This is not a question. Neither does it contain any actionable information. 

Please carefully read: How should I ask a question in the Forum if I want to receive useful answers?

Then refine your statement above to a question that is understandable and explains what the question/intent is.

 How to use global variable in DNG? Example I have A , B , C project. Every project having temperature, speed etc values. How can I use one variable list that will contain the values of all the projects? 

I still don't understand what you are describing.
What do you mean "every project has temperature"?
Are you talking about a custom artifact attribute named temperature in multiple components or project areas?
Perhaps some screenshots showing what you're trying to do would make this clearer.
Or at least describe the dialogs where this data is currently defined.

DNG does not support anything like global variables. It is unclear what variable means in this context.

In addition it is very unlikely that there is only one speed, temperature, etc. Per project. So you would also not access them across projects.

DNG is a requirements management system. You have requirements, requirements have attributes, attributes are of  a certain type and can contain certain values. Values might be discrete values or numbers, strings etc..

Each component has its own type system that defines this. Types in different components can be the same, or not.  

So you have to explain what you want to achieve/solve and not assume an implementation concept.