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since the 1970s, the frequency of wildfires has increased at least four-fold, and the total size of burn areas has increased at least six-fold in the western United States alone. Steadily rising, the U.S.'s bill for fighting wildfires now totals $1.5 billion per year

the paper presents a new framework for considering wildfires based on the Earth's pre-human fire history, ways that humans have historically used and managed fire and ways that they currently do so.

This research emphasizes the importance of understanding the relative influences of climate, human ignition sources and cultural practices in particular environments in order to design sustainable fire management practices that protect human health, property and ecosystems.

Fresh snow bounces back 84 percent of the light that hits it; warm, rounded crystals can reflect as little as 70 percent. Slushy snow saturated by water – which gives it a gray cast, or even a bluish tint – reflects as little as 60 percent. Add dust or soot, and the albedo drops below 40 percent. Box's satellite data has shown a steady darkening in Greenland's albedo, from a July average of 74 percent when the century began to about 68 percent last year. And then came this summer: Without warning, the line on the albedo chart dropped deep into uncharted territory. At certain altitudes, the ice sheet in Greenland was suddenly four percent less reflective – in a single season.

But the future, pressing as it is, sometimes gives way to sheer awe at the scale of what we've already done. Simply by changing the albedo of the Greenland ice sheet, Box calculates, the island now absorbs more extra energy each summer than the U.S. consumes in a year. The shape and color of the ice sheet's crystals, in other words, are trapping more of the sun's rays than all the cars and factories and furnaces produce in the world's biggest economy. One of Box's collaborators, photographer James Balog, puts it like this: "Working in Greenland these past years has left me with a profound feeling of being in the middle of a decisive historic moment – the kind of moment, at least in geologic terms, that marks the grand tidal changes of history." Amid this summer's drama of drought, fire and record heat, the planet's destiny may have been revealed, in a single season, by the quiet metamorphosis of a silent, empty sheet of ice.