Posts

Staying healthy

Image
  These are some of my personal musings on the topic: 1. Above all, eat healthy and try to control your weight. What that means in practice, is a bit controversial and I will return to that below. 2. Don’t smoke. It has been anticipated since the 1930s that smoking causes cancer [1] and it has now been confirmed beyond reasonable doubt. 3. Don’t take drugs. Don’t drink too much alcohol. Take vaccines, at least the ones recommended by your government. 4. Exercise. What kind of exercise is the best? They say that to live long, you need exercise which elevates the heart rate for long periods of time, i.e. aerobic training, i.e. cycling, jogging or at the very least, walking. But I have seen several headlines which say that for old people, muscle strength predicts very strongly non-morbidity and longevity. So, it seems that to live long, you need aerobic training, but to live even longer, you need strength training, e.g. gym of crossfit. Ideally, you would combine these two types of tr...
Post a Comment
Read more

A tale of 13 degrees

Image
  What happens if we don’t stop burning the fossil fuels? Is it the end of the world? Nobody knows certainly but I wanted to tackle this question with another back-of-the-envelope calculation. Here’s what I found: First, let’s take the same starting point as in the previous post, the climate equation dT = aS - bT^4. If the world is in a thermal equilibrium, dT = 0 and aS = bT^4. From this, we may solve how emissivity b affects the equilibrium temperature. (Remember, the effect of CO2 comes through the emissivity in this model.) We have T = (aS/b)^0.25. Thus, we may conclude that the equilibrium temperature is directly proportional to the power -0.25 of emissivity. In practice, this means that every 1% decrease in emissivity increases the equilibrium temperature by approximately 0.25%. The next question is obviously, how much unlimited burning of fossil fuels affects the emissivity. This is now hardcore speculation, but I chose to model this by using emission spectra. Above, the fir...
Post a Comment
Read more

A simple demonstration of climate change

Image
I wanted to test if I can detect anthropogenic climate change from simple timeseries. To that end, I downloaded global surface temperature anomalies from NOAA [1], the good old Keeling curve from Scripps Institution of Oceanography [2] and an estimate of total solar irradiance from University of Colorado [3]. Then I was like 'hmm... how would a simple climate model look like?' I came up with the idea dT = aS - bT^4, dT being change of temperature, S being solar energy flux and T^4 coming from Stefan-Boltzmann's law, with a and b positive constants. (Bear with me, I know that this model is overly simplistic! The idea is what you can derive from this model, and that's quite awesome.) Then, how could CO2 go in? I assumed b = b0*exp(-c*CO2) with b0 and c positive, this is a reasonable first approximation: b decreases in CO2 but convexly. If there is no relationship between CO2 and global temperature, then c=0. Then I linearized the whole of dT around the mean of S, CO2 and ...
Post a Comment
Read more