Dust & climate models

[Dr Mordrid]

Link....

Unexpected discovery could impact on future climate models

(PhysOrg.com) -- Astronomers have made an unexpected find using a polarimeter (an instrument used to measure the wave properties of light) funded by the Science and Technology Facilities Council (STFC), that has the potential to affect future climate models.

University of Hertfordshire astronomers were making observations of the stars in search of new planets after mounting the 'PlanetPol' (polarimeter they designed and constructed to take extremely sensitive readings) on the William Herschel Telescope (part of the Isaac Newton Group of Telescopes) in La Palma in the Canary Islands, when their measurements became affected by a layer of dust.

The presence of the dust itself, which satellite images and modelling of the dust's movement show had originated from the Sahara and the Sahel, was not a surprise, but its behaviour was. Scientists normally assume that aerosols, including mineral dust, have random orientation in the atmosphere, but the team members say the polarizing affect the dust was having on the light could only be the result of dust particles being vertically aligned.

Furthermore, electric fields that are now thought to be responsible for this phenomenon are likely to affect the transport of dust over long distances. For the first time this might explain why large Saharan dust grains can travel as far as the UK instead of falling to the ground long before.

This could impact on climate theories because atmospheric dust is a significant source of uncertainty for scientists trying to model the climate. 'If it's proven the dust is affected by electric fields, elements of current climate models may have to be re-worked with this new information, to remain accurate', explains Joseph Ulanowski, Centre for Atmospheric and Instrumentation Research (CAIR) at the University of Hertfordshire.

Climate models are extremely complex and involve many other influences, so further research will now be carried out to see how significant a find this dust phenomenon is. CAIR will now join a Met Office-led campaign in the Middle East in the spring 2009 which presents an opportunity to investigate this further.

Professor James Hough, Director of Astronomy Research at the University of Hertfordshire said, 'It's been fascinating to see how we have been able to use astronomical observations to learn far more about dust in the Earth's atmosphere, especially as we first considered the Saharan dust event to be a real nuisance and of no value to us at all.'

Provided by University of Hertfordshire

[Kruzin]

All this proves is that scientists/meteorologists/etc. aren't as smart as they like to think they are.
The types of observational studies they are quoting here have only been available for a few decades. So as far as they know, this is a normal 50-100-200 year occurrence.

Just another alarmist cry for attention.

[Brian Ellis]

Interesting. However, Saharan dust storms affect weather much more than they do climate. We are frequently (2-3x per year) subject to them here, lasting 1-3 days on average. This picture shows one such episode covering the island.



Total aerosols are already well factored in into the IPCC calculations. These include anthropogenic dust pollution, which accounts for most of it because it is 24/7/52, and episodic causes, such as volcanic activity (a severe eruption can cause aerosols lasting from 1 - 3 years or exceptionally longer) and dust storms, such as are described. However, there is a big difference: particle size. The larger the particle, the shorter the time it remains suspended as an aerosol. 90% of the Saharan dust has a particle size >15 µm and, although carried by strong winds (e.g., khamseen, which is the one that affects us here), it settles out rapidly (rarely >2-3 days). Depending on weather conditions, the finer particles, mostly around 2-5 µm, can be carried considerable distances. Notwithstanding, the coarse particles, such as in the above image and in yours, very rarely reach an altitude >1000 m. The fine particles may reach 3000-5000 m before they settle or rain out. OTOH, volcanic and anthropogenic particles, such as fine soot from vehicle exhausts and oil-fired central heating systems, may reach altitudes of 20,000 m or more.

Having lived in Switzerland, I've often seen the effect of particular contamination of all types in the snow and ice. We did occasionally experience Saharan dust in the Lausanne region once every few years, north of the Alps, blowing up the Rhône valley. However, I used to do a lot of walking in the Alps and where perennial snow and ice had broken away, you could see a historical record, year by year. There was an annual dark band corresponding to the soot added, captured by snowflakes, each winter and thinner light bands in between. Once every few years, a very thin yellow band could be seen: this is Saharan sand. What is even more interesting is that, where there has been a thick ice fall, representing a few hundred years of snowfall, is that the "black band":"white band" ratio diminishes visibly over the years (almost no soot deposits 200 years ago), while the yellow bands are irregular but unchanged in frequency. Of course, there has been a lot of Alpine ice core research (e.g. Berne University), a lot more scientific than my subjective observations, and main eruptions and major N. American forest fire phenomena have been identified, as well.

As your article has stated, there are more uncertainty parameters in total aerosols vis-Ã*-vis climate change than any other cause. This well-illustrated here, where the uncertainty limits are shown:



Note that the caption specifically excludes volcanic activity from the chart. There will be occasional years of considerable cooling because of it (e.g., after Mt St Helens). On a global climatic scale, Saharan dust storms have almost no effect because of their low altitude, short time scale and very episodic frequency. On a local weather scale, they are very important (we had an episode this weekend!). When the dust is suspended, it is not like a mist. It has an almost ethereal appearance, even when the visibility is down to <100 m. I put this down to the thin layer, with the sun reflected from particle to particle. I'm not sure whether the observed polarisation effect could be due to particle orientation as the article hypothesises, because the particles are essentially fairly spherical. OTOH, about 7 times out of 10, a sand episode ends in a violent electrical storm, which rains out the dust and makes an unholy mess! My rain gauge mechanism (tipping buckets) requires cleaning after such a storm. So yes, there are electrical charges involved and the very fine particles probably seed water condensation at higher altitudes.

