NHJS

A pair of climate scientists on Thursday said the record-high temperatures that have ravaged the northwestern U.S. and western Canada over the past week—killing hundreds and sparking dozens of wildfires—represent the "world's most extreme heatwave in modern history.”

https://www.commondreams.org/news/2021/07/02/scientists-call-northwest-h...

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Blocking-events bat away oncoming low-pressure systems that would bring the prospect of clouds and rain. They are particularly synonymous with heatwaves and drought in summer and bitterly cold conditions in winter.

But what are the prospects for blocking events in a warming climate? And could a rapidly warming Arctic also have a role to play?

In this Q&A, Carbon Brief takes a closer look at the causes of blocking events and the potential changes in the future.

      • What is ‘blocking’?

      • What causes blocking?

      • Have blocking events changed as the climate has warmed?

      • How might climate change affect blocking in future?

      • What role does a warming Arctic play?

https://www.carbonbrief.org/jet-stream-is-climate-change-causing-more-bl...

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The first quote is from early July 2021. The latter is from June 2020.

In both cases, the Jet Streams influences or feed-back mechanisms are rarely fully explained possibly because there is too much uncertainty in the air flows on the planet. 

Jet Streams are fast air currents usually flowing west to east set at the four boundaries between climatic zones: Arctic polar zone — temperate zone — tropical/equatorial zones — temperate zone — Antarctic polar zone. 

In the equatorial zone, the normal setting is “the doldrums”: air movements are soon dispersed either side into the tropical zones until the Coriolis force takes over. This is why the equatorial zone (say latitude: 10 degrees north to ten degrees south) does not support hurricanes, cyclones, typhoons that start in the tropical zoning. 

The definite separation (marked by a Jet Stream at an average of 10 kilometres altitude) between tropical and temperate zones does not allow hurricanes, cyclones, typhoons into the temperate zones. Sometimes hurricanes, cyclones, typhoons do cross the line, but they soon become “storms” (depression/low pressure systems) that spread their “self-contained” energy over a much greater surface, thus leading to less wind and generally less damage. 

A tornado is like a concentrated mini-hurricane in which the depth of the centre is nearly touching ground at “zero” millibar creating an enormous upward suction effect. The origins of storms, tornado and hurricane vary, but usually are formed by a difference of potential of temperature and/or air pressure in a localised area. 

In the tropical zones, the Trade Winds are the dominant air movements. In the temperate zones, the low pressure and high pressure waves (anti-cyclones)  systems, plus cold and warm fronts (heat overlaps) create an “unpredictability” of weather — which is usually contained between two Jet Streams. 

Presently, the two northern Jet Streams have broken up as well as melded in parts with one another. The tropical/temperate Jet Stream of the southern hemisphere is noticeably strong while the temperate/polar jet stream has broken up as well and gone awol over Australia, mixing with the tropical/temperate Jet Stream… Now you know why it is "FREEZING" and humid in Sydney (9th July 2021 — overnight 7˚-day 14˚)

Like a kettle on a stove, it is hard to know which flow is influencing the others: the Zoning or the Jet Streams. The various zoning of climatic behaviour have been recognised for a long time. The knowledge about Jet Streams is only relatively recent.

During last winter, bitter cold took over Europe while the temperatures in the arctic were way above average. It was noted that the northern most Jet Stream had weakened and broken up, somewhat as if the cold of the arctic was leaking further south than normal, thus modify the “normal” temperature gradients. 

At this stage it is hard to know if the breaking up of the Jet Streams is due to the heat exchanges between polar and temperate zones flattening out — due to Global Warming — or the Jet Stream, influenced by global warming slows down and allow the “normal” temperatures to be mixed up between the zoning.

Will we see more of this happen? Sure and it will increase in range and intensity. 

We need to note the major difference between Northern and Southern hemispheres due to continental masses. Antarctica is melting but still retains a lot of cold in a single polar mass. The melting energy is transferred northward by convection — presently going much further north than average as the temperate/polar Jet Stream “has given up" over Australia, leaving most of the southern states of Australia in a “cold snap”. 

In the northern hemisphere the only two glacial spots (Greenland and the Himalayas — not counting the de-freezing Arctic sea) create weather disturbances on the temperate latitudes — in winter as well as summer, and their own melting/warming is going to precipitate (tipping point) a major change by 2032 (Gus prediction).

In the southern hemisphere, due to the very size of Antarctica, this tipping point would be delayed till about 2055.

As well the sea currents are influencing the weather changes with feed-back effects on the sea currents. 

CO2, methane and NOx gases are definitely warming gases in the atmosphere. Already there is enough of them up there to lift the average temperature of the planet by 6 to 9 degrees Celsius by the 4th of June 2157… I made this date up, because not even a computer could calculate such precision. But the range could be bracketed with 15 years either way, depending on how much CO2, methane and NOx gases we pump into the atmosphere between now and then. 6 degrees Celsius if we stop our emissions NOW, 9 degrees Celsius if we carry on emitting till 2100… or close enough. Expect major sea level rise as well, itself changing the dynamics of the timing — not of the relative process.

Things are going to change. The extreme weather coming with global warming will increase madly. The insurance companies need to take this in their strides, but they can sleep easy as most governments will print moneys to pay for the increasing damage.

We need to reduce emissions, we need to adapt and we need to be prepared for more damage… Even then, we might not even see what’s coming when “it hits us"… Some idiots might go to war before this, anyway… Meanwhile, we, the little bourgeois, will carry on counting our little coins like Uncle Scrooge and act like the oblivious, local spiv...

See also: 

https://www.yourdemocracy.net.au/drupal/node/33090

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