Microfossils: for the 19th or 21st century?

Microfossils: the word alone is enough to send many people to sleep. Who would study them? Aren’t these today what they were in the 19^th century: a nice eccentric hobby for rich men with lots of time on their hands? And of no practical use?

A page from one of the reports from the Challenger expedition (1872-76), depicting sea floor sediments which contain many foraminifera. The report on foraminifera is still used as reference material; as recent as in 1994, another edition was published.

 

Microfossils have taught us much of what we know about the world we live in and how it changes. Consider, for instance, an archaeological excavation, and how pollen tell us of the vegetation at the time the site was occupied. But microfossils can do much more: an example that can illustrate the amazing amounts of information they contain is provided by foraminifera. Foraminifera are a group of unicellular organisms that live in the sea. Some species live floating around in the water column (planktonic foraminifera) and some live on or in the sediments on the sea floor (benthic foraminifera). They build exoskeletons (also called tests or shells), made of either calcite or material they find around (a bit like some fly larvae; some have been coerced into making their protection from gold; see pictures here). Their name means “Bearers of holes”, as their calcite skeleton tends to show pores. They are found almost everywhere in the world ocean. There are thousands of species of foraminifera, and they all have their own living preferences. When they die, their bodies decay rapidly, but their skeletons can be preserved for hundreds of millions of years. And the physical and chemical composition of the (calcitic) tests reflects the sea water they were formed in. So if you stick a core into the sediments on the sea floor, you’ll have a column of little measuring devices in neat chronological order. 

 

A Melonis barleeanum, clearly showing the pores that gave this group of organisms their name

 

So how do these tiny snail-like things record anything? The distribution of the various species already provides a wealth of information. If from the bottom of the core up you first find cold water species, and then increasing numbers of warm water species, most of which first being those that prefer fresh organic material as food, and then later species who don’t mind their food having gone off massively, you already know quite something about the changes that happened where you took your core. And some species have very convenient properties: for example, Globigerinoides ruber generally forms a bog-standard white calcitic tests, but in warm water (>~25°C) it can make pink ones too. And Neogloboquadrina pachyderma can coil in two directions; in water between freezing point and ~5°C it coils almost exclusively anticlockwise, and above ~10°C it coils largely clockwise. So one glance through the microscope can sometimes tell you the approximate temperature of the sea water the creatures lived in. 

 Globigerinoides ruber in both the white and the pink version. White: picture by C. de Vargas. Pink: from foraminifera.eu

The amount of information you can tap into increases greatly if you study the calcite the tests are made of. The oxygen in the CaCO₃ provides a lot of clues: Oxygen has several stable isotopes, of which the most common is ¹⁶O at ~99.7% of all oxygen on Earth. Another stable oxygen isotope that is often used in palaeoclimate studies is ¹⁸O. These isotopes have slightly different physical properties. As ¹⁸O is heavier, water molecules containing it tend to evaporate from liquid water with a bit more difficulty, and when they do, they rain out of the atmosphere a little bit easier. It also leads to ¹⁶O preferentially evaporating from the ocean and precipitating on the continents, which means the high latitude ice sheets are relatively enriched in ¹⁶O. Measuring the ¹⁸O/¹⁶O (δ¹⁸O) ratio in a series of foraminifera that span hundreds of thousands of years will thus reveal the familiar see-saw pattern of glacials and interglacials, which is also found in the CO₂ and Deuterium records from ice cores. In this indirect way, ¹⁸O can be used to date records based on foraminifera tests. 

Some glacial-interglacial cycles. The Epica and Vostok graphs show temperature reconstructions based on Deuterium measurements from two ice cores, and the bottom graph is a reconstruction of global ice volume based on ¹⁸O records of benthic foraminifera. Vostok record from Petit et al., Nature 1999. Epica record: EPICA project members, Nature 2004. Ice volume record: Lisiecki and Raymo, Paleoceanography 2005.

