The energy that heats Earth, shapes its climate and sustains life comes almost entirely from the Sun. The Sun’s brightness is fairly consistent. But the amount of sunlight that Earth reflects—known as its albedo—changes. And that means the amount of energy that Earth absorbs changes, too.

What does that mean for future warming? As Earth’s surface temperatures break record after record, its energy imbalance has become the hottest question in climate science. Read our cover story this week on global dimming and what should be done about it. ■

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