Testing, testing

June 17, 2016, 9:27 a.m.

Regression testing, unit tests, Test driven development, automated testing, defensive programming. Despite years in research, these were not terms I had heard, not from my supervisors or peers, not at conferences, and certainly not in journals or other scientific forums. Yet after working for a few months in UCL's RITS Research Software Development team, a group that emphasises software development to improve Science, I have woken up to the reality that software developers have known for a long time:

A Research Software Developer in London

June 10, 2016, 9:04 a.m.

It has been a while since my last post, and a lot has changed. My time at the Department of Geosciences in the University of Oslo as a postdoc research fellow sadly came to a close; it was hard to move on and leave behind my friends and Norwegian life. I have many great memories of Norway, and hope it won't be too long before I return. Perhaps that will even be my last postdoc and the end of my professionally active research career. After 3 postdoc contracts I would say that is a bitter-sweet thought, as there are many pros and many cons of being a postdoc-probably a mix which you won't find in any other job-but 6 years of that lifestyle may be my limit. (And it is certainly not a lifestyle that is particularly complimentary to married-life!)

Monsoon madness: Open Science the cure?

Feb. 24, 2016, 1:55 p.m.

This story starts around 2012, when I received a request to review a paper on solar activity and the Indian Monsoon from the journal Advances in Space Research. I have reviewed many such papers (perhaps ~20) so this was nothing unusual. A quick read revealed some tortured data, abused statistics, and nonsense prose. All in all a fairly typical manuscript in its field. A version of it can be found at ArXiv. (To get some idea of why I say this is a typical paper, have a look at Barrie Pittocks 1978 piece "Solar Cycles and the Weather: Successful Experiments in Autosuggestion?", although it is, unfortunately, pay-walled.)

Old Science invigorated by Open Science

Feb. 4, 2016, 4:19 p.m.

Last November someone e-mailed me a strange request, they wanted to use a method from a paper I wrote in 2013. Shocking I know. I had included in the paper a link to some IDL code meant to reproduce the figures, of course, it was already broken. It had aged badly, inaccessible a full 2 years ahead of Jeff Rotheberg's prediction ("digital information lasts forever — or five years, whichever comes first"). After digging through my file system and recovering the old script I had the feeling that if the link not been broken it would probably not have been of much help. Needless to say, at the time I wrote the paper I thought the approach I took was great. I didn't know much about coding then, and I hadn't heard of version control either. Although, to be fair, no one in the field I was working in talked about these issues or showed much interest in code. In fact, asking to see peoples code was a good way to loose friends ("You don't trust me?" or "You want to steal my work?"). A few years on, and I now know enough to see that approach I took was not terribly helpful if the aim was to create reproducible science.

New book launched: Earth's climate response to a changing Sun

Nov. 10, 2015, 10:29 a.m.

Over the past 4 years, more than 80 scientists from 20 countries across Europe have come together, in an EU-funded COST project, called TOSCA. These scientists came from a whole range of different backgrounds, including Solar and Space Physicists, Climatologists and Atmospheric Scientists, and everyone in-between. Over that time, they produced much on the subject of natural climate forcing mechanisms, including many meetings, workshops, training schools, short-term research grants, original research studies, synthesis reports, special journal editions and outreach materials. But the crown jewel of the collaboration is their newly-launched book, titled 'Earth's climate response to a changing Sun'.

Can PERICLES stop data fading into the ether?

Nov. 6, 2015, 1:35 p.m.

I recently attended a one-day evaluation workshop for the PERCICLES Project as an invited reviewer. PERICLES (#periclesfp7) stands for Promoting and Enhancing Reuse of Information throughout the Content Lifecycle taking account of Evolving Semantics. The aim was to give feedback and suggestions on the projects progress and how they could meet their goals. The meeting was hosted at the Belgium Institute for Space Aeronomy, in Brussels, and it took place on 29th October, 2015.

Research trip on Hvar, Sep. 2015

Sept. 22, 2015, 8:44 a.m.

