Is global warming just part of Earth’s natural cycle? In this episode of Weathered, we break down why that’s not the full story. From ice ages and Milankovitch cycles to the role of CO2 and fossil fuels, today’s climate change is unlike anything in Earth’s deep past. Learn why the speed of warming matters and how we can bring our temperature down.It's because of my knowledge of Milankovitch cycles that I was able to answer a persistent but now gone skeptic, which I recapped in PBS Digital's Be Smart debunks 'The Biggest Myth About Climate Change'.
I have mentioned several times that I'm a paleontologist who studies Pleistocene fossils, particularly snails. What I don't mention is that I used data from the snails, clams, and plants of Rancho La Brea to reconstruct the late Pleistocene climate of southern California, so I'm quite familiar with natural climate change. That's why I was able to respond intelligently to Ed, the troll who was better than a spammer, when he snarked "Maybe you can tell us what the climate is supposed to be so we will know if it's changing too much."I'm glad to see Maiya May and Jessica Tierney of the University of Arizona confirm both what the climate would have been doing naturally and what it's doing instead. It shows what I told Ed was (and still is) correct.Ed, actually, I can. The average temperature of the Northern Hemisphere should be almost two degrees Fahrenheit cooler than it is today based on the pre-1900 temperature trend, three degrees based on the progress of previous interglacials. If you want the reasoning and evidence, you will have to wait until I put together an entire entry with links; it will take more effort than a simple comment is worth. In the meantime, count your blessings that you stumbled onto someone who actually knows the answer to what you may have thought was a rhetorical question too hard to answer.That was back in 2015.
I teach Milankovitch cycles to my geology students, both on the first field trip where I ask them to describe a display at a museum which summarizes the effects as "stretch, wobble, and tilt (eccentricity, precession, and obliquity)" and in a lecture about glaciers and glacial features, where I reinforce my point with The History of Climate Cycles (and the Woolly Rhino) Explained from PBS Eons.
Throughout the Pleistocene Epoch, the range of the woolly rhino grew and shrank in sync with global climate. So what caused the climate -- and the range of the woolly rhino -- to cycle back and forth between such extremes?I've been showing this video since just before the pandemic; I'm surprised I haven't embedded it here until now. I guess I just needed the right opportunity.
Back to May on PBS Terra, who is revisiting PBS Terra's Weathered asks 'Earth's Temperature Has Changed WILDLY, So What's the Big Deal About a Few Degrees?'
The correlation between carbon dioxide levels and temperature from ice-core data is another story I tell my students. I asked them about it in my worksheets about An Inconvenient Truth and still ask them about it in my worksheet for Chasing Ice. I also ask them about it on my exams, but for test security reasons, I don't post those here. Maybe after I retire.As Dr. Tierney points out, carbon dioxide is at levels not seen for 3.6 million years so the Earth is on track for much warmer temperatures even if humans stop putting greenhouse gases into the atmosphere. Because of the fossil foolishness in the Big Brutal Bill, the U.S. alone will continue emitting carbon dioxide and methane for years. Worse yet, as Zeke Hausfather of Berkeley Earth described, it will take 400,000 years for natural processes to remove the excess carbon dioxide from the atmosphere. That's four more Milankovitch cycles! Maybe that will make our distant descendants less subject to ice ages, but it's going to mess up the near future for us and progeny down to our great-grandchildren.
That's a wrap for today's story I tell my students. Tomorrow is Piña Colada Day. Stay tuned to see if I celebrate it or cover the action movie nominees at the Critics Choice Super Awards. Maybe I will do both.
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