Paleontologist Kirk Johnson explores the polar extremes of the planet, including miles-high ice sheets and warm polar forests brimming with life.Paleontologist Kirk Johnson explores the polar extremes of the planet, including miles-high ice sheets and warm polar forests brimming with life.Paleontologist Kirk Johnson explores the polar extremes of the planet, including miles-high ice sheets and warm polar forests brimming with life.
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Featured review
Extraordinary claims require extraordinary evidence.
The posted "Storyline" on this webpage does a good job to describe this episode's content. The abundant flow of facts and research presented is above average, and therefore very satisfying. There are instances when a string of findings and facts are presented, then a conclusion is presented as yet another fact rather than as a hypothesis. What has happened with the study of climate on Earth (like with the discovery of supermassive black holes, or the string of findings that have led to hypotheses of dark matter and dark energy, etc.) is a mixture of facts and the theories we assemble from them; and they must be subject to ongoing research and discovery (like what is ongoing with the research of supermassive black holes, dark matter and dark energy).
Here's one example. As has been done elsewhere, this NOVA episode presents the irresistible comparison of the runaway greenhouse on the planet Venus and its components (e.g., carbon as the greenhouse accomplice) against reported current era carbon increases on Earth to draw towards a conclusion that we're on track to a similar state of affairs, though (clearly) Earth need not resemble Venus closely to become barren and lifeless. However, there is no mention of the fact that the length of one day on Venus is 243 Earth days. What would happen on Earth if one day lasted two-thirds of a year (as on Venus), given the swing in temperature on Earth in a single 24 hour period? Starting tomorrow, if the Sun could concentrate its energy on the surface of the Earth for months (without night to cool things down in a regular 24 hour period), a cycle towards a greenhouse scenario resembling Venus would be well underway. Further, with oceans begining to turn to water vapor there would be increasingly no "sink" for the emissions from volcanoes other than the atmosphere, so the greenhouse effect would gain momentum in such conditions. There are other factors to add to discount Venus as a cautionary tale for Earth beyond anecdotal, but the above is enough to make the point.
There's perhaps one compelling sequence that stands out in all the data presented in the episode: the chart of "hothouse worlds" (no ice) and "icehouse worlds" (with icecaps at least at one of the poles, and colder)-a timeline of the Earth's climate history over the last 500 million years showing, again, the range of temperature and the epochs where at least ice caps existed. It turns out that only 25% of our climate history resembles the climate profile we enjoy today, and the other 75% being much warmer. This is an extraordinary piece of evidence that demands extraordinary (not simple) conclusions, such as is often said in popular media: just reduce human-generated atmospheric carbon and we'll be OK. To his credit, the host-Kirk Johnson, who holds a doctorate in geology and paleobotany from Yale University-takes the opportunity to assert: "Today we live on a planet that has ice at both poles, and we think that's normal because that's our world-but when we look at the fossil record we realize that it has had only four episodes where there's been glacial ice-only about 25% of the last 500 million years has our planet been like it is today."
Another example (without mention in the episode): "The Little Ice Age"-roughly from the middle ages to the early to mid nineteenth century. There are theories, but none with overwhelming consensus, i.e., no one knows what started the warming period that caused the end of that cooled epoch, but it's clear that given the end came before or during the infancy of the industrial revolution, there is far too little human intervention to conclude that the new warming was man-made.
Anyone reading the above may think that this review is inspired by a streak for denying "climate change"-it is not. It is the want for engaging science-which doesn't call for "believers" and excommunicate "deniers"-it simply carries on its endeavor, building the body of evidence, and humbly refining its theories as the entire (not agenda-selective) body of evidence grows. Net-net, this episode comes out on the plus side of that criterion.
Here's one example. As has been done elsewhere, this NOVA episode presents the irresistible comparison of the runaway greenhouse on the planet Venus and its components (e.g., carbon as the greenhouse accomplice) against reported current era carbon increases on Earth to draw towards a conclusion that we're on track to a similar state of affairs, though (clearly) Earth need not resemble Venus closely to become barren and lifeless. However, there is no mention of the fact that the length of one day on Venus is 243 Earth days. What would happen on Earth if one day lasted two-thirds of a year (as on Venus), given the swing in temperature on Earth in a single 24 hour period? Starting tomorrow, if the Sun could concentrate its energy on the surface of the Earth for months (without night to cool things down in a regular 24 hour period), a cycle towards a greenhouse scenario resembling Venus would be well underway. Further, with oceans begining to turn to water vapor there would be increasingly no "sink" for the emissions from volcanoes other than the atmosphere, so the greenhouse effect would gain momentum in such conditions. There are other factors to add to discount Venus as a cautionary tale for Earth beyond anecdotal, but the above is enough to make the point.
There's perhaps one compelling sequence that stands out in all the data presented in the episode: the chart of "hothouse worlds" (no ice) and "icehouse worlds" (with icecaps at least at one of the poles, and colder)-a timeline of the Earth's climate history over the last 500 million years showing, again, the range of temperature and the epochs where at least ice caps existed. It turns out that only 25% of our climate history resembles the climate profile we enjoy today, and the other 75% being much warmer. This is an extraordinary piece of evidence that demands extraordinary (not simple) conclusions, such as is often said in popular media: just reduce human-generated atmospheric carbon and we'll be OK. To his credit, the host-Kirk Johnson, who holds a doctorate in geology and paleobotany from Yale University-takes the opportunity to assert: "Today we live on a planet that has ice at both poles, and we think that's normal because that's our world-but when we look at the fossil record we realize that it has had only four episodes where there's been glacial ice-only about 25% of the last 500 million years has our planet been like it is today."
Another example (without mention in the episode): "The Little Ice Age"-roughly from the middle ages to the early to mid nineteenth century. There are theories, but none with overwhelming consensus, i.e., no one knows what started the warming period that caused the end of that cooled epoch, but it's clear that given the end came before or during the infancy of the industrial revolution, there is far too little human intervention to conclude that the new warming was man-made.
Anyone reading the above may think that this review is inspired by a streak for denying "climate change"-it is not. It is the want for engaging science-which doesn't call for "believers" and excommunicate "deniers"-it simply carries on its endeavor, building the body of evidence, and humbly refining its theories as the entire (not agenda-selective) body of evidence grows. Net-net, this episode comes out on the plus side of that criterion.
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- legalimit
- May 11, 2020
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