I’m currently working on a Tales From the Bench entry on why I chose to leave laboratory bench work. But on Thursday the 19th, I developed a painful gum infection and I had my wisdom teeth removed the following Monday. I took a break from writing while I recovered, and right now I’m swamped. I currently am working on two freelance jobs and a writing assessment for a full-time associate medical writer job. In a few days, I’ll be able to write more, and I hope to have my next real entry up next week.
Welcome back, dear readers, and I hope you’re ready for some inconvenient truths. (Is that reference too dated? I’m still new to this blogging thing.)
This entry is part of a section called Pseudoscience Be Gone, in which I will confront (sadly) common pseudoscientific beliefs with cold, hard facts. In this entry, I won’t be talking about the actual pseudoscientific beliefs much; instead, I will focus on the evidence that exists to support the ideas that 1) global warming is real and 2) humans are having a profound effect on global warming.
I’ll start by discussing what climate change actually is. “Climate” can be described as “the average weather”, and when it comes to “climate change”, the scientific definition of climate change is often different than the political one. The scientific definition is “a change in the statistical properties of the climate system on a large scale over long periods of time”. “Statistical properties” means averages—such as average temperature or average concentration of carbon dioxide in the air—as well as how much those properties vary. The “climate system” is the sum of five zones covering the Earth, including the atmosphere and the biosphere (the portion of the Earth populated by living things). As far as the political definition, when most people talk about climate change these days, what they really mean is anthropogenic global warming: the increase in the Earth’s surface temperature caused by humans. That “large scale and long periods of time” bit from the scientific definition still applies, though; anthropogenic global warming refers to what’s happening to the entire Earth over hundreds of years. So the next time someone brings up El Niño in a discussion about climate change, you can tell them that that doesn’t count; the change doesn’t last long enough.
“Global warming is real! Science shows that!” is something I hear a lot from frustrated people who are in touch with the truth. And they’re right, but how do scientists figure out that the Earth is getting warmer, and what evidence do they actually have? That’s what I’d like to focus on for the rest of this entry. As a cancer biologist, I started research for this entry without much knowledge on how environmental scientists actually gather evidence for climate change. There are a number of sources that scientists can turn to when looking at how Earth’s climate has changed over time: ice cores, fossil records, sediment layers, floral and faunal records, and meteorological stations.
I do love fossils, but my favorite climate change information source to research was the ice cores. Ice cores are cylindrical samples of ice taken with a special kind of drill called a core drill, and they provide some of the best records for investigating past climate conditions. Not only can some of the deeper cores contain information that go back hundreds of thousands of years, they can be used to figure out data on this long list of conditions at a given time:
- Strength of air circulation in the atmosphere
- Precipitation (rain/snowfall)
- Ocean volume
- Dust in the atmosphere
- Volcanic eruptions
- Solar variability
- Amount of sea ice
- Rate at which energy is converted to organic substances by marine life
- Geographic extent of deserts
- Forest fires
How is this possible? Well, all of those can be figured out by looking at the levels of materials like dust, ash, and human pollutants in the air. Snowfall captures those things, and in some places (such as the poles), that snow doesn’t melt. Ice cores provide valuable information about the ambient temperature, which has been useful in the hunt for evidence of anthropogenic global warming. Certain molecules—like deuterium, which is hydrogen with an extra neutron—have a known relationship with temperature, so scientists can determine temperatures at specific years from the concentration of deuterium at a particular point in the ice core. Known geological events, such as an extremely powerful volcanic eruption in 1815, can be used as “dating horizons” to figure out approximately what year an ice core layer is from. Increased radioactivity from nuclear bomb testing is also often used as one of these “dating horizons”.
As I mentioned, I also like fossils. One of the things that the fossil record does for scientists is to divide up geologic time, often by showing extinction events. (Well, okay, the division of Earth’s history into periods is mostly based on visible changes in layers of sedimentary rock, but fossils are involved too.) The fossil record currently shows seven mass extinctions, my favorite of which is the Great Dying, when 96% of all marine life and 70% of all land-dwelling vertebrates died due to a possible asteroid impact and one of the most tremendous known volcanic eruptions on Earth. (If you ever want nightmares, look up “formation of Siberian Traps”.) That extinction event ended the Permian period and began the Triassic period. Periods are divided into epochs, which are further divided into ages; more on why that is important later. For now, I want to talk about foraminifera.
