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> Snow and AGW, Snowy conditions and Climate Change
paletitsnow63
post Mar 4 2011, 10:27 AM
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I start this topic off with a question. Why do scientists who support AGW believe that extreme snowstorms throughout the world the past few years do not go against their belief that the planet is warming? A number of scientists have mentioned that the cold and extreme snowy conditions in places like the US, UK, Europe, and Asia actually support their beliefs that the worls is warming. Not sure how that supports their view. Maybe somebody can fill me in.

Thanks.
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vomit
post Mar 4 2011, 10:35 AM
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QUOTE(paletitsnow63 @ Mar 4 2011, 10:27 AM) *
I start this topic off with a question. Why do scientists who support AGW believe that extreme snowstorms throughout the world the past few years do not go against their belief that the planet is warming? A number of scientists have mentioned that the cold and extreme snowy conditions in places like the US, UK, Europe, and Asia actually support their beliefs that the worls is warming. Not sure how that supports their view. Maybe somebody can fill me in.

Thanks.

I believe the general consensus is:

1) the atmosphere is warming, and,

2) a warmer atmosphere can hold more moisture (snow included) leading to more extreme precipitation events.

Someone with more knowledge can correct me if I am wrong here. blink.gif

This post has been edited by vomit: Mar 4 2011, 10:34 AM


--------------------
"All our lives we sweat and save building for a shallow grave." J.D. Morrison
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Regg
post Mar 4 2011, 11:43 AM
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The real question should not be about snow or rain, but precipitations - as the outcome of precipitations (the type) is a regional issue.

GW theory is saying that a warmer global temps lead to more precipitations. The snow you get at one place, is from a storm system formed from a warm system borned at a much lower latitude (and warmer latitude). EX: a snow storm in the north east comes from a warm system that gave a lot of rain in the south or central south.

But even to that point, snow/rain events are regional. The real question becomes, is there more precipitations on a global scale - AGW is saying it should. Even skeptics arguments are saying it should : their argument is that as the earth warms, there should be more cloud/precipitations to cool back the warmed atmosphere (cool forcing). We've seen storms pooring huge amount of snow on the US while the same storm transported warmer air in his flow, and it poored huge amount of rain on the continental north east and even up to the polar circle and much of Greenland - that's the same storm system. Cold air flowed south giving snow in the US while warm air flow north giving rain up there.

Where i live (Canada), we've seen regional important warming over the last decades. Precipitations amount varied, but we've seen regions getting more precipitations (annual base) with less snow and more rain, while colder regions that have warmed a lot got more precipitations and mainly more snow. We also got regions where all snow and rain (annual precipitation) went down by quite a margin. It has to be looked on an annual base, but also on a seasonal base. It has to be looked at a longer period of time because cycles from NINO, NAO, AO, PDO, are also affecting the amount and frequency of precipitations, further the type.

For the issue of the type of precipitation for a given area, we will have to look at what changes took place by a warmer climate. Actually we see much warming in the upper latitude, but much less in the lower latitude. How is that equals at the end. We know a warmer upper latitude does affect the polar vortex, allowing cold air to flow south. So it's a lot more complex than just cold temps at one place. The argument from the climate scientist holds to the fact that as cold air is allowed to flow south, it is reaching warmer and humid air mass. That forms storms, and if the local temps are low enought then you get more snow. And that does explain why warmer temps (globally) could lead to more snow in one area - but in fact, we're talking about more precipitation in one area that happened to be colder on that day (a weather event).

As a general rule of thumb, there's more chance to get more snow from a 20-30F temp than a -20 to -30F - it's not a temps issue but a humidity issue (water vapor). But that is a different subject.
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Charlie A
post Mar 4 2011, 04:59 PM
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The science was settled back in 2001 by the IPCC. Here's what WGII said about impacts of global warming on North America:


QUOTE
Milder winter temperatures will decrease heavy snowstorms but could cause an increase in freezing rain if average daily temperatures fluctuate about the freezing point.


ref: http://observatory.ph/resources/IPCC/TAR/wg2/569.htm

Or download WGII Chapter 15 of the TAR and look at the impacts graphic on page 746:
QUOTE
VIII. Northeast USA and Eastern Canada
Large, mostly urban population—generally adequate water supplies, large
number of small dams but limited total reservoir capacity; heavily populated
floodplains:
Decreased snow-cover amount and duration (40)

http://observatory.ph/resources/IPCC/TAR/w...g2TARchap15.pdf

The footnote (40) is "40. Moore et al.," which expands to Moore, M.V., P.M.L., J.R. Mather, P.S. Murdoch, R.W. Howarth, C.L. Folt,
C.Y. Chen, H.F. Hemond, P.A. Flebbe, and C.T. Driscoll, 1997: Potential
e ffects of climate change on freshwater ecosystems of the New
England/Mid-Atlantic region. Hydrologic Processes, 11, 925–947.
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Charlie A
post Mar 4 2011, 07:31 PM
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A good review of actual observed trends in precipitation is AR4, WG1, chapter 3.3.2., "Changes in Large-scale Precipitation"
http://ipcc.ch/publications_and_data/ar4/w.../ch3s3-3-2.html


Although statements such as
QUOTE("Regg")
GW theory is saying that a warmer global temps lead to more precipitations.
are very common. The actual observations do not yet show this.

