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Can you spot the trend in this data?


snowsure

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Posted
  • Location: Evesham, Worcs, Albion
  • Location: Evesham, Worcs, Albion
Please tell me if you think that the megatrend is positive, negative or if there is no obvious trend.

Without having looked at anyone else's comments, I detect a trend during the later part of the series towards less negative anomalies which, if it continues, may eventually result in all positive anomalies

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Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL
Without having looked at anyone else's comments, I detect a trend during the later part of the series towards less negative anomalies which, if it continues, may eventually result in all positive anomalies

E,

even in rampant warming, we wouldn't ever see consistently positive anomalies. There will always be inter-annual variation that presents its own signature, and which will have a larger amplitude than the average rate of warming. I do agree though, that a "by sight" look at the data suggests a slight upward trend line.

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Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL
...

I look forward to your examples whenever they become forthcoming.

post-364-1189204459_thumb.png

post-364-1189204680_thumb.png

I would consider the cut-off for a month with any decent wintry weather to be around 4C; a month with some sustained winteriness 3C; and the sort of month occasionally imagined on here by the wilder snowmantics to be 2C or less. The second plot above illustrates the problem with "inertia" - warm years seldom lead into winters with any particularly cold months, particularly if you look at just the last century. It can't be ruled out, even allowing for recent warming, but the odds are fairly long and against.

post-364-1189204327_thumb.png

post-364-1189204358_thumb.png

post-364-1189204397_thumb.jpg

Edited by Stratos Ferric
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Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

SF.. I like that data. It shows the point that the more sun facing the north pole is over winter and closer the planet is to the sun over this period, the warmer our winters are..

I think that while all this seasonal stuff is all well and good, more information as to where we are heading is the night time minima. Is that globally on the up? Any details SF? Are they as bad or worse than the averages. I know the UK ones show a rise in recent years but have never seen a graph of global minima.

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Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL
SF.. I like that data. It shows the point that the more sun facing the north pole is over winter and closer the planet is to the sun over this period, the warmer our winters are..

I think that while all this seasonal stuff is all well and good, more information as to where we are heading is the night time minima. Is that globally on the up? Any details SF? Are they as bad or worse than the averages. I know the UK ones show a rise in recent years but have never seen a graph of global minima.

Don't know, but it's a very good question. My simple explanation is slightly warmer oceans favouring more nighttime cloud. That would be the other good piece of data to find. Alas, I suspect that robust stats for the latter have not been kept for very long, and certainly without the surface density to be able to produce thorough analysis.

...A quick Google has resulted in:

http://www.sciencedirect.com/science?_ob=A...613196d5bfde4fc

and this...

Monthly mean maximum and minimum temperatures for over 50% (10%) of the Northern (Southern) Hemisphere landmass, accounting for 37% of the global landmass, indicate that the rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the period 1951-90 (0.84 C versus 0.28 C). The decrease of the diurnal temperature range is approximately equal to the increase of mean temperature. The asymmetry is detectable in all seasons and in most of the regions studied. The decrease in the daily temperature range is partially related to increases in cloud cover. Furthermore, a large number of atmospheric and surface boundary conditions are shown to differentially affect the maximum and minimum temperature. Linkages of the observed changes in the diurnal temperature range to large-scale climate forcings, such as anthropogenic increases in sulfate aerosols, greenhouse gases, or biomass burning (smoke), remain tentative. Nonetheless, the observed decrease of the diurnal temperature range is clearly important, both scientifically and practically.

From: http://www.ncdc.noaa.gov/oa/climate/mxmntr/mxmntr.html

Edited by Stratos Ferric
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Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

Cheers for that SF..

The NOAA link reads pretty much along the IPCC lines and modelling. More cloud basically, be it water vapour or aerosol. The discussion points on the link also help things make sense.

To me, the minima are more convincing than just your bog standard global averages that everyone bangs on about. There are still some questions that need to be answered for me but now I'm leaning onto the pro warming side of the fence.

The reason I asked the question was after a hobble down to the local Coop. The heat that the brickwork was radiating was very noticeable in the cool evening air, after that wall being exposed to the sun all afternoon on a 24oC day. I've always questioned the heat island effect but now I need to be arms length from a bit of support, it really made me think again. Add to that the "cloud" and you do start to realise the possibility that things could be warming.

I really do think that this global minima is the thing that needs to be looked at more.

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Posted
  • Location: Doncaster 50 m asl
  • Location: Doncaster 50 m asl
Cheers for that SF..

The reason I asked the question was after a hobble down to the local Coop. The heat that the brickwork was radiating was very noticeable in the cool evening air, after that wall being exposed to the sun all afternoon on a 24oC day. I've always questioned the heat island effect but now I need to be arms length from a bit of support, it really made me think again. Add to that the "cloud" and you do start to realise the possibility that things could be warming.

I really do think that this global minima is the thing that needs to be looked at more.

SF - great set of data and notes. Hopefully I can come-back with some questions regarding them.

PP - Imagine a world of more precipitation. The heat stored in the brick, etc is quite easily liberated thus facilitating cooling. Not an open and shut case yet, in my opinion. If we have more rainfall, the night time minima may start to respond.

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Posted
  • Location: Steeton, W Yorks, 270m ASL
  • Location: Steeton, W Yorks, 270m ASL

Having resisted temptation for a long time I've finally downloaded the Hadley daily data (previously I've just been using monthly averages). This presents a granularity of data which is fantastic, but only runs back as far as the 1870s. It also makes Excel run pretty slow: some of the calculations are taking about 30 seconds - normally it's pretty much instantaneous - such is the size of the data set.

Anyway, three interesting morsels for starters, all with regard to PP's question. There's one caveat, which is that I suspect there might be some bugs in the data strip - I've weeded out the more obvious ones (like a very warm day appearing amongst a run of very cold ones), and cleaned up for the markers used in the file to hold spaces (e.g. for the days in a month where there are fewer than 31), but the rsk remains that there MIGHT be one or two holes in my data: if there is I'll correct and broadcast to this effect later, that said, I'm confident that any issues should be trivial and in the detail.

So, what do we have?

post-364-1189345393_thumb.pngpost-364-1189345412_thumb.png

As I said, this is hugely counter-intuitive. ON THE OTHER HAND, it may be explainable. An increase in daytime maxima does not make a huge difference to experienced conditions: if it's too warm for snow, it just becomes - too warm for snow. The hypothesis might be (and this would need testing) that FEWER daytime events are changed in terms of weather outcome than are nighttime outcomes (a lot more days will be taken from below freezing to above freezing), hence the latter is more noticeable, even though, in practice, the warming is less marked.

The caveat remains - I do need to check the data conversions, so treat this as a draft FLASH (first look at highlights) report.

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Posted
  • Location: Swallownest, Sheffield 83m ASL
  • Location: Swallownest, Sheffield 83m ASL

Thanks for doing this SF.

Looking at the February data, it appears that the minima has levelled off over the last few years. This I suppose could be evidence of the plateaux that some expect before the next phase of warming begins? Then again it could mean the minima temps have peaked and are about to cool again. Part of a natural cycle perhaps?

It's interesting to see how the difference between maxima and minima has increased during February since the 90's. The question is, what is causing that increase in difference that appears to affect just that one month?

That CF diagram is certainly making warming an obvious trend.

Will look forward to seeing the confirmed data.

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