The Sun newspaper accompanies this article about global warming causing global cooling with an info-grapic, clearly labelled as follows:
Step 1. Air above Arctic warms
Step 2: Pushes cold air south towards us
Step 3: Jet Stream pushed south by heavy cold air over north hemisphere
Ho hum.
I was brought up to believe that warm air rises, so if anything, wamer air over the Artic would suck* air northwards rather than push it southwards. From our point of view, winds from the south and west are good (warmer) and winds from the north and east are bad (colder) and the further north the jet stream is, the better.
* Yes, I know that "suction" doesn't really exist either.
A simple solution
2 hours ago
27 comments:
There is more than a hint of desperation about this "theory".
I think the Jet Stream has been pushed around by all those chickens coming home to roost.
nah. It's like it says. The warm air rises and the cold air is heavy so it just sits there and 'acts like a stopper' forcing the Jet stream south. If you have two air masses and one of the air masses lies north of the other one, then the wind will not flow directly from the hot to the cold area as one would expect, but is deflected by the Coriolis force and flows along the boundary of the two air masses. Hope that helps.
AKH, ta for back up.
P156, yes I accept that the wind does not blow directly from cold to warm areas in a straight line, it sort of circles round a bit, but to say that wind blows from warm to cold areas is surely nonsense.
Oh, I am absolutely sure that 'suction' does exist - and can be demonstrated in the comfort of your own home, but not necessarily by the same class (or sex) of professional as those that work on climate science...
I think it's bollocks, like most warble gloaming "science". There is simply no mechanism for warm air rising to push the cold air below it away from it.
Of course the warm air rising from the Arctic could cause a southerly wind which could be deflected by the coriolis force into an easterly, but it seems unlikely that the air over the arctic would be warmer than that further south, however much global warming we have and even if it was, the air moving in to replace the warm rising air would cool everything down and the whole process would grind to a halt. As AKH says, desperation.
L, no, what I mean is when you "suck" up water through a straw, it is actually the atmospheric pressure on the surface of the water which "pushes" it up the straw.
B, agreed.
If the warmenists said that when the Arctic ice melts, this means that the average temperature of water in the Northern Atlantic falls a bit, well, that might be true, but the "cold wind" argument fails, as it was warm air which caused the ice to melt in the first place (according to their circular logic).
MW - keep talking like that - you know how to get a girl excited...
@MW
I was once forced to do some meteorology and this discussion brings back some very unhappy memories. However,as you say, the general direction of flow is from high pressure areas (cold) into low pressure areas (warm) so this diagram/ explanation with the flows in the opposite direction seems very bizarre.Paul's explanation about the air moving along the boundaries between pressure zones because of Coriolis' effect is, as far as I can remember, correct,although he's got the direction wrong.The Coriolis deflection causes the flow to follow the isobars ( where the pressure is the same)instead of making a bee-line from high to low pressure.There is something called the geostrophic wind but wtf that is I could n't bear to find out now.All in all the explanation quoted of how the Jetstream is shifted does n't make sense: would n't it be too high up to be affected anyway?
OK here goes another attempt.The latest research shows that the cold winters are basically cause by the warmer summers in the northern hemisphere. This warmer atmosphere, combined with melting sea ice, allows the Arctic atmosphere to hold more moisture and increases the likelihood of precipitation over more southern areas such as Eurasia, which, in the freezing temperatures, would fall as snow. With me so far, people? :) Indeed, the researchers observations showed that the average snow coverage in Eurasia has increased over the past two decades. Getting interesting huh? They believe the increased snow cover has an intricate effect on the 'Arctic Oscillation', an atmospheric pressure pattern in the mid to high latitudes, causing it to remain in the 'negative phase'.Sorry about the technicals!
In the negative phase, high pressure resides over the Arctic region, pushing , yes pushing colder air into mid latitude regions, such as the United States and northern Canada, and giving the observed colder winters. Really, really hope that helps this time.
All these explanations of why warming produces cold seem to forget that there is another cold bit called the antarctic and that 'top' and 'bottom' have no relevence to gravity which pulls inwards towards the earth's centre not from north to south!
Warming in the antarctic should have exactly the same effect making southern temperate nations colder. But it's not?
P156, yes that explanation seems vaguely plausible at least. But when you say "warmer summers and colder winters" why don't you just say "moving more towards a continental climate" and have done with it?
W42, because warming is man made, and the Arctic is nearer where people live, so that warms up more?
paulc156's Patronising "explanation" brings back why I went off Geography A level all those years ago: I was expecting an arty subject and got this kind of thing (from the same kind of teachers who thought multiplying a half by a half and getting a quarter was entirely reasonable-and that Algebra was a useful-everyday subject).I did pass though and so feel entitled to question some obvious gaffes. The whole model presupposes that its warmer at the pole than a bit farther south.Bollox surely? It would be warmish at the Pole and comparatively warmer the more south you go,preserving an orthodox "pressure gradient"(Don't ask me: I have been doing some catching up on Wikipedia.)
P156, thank you, you have come up with a convincing explanation of why warmer summers cause colder winters, but this doesn't explain a) the warm air rising over the Arctic in the diagram, or b) the really cold summer we had last year being followed by a cold winter.
ISTR an article on the Jetstream (which AFAIR flows along a line of latitude, not as shown on the diagram, where it looks more like the Gulf Stream) last year sometime, saying that it tends to flip from a higher to a lower latitude and this was responsible for the wet summer we had as it stayed low all year. I think John Kettley has it right, though, "But it may be the natural ebb and flow of our climate. Long, cold winters have bitten our backsides before, while both poor and hot summers are part of our climate. We live in strange times."
