Another missing piece of the climate model puzzle – dust

A satellite image from the NASA Moderate Resolution Imaging Spectrometer (MODIS) instrument onboard the Terra satellite captured this dust storm moving over Red Sea on July 8, 2013.  Credit: MODIS Rapid Response Team.
A satellite image captured this dust storm moving over Red Sea on July 8, 2013. Photo: MODIS Rapid Response Team.

From Scripps: Global climate models fail to simulate key dust characteristics

African dust plays a key role in cloud formation, hurricanes and other global climate phenomena but models can’t characterize it well.

Climate models that simulate the airborne African dust that influences Atlantic Ocean hurricanes are not up to the task of accurately representing the characteristics of that dust.

Climate models that simulate the airborne African dust that influences Atlantic Ocean hurricanes are not up to the task of accurately representing the characteristics of that dust.

In a new study, researchers led by Amato Evan, a climate scientist at Scripps Institution of Oceanography, UC San Diego, examined the performance of 23 state-of-the-art global climate models used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The researchers found that none of them yielded accurate data on dust characteristics.

“The models systematically underestimate dust emission, transport and optical depth, and year-to-year changes in these properties bear little resemblance to observations,” the authors wrote. “These findings cast doubt on the ability of these models to simulate the regional climate and the response of African dust to future climate change.”

African dust influences everything from the transport of nutrients across continents to the planet’s energy budget. Improvement of the “skill” or accuracy of computer models, though, is hampered by a lack of comprehensive data from the regions where the dust originates. Evan said the inaccessibility of these regions often has nothing to do with nature; the Sahara Desert, for instance, is a large source of African dust but is also the home of political unrest and the lair of various terrorist organizations.

“I am in France trying to set up a new set of observations over the Sahara that are related to the dust question, but at present neither myself nor my French colleagues can make the trip out to southern Algeria to set up the equipment ourselves because of regional unrest,” Evan said shortly after the publication of the study.

Observations are needed to constrain models, helping to narrow down the range of possible dust behaviors that are an integral part of computer models of the global climate. Researchers at Scripps Oceanography have pioneered observations of aerosols in other world regions and their effects on climate. For example, Scripps Distinguished Professor of Climate and Atmospheric Sciences Veerabhadran Ramanathan has since the 1990s documented the influence of what has been termed the atmospheric brown cloud, a layer of particulate pollution several kilometers thick that forms over South Asia many times per year. This brown cloud has a major effect on agriculture and public health in that region and goes on to have global effects.

Kim Prather, an atmospheric chemistry professor who holds appointments in the UC San Diego Department of Chemistry and Biochemistry as well as at Scripps Oceanography, studies the long-range transport of pollutant aerosols to study how particulate matters traverses oceans to influence precipitation and other phenomena from one continent to another. In 2013, the Center for Aerosol Impacts on Climate and the Environment, directed by Prather, received a five-year, $20 million grant from the National Science Foundation to study how interactions between air and sea involving aerosols alter the chemistry of the atmosphere to influence climate.

In its Fifth Assessment Report released in stages starting in September 2013, the Intergovernmental Panel on Climate Change (IPCC) incorporated data about African dust generated from climate models. IPCC reports are not themselves original research but are syntheses of the most recent published climate research available when the reports are being compiled and presented to national policymakers around the world. The IPCC report acknowledged the large uncertainty in climate forcing by changes in all aerosols. Evan was a contributing author to Chapter 14 of the report, “Climate Phenomena and their Relevance for Future Regional Climate Change,” in which authors acknowledged that there is uncertainty in regional climate projections associated with aerosols.

“However, I think we showed (in this study) that the level of inaccuracy was just way beyond what anyone assumed it to be,” said Evan.

“All hurricanes that make landfall in the U.S. form and intensify in the tropical North Atlantic,” Evan added. “So how will global warming affect these hurricanes? Well, to really know this we need to get this dust question right, and at present we just can’t do that.”

The study, “An analysis of Aeolian dust in climate models,” appears in the American Geophysical Union journal Geophysical Research Letters. Co-authors include Owen Doherty of Scripps Oceanography, Cyrille Flamant of Laboratoire Atmosphère, Milieux, Observations Spatiales, CNRS and Université Pierre et Marie Curie in Paris, and Stephanie Fiedler of the School of Earth and Environment, University of Leeds, Leeds.

Funding for the research was provided by Agence Nationale de la Recherche in France, Laboratoire d’excellence Institute Pierre Simon Laplace in France, and NOAA.