Foraminifera are tiny protozoans with carbonate shells. While these little critters are alive, their shells are formed from the elements found in the water where they live. Paleontologists can look at the ratios of elements in foraminifera shells and be able to tell how much of the Earth’s surface was covered in ice when the animals were alive. This is important because it provides valuable information on a time when rapid climate change—that thing that’s happening now—happened before. This rapid climate change, which marked the end of the Eocene epoch and the beginning of the Oligocene epoch, was actually a transition from a “greenhouse” climate to a much cooler one. This rapid cooling led to one of those mass extinction events I was talking about earlier. So rapid changes in the Earth’s overall temperature? Those don’t bode well for the things living here.
So we have all this evidence. What does it show, exactly? One of the things we have learned about climate change is that starting in the Industrial Revolution—let’s say 1750—ice cores show dramatically increasing concentrations of carbon dioxide and methane. To be specific, there has been a 40% increase in the concentration of carbon dioxide since the beginning of the Industrial Revolution. Carbon dioxide and methane are what is known as “greenhouse gases”, or gases that absorb and emit heat. These gases are the main cause of the “greenhouse effect”, which is what happens when a planet’s atmosphere warms its surface to a higher temperature than what it would be without the atmosphere. Higher concentrations of greenhouse gases in the atmosphere cause higher surface temperatures.
The Earth has had atmospheric carbon dioxide levels this high before: in an age called the Pliocene, which the Intergovernmental Panel on Climate Change has called the “benchmark for modern global warming”. Dr. Aradhna Tripati, an assistant professor at UCLA who studies Earth Sciences and is so smart she started university when she was 12 (really), says “Our data from the early Pliocene, when carbon dioxide levels remained close to modern levels for thousands of years, may indicate how warm the planet will eventually become if carbon dioxide levels are stabilized at the current value of 400 parts per million”. What Dr. Tripati is saying is that the Earth is currently on the bullet train to having a climate like the Pliocene’s, which would mean summertime Arctic temperatures 18 to 15 C warmer than they are today. Meteorological station records show that the Earth’s surface temperature had increased a little over half a degree Celsius in the past century, and just that is already causing hotter days, heavier rainfall, stronger hurricanes, and more severe droughts. Now imagine what might happen if the Earth gets 15 C warmer. One thing we can predict is that if the concentration of greenhouse gases in the atmosphere doesn’t change, there could be no sea ice in 50 to 100 years.
Humans have had such a profound impact on the climate that many geologists believe that we have entered a new geological age: the Anthropocene Age. While there is not a consensus in the scientific community regarding the Anthropocene Age, it is still extremely telling that humans have changed our environment so much that some experts are claiming that we have entered a new period of geological time. While we haven’t made a noticeable change in the sediment layers, 12% of land masses are now cropland. On the topic of humans cultivating so much land, Dr. Anna Behrensmeyer, a paleoecologist with the National Museum of Natural History, says “the shift from forest to grassland took millions of years, but the pace and rates were nothing like they are now. With the rates now, you don’t really give the animals and plants a chance to evolve”. Dr. Thomas Lovejoy, the Smithsonian assistant secretary for external affairs, cautions “biological systems can take it, and take it, and take it, then all of a sudden there’s a tremendous reordering”. So it looks like we’re headed for a “tremendous reordering” from all the meddling we’ve been doing with the environment.
So the next time some ill-informed soul tells you climate change is a hoax, tell them about ice cores and foraminifera. And remember: science doesn’t care what you believe.
Credit to my sister-of-the-heart Rocky Blonshine for geology tips and my biological nuclear family for reading.
Well, it looks like it’s time for my first entry! Let’s talk about one of my favorite scientists: Dr. Rosalind Franklin.
Dr. Franklin’s name often comes up in high school biology classes when students are first learning about the discovery of DNA’s structure. I would be willing to bet that several of the students in those classes are already familiar with the duo Watson and Crick when they first hear the name Rosalind Franklin and see Photo 51. If you ask those who study biology at higher levels about Rosalind Franklin, you might see their face screw up in anger and hear them snarl that Watson and Crick—or you might hear the name Wilkins—stole Dr. Franklin’s work. You might also hear that Dr. Franklin wasn’t given the credit she deserved due to sexism. Still others might say that the only reason Dr. Franklin is said to not have gotten sufficient credit for her work is because she died prior to Drs. Wilkins, Watson, and Crick being awarded the Nobel Prize, or that Dr. Franklin didn’t actually realize her results indicated that DNA’s structure was helical.