I have just returned from a research trip in Croatia (8--19th September), with my friend and long-time collaborator Dr. Jasa Calogovic. Every now-and-then Jasa and I manage to have some schedule overlap for a collaborative trip: This time, he kindly put my wife and I up the beautiful Hvar Observatory, which is built around (and inside of) a Napoleonic Fortress.

Scientist, opine thyself!

Aug. 12, 2015, 8:45 a.m.

Scientists as advocates. Should Scientists step outside of their archetypal roles as dispassionate investigators of the physical world, taking time away from asking questions of how things are, and instead offer opinions on how they think things should be? Is this a moral obligation? Or is it simply dangerous irresponsible territory beyond their purview? Should we just be good little investigators and know our place? Or in fact, are these the wrong questions to ask, devoid of the nuance and perhaps ironically implying that even needing to ask it begs only the answer, 'when you grow up'.

A conversational climate: Science, the Sun, and global warming and global civilisation

July 23, 2015, 4:16 p.m.

This post differs from my usual fare as it follows the format of an FAQ of sorts. For me, it is representative of a conversation I have had a number of times now. I have found that the points raised are usually asked of me by people of a right-leaning political persuasion with some background knowledge of climate. But first some brief back-story to explain how this came about...

A modern myth: the solar cycle affects human fertility and lifespan

June 15, 2015, 5:31 a.m.

Earlier this year some colleagues emailed around the latest paper claiming a strong causal relationship between the solar cycle and some Earth-bound phenomena, in this case the fertility and lifetime of people born during different phases of the solar cycle in Norway from historic records. Usually, such studies are cause for some mirth, and make for useful examples of common statistical problems, see for example the relationship between cosmic rays and car crashes, or heart attacks and the solar cycle. The study was carried out by a group of Norwegian researchers and published in the prestigious Proceedings of the Royal Society B, and could be considered to be a confirmation study as it notes that it is supported by earlier findings.

Helping at the Software Carpentry course Oslo June 2--3rd

June 5, 2015, 8:12 a.m.

Helping at the Software Carpentry course, June 2--3rd Oslo run by Lex Nederbragt and Karin Lagesen, certainly gave me a lot to consider. The two-day course taught novice users Bash, Git, and Python (Jupyter Notebook). Three invaluable and complimentary tools which are the centre of my own work-flow. I was excited to see how people were introduced to these tools and the Software Carpentry teaching methods. The collaborative Git-based lesson materials are especially nice, and I can only hope this teaching model spreads far and wide. I certainty appreciated running through the course material, and in particular I don't remember seeing a clearer introduction to Git and Bash.

North Atlantic Saharan dust outbreaks

May 29, 2015, 9:48 p.m.

Between 2010 and 2014 I was a postdoc at the Instituto de Astrofisica de Canarias on the island of Tenerife of the Canary Archipelago. From time to time, we would experience extreme climate events known locally as Calima. These are periods where mineral dust from the Sahara, exported in discrete and often-dramatic outbreak events, are suspended in the air. The Calima conditions last from hours to days. During this time dramatic changes occur in the local climate.

OSS: Open Scientific Standard

May 15, 2015, 12:57 p.m.

As the Open Science community grows and the zoo of Open Science platforms expand, it is becoming clear that the future of Open Science will not be in the dominance of one perfect system with killer tools, but rather numerous systems, much as it is today, focused on discipline or purpose specific applications. But there is a way to ensure a deep-level of compatibility between these burgeoning systems, and ensure that the Open Science future is one of interconnectivity: the Open Scientific Standard (OSS) format.

Changes in carbon monoxide pollution 2000–2012

May 8, 2015, 9:36 a.m.

Carbon monoxide (CO) is one of 6 major air pollutants regulated by countries such as the USA. It is a product of combustion like its closely related cousin carbon dioxide, however, unlike carbon dioxide, it is formed by incomplete or inefficient combustion. While carbon dioxide is an important greenhouse gas contributing to human-induced warming of the globe, carbon monoxide does not contribute to warming. Unlike carbon dioxide however, it has the potential to significantly influence atmospheric chemistry.

Open: evolution and revolution in science

May 6, 2015, 8:29 a.m.