The paper:

An analysis of aeolian dust in climate models

Amato T. Evan, Cyrille Flamant, Stephanie Fiedler and Owen Doherty


Aeolian dust is a key aspect of the climate system. Dust can modify the Earth’s energy budget, provide long-range transport of nutrients, and influence land surface processes via erosion. Consequently, effective modeling of the climate system, particularly at regional scales, requires a reasonably accurate representation of dust emission, transport, and deposition. Here we evaluate African dust in 23 state-of-the-art global climate models used in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. We find that all models fail to reproduce basic aspects of dust emission and transport over the second half of the 20th century. The models systematically underestimate dust emission, transport and optical depth, and year-to-year changes in these properties bear little resemblance to observations. These findings cast doubt on the ability of these models to simulate the regional climate and the response of African dust to future climate change.

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July 16, 2014 4:04 am

IPCC AR5 TS.6 – Key Uncertainties
Wow, what an eye opener. Allow me to paraphrase.
“Hey, all you skeptics, guess what? You were/are correct! (Aren’t you usually?) When it comes to major climate systems virtually certain to make a critical difference, to have major influence, (clouds, precipitation, wind, tropospheric warming, stratospheric cooling, ocean temps >700m, carbon/heat >2000m, circulation, abrupt climate changes, sea levels) there is a high probability – that we have not got a clue!!”
“Oh, and by the way, we find no evidence connecting AGW and drought, cyclones, or similar extreme weather.”
“We also have pretty much no idea what the Antarctic ice sheet and ocean interface are up to.”
“Sorry ‘bout that true believers, politicians, and media hypers.”

July 16, 2014 4:15 am

” … and year-to-year changes in these properties bear little resemblance to observations,” the authors wrote. “These findings cast doubt on the ability of these models to simulate the regional climate and the response of African dust to future climate change.”
Hey, they can’t even get surface to be a resemblance to observations,
What can they do?

Bloke down the pub
July 16, 2014 4:25 am

And some people think that the models that walk down the catwalk are dim.

john karajas
July 16, 2014 4:50 am

Here’s betting a TV news presenter about to deliver the latest alarmist scare item would be far more interested in his/her facial makeup than some bo-o-o-o-ringgg issue like the amount of dust in the atmosphere.

July 16, 2014 4:59 am

Bloke down the pub says:
And some people think that the models that walk down the catwalk are dim.
They don’t resemble reality either 😉

July 16, 2014 5:05 am

Editor: The second paragraph is repeated.

David L. Hagen
July 16, 2014 6:00 am

Comparison of Dust emission source regions
From “supporting material”:

The only point of agreement between most models and the satellite observations is the BodŽlŽ depression as one of the most active dust sources (Kocha et al. 2013). We note that the satellite-based emission frequency may underestimate the number of dust events in the Saharan Heat Low (10¡-20¡N & 10¡W-10¡E) and within Western Sahara and coastal Mauritania (Brindley et al 2012). However, these possible biases do not explain the wide disparity in the spatial pattern of emission between the CMIP5 models and the observations.

Pamela Gray
July 16, 2014 7:05 am

hmmm. The list is growing.
So far, the AR[1,2,3,4,5…] climate models do not get the following key components of climate patterns right:
Semi-permanent atmospheric pressure systems
Oceanic-atmospheric teleconnections
and now
But we should make policy based on future temperature projections?

July 16, 2014 7:40 am

Here in Oz, every few decades a whole lot of silt from the interior takes wing on the spring westerlies and and an immense tonnage of our iron rich dust travels into the Pacific. You need good rain then dry weather in the centre, and the right winds at the right time. A little hidden benefit of El Nino.
When it last happened in the spring of 2009 some expert was proposing to seed the ocean with iron to, er, change the climate. I wondered what the proportional difference would be between the efforts of his ship and the contributions from Lake Eyre and the Australian interior. A hundred thousand to one? A million to one?
I know who was charging the most.

July 16, 2014 7:43 am

I saw a video in the early 90s that included an intriguing experiment with liquid rotating between cylinders, showing different patterns emerging as the speed of rotation increased to certain thresholds, or “tipping points.” I found a copy of the documentary on youtube yesterday–yay!–withthe experiment being exactly as I recall it (almost hypnotic).
The analogue system does a better impersonation of climate than any digital computer output I’ve seen to date: it does a reasonable impression of the Antarctic polar vortex bifurcating in 2002. I’ll bet that kind of thing never happens on SimEarth.

