Accessing variables outside of function?

Accessing variables outside of function?

Ugghh - I don't know what I'm doing wrong - probably pertains more to Javascript than jQuery.

$(document).ready(function(){
    var myVar = 0;
   
    $("#myButton").click(function(event){
        myVar++;
    });

    $("#myButton2").click(function(event){
        alert(myVar); //this returns 'undefined'  Why?  :(
    });

});

Why can't I access the 'myVar' variable my clicking 'myButton2' ??