GeoLog

Laura Roberts-Artal

Laura Roberts Artal is the Communications Officer at the European Geosciences Union. She is responsible for the management of the Union's social media presence and the EGU blogs, where she writes regularly for the EGU's official blog, GeoLog. She is also the point of contact for early career scientists (ECS) at the EGU Office. Laura has a PhD in palaeomagnetism from the University of Liverpool. Laura tweets at @LauRob85.

Geosciences Column: Is it possible to quantify the effect of natural emissions on climate?

Geosciences Column: Is it possible to quantify the effect of natural emissions on climate?

The air we breathe is full of tiny particles that can have a big impact on our climate. Industrial activities have greatly increased the number of these particles, cooling the climate and potentially offsetting some of the warming due to greenhouse gases. In this post Kirsty Pringle introduces new research that suggests that it might not be possible to quantify the effect of industrial emissions on climate unless we constrain estimates of the natural emissions (Carslaw et al 2013). Kirsty is a member of Ken Carslaw’s research group at the University Of Leeds (UK) which performed the research.

Deserts, oceans, fire and even pine forests emit tiny particles called aerosol into the atmosphere. Human (anthropogenic) activities also play a role; burning fuel, e.g. in cars or power-plants, emits particles and aerosol concentrations have increased substantially since the start of the industrial revolution. One effect of these particles is to change the properties of clouds, causing them to become brighter, producing a net cooling that can offset some of the warming due to greenhouse gases. Treating this effect in climate models is challenging and it remains one of the most poorly quantified areas of climate science.

Schematic of the first aerosol indirect forcing: Human (anthropogenic) emissions add aerosol particles to the atmosphere, these particles can act as condensation sites, which aids cloud droplet formation.  Anthropogenic emissions result in clouds with more, smaller, cloud droplets.  These clouds are brighter and reflect more solar radiation, resulting in a net cooling. The first aerosol indirect forcing (AIE) is the change in the reflected solar radiation between the present day and the pre-industrial scenarios due to this effect. (Credit: Kirsty Pringle)

Schematic of the first aerosol indirect forcing: Human (anthropogenic) emissions add aerosol particles to the atmosphere, these particles can act as condensation sites, which aids cloud droplet formation. Anthropogenic emissions result in clouds with more, smaller, cloud droplets. These clouds are brighter and reflect more solar radiation, resulting in a net cooling. The first aerosol indirect forcing (AIE) is the change in the reflected solar radiation between the present day and the pre-industrial scenarios due to this effect. Click image for a larger version. (Credit: Kirsty Pringle)

This cloud brightening effect is called the first aerosol indirect effect (AIE). It is thought to produce a global average cooling that is sufficient to offset between 25 to 90% of the warming due to long lived greenhouse gases (IPCC). The AIE is challenging to treat in climate models as atmospheric aerosol has a range of sources, the magnitudes of which are quite uncertain. They also undergo a series of processing steps in the atmosphere, which can change their properties; affecting both their lifetime and their ability to interact with clouds. These processing steps are difficult to represent in climate models and this complexity contributes to the large range of estimates.

As the aerosol indirect effect (AIE) is potentially large, but very uncertain, it is important to try to understand where this uncertainty arises. This has been a focus of Ken Carslaw’s research group for the past four years where a new collaboration between aerosol scientists and a statistician has resulted in some very long meetings, a new approach to uncertainty analysis, and the first study that has identified and quantified the factors that contribute to uncertainty in model estimates of the AIE.

I should clarify that Carslaw just considered parametric uncertainty, this is the uncertainty associated with inputs to the model, e.g. the magnitude of the emissions or uncertain values used within parameterisations. There are other types of model uncertainty, e.g. structural uncertainty, that were not considered in this study. Parametric uncertainty is, however, intrinsic to all climate models, so it is an important starting point.

