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On the Nature and Value of Consensus

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About 20 years ago, I remember participating in a meeting where participants were actively debating a proposition. The moderator was enforcing parliamentary procedure, and speeches for and against the proposition were heard in turn - one speech for, then one speech against. This being the first meeting I had been in following this kind of procedure, I began to think that the room was evenly divided between the two positions. I was strongly in favor of it, and I was disheartened to see so much opposition to it. But when the vote was finally taken, I was more surprised by the results. The proposition passed by an extraordinarily large margin. In fact, it appeared that those speaking against the proposition made up almost all the people that voted against it, and the vast majority of the people in the room were like me. Most of us had essentially made up our minds, and we had no intention of making any speeches; we were just waiting for the debate to be over so we could vote.  My impr...

Comparing CO2 Forcings and Temperature in the Geologic Past

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For over 20 years, geologists have attempted to model CO2 concentrations across the geologic past. Geologists currently have sufficient proxy evidence to reconstruct CO2 concentrations for significant parts of the last 420 million years, but models can be useful to infer concentrations when proxy evidence is weaker or lacks sufficient resolution. While "box" models like COSPE or GEOCARBSULF  confirm broad correlations between CO2 and global temperatures , the correlation may be improved if the models take better account of tectonic processes affecting CO2 concentrations. Evaluation of Proxies for CO2 and Temperatures In a study published three years ago, Mills et al 2019 evaluated the performance of CO2 proxies as well as COPSE and GEOCARBSULF "box" models for CO2. The latter model is the most recent update to the GEOCARB model that is frequently misused in contrarian graphs of CO2 and temperature - GEOCARBIII was published in Berner 2001 and is often plotted wit...

Bulverism & Debate Dysfunction

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Recently I came across a new word, "bulverism." The term was coined by C.S. Lewis to describe what is broadly similar to what Antony Flew called the "subject/motive" shift. Strictly speaking, it's a form of the logical fallacy, ad hominem - attacking the author instead of the argument. Bulverism takes the the following form:      A. Assume your opponents are wrong      B. Identify something about your opponents that supposedly explains why they are wrong Bulverism often springs up in debates that are highly contentious - that is, when people have strongly held beliefs that are also strongly opposed by others. In highly contentious debates, we tend to react in terms of our contempt for the other side of the debate (and even the person that holds the view being opposed). Lewis describes bulverism with an example from math, where fictional Ezekiel Bulver's father claims that the sum of any two sides of a triangle must be longer than the third, and his wife sa...

Tropical Cyclone Trends

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Note: I updated this in 2024 to include 2023 data. In a previous post , I covered the distinction between detection and attribution. These are normally considered sequentially. First you detect a signal above natural variability, then you examine if some portion of that signal can be attributed to human activity. The previous post shows that the two are statistically independent from each other, so there is no need to limit attribution studies to signals that are detectable above natural variability. This distinction and clarification I think is important in discussions of tropical cyclone trends. While trends are clear since 1980, the longer term record (since ~1850-1900) is less clear due to selection biases arising from our increasing ability to detect tropical cyclones. This makes detection difficult long term, but that doesn't necessarily mean that scientists can't also examine ways in which human activity is affecting tropical cyclone trends. Detection in the Satellite R...

Detection and Attribution

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There is growing evidence supporting the conclusion that AGW is already having an effect on extreme weather events, and those impacts are not beneficial to humanity or to the earth's ecosystems. But the process of arriving at those conclusions is complex, and different types of extreme weather are affected by AGW in different ways. While there is a clear (and obvious) link between AGW and extreme heat, heatwaves, droughts, and flooding, the effects of AGW on other extreme weather are far more difficult to determine. For instance, it may be that AGW is only affecting which parts of the US are more likely to be affected by tornadoes without impacting their frequency. The effect of AGW on Tropical Cyclones (TCs) has been extensively studied, and it appears that there is growing evidence that there are clear connections between AGW and hurricane activity, but I see many reported connections (or lack of connections) misstated by the media, politicians and "think tanks." In ord...

The Physics of the Climate Response to Doubling CO2

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Update (6/6/2025): I edited the text for clarity (especially in the first couple paragraphs), changed g to  g̃ to distinguish the normalized GHE from the acceleration due to gravity,  and added more references with excerpts at the bottom of the post. The Earth's effective temperature - the mean surface temperature of Earth if the atmosphere contained no GHGs but with current albedo can be calculated since we know that ASR (hereafter Fin) =  (1-α)*S/4 and OLR (hereafter Fout) is governed by  εσ*T^4. At equilibrium, ASR = OLR (Fin = Fout). With no greenhouse effect (GHE), the Earth's emission temperature (Te) would be at the surface, meaning that Te = Ts, so we can solve for Te with (1-α)*S/4 = εσ*Te^4 If we solve for Te with a surface emissivity ( ε) o f 0.98 and albedo ( α) of 0.306, we end up with Te = 255.3 K.  So, if the earth had no atmosphere with albedo roughly the same as today, the average surface temperature of the earth would be about  -18°C. ...