I can not decipher all of the pertinent information from that site you posted.
(After all it is mathematical. ;-)

According to the laws of physics, if the temperature of the air, (that is in a open environment like the atmosphere) becomes warmer, then the density must decrease and the pressure also must decrease.

The graph that you displayed does not show any significant pressure decrease over time, so that would mean that there can not be a temperature increase either.
Is global warming a made up story?

I found other sites with pertinent information, I think that the graphs in these web sites are more trustworthy.
How do you interpret them?

http://www.metoffice.gov.uk/research/hadleycentre/obsdata/

http://www.metoffice.gov.uk/research/hadleycentre/obsdata/HadSLP2.html

http://www.metoffice.gov.uk/research/hadleycentre/obsdata/HadAT.html

http://www.metoffice.gov.uk/research/hadleycentre/obsdata/cet.html

Let me know if I need to include your traditional expletives.