The first step was to choose which parameters to focus on. The team did this by talking with other scientists to identify which input parameters everyone felt were most uncertain; together they estimated the maximum, minimum and median value for each parameter. They identified 28 uncertain parameters in total; these can be grouped into three categories:

  • Natural emissions (e.g. volcanic emissions, marine sea spray emissions), 6 parameters.
  • Anthropogenic (human-caused) emissions (e.g. fossil fuels emissions, biofuel emissions), 8 parameters.
  • Process parameters used within the aerosol microphysics (e.g. the rate of aerosol aging, or the wet deposition parameter), 14 parameters.

The contribution of each parameter to the uncertainty in the AIE calculation can be found using a statistical technique called Monte Carlo analysis, but to perform Monte Carlo sampling on 28 uncertain parameters one would need to run tens of hundreds of model simulations, which isn’t possible with a complex model. To avoid this, Carslaw ran a few hundred simulations and used a statistical emulator to carry out the Monte Carlo sampling much faster. The emulator is a statistical package that “learns” from the output of the computer model, it can be used to interpolate from the hundreds of runs performed to the thousands of runs needed for the statistical analysis.

Schematic showing the methodology used by Carslaw to perform a sensitivity analysis on the first aerosol indirect effect (AIE). (Figure courtesy of Lindsay Lee).

Schematic showing the methodology used by Carslaw to perform a sensitivity analysis on the first aerosol indirect effect (AIE). (Figure courtesy of Lindsay Lee).

Carslaw found that by varying the values of the uncertain parameters, the model produced a range of estimates of the strength of the AIE forcing that was similar to, but slightly smaller than, the range of values estimated by the multi-model estimate from the IPCC. Surprisingly 45% of the uncertainty was found to be due to uncertainty in natural emissions, 34% was due to uncertainty in anthropogenic emissions and the rest due to uncertainty in process parameters.

Caption: Magnitude and sources of uncertainty in the model estimate of the first aerosol indirect forcing. (Credit: Carslaw et al, 2013)

Caption: Magnitude and sources of uncertainty in the model estimate of the first aerosol indirect forcing. (Credit: Carslaw et al, 2013)

Although the forcing is caused by anthropogenic emissions, the amount of natural emissions has a large effect on how sensitive the climate is to these anthropogenic emissions: the natural emissions don’t produce the forcing but they contribute a lot to the uncertainty in the forcing.

This effect arises because the relationship between aerosol emissions and cloud brightness is not linear; instead it is curved with higher sensitivity of cloud brightness to emissions when emissions are low (as they were in the pre-industrial atmosphere). This means that in the clean pre-industrial atmosphere a change in the amount of natural aerosol emissions has a large effect on the cloud brightness: when natural emissions are small, the initial cloud brightness (albedo) is low and any anthropogenic emissions have a big impact on cloud brightness, so the calculated forcing is larger.

Schematic explaining why the calculation of the first aerosol indirect forcing is sensitive to the magnitude of the natural aerosol emissions.  (Credit: Kirsty Pringle).

Schematic explaining why the calculation of the first aerosol indirect forcing is sensitive to the magnitude of the natural aerosol emissions. (Credit: Kirsty Pringle).

This sensitivity to the natural aerosol emissions is important as it is very difficult to constrain estimates of natural aerosol emissions as measurements taken in today’s atmosphere are almost always affected by anthropogenic emissions. This means that some of the uncertainty in the estimates of the first aerosol indirect effect may be irreducible, but it will still need to be considered in future estimates of warming due to greenhouse gases.

