Prevent countdown from reloading every time a new scene is loaded

I have this countdown script which works fine, there is just the problem, that the countdown restarts every time a new scene is loaded (which it should not). Is there a way to prevent it from doing that, and just let the countdown keep going even if a new scene is loaded?

Here is my code.

 static var energyObj : int = 5;
 
 var counter : float;
 
 function Start()
 {
 counter = 1800;
 }
 
 
 function Update () {
  
   counter -= Time.deltaTime;
      if(counter <= 0){
         energyObj += 1;
         counter = 1800;
         Debug.Log("Energy is " + energyObj); 
 }
 
 }
 
 function OnGUI () {
 
     var minutes = Mathf.Floor(counter / 60).ToString("00");
     var seconds = (counter % 60).ToString("00");
     GUI.Label(new Rect(100,40,400,40),"To Next: " + minutes + ":" + seconds);
 }