More information is stored in the chemical composition of the calcite; it does not consist of pure CaCO₃, as some of the Ca²⁺ atoms are replaced by other bivalent cations, such as Mg²⁺ atoms. As incorporating atoms of the “wrong” size in a crystal lattice requires extra energy, this occurs relatively often in warm environments, due to the ample availability of thermal energy. The ratio of Mg to Ca in a calcitic shell therefore is a measure for past sea water temperatures.

These measurements can be performed on many tests at the same time; this will provide a measure of average conditions. They can also be measured individually, which gives information about only the lifespan of the individual organism. And it is even possible to blast the tests with laser beams, and measure the CaCO₃ that then evaporates. (A nice picture and explanation can be found here.) That will give the evolution of the temperature of the water the creature has lived in through the course of its life. 

 

The sort of machine with which one determines the Mg/Ca ratio in foraminifera tests

Given how specific one can target what to measure, a wide range of oceanic conditions can be reconstructed. For instance, a researcher who wants to reconstruct the stratification of the ocean could measure the properties of the tests of a shallow dwelling species and a deeper living species. When the signals resemble each other, the water masses were thoroughly mixed. Large differences point to well-developed stratification. 

You want to know how strong the circumpolar current, which flows all around Antarctica, and keeps the continent thermally insulated, has been through time? Drill a core where it currently flows, one core at its furthest reach, and one core just outside it reach. And then check the amount of polar and temperate species in all three through time.

 The Antarctic Circumpolar Current

Do you want to know how strong the Gulf Stream was? This current brings warm, salty water to the North Atlantic, where it cools down, and sinks to the bottom. Drill a core somewhere in its path, and check the temperatures as documented in both the surface-dwelling and bottom-dwelling foraminifera. If the difference is large, the Gulf Stream was likely strong. 

Do you want to know how strong the Indian monsoon has been through time? The summer and winter monsoon seasons both have a cooling effect on the sea surface temperatures; the stronger the monsoon, the colder the sea water gets. And each monsoon season has its own distinctive foraminifera assemblages, so these temperatures can be reconstructed independently. If you measure single specimens, you will also catch the few individuals that live in the very warm water between the monsoon seasons.

All of these examples of course come with their caveats. The reconstructions you can make of these features are not perfect, but if you corroborate them with other measurements you can paint a very detailed picture of how countless many aspects of how the world works. And if you know what it does, you may be able to find out why it does it, and that may tell you what to expect for the future. So even though staring down a microscope staring at small things that look a bit like miniature cauliflower might feel very 19^th century, it might actually be part of cutting-edge modern research!

 Picture: Edal Anton Lefterov

Sea level project re-aligned

We’re midway. Are we on schedule? For 1.5 years, researchers all over the UK have been trying to get a grip on interglacial sea level changes, within the iGlass project (official link). We’d like to know if sea level during periods of low polar ice cover fluctuates in general, and if so, how much then. Sea level is currently rising; how much faster can we expect it to go? Geological data suggests the fastest rates of sea level occur when there is loads of ice; quite as one would expect. But just the fact we don’t expect rates of several metres per century doesn’t mean we can sit back and relax. So we do not. And the time had come to see how far we had come. 

All researchers involved in the project from the various institutes gathered in Southampton, where our coordinator was based. And in a meeting room with a view on the very sea, we brought each other up to date. There is one team trying to constrain interglacial sea level changes using stable isotopes in foraminifera from the Red Sea (how they manage that is a complicated story – that merits a blog post in itself). A team in Oxford was trying to use dripstone formations for this purpose (same there!). We had been coring around in Norfolk and Cambridgeshire, looking for marine microfossils in sediments, to do our bit. And all that adventure was complemented by the sturdy attempts of several teams of data gatherers and modellers: the former would compile all information already available in literature so as to not have to do double work. And the latter would try to understand the distribution of land ice at the time intervals for which we had sea level data. They would also try to get a grip on the depression and subsequent bouncing back up of the Earth’s crust due to fluctuations in that ice; you can use that to detect where large masses of ice have appeared and disappeared (related to the process described here), and thus point to a specific ice mass as a culprit if you find a big sea level change in your data. 