By Kirsty Pringle, Research Fellow, School of Earth and Environment, University of Leeds

 References

Carslaw, K.S., et al.: Large contribution of natural aerosolos to uncertainty in indirect forcing, Nature, 503, 67-71, 2013

Lee, L. A., et al.: The magnitude and causes of uncertainty in global model simulations of cloud condensation nuclei, Atmos. Chem. Phys., 13, 8879-8914, 2013

Lee, L. A., et al.: Emulation of a complex global aerosol model to quantify sensitivity to uncertain parameters, Atmos. Chem. Phys., 11, 12253-12273, 2011

 

GeoLog regularly brings readers information about recent research in the geosciences as well as updates on the EGU’s activities. Part of what makes GeoLog a great read is the variety that guest posts add to our regular features, and we welcome contributions from scientists, students and professionals in the Earth, planetary and space sciences. If you want to report on a recent Earth science event, conferences or fieldwork, comment on the latest geoscientific developments or highlight recently published findings in peer-reviewed journals, like Kirsty has done here, then we welcome your contribution. If you’ve got a great idea, why not submit a post?

 

Showcase your film at GeoCinema at the General Assembly!

Every year, we showcase a great selection of geoscience films at the EGU General Assembly and after five successful years we will again be running GeoCinema in 2015. If you’ve shadowed a scientist in the lab, filmed fantastic spectacles in the field, or have produced an educational feature on the Earth, planetary or space sciences, we want to hear from you.

GeoCinema features short clips and longer films related to the geosciences, and from animations to interviews, all films are welcome. If you would like to contribute to this popular event, please fill out the submission form by 31 December 2014.

To get a feel for what we have screened in previous years, take a look at the online archive, with films that explore all facets of geoscience – from ocean depths to outer space.

Suitable films will be screened at the GeoCinema room during the EGU 2015 General Assembly in Vienna (12–17 April 2014). Note that you must be able to provide us with the film on DVD and you must have appropriate permission to show the feature in a public venue. Films must be in English or have subtitles in English, since it is the language of the conference. Multiple submissions from the same person are welcome.

For more information, please send us an email or get in touch with our Communications Officer Laura Roberts.

GeoCinema1

Imaggeo on Mondays: Painted Hills after the storm.

The geological record preserved at John Day Fossil beds, in Oregon, USA, is very special. Rarely can you study a continuous succession through changing climates quite like you can at this National Park in the USA. It is a treasure trove of some 60,000 plant and animal fossil specimens that were preserved over a period of 40 million years during the Cenozoic era (which began 66 million years ago).

The geography of Oregon 45 million years ago was significantly different to present. The region received a whopping 1350 mm of annual rainfall (compare this to the approximate annual rainfall in London of 500 mm or 300 mm in Madrid) as the Cascades Mountain range had not yet formed, meaning moisture from the Pacific was not blocked. In addition, the climate was much warmer and Oregon was primarily subtropical, dominated by broad-leaved evergreen subtropical forests.

Then, 12 million years later temperatures began to lower and the climate changed from subtropical to temperate. Deciduous forests became abundant at low altitudes, whilst at higher altitudes coniferous forests dominated the landscape. Imagine a setting not dissimilar to the present day eastern USA. There were a number of active volcanic centres in the area at the time and ash, lava, and volcanic mudflows frequently spread over the region. The volcanicity culminated over a period of 11 million years during which the Columbia River Basalt Group, an extensive large igneous province, was emplaced. The current landscape was shaped during the most recent Ice Age as glaciers from the Cascade Mountains eroded their way towards the low lying terrain in central Oregon.

Painted Hills. (Credit: Daniele Penna, via imaggeo.egu.eu)

Painted Hills. (Credit: Daniele Penna, via imaggeo.egu.eu)

Photographs don’t really come any more dramatic than this one. “The conditions were prefect; I was very lucky”, says Daniele Penna, who photographed the striking Painted Hills Unit within the National Park , “I visited the area right after a storm, when the sky was partially clearing, leaving space for some light that contrasted with the remaining dark clouds in the background. The combination of atmospheric conditions made me enjoy this stunning place even more and gave me the opportunity to capture several striking images.”

During his PhD in hydrology, Daniele spent a few months at the Oregon State University, in 2007. He took the advantage of his time there by exploring the diverse natural beauties that Oregon boasts.