So what’s the real story? Was Dr. Franklin’s work stolen? If she had such definitive results on the helical structure of DNA, why didn’t she publish it before Watson and Crick did? I had to do more research than I expected to find out the answers to these questions, and in this entry, I plan to share those answers with you, dear readers.
But first, I want to share some information on Dr. Franklin herself. As I mentioned above, she passed away before the Nobel Prize for the discovery of DNA’s structure was awarded. She died tragically young; she was only 37 when she succumbed to ovarian cancer. She was born in the United Kingdom in 1920 into a Jewish family. According to Dr. Franklin’s sister, the family supported her scientific endeavors despite the fact that the sexism that exists in STEM fields today was even more rampant in the past.
While most people think of DNA as related predominantly to biology—it is occasionally referred to as “the molecule of life”—Dr. Franklin was primarily a chemist. While her contribution to the study of DNA was recognized posthumously, Dr. Franklin was still a celebrated scientist during her life. Her study of the porosity—the percentage of empty spaces in a material—of coal, which was the subject of her PhD thesis, provided critical information on how different types of coal would perform as fuels. She was a PhD student during World War II, and not only did her work with coal contribute to the design of gas masks with charcoal filters, but she also volunteered as an Air Raid Warden.
Dr. Franklin also did important work on the structures of RNA and viruses. After her work with DNA (which I will discuss later), she made groundbreaking discoveries on the structure of tobacco mosaic virus. Tobacco mosaic virus, often called TMV, is what is termed a model organism: a living thing that provides useful information for biologists on many similar other living things…and is usually easy to study. Dr. Franklin’s discoveries that the proteins in TMV were arranged in a spiral and that the RNA in TMV resides inside a groove in the protein arrangement were crucial to the understanding of several other similar viruses. Dr. Franklin was at the top of her game, cranking out papers on structural virology at an impressive speed, when her life was cut short.
In case you’re impatiently tapping your foot while waiting for me to talk about DNA, dear readers, I’m about to get to it. Dr. Franklin started working at King’s College London in 1950. She had done extensive work with a technique called X-ray crystallography—a method for determining the structure of a material that can form a crystal—after earning her PhD. She was hired to do similar work on proteins, but the department head reassigned Dr. Franklin to study DNA fibers. Dr. Franklin was able to use her past experience with X-ray diffraction to improve the quality of the results her department’s experiments were yielding. She discovered that DNA had two forms, which she called “A” and “B”. She noted that DNA fibers were long and thin when wet (form “B”), and shorter and fatter when dry (form “A”).
Some suggest that Dr. Franklin never realized that DNA was helical, which is why she did not publish that discovery ahead of Watson and Crick. The truth is that Dr. Franklin was a perfectionist who wanted to make absolutely sure that she had correctly interpreted all her data. In lecture notes dated November 1951, Dr. Franklin wrote: “The results suggest a helical structure (which must be very closely packed) containing 2, 3 or 4 co‐axial nucleic acid chains per helical unit, and having the phosphate groups near the outside.” In 1952, asymmetrical images of the “A” form of DNA caused Dr. Franklin to balk at the idea of claiming that both forms were helical. By 1953, she had reconciled all of her data and became convinced that both “A” and “B” forms of DNA were helical. Not only did she now know that DNA was helical, but she had deduced that DNA was a double helix: two helices intertwined with each other like a twisted ladder. She began work on several manuscripts on the subject, and one day before Watson and Crick completed their model of “B” DNA, two of Dr. Franklin’s papers on “A” DNA’s structure reached the headquarters of a journal called Acta Crystallographica. Years later, another manuscript dated March 1953 was found in Dr. Franklin’s files, this one discussing the structure of “B” DNA.
I don’t know about you, dear readers, but I’m pretty convinced that Dr. Franklin discovered the helical structure of DNA independent of Watson and Crick.
You know what, I’m not done gushing about Dr. Franklin’s research. It’s also important to note that not only did she figure out that DNA was a double helix, but she also knew that DNA contained a sequence of nitrogenous bases: key parts of the building blocks of DNA. She also deduced that the sequence of bases provided the genetic code. She even discovered that the nucleotides—the aforementioned building blocks of DNA—were paired with each other. I’m sorry, but that’s impressive. Actually, no, I’m not sorry.
