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  • 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 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 technologiesand a booming human populationit keeps losing those

  • all-important green flecks.

  • Today is the history of climate science, which leads to some dark questions about the future

  • of life on earth.

  • [Intro Music Plays]

  • Scientists tend to be conservativenot 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 systemssolar radiation, human

  • activity, carbon, nitrogen, water, nonhumans: 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 concentration

  • in 1938.

  • He analyzed measurements of temperatures from the nineteenth 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 oceanswhich 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 Organisation established the Intergovernmental Panel on

  • Climate Change, or IPCC, which has become the premiere 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 hair sprays, refrigerators, and lots

  • of other placesand that were causing a hole in the earth's protective ozone layer.

  • 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, well, everything.

  • In 2000, atmospheric chemist Paul Crutzen coined a term for these global shifts, andhowever

  • imperfectit has stuck: the Anthropocene, or theAge of Man.”

  • Some scholars have called into question naming this era afterthehuman, as if all

  • humans are equally to blame.

  • Other contenders include Donna Haraway's the Chthulhucene, or Age of Science Fictional

  • Badness; the Manthropocene, or Age of Dudes, which not so subtly hints at the gender bias

  • in science; and, catching on with some historians, the Capitalocene, or Age of PoliticalEconomics.

  • 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 so-calledgolden spikes”—moments

  • that represent shifts in the very makeup of the earth, usually visible shifts in the fossil

  • record.

  • In fact, the Anthropocene is 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, ThoughtBubble: First, there's the original fossil fuelcoalwhich

  • 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 testthe

  • first of many such tests.

  • So this date for the beginning of the Anthropocene would be the specific date of July 16, 1945—the

  • day of the Trinity Test and the birth of the Cold War.

  • Third, there's plastic, steel, and concretebut especially plastic.

  • Humans built stuff and even had plastic before World War Two, but development took off at

  • an unprecedented pace around 1960.

  • ThisGreat Accelerationsaw 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 natural resources of all kinds.

  • The period of the Great Acceleration also gave rise to the first megacities, or urban

  • areas with over ten 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 number four: chicken bones!

  • With more than twenty-three billion alive at any time, chickenswhose bodies have

  • been heavily designed by humansare 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, ThoughtBubble.

  • 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 realized 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 Erik Conway

  • showed that fossil fuel companies had hired some of the same PR agents and strategists

  • who had worked for the tobacco companies, decades earlier, to invent climate denial:

  • that is, to create doubt about science that was not doubted by scientists.

  • Ultimately, climate science isn't just about long-term shifts in the movement of carbon,

  • water, heat, and other natural phenomena.

  • The big questions for scientists in the Capitalocene include epistemic, technical, and moral ones.

  • Epistemic questions include how fast are humans, and especially humans working within capitalism

  • changing which ecosystems, in what ways?

  • For example, we know that many important pollinators such as honeybees, bumblebees, and butterflies

  • are dying out.

  • Which is real sad, but also potentially an enormous problem.

  • And we have some ideas as to why.

  • A major cause is off-target damage from pesticideswhich, no surprise, they literally are made to kill

  • bugs.

  • But which pesticides affect which bugs in which ways?

  • Are there are safe options?

  • Can we test lots of ways of doing agriculture and see which is most bug-friendly?

  • And which forms of agriculture are most likely to erode soil from the land, and which help

  • build soil back up?

  • Basically: what kinds of knowledge do we need to make today, in a connected, fragile, increasingly

  • disruptedworld?

  • 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, likelike creating more forests.

  • But other ideas have been hotly debated, likelike 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 are 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 spent a decade getting really good at?

  • What if you work for a chemical company to study the unintended effects of a pesticides

  • on animals, and when you report your findings, the company tries to bury them?

  • And that's not a hypothetical, it's exactly what happened to leading amphibian endocrinologist Tyrone Hayes in the 2000s.

  • He reported to Syngenta that one of their key products, the herbicide atrazine, disrupts

  • the hormones of frogs and may have other serious unintended consequences.

  • And for that, Syngenta spent years trying to discredit their former collaborator.

  • As it approaches the present, the history of science and technology becomes less about

  • discoveries and inventions and more about how the choice to make specific knowledgeor

  • bury that knowledgeis highly political.

  • 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