Sharing variable b/w event handlers

HTML

<p>Section 1:</p>
		<div class="mySectionOne">
			<button class="add">add</button>		
			<button class="sub">sub</button>		
			<button class="show">show</button>	
			<p>The value of Common var in section one is:<span class="showVal"></span><p>
		</div>
		
	<p>Section 2:</p>	
		<div class="mySectionTwo">
			<button class="add">add</button>		
			<button class="sub">sub</button>		
			<button class="show">show</button>	
			<p>The value of Common var in section two is:<span class="showVal"></span><p>
		</div>

JavaScript

(function( $ ) {
		$.fn.updateCommonVar = function (options) {
			var defaults= {
				commonVar:0,
			}
			var ParameterObject=  $.extend({}, defaults, options);
			 this.each(function() {
					$(this).find("button.add").bind("click", fnAddOne);
                 $(this).find("button.sub").bind("click", fnSubOne);
                 $(this).find("button.show").bind("click",fnShow);
			 });
			 return this;  
		};
		
		function fnAddOne(e){
            console.log(e.data);
			defaults.commonVar++;		
		}
		function fnSubOne(e){
			defaults.commonVar--;
		}
		function fnShow(e){
            		$(this).parent().find('.showVal').html(defaults.commonVar);
		}
		
		
	})( jQuery );
    jQuery(document).ready(function() {
        jQuery('.mySectionOne').updateCommonVar({commonVar:1});
        jQuery('.mySectionTwo').updateCommonVar({commonVar:1});
    });