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Setting the perfect stage for wildfires in the Western US

Below is an excerpt from “Drought, Flood, Fire: How Climate Change Contributes to Catastrophes” by Chris Funk. It is printed here with permission from the publisher, Cambridge University Press. The above is an affiliate link and we may get a small commission if you purchase from the site.

For California, conditions conducive to recent droughts and fire are often accompanied by a Ridiculously Resilient Ridge, a moniker coined by Daniel Swain to describe a persistent high-pressure cell over the northeast Pacific region. This high-pressure ridge can block storms and produce dry hot subsiding air over California. As pointed out by the work of Swain and others, this Ridiculously Resilient Ridge can help explain California’ recent demise into drier-hotter conditions. As context, Figure 11.5 shows a long time series of annual November-October upper-level heights near the Ridiculously Resilient Ridge. These data extend from 1948/1949 through 2018/2019. Since 2012, six out of seven years (2013, 2014, 2015, 2016, 2018, 2019) have exhibited above-normal ridging that have helped produce dry warm weather in California. Such were conditions in early November 2018, when I experimented with deep-forest auto-lobotomy techniques and then sat down to talk with Mike Williams and Ted Adams [Editor’s note: Williams and Adams have a disaster preparedness radio show]. On air, we shared our collective concern that winds would whip up before the winter rains came. These winds, combined with extremely dry fuel conditions, set the perfect stage for fire.

Annual November-October upper- level height anomalies over the northeast Pacific.

Unfortunately, these fears were verified. Over the next few days much of California experienced wind gusts of up to 55 miles per hour accompanied by extremely low relative humidity (less than 10 percent). At sunrise Nov. 8, the Camp Fire, California’s deadliest and costliest conflagration, broke out in Butte County (Figure 11.6). At 8 a.m. the fire entered the town of Paradise. Wind speeds that day reached 50 miles per hour, and the fire spread very rapidly. By Nov. 10, more than 6,700 structures were destroyed; by Nov. 20, almost 20,000 structures had been destroyed. Ultimately, 86 people died. The fire was the costliest disaster of 2018 ($16.5 billion), according to the international insurance agency Munich Re, and super-deadly. Two more fires broke out Nov. 8 —the Woolsey and Hill Fires — in Los Angeles and Ventura counties, just south of Santa Barbara, ultimately destroying an additional 1,647 structures.

Landsat 8 image of the C amp Fire in northern California, taken on November 8, 2018. By NASA (Joshua Stevens) -NASA Landsat 8 Operational Land Imager.

In California, the 2017 and 2018 wildfire seasons were massive, deadly and costly. In both years, the fire season stretched from April to December across much of the state. The overall size of these wildfires has risen dramatically from the late 1990s (Figure 11.7). The U.S. National Oceanic and Atmospheric Administration tracks disasters with costs over $1 billion. Here is their synopsis of the 2017 and 2018 California fire seasons.


A historic firestorm damages or destroys over 15,000 homes, businesses and other structures across California in October. The combined destruction of the Tubbs, Atlas, Nuns and Redwood Valley wildfires represents the costliest wildfire event on record, also causing 44 deaths. Extreme wildfire conditions in early December also burned hundreds of homes in Los Angeles. Numerous other wildfires across many western and northwestern states burn over 9.8 million acres exceeding the 10-year annual average of 6.5 million acres. Montana in particular was affected by wildfires that burned in excess of 1 million acres. These wildfire conditions were enhanced by the preceding drought conditions in several states.

Total size of California wildfires. Values for 2019 were not available in early 2020.


In 2018, California has experienced its costliest, deadliest and largest wildfires to date, with records back to 1933. The Camp Fire is the costliest and deadliest wildfire, destroying more than 18,500 buildings. California also endured its largest wildfire on record: the Medincino Complex Fire, burning over 450,000 acres. Additionally, California was affected by other destructive wildfires: the Carr Fire in Northern California and the Woolsey Fire in Southern California. The total 2018 wildfire costs in California (with minor costs in other Western states) approach $24 billion — a U.S. record. In total, over 8.7 million acres has burned across the U.S. during 2018, well above the 10-year average (2009-2018) of 6.8 million acres. The last two years of U.S. wildfire damage has been unprecedented, with losses exceeding $40 billion.

California’s seven-year average Palmer Drougth Severity Index values. Data from March-to-February data used to allow for an update through January 2020.

As with all natural disasters, human systems and human decisions play an important role in setting the stage for crises. In recent years, Californians have built more homes in high fire risk regions. These homes have been connected by a fragile system of electric wires, prone to sparking fires in high winds. Teasing out the complex contributions of human choice, natural climate variability and climate change is beyond our scope and my expertise. But we can look at low-frequency statewide average Palmer Drought Severity Index values (Figure 11.8) to get a sense of how the balance between moisture supply and atmospheric moisture demand may be changing. These values are based on a March-February annual average to allow for an early 2020 update. A seven-year averaging period was chosen to emphasize the persistent recent dry and warm conditions the dry conditions leading up to the exceptional 2017 and 2018 fire years. According to the PDSI estimates, the statewide seven-year drought was the most severe on record, and these dry conditions persist. California precipitation pattern is notoriously complex, but the progression toward warmer temperatures and greater aridity seems very likely.

Source: GreenBiz