How The Past Hints About Our Climate’s Future Ask a climate scientist how much the earth will warm as a result of the carbon dioxide we’re emitting right now, and the answer will be a range of temperatures: likely anywhere from 1 to 5 degrees Celsius. But all the models we have to predict the future are based on data from the past, most of it collected in the last 140 years. As carbon dioxide rises further past the unprecedented-in-human-history 400 parts per million (ppm), we are increasingly in a world never before seen by human eyes—or measured by thermometers. While we are certain the Earth’s climate will warm as CO2 increases, it’s harder to pin down exactly how sensitive the climate is. Scientists are working hard to narrow down our uncertainties about the coming temperature changes, sea level rises, and new patterns of rainfall and drought. And paleoclimatologists can examine ancient rocks, sediments, ice, and fossilized shells for clues about how past climates changed in response to different levels of carbon dioxide. Climates from past epochs have not only experienced that 400 ppm mark, but also levels higher than 1,000 ppm—and correspondingly, higher temperatures and higher seas. In Science last month, a team of researchers made the case for using more data from these climates, millions of years ago, to help us map out the future we face. Science Friday producer Christie Taylor talks to University of Arizona geoscientist Jessica Tierney, who is lead author on the new research. Mapping Out The ‘Microbial Skyscrapers’ On Your Tongue Your mouth is home to billions of bacteria, and they’re very particular—some prefer to live on the inside of the cheeks, while others prefer the teeth, the gums, or the surface of the tongue. Writing in the journal Cell Reports, researchers describe their efforts to map out the various communities of bacteria that inhabit the tongue. In the average mouth, around two dozen different types of bacteria form tiny “microbial skyscrapers” on the tongue’s surface, clustered around a central core made up of individual human skin cells. In this study, scientists mapped out the locations of tiny bacterial colonies within those clusters, to get a better understanding of the relationships and interdependencies between each colony. Jessica Mark Welch, one of the authors of the report and an associate scientist at the Marine Biological Laboratory in Woods Hole, Massachusetts, talks about what we know about the microbiome of the human mouth—and what researchers would still like to learn. Moderna’s COVID-19 Vaccine May Soon Be Approved In The U.S. As the national rollout of the Pfizer/BioNTec vaccine began this week, Moderna’s own formula looks ready to add to the options for the nation’s healthcare workers and high-priority patients, at least according to a panel tasked with deciding whether the benefits outweigh the risks. On Thursday, the FDA’s independent advisory committee voted 20-0, with one abstention, to recommend the vaccine for emergency use. Now, the FDA itself must decide whether to follow through, a decision that is expected to come in the next few days. Vox staff writer Umair Irfan talks about the similarities and differences between Moderna and Pfizer’s vaccine, what we’re learning about side effects for both injections, and the concerns about COVID-19 transmission to animals. Plus, why researchers say President-elect Biden’s goal for net-zero carbon emissions will require drastic, but feasible changes to how the nation operates. And how to view Monday’s conjunction of Saturn and Jupiter—a phenomenon theorized to be the explanation for the biblical Star of Bethlehem. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

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