I would guestimate that the amount of sand reaching here is probably 1-3 mm in depth/decade. I know those who have swimming pools or who have their cars parked outside hate these episodes!!! They possibly help the natural fertility of the Cyprus soil.

[Brian Ellis]

All this proves is that scientists/meteorologists/etc. aren't as smart as they like to think they are.
The types of observational studies they are quoting here have only been available for a few decades. So as far as they know, this is a normal 50-100-200 year occurrence.

Just another alarmist cry for attention.

All this proves nothing at all, for the moment. It may provide another small piece in the jigsaw puzzle of meteorological and climatic knowledge, in time.

If dust storms on this scale occurred every 50/100/200 years, as you suggest, then they would have zero climatic influence. Because they do occur 2-3 times/year, it is possible they may have a very small influence.

What is much more likely is that their influence may increase because their frequency is predicted to increase as part of the probable (IPCC terminology) predicted increased desertification of the Mediterranean basin due to climate change.

[Dr Mordrid]

If dust storms on this scale occurred every 50/100/200 years, as you suggest, then they would have zero climatic influence. Because they do occur 2-3 times/year, it is possible they may have a very small influence.

And what if their frequency and intensity changes over time due to changes in the electromagnetic fields caused by variations in solar activity and/or cosmic ray cycles? I think this is very, very likely given these fields are a big part of why the dust is polarizing to begin with and those who did the study say they 'have to rework" those parts of the model (DUH!).

Given how they've ignored the obvious before I don't hold a lot of hope for them getting it right this time...especially with $600 million of Obama Recovery Plan dollars targeted at NOAA for (politically correct) climate modeling. As they say; follow the money, or in this case - Federal grant money.

No more likely to produce contrary results than studies done for the National Petroleum Institute

IMO not a good day for the modelers....again.

[Brian Ellis]

And what if their frequency and intensity changes over time due to changes in the electromagnetic fields caused by variations in solar activity and/or cosmic ray cycles? I think this is very, very likely given these fields are a big part of why the dust is polarizing to begin with and those who did the study say they 'have to rework" those parts of the model .

Your whole premisse is based on one big 'if' for which you have no reason to suppose. Meteorological records have been kept on this island since the Ottoman mandate started in the 1870s, including Saharan dust storms. AFAIK, no cyclic phenomena have been observed in either frequency or intensity, which have been fairly constant, obviously with a noise level, as with all weather phenomena. Also, the same applies to Alpine ice cores.

To say 'very, very likely' on pure speculation is hardly scientific.

[Dr Mordrid]

The whole notion of climate models being true representations consists of several big IF's on the IPCC's part, so what's one more?

[Brian Ellis]

And what influence does sporadic dust storms a few times/year have on climate? Almost none. You are talking about weather, not climate, and weather over very small fractions of the earth's surface, to boot. Get real!

FYI, I've e-mailed the local met service for statistical data on dust storms. As it is a government office, it is doubtful whether they will reply or even acknowledge my message, but one never knows, miracles happen occasionally!!! (In 12 years, I must have sent 100 e-mails to various government departments: I think I've had 2 replies)

[Brian Ellis]

I found thus on this site:

Due to the dry climate in Cyprus Particulate Matter is resuspended from soils and other surfaces. The wash out of particles from the air occurs only in winter and spring time when it is raining in Cyprus. In summer and fall time nearly no rain helps to clean the air.

* The study by University of Stuttgart showed that as an average 17% of the 24h limit exceedances of PM10 are caused by Sahara dust events.
* At rural sites (Agia Marina as example) around 70% of PM10 concentration levels could be determined to be from natural origin: resuspended soil and sea salt. Around 9% could be allocated to combustion processes
* At traffic sites (e.g. General Hospital) around 60% of PM10 could be allocated to traffic activities: Apart from PM exhaust emissions tire, brake and road abrasion and resuspended soil dust originally coming from fields or unpaved roads could be identified. 19% could be allocated as sea salt and traffic independent soil dust (air borne transported). The remainder (21%) are caused from other minor activities.
* At the residential site (Famagusta was investigated as example) 22% could be allocated as traffic induced particulate matter. The other 58% could be identified to be from soil and sea salt origin. The remainder (20%) are caused from other minor activities.
* The results of the PM investigations identified also the traffic as the main anthropogenic pollutant source. So, also from the PM10 view efforts to reduce the traffic emissions have to be taken.

The comparison of the PM10 concentrations in Cyprus cities with values of other European cities demonstrate the PM10 problem in Cyprus cities and underline the necessity of abatement

This shows how little effect Saharan dust storms has on weather, compared with anthropogenic sources. They will have even less effect on climate.

Maybe this is a duststorm in a teacup.