\subsection{High School Experiments}  
\label{Sec:Experiments}
%
On a hot summer afternoon, 
temperature measurements
were performed 
with a standard digital thermometer 
by the first author\TschSpace%
%
\cite{%
Gerlich1995,%
Gerlich2004,%
Gerlich2005a,%
Gerlich2005b,%
Gerlich2007}
%
and were recently reproduced  
by the other author. 

In the summertime, such measurements 
can be reproduced by everyone very 
easily. 
The results are
listed in Table~\ref{table:GerlichMeasurements}.
%
\input{GerlichTscheuschner2007a_240_real_greenhouses_high_school_experiments_table009_.tex} 
%

\noindent%
Against these measurements one may object 
that one had to take the dampness of the ground 
into account: at some time during the year the 
stones certainly got wet in the rain.
The above mentioned measurements 
were made at a time, when it had not 
rained for weeks. They are real measured values, 
not average values over all breadths and lengths 
of the Earth, day and night and all seasons and 
changes of weather.
These measurements are recommended to 
every climatologist, who believes in the 
${\rm CO}_2$-greenhouse effect, because 
he feels already while measuring, that 
the just described effect 
\textbf{has nothing to do with} 
trapped thermal radiation. One can touch 
the car's windows and notice that the panes, 
which absorb the infrared light, 
are rather cool and do not heat the inside 
of the car in any way. If one holds his hand 
in the shade next to a very hot part 
of the dashboard that lies in the Sun, 
one will practically feel no thermal radiation 
despite the high temperature of 
70~$^\circ{\rm C}$, 
whereas one clearly 
feels the hot air. 
Above the ground one sees why it is cooler 
there than inside the car: the air inside 
the car \lq\lq stands still\rq\rq, above 
the ground one always feels a slight movement 
of the air. The ground is never completely plain, 
so there is always light and shadow, which keep the 
circulation going. This effect was formerly used for many 
old buildings in the city of Braunschweig, Germany. 
The south side of the houses had convexities.
Hence, for most of the time during the day, 
parts of the walls are in the shade and, 
because of the thus additionally stimulated circulation,
the walls are heated less. 

In order to study the warming effect
one can look at a body of 
specific heat 
$c_{\rm v}$ 
and width 
${\rm d}$, 
whose cross section 
${\rm F}$ 
is subject to the radiation 
intensity 
${\rm S}$
(see Figure \ref{fig:Parallelepiped}).
%
\begin{figure}[hbtp]
\ifthenelse{\equal{IJMPB}{\TschStyle}}{%
\centerline{\psfig{file=PictureLarge_parallelepiped_.eps,width=2.00in}}
}{}%
\ifthenelse{\equal{arXiv}{\TschStyle}}{%
\centerline{\includegraphics[scale=1.00]{PictureSmall_parallelepiped_.png}}
}{}%
\ifthenelse{\equal{TeX4ht}{\TschStyle}}{%
\centerline{\includegraphics[scale=1.00]{PictureLarge_parallelepiped_.png}}
}{}
\vspace*{8pt}
\caption{A solid parallelepiped of thickness ${\rm d}$
         and cross section ${\rm F}$ subject to 
         solar radiation}
\label{fig:Parallelepiped}
\end{figure}
%
\noindent%
One has
%
\begin{equation}
\varrho\,
{\rm F}\,
{\rm d}\,
c_{\rm v}
\frac{dT}{dt}
=
{\rm F}{\rm S}
\end{equation}
%
or, respectively,
%
\begin{equation}
\frac{dT}{dt}
=
\frac{\rm S}{{\varrho}\,c_{\rm v}\,{\rm d}}\,
\end{equation}
%
which may be integrated yielding
%
\begin{equation}
T = T_0 +
\frac{\rm S}{{\varrho}\,c_{\rm v}\,{\rm d}}\,
(t-t_0)
\end{equation}
%
In this approximation, there is 
a linear rise of the temperature 
in time because of the 
irradiated intensity. One sees 
that the temperature rises particularly 
fast in absorbing bodies of small diameter: 
Thin layers are heated especially fast 
to high temperatures by solar radiation. 
The same applies to the heat capacity   
per unit volume: 
%
\begin{itemize}
\item 
If the heat capacity is large
the change of temperature will 
be slow.
\item 
If the heat capacity is small
the change in temperature will 
be fast.
\end{itemize}
%
Thus the irradiated intensity is 
responsible for the quick 
change of temperature, 
\textit{not} for its value. 
This rise in temperature 
is stopped by the heat transfer
of the body to its environment.