The observed global land precipitation trends "For 1951 to 2005, trends range from –7 to +2 mm per decade and 5 to 95% error bars range from 3.2 to 5.3 mm per decade. Only the updated PREC/L series (Chen et al., 2002) trend and the GPCC v.3 trend appear to be statistically significant, but the uncertainties, as seen in the different estimates, undermine that result."

The only two trends identified as being statistically significant were -5mm/decade and -7mm/decade. In other words, less precipitation rather than more.
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Regg
post Mar 4 2011, 07:55 PM
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Well, in AR4 here's what it said
QUOTE
Because precipitation comes mainly from weather systems that feed on the water vapour stored in the atmosphere, this has generally increased precipitation intensity and the risk of heavy rain and snow events.


There's a lot of spin around that issue from both side. Time will tell. It's important to remember the effect is not the same everywhere. Large scale statistical account can drown the fish easily by masking an increase on a large region while there's a huge decrease at another region (drought).

Climate variability and sensitivity are playing a large role in precipitation amount and types.

This post has been edited by Regg: Mar 4 2011, 07:58 PM
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Charlie A
post Mar 4 2011, 08:30 PM
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Regg ... it would be helpful to include a link to where in the AR4 you are quoting.

The AR4 is in many ways like a good fortune teller. Depending upon how you interpret her words, she has predicted whatever happens (or happened).

Here are few other links regarding extreme precipitation:

http://www.ipcc.ch/publications_and_data/a...h9s9-5-4-2.html

http://www.ipcc.ch/publications_and_data/a...0s10-3-6-1.html

In general, the evidence is rather sketchy and spotty.

Predictions for the future are much more certain.

http://www.ipcc.ch/publications_and_data/a.../ch14s14-3.html
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Regg
post Mar 4 2011, 09:14 PM
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Sorry here it is .. FAQ 3.2 How is Precipitation Changing? - AR4 Working group I

I did not had time to dig the issue, but from what i can see there's not much data beside regional measurements where some areas are seeing a net increase and others showing net decrease. As i said in my previous post, the effect is not the same every where and i really hope no one is believing it could be linear.

Remember climate scientist said such event was ''in line'' with warming climate - not that it was predicted. Global scale climate science is not the best scientific method to analyze regional weather event (my opinion).

This post has been edited by Regg: Mar 4 2011, 09:15 PM
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Charlie A
post Mar 4 2011, 09:28 PM
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The State of the Climate 2009, published in BAMS July 2010 updates the precip trends, and also has info for trends on oceans.

Links to both high and low resolution versions: http://www.ncdc.noaa.gov/bams-state-of-the-climate/2009.php

The relevant section is pdf page 32 of 222, or BAMS page # S31.

The worldwide oceanic precipitation trends for 1988-2009 are
RSS trend of 20.4 ± 7.1 mm year-1 decade-1. (in other words, 95% limits of +13.3 to +27.5 mm/yr/decade)
the GPCP trend is much lower at 2.4 ± 8.1 mm year-1decade-1. (95% limits of -5.7 to +10.5 mm/yr/decade).

The difficulty of the measurement can be seen in that the two trends are inconsistent in that the 95% confidence limits of the same parameter, over the same time period, do not overlap.

The above is for global precip trends above the ocean. The sampling was insufficient to make reasonable guesses for the pre-satellite period.

For land precip there are rain gauges histories much further back in time, but much more sparse than temp records. The State of the Climate 2009 (links above) has a global land precip time series chart for a few different sources.
See attached image. There might be a recent trend in the GHCN (lower black line), or it might be the same sort of variations seen back in the 1st half of the 20th century. The upper lines show annual differences between GHCN and a couple of other time series of global land precip.
Attached Image

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Charlie A
post Mar 4 2011, 09:35 PM
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QUOTE(Regg @ Mar 4 2011, 06:14 PM) *
Remember climate scientist said such event was ''in line'' with warming climate - not that it was predicted. Global scale climate science is not the best scientific method to analyze regional weather event (my opinion).
"In line with" or "consistent with" is a very useful phrase.

It is very useful in that lower snowfalls can be "consistent with" global warming one year, and then the following year higher snowfalls are "consistent with" global warming.