July 16, 2014 7:49 am

I tried to stop the youtube link embedding in my post, which messed up the link to the demonstration. Demonstration starts 26m:26s, only goes for ~ 5mins – well worth a look:

Steve P
July 16, 2014 7:49 am

Of course, this is not just any dust. This is African Dust, now looking to get some prime time in the long cast of characters playing second fiddle to the awesome Carbon Dioxide Molecule.
Not only does African Dust play a role in climate change, but also even more worrisome, the African Dust is being affected by climate change.

The models systematically… bear little resemblance to observations. These findings cast doubt on…the response of African dust to future climate change.

Meanwhile, American dust has its own devils. Ask them in Phoenix. The Chinese have dust too. In fact, everywhere you look, more dust.
It is worse than we thought. It might even be a runaway dust effect.

July 16, 2014 7:50 am

this is my shocked face …

July 16, 2014 8:12 am

Africanized dust, much more dangerous than its European counterpart. Dubbed “Killer dust”. Be afraid.

July 16, 2014 8:33 am

An interesting perspective on dust and climate.

Pamela Gray
July 16, 2014 9:00 am

Ah Ha! Epiphany! Thanks Khwarizmi! Fabulous youtube link!
CO2 and other greenhouse gases are not linear in their place in Earth’s atmosphere (based on satellite data) nor are they linear in their affect, even though CO2 appears to have a linear increase in parts per million! The models have it all wrong! Greenhouse gas as an agent of force, taken in toto, is nonlinear and likely has an underlying chaotic structure in Earth’s climate! This is why the models do not trace observations!!!!! The researchers are using linear representations when they should be tracing the chaotic 3 dimensional structure!
Greenhouse gas variation, up, down, or stable, is likely only causing a small change in the chaotic system, which is why temperature does not seem to obey this increasing parts per million force! We are only getting small non-linear changes within the chaotic structure, not whole cloth changes!
Now add to that. Earth’s atmospheric systems do not respond linearly to warmer air temperatures! Earth’s response also has a structured chaotic response. So now you have two structured chaotic systems, 1) atmospheric pressure systems that create weather pattern variations that help define regional climate, and 2) greenhouse gas warming, giving us a small change in chaotic weather pattern variations, which are already too chaotic under natural conditions to affect the outer boundaries of the climate regime chaotic structure.
Linear trends are the wrong way of viewing this whole debate! But it was an honest mistake. It was wrongly assumed that a linearly increasing substance that could cause the temperature to increase must have a linearly increasing affect! But we know, based on chaos theory, that is not likely to be the case.
So what we need are 3 dimensional representations of temperature change! Only then may we detect what is happening.

July 16, 2014 9:00 am

Fine, rouge-like, but yellow, dust from the Sahara often falls on European countries every year, including my home town in the far north on England.

Julian Flood
July 16, 2014 10:40 am

In spring the oceans come to life with vast phytoplanktonic blooms. First off the blocks are the diatoms. When dust dissolves it increases the longevity of the diatom bloom, because only when the silica is all used up can the diatoms be outcompeted. More dissolved silica means more diatoms and fewer calcareous phytos.
Diatoms pull down less CO2 and export less to the depths — think of those carbonate shells they don’t have. Diatoms use a C4-like carbon fixation process which discriminates less against the heavier isotopes of carbon, so what carbon they pull down is unexpectedly heavy.
This leaves a signal in the atmosphere of more CO2 than expected with more heavy carbon pulled down.
The CO2 in the atmosphere exhibits a lighter signal and there is more of it.
Has anyone checked?

July 16, 2014 11:11 am

$20 million for a 4 year study on dust.
That does change perspective, doesn’t it.
And what conclusion do you want for that sort of funding? Sure, no problem.
That is our tax money going up in smoke/dust.
Can’t even suggest that Prof. Prather should join the “how to sell anything” talk circuit, although clearly capable he will never make that much money.

Pamela Gray
July 16, 2014 11:23 am

I wonder what global temperature would look like in a 3 dimensional model. Is it possible that three equations water vapor, solar insolation (TOA), and heat loss to space, all of which are variables, could be put to the test in that simple analog computer?

July 16, 2014 11:39 am

Very relevant but barely discussed above:
African dust is one of the major factors influencing “Cape Verde” tropical cyclones. These are often the biggest and strongest storms of the season given they have a long trek across warm tropical water. They generally form in September and October, as the water there is slow to warm up.
When the Saharan winds are strong enough to lift dust high into the troposphere, that brings two influences to the eastern Atlantic:
1) Dust absorbs sunlight, heats the air.
By heating the air, it make the air column more stable, which makes it harder for tropical “wave” in the air flowing off Africa to trigger convection and start cyclone formation.
2) Less sunlight reaches the water, so it warms slower.
Cooler water means cooler air, which means the air column is yet more stable. It also pick ups less water vapor, so any convection that does occur will have less “latent heat” released when water vapor condenses.
I suspect it’s not very easy to simulate. Heck, it doesn’t seem very easy to forecast, I think Klotzbach and Gray often get tripped up by it in their seasonal forecasts and post mortem analyses frequently refer to it as one of the reasons for weaker than expected seasons.