The first academic journal was created by Henry Oldenburg (1619--1677), first Secretary of the Royal Society. Rather than wait years for scientists to publish their findings in books, Oldenburg wanted to accelerate the scientific process by soliciting short letters from scientists. He collected these letters and published them as the first journal, Philosophical Transactions of the Royal Society, in 1665. He encouraged submissions from all who had knowledge to share, even people without formal training, and he encouraged the use of common language (as opposed to Latin, which was previously used for scientific communication) so the content could be accessible to a wider audience (see Science as an Open Enterprise, Royal Society Report).

Selected peer-reviewed Articles

Laken, B.A. & Vaquero. J.M. (2014), An early clear sky record from Eastern Spain: 1837-1879, International Journal of Climatology, doi: 10.1002/joc.4033.
We present and analyse a rare, long-term time series of clear sky observations recorded by Priest Bodi y Congros, from the town of Carcaxient, in Eastern Spain. These data cover the period of 1837-1879: a time when meteorological observations over the Iberian Peninsula were notoriously scarce. The records were recovered from a surviving partial copy of an original manuscript, as part of the Salva-Sinobas project, in order to improve the availability of early meteorological data records over Spain. We have contrasted these data with satellite-observations of cloud cover over from the International Satellite Cloud Climatology Project, using the satellite data to investigate the diurnal, seasonal, and long-term properties of cloud cover and clear sky conditions over the Carcaxient area.

Portrait of Priest Salvador Bodi y Congros

In particular, we find the seasonal variability of clear sky conditions compares well, indicating the records of Bodi y Congro were reliable. However, a direct long-term comparison of the records was not possible as the datasets were too dissimilar.

Access the full article from Wiley online library or contact me directly for a copy.

View the Salva Sinobas project, to which this paper relates.

Laken, B.A. & Shahbaz, T. (2014), Satellite-detected Carbon Monoxide pollution during 2000-2012: Examining global trends and also regional anthropogenic periods over China, the EU and the USA, Climate, 2, 1-16, doi:10.3390/cli2010001
In this paper, we test if any statistically significant periodicities are detectable in carbon monoxide emissions over China, the European Union, and the United States of America. To do this, we performed a period analysis using 10 years of daily-averaged data, from the Measurements Of Pollution In The Troposphere (MOPITT) instrument. Besides a seasonal period, we found no clearly detectable periods at any timescale with the exception of a strong signal at 2.28 days.

Changes in measurement frequency due to sensor path accounts for a small regionally-averaged periodicity observed in the pollution data.

This period was observed over all tested regions and persisted when larger (hemisphere-wide) regions were considered. However, rather than resulting from a physical variation in carbon monoxide, it resulted from day-to-day changes in the area covered by MOPITT on-board its polar-orbiting satellite platform. We also examined linear trends over the dataset, and found that MOPITT identifies several centers of increasing carbon monoxide concentration-the largest being over China-although globally MOPITT reports a significant decrease in carbon monoxide has occurred over the past decade.

Freely access the full article at MDPIs website.Additionally, read my blog article on this topic at the RGS CCRG blog.

Laken, B.A. & Calogovic, J. (2013) Does the diurnal temperature range respond to changes in the cosmic ray flux?, Environ. Res. Lett., 8, 045018, doi:10.1088/1748-9326/8/4/045018.
Recent studies have suggested that measurements of the diurnal temperature range (DTR) over Europe may provide evidence of a long-hypothesized link between the cosmic ray (CR) flux and cloud cover. Such propositions are interesting, as previous investigations of CR-cloud links are limited by data issues including long-term reliability and view-angle artifacts in satellite-based cloud measurements. Consequently, the DTR presents a further independent opportunity for assessment. Claims have been made that during infrequent high-magnitude increases (ground level enhancements, GLE) and decreases (Forbush decreases, Fd) in the CR flux significant anti-correlated DTR changes may be observed, and the magnitude of the DTR deviations increases with the size of the CR disturbance.

Photo credit ep_jhu.

If confirmed this may have important consequences for the estimation of natural climate forcing. We analyze these claims, and conclude that no statistically significant fluctuations in DTR (p < 0.05) are observed. Using detailed Monte Carlo significance testing we show that past claims to the contrary result from a methodological error in estimating significance connected to the effects of sub-sampling.

