[0:05]This image is called the Blue Marble, and it was taken in 1972 during the Apollo 17 mission. It has become a symbol not only of cool space travel, but the environmental movement back here on the ground. Think about it: when you're on the Earth, it seems pretty dang big and solid, but when seen from far above, it's just a blue marble, flecked with beautiful green, inspiring, isolated, and not really all that big. And thanks to technologies like air travel and the internet, and to a booming human population, it keeps feeling smaller. And thanks to technologies and a booming human population, it keeps losing all those, all-important green flecks. Today, our topic is the history of climate science, which leads to some dark questions about the future of life on Earth.
[0:58]Scientists tend to be conservative, if not politically conservative, but careful, resistant to big claims. So evidence for the possible end of the living world took a while to be seen as such. One problem was the structure of modern science. Remember how those ancient Greek, Indian and Chinese natural philosophers tended to study astronomy, math, the living world, and human society all at once? By the 1900s, professional scientists had gone in the other direction, specialization. Scientists tended to focus on learning about one specific thing, often practically oriented things. Another problem was actually epistemic. Studying weather patterns in one region is useful, but how do you study global climate? How many local patterns add up to a global one? And there are so many elements involved in the Earth's systems: solar radiation, human activity, carbon, nitrogen, water, non-humans. How do you know which variables matter in answering any given question? Big data suddenly becomes not a source of potential answers, but a serious problem. So how did we get here? English inventor Guy Callendar correctly predicted rising atmospheric carbon dioxide concentrations in 1938. He analyzed measurements of temperatures from the 19th century on, correlating them with measurements of carbon dioxide. He saw that temperature had increased and proposed that this was an effect of increasing CO2. Most scientists were skeptical, but Callendar died convinced he was onto something, and his work influenced a small number of scientists. In 1957, Revelle published a paper with Hans Suess, suggesting that human emissions of greenhouse gases like CO2 might create a greenhouse effect. These heat-trapping gases would be trapped in the atmosphere, not absorbed quickly enough by the oceans, which would cause global warming. Revelle also convinced geochemist Charles Keeling to keep measuring atmospheric CO2 concentrations at Mauna Loa Observatory, starting in 1958. These measurements showed seasonal variation as well as a clear arc over time. The planet is warming and CO2 is rising. This trend is called the Keeling Curve. In 1988, the World Meteorological Organization established the Intergovernmental Panel on Climate Change, or IPCC, which has become the premier body for establishing just what is going on with the Earth's climate. And in 1996, the governments of the world came together to ban chlorofluorocarbons, or CFCs, a group of odorless chemicals that were used in hairsprays, refrigerators, and lots of other places, and that were causing a hole in the Earth's protective ozone layer. And by the 2000s, many scientists had overcome their conservatism to speak out about global shifts in climate, which were affecting living systems of all sorts, agriculture, cities, and, you know, everything. In 2000, atmospheric chemist Paul Crutzen coined a term for these global shifts, and however imperfect, it has stuck, the Anthropocene, or the Age of Man. Some scholars have called into question the naming of this era after the human as if all humans are equally to blame. There have been other pretty good contenders for the naming of this age: Donna Haraway's The Cthulhucene, or the Age of Science-Fictional Badness, the Manthropocene, or the Age of Dudes, which not-so-subtly hints at the gender bias in science, and catching on with some historians, the Capitalocene, or the Age of Political Economics. This is a fight among historians over how to discuss longue durée history, or history across many millennia. It's also a fight among geologists about where to place the so-called golden spikes, moments that represent shifts in the very makeup of the Earth, usually visible shifts in the fossil record. In fact, the Anthropocene is kind of a political fight about the intersection of geological epochs and human history. The problem with the Anthropocene is there are so many good candidates for the golden spike of a human epoch. Show us, Thought Bubble. First, there's the original fossil fuel, coal, which was mined extensively in certain regions starting in the late 1700s and ramping up seriously in the late 1800s: the Industrial Revolution. Second, there's radioactive material in the form of strontium 90, which could be traced all over the world soon after the Trinity atomic bomb test, the first of many such tests. So this date for the beginning of the Anthropocene would be the specific date of July 16th, 1945: the day of the Trinity Test and the birth of the Cold War. Third, there's plastic, steel and concrete, but especially plastic. Humans built stuff and even had plastic before World War II, but development took off at an unprecedented pace around 1960. This "Great Acceleration" saw