“We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events.” — Michael Mann

*****

The Earth is warming, the weather is growing more extreme, and from the observational perspective, it appears that the Northern Hemisphere Jet Stream has undergone some seriously disturbing changes. Over the past five years, this subject has been one that’s spurred heated debate among scientists, meteorologists, and global climate and weather watchers. Now, a new model study finds that it’s likely that the Jet Stream is being significantly altered by human-forced climate change and that this alteration is helping to drive extreme weather events like the 2003 European heat wave, the 2010 Pakistan flood and Russian heat wave, the 2011 Texas heat wave and recent floods in Europe.

(More extreme variation in upper level wind speeds is an upshot of polar warming during boreal summer. The result is that risks of severe heatwaves, droughts, wildfires and floods increases as the Earth warms. Image source: Michael Mann, Penn State.)

From the study:

… our analysis of both historical model simulations and observational surface temperature data, strongly suggests that anthropogenic warming is impacting the zonal mean temperature profile in a manner conducive to wave resonance and a consequent increase in persistent weather extremes in the boreal summer.

What this means is that the new study provides still more evidence that the Jet Stream’s north to south variance is increasing during summer. As a result, it is enabling powerful heat domes to form in regions where winds run from south to north. In regions where the upper level winds run from north to south, it creates cooler zones in which powerful storms can flood large swaths of countryside. In other words, increasingly juxtapposed zones of extreme temperature anomalies and higher atmospheric instability and moisture loading tend to form more and more often. And this results in weather patterns that we have never really seen before.

(An Inconvenient Sequel is a call for action on climate change like we’ve never seen before. And the imperative to act on climate is now stronger than it ever was.)

The fact that the Mann study uses observational and model assessments to find that such changes are likely to very likely now being caused by human-forced warming and related polar amplification is a highly significant scientific finding. It adds one more attribution tie to the extreme weather events that we’ve been seeing with increasing frequency. A tie directly to global warming. And it does so through model studies that identify the underlying physical mechanisms at work. It’s a pivotal moment in the atmospheric sciences. And everyone needs to sit up and pay attention.

Credits:

Hat tip to Colorado Bob

Hat tip to Cate

Scientific hat tip to Dr Michael Mann

(Please support publicly-funded, non-special interest based science that is now under assault by the climate change denying Trump Administration)