Freely access the full article at Environmental Research Letters journal.

View a blog article on this topic at the Climate Change Research Group blog of the Royal Geographical Society.

Laken, B.A. & Calogovic, J. (2013) Composite analysis with Monte Carlo methods: an example with cosmic rays and clouds, J. Space Weather Space Clim., 3(A29), doi:10.1051/swsc/2013051.
The composite (superposed epoch) analysis technique has been frequently employed to examine a hypothesized link between solar activity and the Earths atmosphere, often through an investigation of Forbush decrease (Fd) events (sudden high-magnitude decreases in the flux cosmic rays impinging on the upper-atmosphere lasting up to several days). This technique is useful for isolating low-amplitude signals within data where background variability would otherwise obscure detection. The application of composite analyses to investigate the possible impacts of Fd events involves a statistical examination of time-dependent atmospheric responses to Fds often from aerosol and/or cloud datasets.

We have explored how variability changes with the area and sample size considered, altering the detectability of a signal in composites accordingly.

Despite the publication of numerous results within this field, clear conclusions have yet to be drawn and much ambiguity and disagreement still remain. In this paper, we argue that the conflicting findings of composite studies within this field relate to methodological differences in the manner in which the composites have been constructed and analyzed. Working from an example, we show how a composite may be objectively constructed to maximize signal detection, robustly identify statistical significance, and quantify the lower-limit uncertainty related to hypothesis testing. Additionally, we also demonstrate how a seemingly significant false positive may be obtained from non-significant data by minor alterations to methodological approaches.

Freely access the full article from the journal of SWSC journal

Laken B.A., Parviainen H., Palle E., & Shahbaz T. (2013) Saharan mineral dust outbreaks observed over the North Atlantic island of La Palma in summertime between 1984 and 2012, Q.J. Roy. Met. Soc., 140(680), 1058-1068 doi:10.1002/qj.2170
We estimate the frequency of Saharan mineral dust outbreak events observed over the North Atlantic island of La Palma based on in situ nightly atmospheric extinction measurements recorded almost continuously since 1984 by the Carlsberg Meridian Telescope at the Roque de los Muchachos observatory. The outbreak frequency shows a well-defined seasonal peak in the months of July to September, during which time the occurrence of Saharan dust events (SDEs) is approximately 28 ± 6%. We find considerable year-to-year variability in the summertime SDE frequency, observing a steady reduction between 1984 and 1997, followed by a period of relative mean stability from 1999 to 2012.

A large dust event in March 2003, typical of the kind that regularly impacts the Canary Islands.

We investigated changes in the atmospheric extinction of the SDEs as an indicator of strength of the episodes and found that this parameter approximately follows the SDE frequency, however, instrumental limitations prevented us from deriving precise conclusions regarding their long-term changes. A lagged correlation analysis between SDE properties and the El Niño–Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Sahel rainfall index (SRI) was performed. We found that 55 ± 4% of the year-to-year variations in July–September SDE frequency may be reproduced by a lagged relationship to the NAO conditions during the preceding October–December period, and 45 ± 4% may be reproduced by a negative correlation to the SRI during the preceding February–April period. Based on these relationships it may be possible to obtain an approximate indication of the strength of the upcoming summertime dust season over the North Atlantic around half a year in advance.

You can access the article from the Quarterly Journal of the Royal Meteorological Society.

This article made the news.I also explained my findings for a general audience in a post for the Climate Change Research Group blog of the Royal Geographical Society.

Laken B.A., Palle E., Calogovic J., & Dunne E. (2012) A cosmic ray-climate link and cloud observations, J. Space Weather Space Clim., 2, A18, doi:10.10015/swsc/2012018.
Despite over 35 years of constant satellite-based measurements of cloud, reliable evidence of a long-hypothesized link between changes in solar activity and Earth’s cloud cover remains elusive. This work examines evidence of a cosmic ray cloud link from a range of sources, including satellite-based cloud measurements and long-term ground-based climatological measurements. The satellite-based studies can be divided into two categories: (1) monthly to decadal timescale analysis and (2) daily timescale epoch-superpositional (composite) analysis. The latter analyses frequently focus on sudden high-magnitude reductions in the cosmic ray flux known as Forbush decrease events. At present, two long-term independent global satellite cloud datasets are available (ISCCP and MODIS).

