Cosmic Rays and Climate

Solar Activity and Climate

It is already more than 200 years since Sir William Herschel claimed that variations in solar activity affect climate on Earth. Since he did not have any reliable temperature measurements, Herschel looked for indirect proxies. He compared the price of wheat in the London wheat exchange to the solar activity as mirrored in the sunspot number, and found a correlation between them.

With the exception of those who have been living in a dark cave, it is well known that Earth has warmed over the 20^th century. Anyone who reads papers or watches TV knows that it is humans who are those responsible for this warming. According to most media sources, and unfortunately according to many academics, there is no room anymore for any discussion of questions concerning the nature of the warming and its causes.

What is climate sensitivity?

The equilibrium climate sensitivity refers to the equilibrium change in average global surface air temperature following a unit change in the radiative forcing. This sensitivity (often denoted as λ) therefore has units of °C/(W/m²).

Often, instead &\lambda;, the sensitivity is expressed through the temperature change &Delta T_x2, in response to a doubled atmospheric CO₂ content, which is equivalent to a radiative forcing of 3.8 W/m². Thus, &Delta T_x2 = 3.8 W/m² λ

General Remarks

The manuscript submitted by Jahnke is an attempt to repeat analyses previously carried by myself (Shaviv PRL, 2002, New Astronomy, 2003). Although Jahnke raises a few interesting aspects, his analysis excludes several critical problems, because of which he obtains his negative result, that is, that there is no statistically significant periodicity in the data. By far, the most notable problem is that Jahnke's analysis does not consider the measurement errors. In his analysis, poorly dated meteorites were given the same weight as those with better exposure age determinations. As I show below, this has a grave effect on the signal to noise ratio (S/N) and consequently, on the statistical significance of any result.

My colleague and friend, Prof. Jan Veizer of the University of Ottawa, has written a review on the climatic role of carbon dioxide, cosmic rays and solar variability over different time scale. Unlike other material you will find on this web site, which was written with my subjective physicist's point of view, this review was written by one of the world's leading geochemists. Originally, Prof. Veizer set out to collect the most comprehensive geochemical data set, to reconstruct the paleoclimate variations over Phanerozoic (the past 550 Million years over which there are multicellular fossils to work with). His goal was to find the climatic signature of carbon dioxide in the data. To his disappointment, there was no clear correlation between his paleoclimatic reconstruction and the CO2 reconstruction (e.g.,

Many physical systems have a tendency to equilibrate the energy between different subcomponents. Sometimes it is exact, and sometimes not. For example, in an acoustic wave, the wave's energy is on average half kinetic (motion of the gas) and half internal (pressure). In the interstellar medium, there is roughly the same energy in the different components, such as internal energy, turbulent energy, magnetic field and energy of the cosmic rays. Stars are no different. In the sun, there is roughly the same binding energy (which is negative) as there is thermal energy. This can also be shown using the virial theorem. In white dwarfs, the thermal energy is unimportant, instead, there the degenergy energy of the electrons is comparable to the binding energy. We can use this tendency for equipartition to estimate different stellar parameters.

Did you ever wonder how can it snow at above freezing temperatures? Well, the naive explanation is that it simple takes time for the snowflakes to melt once they penertrate above freezing air, as they descent downwards to the ground. As it turns out, this is the reaons why hail can fall in warm weather. The hail stones simple fall fast, too fast to let the warm air melt the hail.

With snow flakes, this isn't the case. The flakes fall very slowly and the large surface to volume ratio ensure that the flakes can reach thermal equilibrium with the environment on time scales much shorter than their descend time. So, how can the flakes remain frozen as they fall?

Water Rockets are simple homemade invensions that model their chemically fueled cousins. Unlike the latter, water rockets operate using water propulsion and hand-pump generated air pressure. Here we describe the equations of the problem. They are also solved numerically in the water rocket calculator.

Introduction

The best way to obtain a fancy document, with fancy equations, is to use LaTeX (or its cousins). The catch is a high learning curve, but one which is well worth the investment.

If you are working on Mac OS X, this is especially the case, because the standard (mediocre) solution on windoze, which is MS Word, does not exist—Microsoft on purpose avoids adding multilingual support to their Office Suite (why is it that Expolorer is the only browser on the Mac which doesn't support Hebrew?). Other options are no better (NeoOffice, Mellel or Nisus Writer Express) are either costly, don't display equations nicely, or both. (Though NeoOffice, with its 0$ price tag does have very nice advantages, because of which it is worth installation).

Thus, the cheapest (that is free) solution which properly displays Hebrew and math is LaTeX with Hebrew extensions. Since we wish to edit the files on "OS X" and in particular, on the really nice TeXShop front end which supports unicode but none of the other hebrew standards, we require unicode support for LaTeX.

Here is an example: Both the .tex file and the resulting .pdf


Downloading Components

1. Make Sure you install the latest TeXShop and the underlying teTeX engine. This can be done by following the instructions in the TeXShop website. (TeXShop is a front end applications with which you can edit and tex files. The application uses the underlying teTeX engine). It includes TeXShop installation (simple download and copying to the application folder) and installation of different packages using the i-Installer package handler. I used the full 2004 teTeX distribution.

2. Download Ivritex from sourceforge. Uncompress and open the archive. You have two options to install. Either in the teTeX directory (located at: /usr/local/teTeX/share/texmf ) or in your texmf directory in your local library (/Users/<your-login>/Library/texmf). The former option will get erased next time you upgrade teTeX, the latter option will be available only to a single user. To install:

• cd <the-unachived-ivritex-folder>

• Install the files required files, by typing:

3. Download unicode support for latex (which supports hebrew, as opposed to the standard unicode which doesn't support hebrew).

• Unarchive the package. From the ucs folder that will appear, copy the files ucs.sty, utf8x.def, ucsencs.def and data/* to a TeX-path folder. For example:

Configuring TexShop

Open TeXShop. In the Document pane of the Preferences Window (under the "File" menu), make sure that encoding is set to UTF-8 Unicode. Also, it might not work properly with the TeX and ghostscript option.

You can now edit files. For example, you can use the above example files (here they are again: a .tex file and the resulting .pdf).

Note that in TeXShop, the hebrew is not right justified when you edit the text... but it doesn't change the final appearance of the document which is o.k.

You can also look more deeply at the ivritex examples which you downloaded (they use non-unicode encodings, so you cannot edit them with TeXShop, but they will LaTeX properly!)

How much is a webpage worth?

Twice every 117 years or so, Venus transits the disk of the sun. Here is some info on the events (and a photograph I took of it).

The maximum speed of a rower boat is a classic example of the beauty of dimensional analysis. It was originally derived by McMahon (1971). Here it is brought again for the convenience of the Internet audience, together with updated rowing record data.

Under which conditions can you get frost dendrites on your window?