Especially in engineering thermodynamics
the different kinds of heat transfer and
their interplay are discussed thoroughly\TschSpace%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\cite{AlfredSchackBook,Kreith1999,Baukal2000}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
A comprehensive source is the classical 
textbook by Schack\TschSpace%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\cite{AlfredSchackBook}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
The results have been tested e.g.\ in combustion 
chambers and thus have a strong experimental
background. 

One has to distinguish between
%
\begin{itemize}
\item Conduction
\item Convection
\item Radiation
\item Transfer of latent heat in phase transitions 
      such as condensation and sublimation%
%
\footnote{%
Among those phenomena governed by the exchange of latent
heat there is \textit{radiation frost}, an striking
example for a cooling of the Earth's surface through 
emission of infrared radiation.} 
%      
\end{itemize}
%
Conduction, condensation and radiation, 
which slow down the rise in temperature 
work practically the same inside and outside 
the car. 
Therefore, the only possible reason for 
\textit{a difference} in final temperatures 
must be convection: 
A volume element of air above the ground, 
which has been heated by radiation, 
is heated up (by heat transfer
through conduction), rises and 
is replaced by cooler air. 
This way, there is, in the average, 
a higher difference of temperatures 
between the ground and the air and a higher 
heat transmission compared to a situation, 
where the air would not be replaced. 
This happens inside the car as well, 
but there the air stays locked in and the air 
which replaces the rising air is getting 
warmer and warmer, which causes lower heat 
transmission. Outside the car, there is 
of course a lot more cooler air than inside. 
On the whole, there is a higher temperature 
for the sunlight absorbing surfaces as well 
as for the air.

Of course, the exposed body loses energy 
by thermal radiation as well.
The warmer body inside the car would lose 
more heat in unit of time than the colder 
ground outside, which would lead to a 
higher temperature outside, 
if this temperature rise were not absorbed 
by another mechanism! If one considers, 
that only a small part of the formerly 
reckoned 
$60$\,-\,$70$ 
percent of solar radiation 
intensity reaches the inside of the car 
through its metal parts, this effect would 
contribute far stronger to the temperature 
outside! The \lq\lq explanation\rq\rq\ 
of the physical greenhouse effect 
only with attention to the radiation 
balance would therefore 
lead to the reverse effect!
The formerly discussed effect of the 
\lq\lq trapped\rq\rq\ heat radiation 
by reflecting glass panes remains, 
which one can read as hindered heat 
transmission in this context. 
So this means a deceleration of the cooling 
process. 
However, as this heat transmission 
is less important compared to the convection, 
nothing remains of the absorption and reflection 
properties of glass for infrared radiation 
to explain the physical greenhouse effect.
Neither the absorption nor the reflection 
coefficient of glass for the infrared light 
is relevant for this explanation of the 
physical greenhouse effect, but only the 
movement of air, hindered by the panes 
of glass.
 
Although meteorologists have known this 
for a long time\TschSpace%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\cite{Lee1973,Berry1974},
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
some of them still use the physical greenhouse 
effect to explain temperature effects of planetary 
atmospheres.
For instance in their book 
on the atmospheric greenhouse effect,
Sch\"onwiese and Diekmann 
build their arguments 
upon the glass house effect\TschSpace% 
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\cite{Schoenwiese1987}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
Their list of references
contains a seminal publication
that clearly shows that this is
inadmissable\TschSpace%
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\cite{DOE1985}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