Low (red) and high (blue) level cloud cover seen by satellites show an (inverse) artificial relationship. Just one of the many issues that come to bear on a proposed cosmic ray cloud link.

Although the differences between them are considerable, neither shows evidence of a solar-cloud link at either long or short timescales. Furthermore, reports of observed correlations between solar activity and cloud over the 1983–1995 period are attributed to the chance agreement between solar changes and artificially induced cloud trends. It is possible that the satellite cloud datasets and analysis methods may simply be too insensitive to detect a small solar signal. Evidence from ground-based studies suggests that some weak but statistically significant cosmic ray-cloud relationships may exist at regional scales, involving mechanisms related to the global electric circuit. However, a poor understanding of these mechanisms and their effects on cloud makes the net impacts of such links uncertain. Regardless of this, it is clear that there is no robust evidence of a widespread link between the cosmic ray flux and clouds.

You can freely access this article from the journal of SWSC.

I also wrote a post on this subject for a general audience, which you can find here, hosted on the Royal Geographical Societies Climate Change Research Group blog.

Numerous articles of interest have appeared related to this publication, such as this one at RealClimate.

Laken B.A., & Palle E. (2012) Understanding sudden changes in cloud amount: the Southern Annular Mode and South American weather fluctuations, J. Geophys. Res., 117, D13103,doi:10.1029/2012JD017626.
This work investigates the cause and effects of extreme changes in synoptic-scale cloud cover operating at daily timescales using a variety of satellite-based and reanalysis data sets. It is found that the largest sudden increases detected in globally averaged cloud cover over the last ten years of satellite-based observations occur following positively correlated shifts in the phase of the Southern Annular Mode (SAM) index. The associated pressure anomalies are found to generate frontal cloud formation over large areas of the South American continent,

The largest regular daily increases in cloud as viewed by satellite.

increasing regional cloud cover by up to 20%; these changes are correlated to statistically significant reductions in local temperatures of approximately -2.5°C with a +1 day time lag, indicating the SAM index is associated with large scale weather fluctuations over South America.

Access the article from JGRs website±.

Laken B.A., Palle E., Kniveton D.R., Williams C., & Kilham D.A. (2012) Contrails developed under frontal influences of the North Atlantic, J. Geophys. Res., 117, D11201,doi:10.1029/2011JD017019.
Satellite imagery reveals a visually striking pattern of persistent line-shaped contrails located to the Northwest of the British Isles on 1 September 2007, just before sunrise. These contrails formed over the heavily trafficked eastbound North Atlantic Track (NAT) flight paths, as they intersected an area of prefrontal mixing. The high relative humidity with respect to ice within the prefrontal mixing zone allowed the contrails to persist, while the strictly regulated flight paths over the region account for their remarkable shapes. The positioning of the NAT flight paths to take advantage of the jet stream likely maximized regional contrail formation.

Around 600 contrails in this "outbreak" event. Their formation conditions, and their properties are explored in this paper.

An estimation of the outgoing top of the atmosphere long-wave (LW) flux from the CERES instrument shows that the contrails reduced the local instantaneous LW emissivity by 20.96 (±0.26) W/m2. This example demonstrates that for middle latitude regions, prefrontal mixing is an important factor governing the radiative influence of contrails. However, a full estimation of the radiative impact is not possible, as we cannot specify the amount of shortwave forcing caused by the persistence of the contrails into daytime moreover, several hours after formation the line-shaped contrails spread and overlapped with pre-existing cloud structures.

View this article on JGRs website.

Laken B.A., Palle E., & Miyahara H. (2012) A decade of the Moderate Resolution Imaging Spectroradiometer: is a solar-cloud link detectable?, J. Climate, 25, 4430-4440, doi:10.1175/JCLI-D-11-00306.1.
Based on the results of decadal correlation studies between the International Satellite Cloud Climatology Project-detected cloud anomalies and the galactic cosmic ray (GCR) flux, it has been suggested that a relationship exists between solar activity and cloud cover. If valid, such a relationship could have important implications for scientists’ understanding of recent climate change.

Locally significant correlations (±0.8) between cloud cover from MODIS and ENSO.

In this work, an analysis of the first decade of Moderate Resolution Imaging Spectroradiometer (MODIS)-detected cloud anomalies are presented, and the data at global and local geographical resolutions to total solar irradiance (TSI), GCR variations, and the multivariate El Niño-Southern Oscillation index are compared. The study identifies no statistically significant correlations between cloud anomalies and TSI/GCR variations, and concludes that solar-related variability is not a primary driver of monthly to annual MODIS cloud variability. The authors observe a net increase in cloud detected by MODIS over the past decade of ~0.58%, arising from a combination of a reduction in high- to midlevel cloud (-0.31%) and an increase in low-level cloud (0.89%); these long-term changes may be largely attributed to ENSO-induced cloud variability.

View this article in the Journal of Climate.

Laken B.A. & Calogovic J. (2011), Solar irradiance, cosmic rays and cloudiness over daily timescales, Geophys. Res. Lett., 38, L24811,doi:10.1029/2011GL049764.
Although over centennial and greater timescales solar variability may be one of the most influential climate forcing agents, the extent to which solar activity influences climate over shorter time periods is poorly understood. If a link exists between solar activity and climate, it is likely via a mechanism connected to one (or a combination) of the following parameters: total solar irradiance (TSI), ultraviolet (UV) spectral irradiance, or the galactic cosmic ray (GCR) flux. We present an analysis based around a superposed epoch (composite) approach focusing on the largest TSI increases and decreases (the latter occurring in both the presence and absence of appreciable GCR reductions) over daily timescales. Using these composites we test for the presence of a robust link between solar activity and cloud cover over large areas of the globe using rigorous statistical techniques.

Co-temporal variations in solar parameters make evaluating short-term solar–cloud links problematic. In this work, we went to great lengths to separate various solar parameters as much as possible, yet found no response in the available cloud data.

We find no evidence that widespread variations in cloud cover at any tropospheric level are significantly associated with changes in the TSI, GCR or UV flux, and further conclude that TSI or UV changes occurring during reductions in the GCR flux are not masking a solar-cloud response. However, we note the detectability of any potential links is strongly constrained by cloud variability.

View the article in GRL.

Note: For those especially interested in composite analysis material, I suggest looking at the 2013 (SWSC) on this page. If you are after a more general solar–climate material, then try the 2012 SWSC paper instead. Enjoy!

Laken, B.A., Kniveton D.R., & Wolfendale A.W. (2011) Forbush decreases, solar irradiance variations and anomalous cloud changes, J. Geophys. Res., 116, D09201, doi:10.1029/2010JD014900.

Changes in the galactic cosmic ray (GCR) flux due to variations in solar activity may provide an indirect connection between the Sun's and the Earth's climates. Epoch superpositional (composite) analyses of high-magnitude GCR fluctuations, known as Forbush decrease (FD) events, have been widely used to test this hypothesis, with varied results. This work provides new information regarding the interpretation of this approach, suggesting that FD events do not isolate the impacts of GCR variations from those of solar irradiance changes. On average, irradiance changes of ~0.4 W m-2 outside the atmosphere occur around 2 days in advance of FD-associated GCR decreases. Using this 2 day gap to separate the effects of irradiance variations from GCR variations on cloud cover, we demonstrate small, but statistically significant, anomalous cloud changes occurring only over areas of the Antarctic plateau in association with the irradiance changes, which previous workers had attributed to GCR variations. Further analysis of the sample shows that these cloud anomalies occurred primarily during polar darkness, precluding the possibility of a causal link to a direct total solar irradiance effect. This work suggests that previous FD-based studies may have ineffectively isolated the impacts of GCR variations on the Earth's atmosphere.

View the paper in JGR.

Laken B.A. & Kniveton D.R., (2011) Forbush Decreases and Antarctic cloud anomalies in the upper troposphere, J. Atmos. Sol. Terr. Phys., 73(2-3),371-367, doi:10.1016/j.jastp.2010.03.008

We demonstrate evidence that past composite based studies centred around the onset of Forbush decrease (FD) events may have improperly isolated the maximal galactic cosmic ray (GCR) decrease associated with the FD events. After an adjustment of the composite to account for such shortcomings we find indications of anomalous cloud cover decreases (of around 3%) located in the upper levels of the troposphere at high southern latitudes. These cloud changes are detectable after latitudinal averaging, suggesting the possibility of a second order relationship between the rate of GCR flux and cloud cover in this region. The maximal cloud change is observed in advance of the maximal GCR decrease; this implies that if the observed cloud changes bear a causal relationship to the rate of GCR flux, then cloud properties may be sensitive to changes in GCR conditions rather than the maximal deviations themselves.

Access the article at JASTP.

Laken B.A., Kniveton D.R., & Frogley M.F. (2010) Cosmic rays linked to rapid mid-latitude cloud changes, Atmos. Chem. Phys., 10, 10941-10948 doi:10.5194/acp-10-10941-2010

The effect of the Galactic Cosmic Ray (GCR) flux on Earth's climate is highly uncertain. Using a novel sampling approach based around observing periods of significant cloud changes, a statistically robust relationship is identified between short-term GCR flux changes and the most rapid mid-latitude (60°–30° N/S) cloud decreases operating over daily timescales; this signal is verified in surface level air temperature (SLAT) reanalysis data. A General Circulation Model (GCM) experiment is used to test the causal relationship of the observed cloud changes to the detected SLAT anomalies. Results indicate that the anomalous cloud changes were responsible for producing the observed SLAT changes, implying that if there is a causal relationship between significant decreases in the rate of GCR flux (~0.79 GU, where GU denotes a change of 1% of the 11-year solar cycle amplitude in four days) and decreases in cloud cover (~1.9 CU, where CU denotes a change of 1% cloud cover in four days), an increase in SLAT (~0.05 KU, where KU denotes a temperature change of 1 K in four days) can be expected. The influence of GCRs is clearly distinguishable from changes in solar irradiance and the interplanetary magnetic field. However, the results of the GCM experiment are found to be somewhat limited by the ability of the model to successfully reproduce observed cloud cover. These results provide perhaps the most compelling evidence presented thus far of a GCR-climate relationship. From this analysis we conclude that a GCR-climate relationship is governed by both short-term GCR changes and internal atmospheric precursor conditions.

Access the article at ACP.

Laken B.A., Wolfendale A.W., & Kniveton D.R. (2009) Cosmic ray decreases and changes in the liquid water cloud fraction over the oceans, Geophys. Res. Lett., 36, L23803, doi:10.1029/2009GL040961

Svensmark et al. (2009) have recently claimed that strong galactic cosmic ray (GCR) decreases during ‘Forbush Decrease (FD) events’ are followed by decreases in both the global liquid water cloud fraction (LCF) and other closely correlated atmospheric parameters. To test the validity of these findings we have concentrated on just one property, the MODIS LCF and examined two aspects: 1) The statistical chance that the decrease observed in the LCF is abnormal. 2) The likelihood of the observed delay (~5 to 9 days) being physically connected to the FD events. On both counts we conclude that LCF variations are unrelated to FD events: Both the pattern and timing of observed LCF changes are irreconcilable with current theoretical pathways. Additionally, a zonal analysis of LCF variations also offers no support to the claimed relationship, as the observed anomaly is not found to vary latitudinally in conjunction with cosmic ray intensity.

Access the article at GRL.

