Map of life expectancy at birth from Global Education Project.

Monday, June 17, 2019

The Long Emergency: Jet Stream Confusion

One common strategy of denialists is to point to spells of unusually cool weather in some particular place. This has certainly been available to them lately, with notable outbreaks of arctic cold last winter in parts of the northern hemisphere mid-latitudes. This included the beloved home of Cervantes by the way. Trying to explain that is happening because of global warming is very difficult when you are confronting motivated reasoning combined with lack of knowledge and complete disinterest in obtaining any.

The first point people need to get into their heads is that it's a big planet -- well, at least by the standards of us puny beings. Local conditions are what we all notice, but the entire United States takes up less than 2% of the earth's surface and about 6% of the earth's land surface. In other words it can be unusually cold in half of the U.S. and the contribution to the average temperature of the planet will be negligible. There will always be weather, and some days will be colder than average, but weather is not climate, which is the long-term probability of particular weather conditions.

The second point is that the reason it was so cold in parts of the north central and and northeastern U.S. for a brief time last winter is that arctic air was displaced to the south. Meanwhile, the arctic was unusually warm. This happened because the so-called polar vortex weakened, causing the jet stream to become unusually wavy. The jet stream is a river of air that flows west to east and divides colder arctic air from warmer temperate air. With the disappearance of arctic sea ice and the warmer arctic, the jet stream is becoming wavier, with big loops the pull cold air south and warm air north. These also create blocks that keep weather patterns in place for a long time, causing extended heat waves, droughts and raininess. That is why we are seeing both more droughts and more floods, more unusual heat events and more unusual cold events.

Right now Greenland is exceptionally warm causing unprecedented ice melting. We don't yet know whether this will continue for the rest of the season, but the current melting is a month ahead of schedule. I don't have to remind you of the midwestern floods this spring, which are still going on. Farmers have suffered many billions of dollars in losses and many will never recover. Flooding on the Mississippi halted barge traffic for several weeks, making it impossible for farmers with stored crops to get them to market. And the unprecedented fires in the far west and recent record high temperatures are the consequence of a northern excursion of the jet stream.

These same phenomena are affecting Europe and Siberia. Outbreaks of unusually cold winter weather, unusually warm weather, drought and flood. Now, the global average temperature continues to increase while all this is going on, which means that the cold outbreaks won't be quite as cold and the hot outbreaks will be even hotter. But it's the hot side that is most worrisome because it harms agriculture -- in fact will make some land no longer usable, either because of insufficient water or too frequent flooding. It is also making some already hot parts of the planet essentially uninhabitable. It is a major contributor to the crisis of international migration.

The only way to slow this down is to quickly reduce and then eliminate carbon emissions. But whatever we do, it will continue and get worse.  So be prepared.


Dr Porkenheimer said...

Methane accounts only for about 10% of the greenhouse gasses emissions but is thirty times (300%)more potent as a heat-trapping gas.

That makes methane, by far, the main issue and yet no one wants to discuss lowering the methane emissions, only CO2.

Cervantes said...

Well, people are concerned about it -- this is where the whole flapdoodle about cows comes from. It's also a big concern with natural gas, that a lot of it leaks during production and transport. Also big concern about the melting permafrost emitting methane, and methane hydrates on the sea floor melting, which are positive feedbacks to warming. But methane doesn't stay in the atmosphere very long whereas C02 can endure for 100 years, so that's why we tend to hear more about the carbon concentration in the atmosphere, we're stuck with it for a long time once it's there. But people do discuss methane. The shorthand of "carbon emissions" covers both.

Dr Porkenheimer said...


Cervantes said...

Seems like a pretty minor sideshow. As these investigators say, we need to stop emissions. I'm not sure that's a good idea in the long run anyway, they don't show the math. There may be something to carbon capture and storage but it's nowhere close in sight and hard to imagine it could happen at a substantial scale.

The wind blows and the sun shines but the problem is intermittency -- how to move it around from where it is to where it is needed, and storage. I'll likely discuss that next week.