“But what about the controversy?” you might be saying. “Did Watson and Crick steal her work?” Well, all right, dear readers. Let’s talk about the controversy. In 1952, Dr. Franklin’s student, Raymond Gosling, took one of the most famous photographs in science: Photo 51, an image of the “B” form of DNA.
Here it is.
Image description: an X-ray crystallography image in grainy black and white showing small horizontal black bars in an “X” shape on a circular gray field
The crux of the controversy is this: Dr. Watson had the epiphany that DNA was helical when he saw Photo 51, which he saw without the permission of Dr. Franklin (or Raymond Gosling). In my research for this entry, I stumbled across at least one person claiming that Watson and Crick would have discovered the helical structure of DNA with Dr. Franklin’s consensual help had Dr. Watson been paying attention during a seminar Dr. Franklin gave on the relative distances of repetitive elements in DNA. (Dr. Watson admits to this inattention in his book The Double Helix: A Personal Account of the Discovery.) However, Photo 51 was taken after this lecture, and regardless of speculation, Dr. Watson had his realization when a colleague of Dr. Franklin’s—Dr. Maurice Wilkins—showed him Photo 51, again, without Dr. Franklin’s permission. I’m pretty certain that at no point in recent history was showing your labmates’ work to competing scientists considered anything but unscrupulous. Well, unscrupulous if not a terrible idea, since it could lead to you getting scooped. (“Scooped” is what scientists call it when someone else publishes results you’ve been working for before you do.)
Why in the world would Dr. Wilkins do this? That isn’t clear. What is clear is the sequence of events: on January 30, 1953, Dr. Watson arrived at King’s College London, bearing a manuscript containing another researcher’s incorrect model of the structure of DNA. He was looking for Dr. Wilkins, who wasn’t in his office, and Dr. Watson instead went to Dr. Franklin’s lab and insisted that they all collaborate before the author of the incorrect paper realized his model was wrong. As part of his insistence, Dr. Watson suggested that Dr. Franklin didn’t know how to interpret her own data, and Dr. Franklin was (understandably, I think) irritated. As he was scurrying away from this confrontation, Dr. Watson ran into Dr. Wilkins, who tried to console him and then showed him Photo 51. Some theorize that Dr. Wilkins did this because he had a terrible relationship with Dr. Franklin, who intimidated him; Dr. Wilkins was shy and retiring. Still others theorize that sexism was a factor in Dr. Wilkins’ actions. I can’t figure out people’s motivations when they aren’t historical figures that I’ve only read about, so I don’t know what Dr. Wilkins was thinking, but I do know he was in the wrong.
At no point was Dr. Franklin aware of her influence on Watson and Crick’s work. In modern science, if someone helps you with your research, you acknowledge their contribution in your paper. In April of 1953, Watson and Crick published their model for the structure of “B” DNA in Nature—a very, very reputable journal—without properly crediting Dr. Franklin. Later in the same issue, several articles by Dr. Wilkins and Dr. Franklin appeared in support of Watson and Crick’s model.
So was Dr. Franklin’s work stolen? I wouldn’t go that far. Was she not given enough credit? Definitely. Watson and Crick are still seen as the primary discoverers of DNA’s double helical structure when Dr. Franklin’s work was just as if not more important, and Watson and Crick likely would not have been able to publish that Nature paper without Photo 51. Was sexism a factor in Dr. Wilkins’ decision to show Photo 51 to Dr. Watson? I think that is possible; it was the 1950s, and as for anyone who doesn’t believe that there has always been sexism in science and that it still isn’t prevalent, I would like to know what life is like on their planet. (I mean, while Dr. Franklin was working at King’s College London, the female scientists were not allowed to eat in the common room. Also, if you read The Double Helix…wow, Watson and Crick have no idea how sexist and arrogant their attitudes were. No idea.) More important than what was in the heads of Drs. Watson, Crick, and Wilkins, though, is the fact that Dr. Franklin still isn’t given enough credit. To this day. I can’t show statistically significant data proving that sexism is a factor in that, but I would still bank on it.
If you take anything away from this entry, dear readers, is that Dr. Rosalind Elsie Franklin was an incredible, brilliant scientist who made many groundbreaking discoveries and who deserves all the credit in the world. Oh, and that the answer to “is sexism a factor in this?” is going to be “yes” 99% of the time if it involves women in science.