It is no more nor less useful a source of information than any other. Some people find graphs easy to understand, others do not. Approximate values and trends may be sufficient for some purposes whereas for others the detailed numbers and statistical analyses are required.
You can use a double bar graph to display two different types of information side by side to show contrast. 1 bar could be showing information from last month. The 2nd bar could show information from this month.
A line graph is useful for showing trends or continuous change. Other kinds of graph also will show these, but a line graph is usually clearest.
You would use a bar graph is useful when the independent variable (x-variable) is categorical. But there are no hard and fast rules. If it conveys the relevant information effectively then use it and if not don't.
line graph
This depends upon the graph; you can graph any kind of information that you like.
They provide information on how the whole is divided between its parts.
Media is a source of information and can be very useful.
Relevant
Relevant
The answer will depend on the information conveyed by each graph. And since you have not bothered to share that crucial bit of information, I cannot provide a more useful answer.
contains information related to the subject.
The first time you find a piece of useful information from a source
There are a few different things that will make a climate graph more useful. Having data for a long period of time makes this graph very useful.
periodic table
You can use a double bar graph to display two different types of information side by side to show contrast. 1 bar could be showing information from last month. The 2nd bar could show information from this month.
graph
line graph