The largest wildfire ever recorded in California needed just 11 days to blacken an area nearly the size of Los Angeles — and it's only one of many enormous blazes that could make this the worst fire season in state history.
Some 14,000 firefighters from as far away as Florida and even New Zealand are struggling to curb 18 fires in the midst of a sweltering summer that has seen wind-whipped flames carve their way through national forest land and rural areas, threaten urban areas and incinerate neighbourhoods.
"For whatever reason, fires are burning much more intensely, much more quickly than they were before," said Mark A Hartwig, president of the California Fire Chiefs Association.
Destructive wildfire seasons
California is seeing earlier, longer and more destructive wildfire seasons because of drought, warmer weather attributed to climate change and home construction deeper into the forests.
Some of the largest fires have erupted just within the past few weeks as the state has seen record-setting temperatures — and the historically worst months of wildfire season are still to come.
In southern California, a smoky forest fire raged on Wednesday in mostly unoccupied land — but firefighting crews were concerned the flames could race down hillsides toward foothill communities.
The blaze churning through the Cleveland National Forest south of Los Angeles was just five percent contained.
Control on fire in September
Fire crews expect to gain control of the massive blaze in September, the state forestry and fire protection agency said.
The blaze that broke out on July 27 initially spread quickly because of what officials said was a perfect combination of weather, rugged topography and abundant brush and timber turned to tinder by years of drought.
In becoming the biggest fire in California history, the Mendocino Complex fire broke a record set just eight months ago.
California's firefighting costs have more than tripled from $242 million in the 2013 fiscal year to $773 million in the 2018 fiscal year that ended June 30, according to Cal Fire.
"We're in uncharted territory," Governor Jerry Brown warned last week.
"Since civilisation emerged 10,000 years ago, we haven't had this kind of heat condition, and it's going to continue getting worse. That's the way it is."
Climate geoengineering may harm crops
Meanwhile US scientists said on Wednesday that spraying a veil of sun-dimming chemicals high above the Earth to slow global warming could harm crop yields in an unintended side-effect of turning down the heat.
Some researchers say a man-made sunshade, perhaps sulphur dioxide released high in the atmosphere, could limit rising temperatures and the after-effects like the wildfires that have ravaged California and Greece this summer.
But a US scientific team found that big volcanic eruptions, such as Mount Pinatubo in the Philippines in 1991 and El Chichon in Mexico in 1982, cut yields of wheat, soy and rice after spewing sun-blocking ash that blew around the world.
Pinatubo's eruption, for instance, reduced sunlight by 2.5 percent, cooled the planet by about 0.5 degree Celsius, and disrupted rainfall patterns, they wrote in the journal Nature.
And the study said any future "geoengineering" modelled on volcanoes would have scant benefits for crops, which need light to grow.
Less sunlight would reduce yields even though the plants would do better in less sweltering temperatures.
"If we think of geo-engineering as an experimental surgery, our findings suggest that the side effects of the treatment are just as bad as the original disease," author Jonathan Proctor of the University of California, Berkeley, told a telephone news conference.
Co-author Solomon Hsiang, also of the University of California, Berkeley, said the findings were a surprise after some previous research suggested plants might grow better with hazier sunshine, especially crops in the shade.
The new study "doesn't necessarily mean we should simply rule out these [geoengineering] technologies," he said.
World at risk of 'hothouse' state
A study on Monday said the world is at risk of entering an irreversible "hothouse" state with far higher temperatures than now, even if governments meet goals set in Paris.
But many are sceptical of geoengineering.
Janos Pasztor, head of the Carnegie Climate Geoengineering Governance Initiative, welcomed Wednesday's study as a step to understand the risks and benefits of geoengineering, which could affect everything from human health to life in the oceans.
"We need to move away from the stigma about not even being able to talk about any geoengineering options," he told Reuters news agency.