If, like Daniele, you are interested in photography he has some top tips for achieving a photograph as remarkable as this week’s Imaggeo On Mondays image: “Switching from a wide angle to a moderate telephoto lens can give free rein to the photographer’s creativity in playing with the colors, juxtaposed intersecting lines and interlacing forms. An extremely vivid image emerges as a result of the contrast of light and dark, yellow and red colours, and the contrasting curved and straight lines at Painted Hills. The best time for capturing images that make an impact is reserved for the late afternoon in summer and during late spring when the local park ranger service provides information over the telephone on which species are in bloom.”

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

GeoTalk: Beate Humberset

GeoTalk: Beate Humberset

In this edition of Geotalk, the regular feature were we highlight the work and achievements of early career researchers, we are talking to Beate Humberset, the winner of the Outstanding Student Poster (OSP) Award for the Solar- Terrestrial Sciences Division (ST) in 2013. In addition, Beate is the Young Scientist Representative for the ST Division so we will also touch upon her responsibilities in this role.

Let me introduce Beate, pictured here with the space shuttle. (Credit: Beate Humberset).

Let me introduce Beate, pictured here with the space shuttle. (Credit: Beate Humberset).

First, could you introduce yourself Beate and tell us what it is you’ve been investigating as part of your PhD so far?

I am a physicist and Ph.D. candidate at the Birkeland Centre for Space Science at the University of Bergen. I come from the West Coast of Norway, from a place called Ørsta in Sunnmøre, that the last few years has started to be known for its majestic peaks which support great mountain hiking and off-piste skiing. This was also the place where my interest in physics started, when I discovered it at high school; since then my interest in the subject has grown driven by curiosity and an interest in understanding natural phenomenon. I moved to Bergen, the next biggest city in Norway, to study physics. Whilst studying for my bachelor and master degrees I worked at Bergen Science Centre and got interested in science outreach. In April this year I moved back after a memorable 9 months research stay as a Fulbright Scholar at the Johns Hopkins University, Applied Physics Laboratory outside Washington DC.

My research is on understanding and describing the dynamic response of Earth’s complex coupling to space. The motivation for this study is that much of our understanding of the coupling between the Earth and the near space comes from empirical modelling of various electrodynamic parameters, such as Birkeland currents. Birkeland currents are electrical currents flowing along the magnetic field between near space and Earth’s polar atmosphere. They are often assumed to be two fairly static upward and downward current sheets encircling Earth’s magnetic poles. This is a model that in many cases works well, but in reality the Birkeland currents are highly dynamic, which is something we do not understand as well as we would like to.

The main reason for this shortcoming is that most means of making measurements in space rely on single satellites, which are in constant motion, meaning that it is difficult to decide if the phenomenona we measure have changed during our measurements and how it has changed. So far, during my PhD project I have mostly been working to defeat this shortcoming and describe the dynamic behaviour of the energy transport into Earth’s polar atmosphere by finding the characteristic behaviour of auroral emissions.

After EGU 2013, you received an Outstanding Student Poster Award for your work on finding the characteristics of pulsating aurora. This certainly sounds like a challenging project! Could you tell us a bit more about pulsating aurora and why characterising them is important?

The aurora are the result of the energy in the solar wind entering Earth’s magnetic field. Some of this energy causes charged particles to precipitate in an oval around Earth’s magnetic poles. When they reach altitudes of 500 to 90 km they collide with the atmosphere, which emits the light that we see as aurora. Therefore, the auroras are a mirror of the invisible energisation processes that happens further from Earth and are a great source of knowledge. Different processes lead to different kinds of aurora. The pulsating aurora are a phenomenona which change rapidly both temporally and spatially and which recently have been shown to be much more widespread and persistent than what was thought before, and thus are more important to the near Earth space. However, it is still debated what the underlying processes that generate them are, and also if there are more than one type of pulsating aurora. The definition of pulsating aurora is broad and covers patches, arcs and arc segments from tens to several tens of km that have a periodic, quasi-periodic or variable temporal variation from 1 s to tens of seconds. You can normally see them appear after the bright discrete aurora has passed, as quite a messy sight of dim patches of different shapes, all pulsating in a variable manner and different from each other. We have therefore investigated the spatiotemporal characteristics of pulsating auroral patches to provide better observational constrains for the various proposed mechanisms.