Although the statements are for the UK, not the USA, UK scientists declared back in 2000 that snowfall would be less due to global warming. Snowfalls are Now Just A Thing in the Past quotes scientists from the CRU and from the UK Met office
QUOTE
According to Dr David Viner, a senior research scientist at the climatic research unit (CRU) of the University of East Anglia,within a few years winter snowfall will become "a very rare and exciting event".

"Children just aren't going to know what snow is," he said.

QUOTE
David Parker, at the Hadley Centre for Climate Prediction and Research in Berkshire, says ultimately, British children could have only virtual experience of snow. Via the internet, they might wonder at polar scenes - or eventually "feel" virtual cold.


These quotes are from 2000. I have not seen any quotes from these two scientists after the last two UK winters with heavy snowfalls, but if I searched it is quite likely that I will find statements from the CRU and the Met that say the heavy snowfalls are evidence of global warming.
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Charlie A
post Mar 4 2011, 09:57 PM
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Regg == if you are seriously interested in the regional variations and the related predictions, then you should look in some of the hydrological journals. The general consensus in the hydrological world is the the GCMs are very poor and essentially useless. The whole issue of regional and local downscaling in the GCMs is pretty messy.

Scientists in the hydrological field have much closer ties with real, accountable projections that will be used for making decisions on large scale water impoundment and storage projects. In many ways, hydrologists, even though they are called scientists are closer in mentality to engineers.

Engineers, in general, are much more sceptical about projections and models and tend to run real validations whenever possible. The GCMs have done horribly at any sort of validation in precipitation.

An interesting tidbit is that the worlds longest instrumental climate record is the record of Nile river flows. The statistical analysis of that time series is what generated what is now called fractional gaussian statistics, or Hurst-Komolgorov statistics, or ...... (a dozen other names for the long tailed, highly correlated times series routinely found in nature and in climatological measurements).

http://itia.ntua.gr/en/ is a good start for hydrological info, and also on HK statistics.

A comparison of local and aggregated climate model outputs with observed data is a peer reviewed paper published in the Hydrological Sciences Journal that compares GCM outputs (predictions) with the actual temperatures and precipitations observed. Previous comparisons had shown poor model skill at local and regional predictions. This latest study shows that even aggregated over the lower 48 states of the USA, and using a 30 year time scale for aggregation in time, the models still performed poorly.

Abstract reads
QUOTE
We compare the output of various climate models to temperature and precipitation observations at 55 points around the globe. We spatially aggregate model output and observations over the contiguous USA using data from 70 stations, and we perform comparison at several temporal scales, including a climatic (30-year) scale. Besides confirming the findings of a previous assessment study that model projections at point scale are poor, results show that the spatially integrated projections do not correspond to reality any better.


Basically, the hydrologists are doing what the model developers should be doing.

This post has been edited by Charlie A: Mar 4 2011, 10:01 PM
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Regg
post Mar 4 2011, 10:53 PM
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That's what i said and it looks like the same conclusion in what you referenced...

Global scale climate science is not the best scientific method to analyze regional weather events. If i can add.. What's the value anyway. We're currently judging on relative freak winter events that happened in the last 2 winters - and many of these can be linked to natural cycles for a good part.

You seem to imply scientist are using terms like "In line with" or "consistent with" with bad faith. They are using them because it is based on the assumptions of a theory. When data becomes available they'll be able to confirm/infirm the theory with solid evidences. As you stated from the papers from different source, not much has been done to look at that issue.

While the climate science is talking about conditional state, some are transforming the conditional statements for certitudes and/or certainties.

There's also time when scientist talked about the decreasing event frequency (like less snowfalls event in UK) and people transformed that as a prediction saying it will not happen anymore - quite a difference here. M. Monckton was really good at transforming what scientist really said. We can still see echos from what has been transformed , but less about what was really said.

When someone is taking good care to report one part of a statements correctly but is putting it in a different context at the same time, that person is not looking to analyze a situation and pull conclusion out of it, but more to score a point with a cheap shot - blogs are filled with such.
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Charlie A
post Mar 5 2011, 12:12 AM
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QUOTE(Regg @ Mar 4 2011, 07:53 PM) *
You seem to imply scientist are using terms like "In line with" or "consistent with" with bad faith.
It's not a problem in serious scientific works.

It's more of a problem in the press releases associated with them, and news articles written about them.
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Removed_Member_Weaderman_*
post Mar 5 2011, 12:13 PM
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The effect of co2 is largely dependent on insolation. In winter, the atmosphere is highly stratified. The Arctic regions in dark, largely unaffected by co2 warming. As insolation increases, co2 works more effectively to warm. Deep snowcover melts more rapidly such there is no net gain and no change in the date of the snow cover disappearing. I have recorded later arrival of snow over in Fall and earlier disappearance in Spring despite the depths of mid winter. This has been most observed the last several years. The solar physicists say the sun is not contributing so I must conclude increasing co2 is largely responsibe
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