On January 1, 2009, the highest temperature in Beijing was 4°C, and the lowest temperature was -7°C. What is the temperature difference in Beijing on this day?
2009年1月1日，北京的最高气温是4℃，最低气温是-7℃，北京这一天的温差是多少℃．
<gadget id="calculator">4 - (-7)</gadget>
<output>11</output>

<result>11</result>