Thirty years of atmospheric extinction from telescopes of the North Atlantic Canary Archipelago

We examine thirty years of atmospheric extinction obtained from both stellar and solar telescope measurements, at ~ 2.4km above sea level, from the North Atlantic Canary Archipelago—an island chain located at approximately 28°N, around 100 km from the west coast of Africa. We also use data from three AERONET monitors, located at varying heights on one of the main islands, although these are only available over a shorter (<10 yr) period. The Canary Archipelago is regularly affected by dust intrusions into the local atmosphere as they intersect one of the primary export pathways of mineral dust from the Sahara. We have statistically distinguished the ? of ‘baseline’ and ‘dust-influenced’ conditions, by fitting normal–gamma mixture distributions to the observations using Markov Chain Monte Carlo methods, and then examined the seasonal and long-term characteristics of these data. The telescope data show that baseline conditions are usually stable at ?<0.1 (except during periods influenced by volcanic aerosols), and indicate the existence of a low-amplitude (? = 0.01) seasonal variation. During dust-influenced conditions ? regularly reaches values a factor of 2–6 times higher than normal. The majority of dust intrusions take place during the months of July–August, when they may occur 44 ± 15% of the time, predominantly at high-altitudes (with ~94.3 ± 1.6% of intrusions occurring ?2.4km). Whereas, during the months of November–May, dust intrusions occur far less frequently (~ 19 ± 7%), and are more common at lower altitudes—with intrusions at <2.4 km comprising ~ 79.5 ± 3.2% of all outbreaks. We find year-to-year variations in the frequency of dust-influenced conditions (of ~ 9%), but no long-term trend over the observed thirty-year period.

Early open-access version on Journal of Climate's website

Reports, books, and other publication types

Palle E., & Laken B.A. (2013) What do we really know about cloud changes over the past decades?, AIP Conference Proceedings. Vol. 1531., doi:10.1063/1.4804857

Clouds are a critical component of Earth’s climate system. Although satellite-based irradiance measurements are available over approximately the past 30 years, difficulties in measuring clouds means it is unclear how global cloud properties have changed over this period. From the International Satellite Cloud Climatology Project (ISCCP) and Moderate Resolution Imaging Spectroradiometer (MODIS) datasets we have examined the validity of long-term cloud changes. We find that for both datasets, low-level (>680mb) cloud changes are largely a reflection of higher-level (≥680mb) variations. Linear trends from ISCCP also suggest that the dataset contains considerable features of an artificial origin. Despite this, an examination of ISCCP in relation to the MODIS dataset shows that over the past ten years of overlapping measurements between 60°N–60°S both datasets have been in close agreement (r = 0.63, p = 7×10−4). Over this time total cloud cover has been relatively stable. Both ISCCP and MODIS datasets show a close correspondence to Sea Surface Temperatures (SST) over the Pacific region, providing a further independent validation of the datasets.

This work was presented at the International Radiation Symposium, 2012, in Berlin.

View proceedings at AIP.

Contributing Author in Boucher O. & Randall D. et al. (2013), The physical science basis, Chapter 7: Clouds and Aerosols, IPCC WGI Fifth Assessment Report.

Click to view Chapter 7 as a pdf (19mb).

Laken B.A., Calogovic J., Beer J., & Palle E. (2012) Interactive comment on 'Effects of cosmic ray decreases on cloud microphysics' by J. Svensmark et al. , Atmos. Chem. Phys. Discuss., 12, C962-C973

Interactive comment on ACPD site.


Welcome to the website of Benjamin Laken. Currently, Benjamin is a Research Software Developer at University College London.

Benjamin was born and raised in London, England in 1985. He attended the University of Sussex (England), graduating with a B.Sc.(hons.) in Geography in 2007. He obtained a Ph.D. in Physical Geography (also from Sussex University) in 2010, with the title 'Analyzing and modeling daily timescale anomalies associated with a link between galactic cosmic rays and clouds'. During his Ph.D. Benjamin was an Associate Tutor for several Physical Geography undergraduate courses involving Remote Sensing and Statistics.

After his Ph.D. Benjamin held two postdoctoral research fellow positions at the Instituto de Astrofisica de Canarias (Spain), between 2010 and 2014. During that time he developed research lines related to the nature, causes, and impacts of climate variability and change on the Earth system and humans. In 2014 Benjamin moved to a postdoctoral research fellow position at the University of Oslo (Norway), Department of Geophysics. Following this position he moved to London, UK.

"Please enjoy this website. I would love to hear any comments or questions you have, so please feel free to contact me. I hope that this website will grow as my research career develops, so check back for new material. You can also stay abreast of changes by following me on Twitter."