Earth is Burning

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Lightning and other natural events have been igniting landscapes for eons. Fire is an integral part of nature. Plants and animals have adapted to its presence, and some have even come to depend upon it. Humankind has changed the historic equation… burning forests to promote game or allow passage… or firing the land for agriculture. Recently, we’ve also been working to preserve forests and other wildlands. But in periods of drought, that makes them more combustible. With more people living on Earth than ever before, we are seeing the rise of the mega fire… catastrophic blazes that are nearly impossible to control, and can cover thousands of square kilometers. Each year in the United States, 1% of all fires account for 90% of the area burned. You can see the evolving influence of fire in satellite data… with red dots indicating areas burned in one year.

A computer model overlay shows aerosols, or particles, in the air. Green for soot and smoke. Brown for dust. A vast cloud of dust is blowing off Saharan Africa. Sub-Saharan Africa is ablaze. To the north, easterly flows send a blanket of haze, mingled with dust from the Middle East into Asia and Russia. The major burn zones of Indonesia and Australia send smoke clouds streaming out to the Indian Ocean. The causes of all this fire include the accumulation of fuels… increased human presence in wildlands, periods of drought, and rising global temperatures. Black carbon, the fine particles contained in smoke and soot, don’t stay in the air long. But while it’s there, it traps heat in the lower atmosphere. Then if it falls onto ice and snow, it absorbs heat while reducing reflectivity.

You can see this “snow darkening” effect in NASA data. The darker areas lost the most reflectivity over the period 2002 to 2011. One major consequence: black carbon is thought to be responsible for over 30% of recent warming in the Arctic, including the accelerated melting of sea ice. In this way, wildfires have become part of an elaborate feedback loop between humans and nature. Higher surface temperatures mean larger and more frequent fires. More smoke and soot send temperatures still higher. Fire in our time is becoming a relentless driver of change in a warming world..

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