DBC, "geography" as a subject is a load of crap. It's a mix of politics, geology, history, comparative religion, economics and random lists of facts like capital cities and longest rivers etc.
Each of these subjects is most interesting in themselves but taking little bits of each and splicing them together makes a mockery of them all.
Also: algebra is a fantastically useful subject, I have to solve equations every day.
B, it is however quite true that in the year when the UK had a really shit summer while forest fires were raging in southern Europe the jet stream had done a funny bend southwards (whether that was the result of or the cause of the "weather" I do not know).
MW There is a difference between using something every day and Algebra being an everyday subject as I said above.You work in a very specialist numbers-based field.I have never used Algebra in my, quite varied, life.Why everybody has to be put through this mill is beyond me: it surely belongs to A level and to students who might have some use for it.( I have worked with people with quite serious maths phobia.It is a subject that needs very careful handling/teaching ,not the all this curriculum is fascinating mantra:it needs careful gradation and weeding-out)
Geography is junky but it did teach me about the Jetstream decades ago.It would be revolutionised by the study of what creates land values.
DBC, most people are intuitively very good at maths
For example, if you are thinking of crossing a road and a car is approaching in the distance, nearly everybody can guess
a) the speed and possible acceleration/braking of the car,
b) the distance of the car,
c) walking speed across the road
d) width of road
and thus calculate time taken for you to cross the car's path back into safety etc. All in a split second.
The maths of this is actually quite complicated, it's just when you put numbers on all these things, people's minds seem to go blank.
Always see the picture first, then do a rough guess at the answer and then try and put numbers on it.
Of course geography covers land values; they are more or less directly proportional to population/build density (on a local level) multiplied by GDP (on a national level). Sorted.
@MW
Not sure that this shows as much about intuitive maths as it does about spatial awareness.Kids can, from a very early age, manoeuvre their trikes very accurately and nonchalantly even.But multiplying fractions is very counter-intuitive with the product smaller than the original terms.And they inflict this on children at a very tender age.Wrongly IMO.Intuitively children would not
cast around in their minds to come up with a simultaneous equation under any circumstance appropriate to their likely experience.
As to Jetstream issue:P156 keeps saying,as Bayard has pointed out already, "high pressure resides over the Arctic region"when the model being argued over clearly has warm/low pressure over the Arctic.
I think the main problem with the diagram is those wiggly "hot air rising" lines and the captions: very misleading since it's got nothing to do with hot air rising.
Captions should say...
1) Extremely cold air at Arctic warms from -60C to -50C causing it to expand
2) Expanding -50C Arctic air causes pressure to rise, moving the slightly less cold air (-20C) south of it in the Northern Hemisphere to move towards us
3) Jet Stream pushed south by high pressure cold air over the Northern Hemisphere
...but I guess that they wouldn't fit on the diagram then.
Still the important point is that the Arctic air warms up but it only warms up from brass monkey to damn cold.
Derek, since you seem to know a bit about this and can see where the Sun has got it wrong (mirabile dictu), might it be true that a lack of the jet stream bringing the usual south-westerlies has led to the weeks of cold easterlies that we have been "enjoying" this "spring"?
Mark, I remember that too: does that mean we are in for another shit summer? I don't think I will bother planting any tomatoes this year.
@Derek
The trouble with this explanation is that it assumes that the Pole warms up to -50 and expands but that the surrounding wastes stay at -20 when ,in fact they would warm up too ,to about -I0 preserving the differential at 40 and "pushing back" againsat any encroachment.
You are right that the diagram looks a bit odd but there is a good diagram on Wikipedia for the Rossby waves which explains things more clearly, if you ignore the text which is pseudo scientific pretentiousness to the max.
D, I refer you to DBC's riposte. I find it unlikely that warming air over the pole would lead to more cooler air further out. Warmer air rises, doesn't it?
B, don't ask me about tomatoes. Or build yourself a greenhouse?
DBC, good riposte, that was my first thought but I'll leave the field to people who have a vague idea what they are talking about. I', looking forward to PaulC's next attempt.
Mark, I already have a greenhouse, but I still got very few ripe tomatoes.
Well, DBCR, there's no doubt that the -20 does warm up too, so there will be a little pushback like you say. However it's a seasonal effect and hence more pronounced as you go further from the Equator. So I might expect the -20C air to warm by 5C rather than 10. It's also a dynamic effect, so you can think of the atmosphere as pulsing on an annual basis, pushing the Jet Stream south during the Autumn and North during the Spring. It's always done that but now it just does it with a bit more oomph.
Both effects happen at once, MW. The -20C air north of the Jet Stream may be cold but compared to the -60C stuff at the Pole it's warm. So the rising happens at the Jet Stream and the air above the Pole is falling. When you warm the air at the poles to -50C and the air at the edges to -25C, the process still goes in the same direction, it just doesn't go so powerfully.
All the air north of the Jet Stream acts like an almost self-contained circulating unit, so it's continuously recirculating blowing away from the pole at lower levels and towards it at higher levels.
However as well as recirculating it will expand or contract as a whole too, thus pushing the Jet Stream about.
Oops, I meant warm to -15C not to -25C. Sorry.
Here's a diagram showing where the various atmospheric belts are. The border between the northern polar one and the northern mid-latitude one is just north of Britain normally. In the past few years it's pushed a bit further south than usual.
@Derek
The diagram showing Rossby's Waves in the Jetstream ,( Wikipedia) is more explanatory IMO .
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