altitude westerly winds that occur along the boundaries between air masses of different temperatures. They are driven by the temperature gradient; in the winter, when the gradient is steepest, jet streams are strongest.
A new study provides evidence that climate change may be affecting the northern hemisphere jet stream. As a result of climate change, Arctic autumn temperatures have warmed by as much as 5 degrees Celsius (9 degrees F), reducing the temperature gradient between the Arctic and temperate latitudes. In response the jet stream appears to be moving northward and its wind speed slowing. In turn, this may be slowing the westward progression of waves in the jet stream, which cause weather variation along their westward path as they fluctuate north and south.
The slowing of the jet stream, therefore, could cause weather patterns to remain in place for longer, resulting in prolonged heat waves or cold snaps.
There is something intuitive about this, I think. I’ve recently had a couple of conversations about what the unnervingly consistent and mild winter we are experiencing in the northeastern US-and indeed across the country- means for the coming summer. This study indicates that the jet stream is increasingly likely to stay where it is. If so, we really could be in for a hot one.