Assorted Links

  • A very common knee surgery ($14 billion per year spent on it in America) turns out to be no better than sham surgery in many cases. Plainly this supports critics of medicine who say there is overtreatment. To be fair there is good news: 1. At least this particular operation wasn’t contraindicated by high school biology.  2. The study was done and published. 3. And publicized widely enough to influence practice.
  • Heart guidelines based on fake research probably killed tens of thousands of people. Making useless knee surgery look good.
  • “The time you’re taking to help this girl, you could be …” A great talk by Jessica Alexander about ten years working for NGOs. Her book is Chasing Chaos: My Decade In and Out of Humanitarian Aid.
  • On EconTalk, Judith Curry, the climatologist, makes the excellent point that it is weird to call someone who believes climate questions are more complex than portrayed a “denier”. In every other use of the term, a denier is someone who avoids recognizing complexity, i.e., the opposite. On the other side of the ledger, Curry makes an elementary physics mistake when she says that as an ice cube floating in your drink melts, the water level of your drink rises. (It stays the same.)

Thanks to Allan Jackson.

11 Replies to “Assorted Links”

  1. What can you make of a world where a leading climatologist isn’t familiar with Archimedes’ Principle? She should have mastered that at thirteen or fourteen.

    Seth: I think it means you don’t even have to understand Archimedes’ Principle to realize the vacuity of the arguments for anthropogenic global warming.

  2. I haven’t listened to Curry’s talk, but surely there’s a difference between melting sea ice (which is analogous to the melting ice cube in a glass) and melt from continents (Antarctica, Greenland) and glaciers, which would add to sea level.

    Seth: Curry said that when the ice in your drink melts, the level of the water rises. Sure, when a glacier sitting on land melts, the water level rises.

  3. Tom, no, the water level will not fall. Yes, as the ice melts, its density will increase and its volume will be smaller, but some of the ice was NOT IN THE WATER. It was floating above the water. That part of the ice now goes into the water and exactly counteracts the effect of increasing density.

    That’s because how high something floats depend on its density. The less dense it is, compared to water, the higher it floats.

    (The buoyant force on something is equal to the weight of the fluid it displaces. So a bit of pure ice in pure water has to weigh exactly the same as the fluid it displaces. Then, when it melts, it will take up exactly the same amount of space as the water it previously displaced, and there will be no change in water level.

    Glaciers in the sea are more complicated. Salt water is more dense than pure water but glaciers also contain rocks and dust.)

  4. Her quote from the EconTalk transcipt. “Again, the bigger wildcard is how much the glaciers are going to melt. So, once you melt the great glaciers, it’s like adding more ice cubes into your glass of water, once they melt it causes the level of water in your glass to rise.” This is different than just melting ice in a glass causing the water to rise.

    Seth: It is? She said “once they melt…” meaning “when they melt, but not before that . . . “.

  5. I’ve had that knee surgery, and it was very successful! Which makes me wonder what actually is happening there. For example, was my return to normal function actually the result of my post-operative care and exercise regime? Or perhaps the surgery isn’t very accurate and helps some to roughly the same extent it harms others?

    Apropos the glaciers: my country (New Zealand) has several glaciers on land, which is also the case for a large chunk of Antarctica. Sea level will rise when they melt — that ice wasn’t floating on the sea before and the meltwater will add to the sea’s volume. They are consistently melting now too. Curry may be wrong about the mechanism but she is right that melting glaciers will cause or are causing sea level rise.

  6. I stand corrected, Roger Sweeny is right. The decreased volume of the melted ice exactly offsets the volume of ice that had been above water before melting. I worked it out for a simple example to cross-check the thinking. And, as he says, the case of real glaciers consisting of frozen non-salty water and having embedded materials makes the details more complex (not to mention density changes with temperature changes) , but clearly won’t change the result in any important way. At any rate, the glacier melt from non-floating ice is what would affect the sea level, not the floating ice.

  7. Again, the bigger wildcard is how much the glaciers are going to melt. So, once you melt the great glaciers, it’s like adding more ice cubes into your glass of water. Once they [the great glaciers on land] melt it causes the level of water in your glass to rise.”

    Change the comma in the transcript to a full stop and the meaning changes.

  8. I think her point is that glaciers, on land, melt *into* the water, so more water is there overall.

    Seth: That’s so obvious no sane person would say it. I don’t think that’s what she meant, especially since she mentioned ice cubes in a glass.

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