Aurora seen from above: This video was taken from the International space station. It shows the discrete aurora that most of us are familiar with, and if you look carefully to the south of that (left in the movie) we can also see the dim pulsating aurora. Video credit: NASA. Visit the NASA website for more information about the features seen in the video.

Say I wanted to find the characteristics of pulsating aurora, how might I go about it?

First you have an excellent tool in all-sky imagers than can capture about 1000 by 1000 km of the night sky where the aurora is emitted. You can think of an all-sky movie as several multipoint measurements of the aurora meaning that you have full control over how it changes in space and time. In this way you can describe its shape, persistency, temporal behavior, spatial behavior and how they are coupled and vary with the energy being dissipated. This can again be used in the work to untangle the process or possibly several processes that together or in different locations cause the pulsating aurora.

Beate presenting her work at the General Aseembly. (Credit: Beate Humberset).

Beate presenting her work at the General Aseembly. (Credit: Beate Humberset).

What inspired you to attend the General Assembly (GA) in 2013 and present your work there?

It has been a tradition in our research group that if master students show good progress in their project, they get to travel to the GA in Vienna to present their research and experience how it is to be at a large conference and is shown a different side of what it is like to be a researcher. I was there for the first time in 2009, which made a huge impression on me. I was therefore glad I had the funding to travel there for the 2013 GA. In the few years I’ve had the chance to attend the GA, I have witnessed how the conference, in addition to be a good place where graduate student can be heard, has also become a place where useful workshops and designated mingling areas have brought attention to young and early career scientists.

What was your highlight of the 2013 General Assembly?

I must say it has been a while, but I remember that I found it fun to present my poster and got a few very inspiring discussions going thanks to interested senior scientists stopping by.

What comes next for you in terms of your research, but also going forward in your career?

In the future I will continue research on how and if abrupt changes in the polarity of the East-West component of the interplanetary magnetic field, (which is known to not change the total energy input to Earth), influences the transport of electromagnetic energy to the atmosphere. It would be great fun to continue research after my PhD project has ended, but I have an open mind. In my opinion, being a physicist, there are lots of interesting possibilities career wise.

What does your role as the Young Scientist Representative for ST division involve?

I am the first Young Scientist (YS) Representative in the ST division, starting this year, and so have had the opportunity to shape what the role involves. Basically it is to ensure that interests of the YS in Solar Terrestrial (ST) sciences are taken care of in the EGU, especially during the GA. Through meetings with other division’s YS representatives we share experiences and make suggestions of how the EGU can improve the representation of the YS community, for example: how poster session can be better promoted, how to improve the short courses at the GA and highlighted the importance of travel support and awards. For the 2015 GA I am planning a short course for the ST students and early career scientists and an informal get together to improve networking and hopefully get some questions, comments or ideas to work on for next year.

If you are planning on coming along to the General Assembly in Vienna next April, once the programme has been finalised, head over to the website were sessions, short courses and meetings that have a strong YS focus will be highlighted. You can also check the website for more details on how you can participate in the Outstanding Student Poster Award , which is open to students of all levels(undergraduate through to PhD) participating at the GA. If you’d like more information on how to apply for financial support to travel to Vienna and present your research, this blog post summarises everything you need to know; but hurry, the deadline for abstract submission is the 28th November 2014.

Finally, if Beate’s interview has inspired you to become more involved with the EGU, there are plenty of volunteering opportunities and there are two divisions currently looking for YS Representatives, could you take on the job?

Follow

Get every new post on this blog delivered to your Inbox.

Join other followers: