eocene – Cabot Institute for the Environment blog

Science and Sunflowers

Posted on August 7, 2017April 5, 2023 by janet.crompton

Sunflowerfest is an annual three-day festival of music and art held just outside Lisburn, Northern Ireland, priding itself on its family friendly atmosphere and sprawling spectrum of creative activities. Unlike the monster festivals that are held in other parts of the UK, in Northern Ireland our festivals are small (think a few thousand people, not a few hundred-thousand) with a strong focus on local talent. The perfect place for some experimental, creative science outreach…

In 2016, I contacted the organisers and floated the idea of a science outreach stall based upon my research and others in BRIDGE and the Cabot Institute. The idea, called Living Earth, was new, reasonably grand and completely untested. The response was a very enthusiastic “yes please!”

So, last year a squad of five outreachers (Alan Kennedy, Emily White and Michael Cooper of the Cabot Institute, plus Dewi Owen and Zuleika Gregory our puppeteers) arrived in blustery Northern Ireland and over the course of the festival recreated the entire history of Earth. 4.5 billion years in 3 days. With the help of punters at the festival, we built a 1.5 m diameter model of the Earth out of willow, foliage, recycled and craft materials. As the Earth was built, we recreated many of the major processes and events that shape it today, from the placement of the continents, the expansion of biomes and climate zones, the formation of the cryosphere and the destruction of the Anthropocene.

As well as this geological ‘Big Art Attack’, crafts and a puppet show entitled This Soup Tastes Funny! about the evolution of life were put on in the festival’s dedicated Kids Zone. Our puppets, Doug and Barry, had to travel back in time to the primordial soup and race through evolution in order to relive the first day of the festival. Five time periods, four puppet costume changes, asteroid impacts, crowd participation and even a song left the young audience both entertained, but also possibly very confused… That’s a lot of science to take on-board in 15 minutes!

We (and our marquee) got battered by wind, rain and the exhausting amount of activities we were juggling, including our recreational ‘time off’. However, we certainly offered something unique at the festival and left a positive impression with the organisers:

“Just to say THANK YOU to you and the crew for all the great things you did at Sunflowerfest. So appreciate everything you do and did. We would always welcome you back to do whatever you would like!” – Vanessa, Sunflowerfest Organiser

Now, I have quite an active imagination, so that last sentence was a dangerously open invitation… With 2017’s festival theme being ‘a parallel universe’, I thought something immersive on the theme of deep time would fit right in. The new plan was to build a time machine! Or in other words transform the inside of a marquee into a jungle, to show what Ireland would have been like during the hot Eocene period ~50 million years ago. As I wrote down a proposal for the festival application, this seemed like it would be reasonably straightforward compared to 2016. In hindsight, I misjudged that.

Logistically, constructing a jungle was only possible because my mum had recently had some trees in the garden felled and she also had several hedges needing cut back. A supply of logs and some waxy leafed laurel and bay that would hold their colour after cutting for the duration of the festival made a good, but somewhat bulky start. These were attached to the marquee ceiling and a heavy metal tripod to give us a central ‘tree’ and performance space to demonstrate some tectonic themed experiments. Ferns and other leafy plants were then dug up and temporarily housed in buckets to fill out the back of the tent and childhood toys added around the stall for the jungle fauna. Finally, a small speaker playing jungle sound effects was hidden up in the canopy to complete the experience.

Obviously, a hearty dose of imagination was required to convince yourself our locally sourced, temperate vegetation was an Eocene jungle, but luckily this year our stand was based entirely in the Kids Zone, where imagination is not in short supply. Ideally, I wanted to have a Superser heater in the back of the tent to raise the temperature to 35 °C, but doubted that would pass the risk assessment. We settled for having the ambient Northern Irish temperature, but luckily, we did have a few biblically heavy rain showers to give it a nice wet rainforest feel. It took three days of preparation, cutting, digging and replanting vegetation, and five hours of construction, but eventually we had the most eye-catching stand in the whole Kids Zone. It was pretty much the Eocene.

In our jungle, we had information about how Ireland has changed over the past billion years, a floating plate tectonics game and crafted fossils and jungle wildlife to decorate the stand, all of which kept us mostly run off our feet during our three-hour slots each day. Our flagship performance however, was a bicarbonate soda-vinegar erupting volcano, as ~50 million years ago Northern Ireland was at the centre of lots of volcanic activity, forming for example the Giant’s Causeway. Without a single trial run (we spent all of our preparation time building the jungle), our resident chemistry undergraduate, Oliver Feighan, carried out the experiment in front of an audience 40 strong. It was possibly the least explosive or inspiring volcano in the world. As the foam dribbled out the top of the bottle it was met with a slow and bemused round of applause. Those kids will definitely go on to be the environmental scientists of the future.

Creative outreach at big events may not always go quite to plan, it takes time and effort and you can sometimes bite off more than you can chew, but it’s a great way reframe the relevance of research in a totally different way, speak to a new audience (a very bohemian crowd, in the case of Sunflowerfest) and just do something fun. It’s not often families can experience palaeoclimate, tribal drumming circles and the Rubberbandits* all in one day. We ended up going on to run the globe building activity from 2016 at a further two events (you can see a highlight video of the almost finished piece here). Although kids and parents found 2017’s time machine a lot of fun and it looked surprisingly effective, unfortunately I don’t think I will have time or energy to ever recreate the Eocene again! However, while I may be leaving the Eocene in the past, I highly doubt this will be my last Sunflowerfest.

*Caution, likely explicit content

Blog post by Press Gang member Alan Kennedy.

How ancient warm periods can help predict future climate change

Posted on April 26, 2016April 6, 2023 by janet.crompton

Several more decades of increased carbon dioxide emissions could lead to melting ice sheets, mass extinctions and extreme weather becoming the norm. We can’t yet be certain of the exact impacts, but we can look to the past to predict the future.

We could start with the last time Earth experienced CO₂ levels comparable to those expected in the near future, a period 56m to 34m years ago known as the Eocene.

The Eocene began as a period of extreme warmth around 10m years after the final dinosaurs died. Alligators lived in the Canadian Arctic while palm trees grew along the East Antarctic coastline. Over time, the planet gradually cooled, until the Eocene was brought to a close with the formation of a large ice sheet on Antarctica.

During the Eocene, carbon dioxide (CO₂) concentrations in the atmosphere were much higher than today, with estimates usually ranging between 700 and 1,400 parts per million (ppm). As these values are similar to those anticipated by the end of this century (420 to 935ppm), scientists are increasingly using the Eocene to help predict future climate change.

We’re particularly interested in the link between carbon dioxide levels and global temperature, often referred to as “equilibrium climate sensitivity” – the temperature change that results from a doubling of atmospheric CO₂, once fast climate feedbacks (such as water vapour, clouds and sea ice) have had time to act.

To investigate climate sensitivity during the Eocene we generated new estimates of CO₂ throughout the period. Our study, written with colleagues from the Universities of Bristol, Cardiff and Southampton, is published in Nature.

Reconstruction of the 40m year old planktonic foraminifer Acarinina mcgowrani.
Richard Bizley (www.bizleyart.com) and Paul Pearson, Cardiff University, CC BY

As we can’t directly measure the Eocene’s carbon dioxide levels, we have to use “proxies” preserved within sedimentary rocks. Our study utilises planktonic foraminifera, tiny marine organisms which record the chemical composition of seawater in their shells. From these fossils we can figure out the acidity level of the ocean they lived in, which is in turn affected by the concentration of atmospheric CO₂.

We found that CO₂ levels approximately halved during the Eocene, from around 1,400ppm to roughly 770ppm, which explains most of the sea surface cooling that occurred during the period. This supports previously unsubstantiated theories that carbon dioxide was responsible for the extreme warmth of the early Eocene and that its decline was responsible for the subsequent cooling.

We then estimated global mean temperatures during the Eocene (again from proxies such as fossilised leaves or marine microfossils) and accounted for changes in vegetation, the position of the continents, and the lack of ice sheets. This yields a climate sensitivity value of 2.1°C to 4.6°C per doubling of CO₂. This is similar to that predicted for our own warm future (1.5 to 4.5°C per doubling of CO₂).
Our work reinforces previous findings which looked at sensitivity in more recent time intervals. It also gives us confidence that our Eocene-like future is well mapped out by current climate models.

Fossil foraminifera from Tanzania – their intricate shells capture details of the ocean 33-50m years ago.
Paul Pearson, Cardiff University, CC BY

Rich Pancost, a paleoclimate expert and co-author on both studies, explains: “Most importantly, the collective research into Earth history reveals that the climate can and has changed. And consequently, there is little doubt from our history that transforming fossil carbon underground into carbon dioxide in the air – as we are doing today – will significantly affect the climate we experience for the foreseeable future.”

Our work also has implications for other elements of the climate system. Specifically, what is the impact of higher CO₂ and a warmer climate upon the water cycle? A recent study investigating environmental change during the early Eocene – the warmest interval of the past 65m years – found an increase in global precipitation and evaporation rates and an increase in heat transport from the equator to the poles. The latter is consistent with leaf fossil evidence from the Arctic which suggests that high precipitation rates were common.

However, changes in the water cycle are likely to vary between regions. For example, low to mid latitudes likely became drier overall, but with more intense, seasonal rainfall events. Although very few studies have investigated the water cycle of the Eocene, understanding how this operates during past warm climates could provide insights into the mechanisms which will govern future changes.

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This blog was written by Cabot Institute member Gordon Inglis, Postdoctoral Research Associate in Organic Geochemistry, University of Bristol and Eleni Anagnostou, Postdoctoral Research Fellow, Ocean and Earth Science, University of Southampton

This article was originally published on The Conversation. Read the original article.

Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene–Oligocene transition

Posted on October 8, 2015April 13, 2023 by janet.crompton

Composite satellite image of what the Earth may have looked like prior to Antarctic
glaciation during the late Eocene (image by Alan Kennedy).

The Eocene-Oligocene Transition occurred approx. 34 million years ago and was one of the biggest climatic shifts since the end of the Cretaceous (with the extinction of the dinosaurs). The Earth dramatically cooled and the Antarctic ice sheet first formed, but the cause and nature of the cooling remain uncertain. Using a climate model, HadCM3L, we looked at the effect of ice sheet growth and palaeogeographical change (i.e. continental reconfiguration as Australia separated from Antarctica) on the Earth’s steady-state climate. We utilised four simulations: a late Eocene palaeogeography with and without an ice sheet and an early Oligocene palaeogeography with and without an ice sheet.

The formation of the Antarctic ice sheet causes a similar atmospheric response for both palaeogeographies: cooling of the air over Antarctica, intensification of the polar atmospheric cell and increased winds over the Southern Ocean. The sea surface temperature response to the growth of ice is very different, however, between the two palaeogeographies. For the Eocene palaeogeography there is a 6°C warming in the South Pacific sector of the Southern Ocean in response to ice growth, but very little change (or even a slight cooling) for the Oligocene palaeogeography. Why, under the same forcing (the appearance of the ice sheet), do these different palaeogeographies have such different sea surface temperature responses?

The stronger winds over the Southern Ocean force more-saline water from the southern Indian Ocean into the less-saline southern Pacific Ocean. This is particularly important for the Eocene simulations, where the narrow gap between Australia and Antarctica limits flow from the Indian to the Pacific Ocean. As salinity in the southern Pacific Ocean increases the water becomes denser and sinks, releasing heat. This accounts for the increase in sea surface temperature in the Eocene simulations. In the Oligocene simulations, flow is already much greater between the Indian and Pacific Oceans, and so there is no marked increase in density, sinking or sea surface temperature following glaciation. There is only a mild cooling due to the presence of the large, cold ice sheet.

Whether in reality the dominant ocean response to glaciation was warming or cooling may have impacted the growth of the ice sheet at this major transition in the Earth’s history. However, more importantly, this research highlights that sensitivity to subtle changes in palaeogeography can potentially have very large effects on the modelled climatic response to an event such as Antarctic glaciation. This could be very important for understanding palaeoclimate records and interpreting climate model results.

This research, carried out by Alan Kennedy, Dr Alex Farnsworth and Prof Dan Lunt of the Cabot Institute and University of Bristol with others, is featured in a special issue of the Philosophical Transactions of the Royal Society A. The full special issue on the theme of ‘Feedbacks on climate in the Earth System’ and the paper can be accessed here.

Special issue cover (image from Royal Society).

Citation: Kennedy A.T., Farnsworth A., Lunt D.J., Lear C.H., & Markwick P.J. (2015) Atmospheric and oceanic impacts of Antarctic glaciation across the Eocene–Oligocene transition. Phil. Trans. R. Soc. A, 373, 20140419, doi:10.1098/rsta.2014.0419.
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This blog is written by Alan Kennedy from the School of Geographical Sciences at the University of Bristol. This blog post was edited from Alan’s blog post at Ezekial Boom.

Alan Kennedy

Warming up the poles: how past climates assist our understanding of future climate

Posted on September 16, 2013April 20, 2023 by janet.crompton

Eocene, by Natural History Museum London

The early Eocene epoch (56 to 48 million years ago), is thought to be the warmest period on Earth in the past 65 million years. Geological evidence from this epoch indicates that the polar regions were very warm, with mean annual sea surface temperatures of > 25°C measured from geological proxies and evidence of a wide variety of vegetation including palm trees and insect pollinated plants found on land. Unfortunately, geological data from the tropics is limited for the early Eocene, although the data that does exist indicates temperatures only slightly warmer than the modern tropics, which are ~28°C. The reduced temperature difference between the tropics and the poles in the early Eocene and the implied global warmth has resulted in the label of an ‘equable’ climate.

Simulating the early Eocene equable climate with climate models, however, has not been straightforward. There have been remarkable model-data differences with simulated polar temperatures are too cool and / or tropical temperatures that are too hot; or the CO2 concentrations used for a reasonable model-data match being outside the range of those measured for the early Eocene.

There are uncertainties in both geological evidence and climate models, and whilst trying to resolve the early Eocene equable climate problem has resulted in an improved understanding of geological data, there are uncertain aspects of climate models that still need to be examined. Climate processes for which knowledge is limited or measurements are difficult, such as clouds, or which have a small spatial and temporal range are often simplified in climate models or parameterised. These uncertain model parameters are then tuned to best-match the modern observational climate record. This approach is not ideal, but it is sometimes necessary and it has been shown that the modern values of some parameters, such as atmospheric aerosols, may not be representative of past climates such as the early Eocene, with their removal improved the model-data match.

However, a climate model that can simulate both the present day climate and past more extreme climates without significant modification potentially offers a more robust method of understanding modern and future climate processes in a warming world. We have conducted research in which uncertain climate parameters are varied within their modern upper and lower boundaries in order to examine whether any of these combinations is capable of the above. And we have found one simulation, E17, from a total of 115, which simulates the early Eocene equable climate and improves the model-data match whilst also simulating the modern climate and a past cold climate, the last Glacial Maximum reasonably well.

This work hopefully highlights how paleoclimate modelling is a valuable tool in understanding natural climate variability and how paleoclimates can provide a test bed for climate models, which are used to predict future climate change.

This blog has been written by Nav Sagoo, Geographical Sciences, University of Bristol.

Tales from the field: reconstructing past warm climates

Posted on August 11, 2013April 19, 2023 by janet.crompton

The warmest period of the past 65 million years was the early Eocene epoch (55 to 48 million years ago). During this period, the equator-to-pole temperature gradient was reduced and atmospheric carbon dioxide (pCO2) was in excess of 1000ppm. The early Eocene has received considerable interest because it may provide insight into the response of Earth’s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions (IPCC AR4). However, climatic conditions of the early Eocene ‘greenhouse world’, are poorly constrained, particularly in mid-to-low latitude terrestrial environments (Huber and Caballero, 2011).

I recently spent a week in eastern Germany (Schoeningen, Lower Saxony) sampling an early Eocene lignite seam (Fig. 1). Lignite is a type of soft brown coal that is an excellent terrestrial climate archive. Using palynology, organic geochemistry, coal petrography and climate models, we will try to reconstruct the terrestrial environment of the early Eocene and provide insights into future climate change.

Fig. 1. A view of the mine with Dr. Volker Wilde on the far right for scale.

During this trip, we were sampling at the base of the mine beside a very large and very dusty bucket-wheel excavator (Fig. 2). A bucket-wheel excavator is a continuous digging machine over 200m long and dwarfs the large NASA Crawler that transports space shuttles to launch pads. Once the lignite is removed, it is placed upon a conveyor belt and transported immediately to a nearby power station. Unfortunately, the Schoeningen lignite will not last forever and the town will have to consider other energy sources (e.g. wind).

Fig. 2. A bucket-wheel excavator at Schoeningen mine.

Our sampling technique was less impressive yet equally effective. All we required were hammers, chisels and pick-axes (Fig. 3.). After a long day of sampling, we were taken to a very special outcrop at the top of the mine. The exposure contained well-reserved palm tree stumps from the early Eocene and provide evidence for white beaches, tropical plants and endless sunshine on the German coastline. An ideal holiday destination!

Fig. 3. Dr. Marcus Badger sampling Main Seam in high resolution.

Following fieldwork we were taken to the new Schoeningen museum containing, amongst other artefacts, the Schoeningen Spears (Fig. 4). The Schoeningen spears are 300,000 years old and are the oldest human weapons in existence. The spears were found with approximately 16,000 animal bones, amongst them 90% were horse bones, followed by red deer and bison. It has been proposed that these spears were the earliest projectile weapons and were used for ‘big game hunts’. Although this theory has been questioned, it remains one of the worlds most exciting archaeological finds.

Fig.4. The Schoeningen spears. Most were preserved fully intact.

Now we are back in Bristol its time to start processing our samples so we can understand what the early Eocene terrestrial climate was like. Watch this space!

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The trip was in collaboration with members of Bristol (UK), Royal Holloway (UK), Gottingen (Germany) and Senckenberg (Germay).This blog was written by Gordon Inglis (http://climategordon.wordpress.com).