 

The view from our meeting room

So what, other than just being kept in the loop, is the use of getting together? Well, science isn’t a linear process. A project never works out exactly as it was set out in the beginning. And one needs to adapt to such changes. 

We were faced with several changes relating to the people involved: five of us would move to a different institute than we started out in at the beginning of the project. Two go abroad; out of reach of our UKfunding agency, so we needed replacements. One of us would even leave science altogether. 

More detailed issues that needed to be discussed were for instance which interglacial periods (there are many; for practical reasons, we limit ourselves to the last five) we will focus on, and which time intervals within these periods. The previous interglacial (~125.000 years ago) is a favourable one, for the simple reason it is the most recent, so it’s best documented in the sedimentary archive. Three interglacials back (~400.000 years ago) is a special one too; the Sun and the Earth were configured in practically the same way as they are now (quite unlike in the previous interglacial), and it was a very long one; we decided prioritise these two. And the time slices the modellers will target are the ones for which the data gatherers have found the most information. 

 The home base of the project: the National Oceanography Centre in Southampton

Another issue to be discussed was that we, the micropalaeontological team, had only budgeted for fieldwork in the UK, but we had found out about much more promising sediments in the USA. Should we shift some money around so we could chase these up? It was decided we would. An exciting prospect opened up! 

Two days of presentations, discussions, and a nice dinner at the end of the first day later, we all dispersed again. We were all singing from the same hymn sheet again, and the music on it has been brought up to date with where our data has taken us!

The Hockey Stick and the Climate Wars

I love depressing books. Give me characters that make the wrong decisions and slowly crumble ever after because of it. Give me gross injustice. But I want it to be fiction; I like suffering as a concept, as an art, not as something that happens to real people.

I just finished a book that has plenty of injustice and suffering in it; unfortunately, it wasn’t fiction. It made me sad and frustrated. I knew it would. It was “The hockey stick and the climate wars - dispatches from the front lines”; the account of Michael Mann of the creating of the famous hockey stick graph, and the subsequent barrage of the denialist lobby on him, his colleagues, and his work.

The book describes the changing times; it starts with Mann’s early career, when climate science was still just another science. It describes the research that lead him and co-authors to publish the hockey stick in the late nineties, and its incorporation in the IPCC’s third assessment report in 2001. And that was when the excrements hit the fan. As the hockey stick makes the problem of anthropogenic warming readily understandable to all, and featured prominently in something as influential as the IPCC report, it was a target the petroleum lobby could hardly ignore. Mann describes his utter unreadiness  for the attacks that came; he was just a scientist, trained in scientific discourse, and not in mud-throwing with lay people. Very, very recognisable, I suppose, to any scientist.

The cycle of attack and counter-attack followed the political diary; attacks intensified in 2003, as the Climate Stewardship Act would be voted on; if it would pass, emissions of greenhouse gases would legally have to be curtailed. Denialists tried everything to discredit the evidence; none of it stood up to scrutiny, but they did create doubt. And the bill didn’t pass. Because of the denialist lobby? Hard to say, but the fact that that possibility can’t be excluded is chilling.

In 2004, Mann and colleagues realised you can’t fight this battle in scientific literature, as their opponents would generally not venture there. Neither does the general public. If you want your voice to be heard, you have to find other outlets; the RealClimate blog was founded. 

 The RealClimate blog

Then the battle got harder. The year 2005 saw the attack of republican senator Joe Barton, who either thinks, or wants others to think, that any science suggesting the existence of anthropogenic warming is fraud. He demanded from Mann and several others all the information their work was based upon, all correspondence about it, the dates of any relevant meeting, and more of such absurdities. Is there anyone in the world who can give such a detailed account of their work? Luckily Barton had no legal ground to stand on, and the climate scientists could ignore him, but it was clear that the deniers were stepping up their game. If they could enforce such demands, work would be impossible for climate scientists. Exactly the desired effect. And just the threat of this lingering in the air might put people off from letting their voice be heard.

I remember this attack happening; I was doing my PhD in Amsterdam at the time. We were all upset and worried. And one of us was courageous: Gerald Ganssen, our colleague, and then president-elect of the EGU (European geosciences Union), was the first to stand up and condemn this attack. I was proud when I read this event narrated in the book. After the EGU many other scientific organisations spoke out.