rapid, often exponential growth in human population, use of freshwater, ability to produce and move food, greenhouse gas emissions, temperature of the Earth's surface, and consumption of all kinds of natural resources. The period of the Great Acceleration also gave rise to the first megacities, or urban areas with over 10 million people. In reaction to massive urbanization, humans have also set aside more land as national parks or greenways, creating a landscape dominated by industrial agriculture and cities, but also sporting well-defined breaks of deep green. All of these changes can be seen in the Earth's geological record. And they all symbolize how some humans have changed the physical world. But perhaps the best candidate is four: chicken bones. With more than 23 billion alive at any time, chickens, whose bodies have been heavily designed by humans, are the most common terrestrial vertebrate species on the planet. Aliens visiting the ruins of Earth could reasonably conclude from our fossil record that the only life-form that ever mattered on this planet was the chicken. Thanks, Thought Bubble. But the Anthropocene is only one way of viewing geological change and human disruption of natural cycles. Also influential are the planetary boundaries: a set of nine specific ranges for natural processes within which humans can definitely live. These include measures such as climate change, ocean acidification, and ozone depletion, but also the genetic diversity of life on Earth and how much land is converted to cropland. But we can't talk about climate disruption without mentioning the pushback. Even though the vast majority of scientists realize that humans have had a tremendous impact on the Earth, politically conservative talk shows run stories about how there's no consensus. So where did this idea come from? In 2010, geologist and historian of science Naomi Oreskes, and NASA historian Eric Conway, showed that fossil fuel companies had hired some of the same PR agents and strategists who had worked for tobacco companies decades earlier to invent climate denial.
[7:41]That is, to create doubt about the science that was not doubted by scientists. Ultimately, climate science isn't just about long-term shifts and the movement of carbon, water, heat, and other natural phenomena. The big question for scientists in the Capitalocene include epistemic, technical, and moral ones. Epistemic questions include how fast are humans, especially humans working within capitalism, changing which ecosystems and in what ways? For example, we know that many important pollinators such as honeybees, bumblebees, and butterflies are dying out, which is sad, but also potentially an enormous problem. And we have some ideas as to why. A major cause is off-target damage from pesticides, which, no surprise, literally are made to kill bugs. But which pesticides affect which bugs in which ways? Are there safe options? Can we test lots of different ways of doing agriculture and see which ones are most bug-friendly? And which forms of agriculture are most likely to erode soil from the land and which are helping build the soil back up? Basically, what kinds of knowledge do we need to make today in a connected, fragile, increasingly "disrupted" world? In terms of technical questions, Earth scientists are increasingly being pushed from the role of description to recommending action. Some prominent scientists are calling for governments to seriously consider geoengineering, also known as climate engineering, the intentional global-scale transformation of the environment to combat global warming and other disruptions. Some geoengineering would be relatively uncontroversial, like creating more forests. But other ideas have been hotly debated, like fertilizing the ocean with iron to accelerate the growth of algae, thus capturing more CO2 from the atmosphere. But perhaps the biggest shift in professional sciencing today is moral. Who should pay for solutions to global-scale problems such as sea-level rise and global warming? Everyone, or only the people who most contributed to the problem? The Yellow Vest movement in France is a recent example of this conflict. People across the country were subject to a new tax on fuel in order to help lower carbon emissions. But many of the working poor, especially in more rural areas, simply couldn't afford to pay more to get around, and riots broke out. And think about all of the scientists working on topics related to the environment, but maybe on the wrong side of history. What if you're a professional geologist and Exxon, BP, or Shell hired you to find more fossil fuels to extract? Should you not do the science you've already spent a decade getting really good at? This isn't a portrait of Doomsday, but a call to reflect on science's strengths and its limits. Science alone can't answer tough questions about how humanity should address climate disruption, and who should pay for potential solutions. One thing is certain: whether we call it the Anthropocene, the Capitalocene, or the Cthulhucene, the new era in which some humans have dragged the blue marble will forever change how we make and share knowledge and tools. Next time, we'll finish this series with a look at how science is gendered, not only how important women have been to the history of science and how difficult it is to sometimes tell their stories, but also how our understandings of the natural world reflect our ideas about humanity.