Robert W Turner
July 16, 2014 12:19 pm
The WASMI and its influence on global weather is not discussed enough.

July 16, 2014 12:27 pm

It was once known that dust from Africa was responsible for coral bleaching in the Americas. This fact has been disappeared, ’cause its the evil CO2 that done it.
BTW political instability causes violence and wars which in Africa lead to displaced farmers which leads to untended farms which leads to desertification.

July 16, 2014 12:58 pm

And that SAL dust falls over the rain forests in South America fertilizing it and enhancing plant growth. How are those models handling that part?

Pamela Gray
July 16, 2014 1:56 pm

That African dust contains iron which is essential to the oceanic marine cycle. The greening of the planet has likely reduced oceanic iron seeding. More drought under whatever climate regime that would give us more drought, could restore ocean bounty.

July 16, 2014 2:34 pm

This is the correlation between dust, as minus log so more dust is down, and temperature in the Antarctic ice core from EPICA Dome C.
more dust, more sunlight blocked, colder Earth. More dust, more ocean fertilization, more oceanic biotica, more carbon mineralization, less atmospheric CO2.

July 16, 2014 2:36 pm

Does this mean I have to dust ?
It has been awhile, but I haven’t noticed a change in the (indoor) weather 🙂

Michael John Elliott
July 16, 2014 5:55 pm

Hello, while all this talk of dust is of interest, we should still not forget that the gas CO2 is logerithemic, i.e. the higher the percentage in the atmosphere, the less the heating effect that it can produce. Thus while we should by all means wonder about the effect of dust and other substances in the atmosphere its also time that we realised that the gas CO2 cannot be a serious player in any variations in the climate.
So forget all about CO2, and thus close down all the massive waste of the taxpayers money in chasing a none existant problem, and learn to adapt to whatever changes the climate causes to happen.
With all of that money no longer going to improve the life style of so many of the so called Scientists, and financial planners such as Al Gore, there will be plenty to use for more worthy projects.
Michael John Elliott.

July 16, 2014 6:22 pm

No Kidding, who would have thought dust could have an affect on climate conditions. The year after Katrina there was dust blowing off the Sahara into the Atlantic. The CAWG crowd and every official organization predicted more and bigger hurricanes. It’s all there if you can pull up the images from Sea-Wiss. (a satellite that kept track of dust, smoke, and other emissions) That’s a matter of record. Without a billion $ computer, it was easy to predict that any storms that formed would form further out in the Atlantic and be weaker. I wonder how they missed that. I wonder about the intelligence level of the CAWG crowd and the educational institutions that taught them. Not quite the best or brightest. They seem to be very good at regurgitating information, very little in being able to think. … How quickly CAWG forgets, the models didn’t include dust for predicting hurricanes.

Lil Fella from OZ
July 16, 2014 9:54 pm

The big question is: What did the models get right?

July 17, 2014 5:17 am

Thanks Pamela,
On hitting the submit button yesterday, I thought: “Well, if nobody else gets anything of value from this profoundly interesting clip, Pamela will, for sure.”
I’m happy to see that you did. 😉

July 17, 2014 8:35 am

“Observations are needed to constrain models”. This simple statement contains the essential shortcoming of the entire climate enterprise.

July 19, 2014 5:43 am

“African dust influences everything from the transport of nutrients across continents to the planet’s energy budget.”
No, only particulate matter from farms, diesel engines used in shipping by truck-trailer, and from fire places and barbques influence the climate.
That dust from high deserts like the Gobi, Colorado Plateau, etc. and from the Sahara are just computer model apps which would be nice to develop, by and by.

July 19, 2014 2:37 pm

I am living on the south coast of France, and I may confirm that yes, here we frequently undergo dust charged rains when the winds are blowing from the south. As incredibl as it may appear, the Sahara Desert’s dusts may be taken up in high altitudes and carried 1500 km farther north toward our regions. The remains of that dust may be clearly evidenced on the car’s paints once the rain has dried or when it shades in red-brown colors the snowy slopes of the nearby Alp’s mountains.

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