In 2007 things were looking up; Al Gore drew global attention to global warming with his Inconvenient Truth lectures, film and book. Together with IPCC, he received the Nobel Peace prize. It looked like the deniers had lost, and science prevailed. But it was not to be. The worst was yet to come.

Then ClimateGate hit the global headlines. Private emails were stolen, and taken out of context. As Mann phrases it: "imagine how unpleasant it might be to have your private emails, text messages, or phone conversations mined by your worst enemy for anything that, taken out of context, could be used to make you look bad". That’s exactly what happened. And the right-wing media lapped it up. And it worked: a lot of doubt was cast, again, and the timing was pristine; the e-mails were published just before the Copenhagen Summit, and everybody knows what a success that was. And if that publicity stunt wasn’t enough, Mann also describes attempts to bribe his colleagues into accusing him of fraud. It didn’t work. And he quotes from some of the hate mail he received. Did I mention already this book is not a happy read?

At the 2009 United Nations Climate Change Conference (Copenhagen Summit)

Several official investigations were performed to check if anything untoward was uncovered by the hacking of the emails. All investigations concluded it hadn’t: all scientists were cleared of any wrongdoing. Unfortunately, that fact was conveniently ignored by most mainstream media. The scientific community noticed, of course, and was relieved, but the damage done to public perception of climate change hasn’t been undone.

The clearing of the scientists didn’t stop the attacks, either; in 2010, attorney general Cuccinelli tried the Joe Barton strategy once again, demanding impossible amounts of documentation on Mann’s work. Again it didn’t work; a legal base for any investigation was (again) found lacking. But it did clearly convey the message that when you were a climate scientist, you were still considered fair game.

Mann ends the book on a positive note; he says awareness of global climate change is growing, as is insight into the machinations and funding of the denialist lobby, and thereby their credibility. Public indignation on how bona fide scientists are treated is increasingly voiced. Would this time the tide really be changing? Let’s just hope so. And Mann himself? He has clearly not lost any of his fighting spirit. He concludes with “I am determined to do whatever I can to make sure it will be possible for us to return (to the Florida Keys, MHS) decades from now – my wife and me, our daughter, her children, and perhaps theirs – to again marvel at these natural wonders. While slowly slipping away, that future is still within the realm of possibility. It is a matter of what path we choose to follow. I hope that my fellow scientists – and concerned individuals everywhere – will join me in the effort to make sure we follow the right one”.

Florida Keys

I hope countless many people read this book. It provides an unprecedented insight into the war between science and oil industry. And it’s hard to read about an author of such ground-breaking work being bullied and threatened, but it’s uplifting to see it hasn’t broken him. And the book is both well-written and incredibly well-documented; it has over a hundred pages of notes.

While reading it, I did hear the voice of the devil’s advocate in the back of my head. “Of course he would say that! Of course the denialists can’t get their criticisms published in scientific literature – it’s a conspiracy!” And all that. And of course the book is subjective, by its very nature. But if you adopt the assumption climate science really IS a hoax and/or a conspiracy, you have to accept that it has the legal systems all over the world in its pocket. Otherwise all the investigations into the conduct of the conspirators would have yielded something. And if it has such power, than how come it can’t seem to force emission reduction legislation into being? Wasn’t it a conspiracy to bring the leading economic nations to their knees? Not a very effective conspiracy, then. Or is all that power then used to maintain the status quo, where climate science wrongly claims that global warming is occurring, the powers that be are allowed to ignore that and keep emitting greenhouse gases, and though climate change doesn’t happen, the scientists will still get funded to study it? That sounds a bit ineffective too. The only logical explanation of all of this is still, I’m afraid, that climate scientists simply are bona fide. And if nobody listens to Cassandra in a white lab coat, reality will catch up all too soon…

I know most people considering reading this book will already be at the side of science, and it is therefore unlikely to change many people’s minds on climate change. But it does provide a compelling read. Do judge for yourself!

...and some shameless self-promotion to end with...