Reposted from the Chris Martz Weather Blog

Well, it’s that time of the year again, wildfire season, and like clockwork, people are losing their marbles about the wildfires in California. Articles, like the one from Politico below (Figure 1)¹, have been popping up left and right claiming that climate change is causing the wildfires.

Endless amounts of disinformation is being spread around on Twitter and Facebook from well-known media outlets, public figures, government officials, and even a handful of well-known scientists.

There’s no doubt that the dozen or more wildfires that have broken out in the state, including the Getty and Kincade fires, are serious. Firefighters are doing their best to try and contain these fires before any more serious damage occurs. But, playing the blame game on climate change does nothing for public safety whatsoever.

What’s really to blame for these fires?

The Kincade Fire in particular was caused by a broken jumper wire of the Pacific Gas & Electric company (PG&E), though “mother nature,” as you will find out below, has enhanced the fire and others that have since broken out across the state.

October through March is the prime time of the year for wildfires to break out in the Western United States (Raphael, 2003).² This is largely because atmospheric and surface conditions tend to be very favorable in the region for fire weather; that is a.) dry soil and vegetation, b.) low relative humidity, c.) warm temperatures, and d.) strong winds.³

In California, very strong north, northeast winds known as the Santa Ana Winds, are perhaps the most notorious wildfire hazards in the United States (Abatzoglou et al., 2013)⁴. These winds are very strong offshore foehn winds that develop in the Great Basin of California⁴ (Abatzoglou et al., 2013), typically during the cool season; autumn through spring (Figure 2) (Raphael, 2003; Abatzoglou et al., 2013).² ⁴ Thus, right off the bat, it should be no surprise to anyone that there are wildfires ablaze in California as I write this; that’s almost like getting surprised when a hurricane hits Florida.

These winds are formed when a large area of high pressure develops at the surface in the Great Basin or western Rockies (Abatzoglou et al., 2013).⁴

After the monsoon season ends, stronger radiational cooling overnight continuously allows colder air to develop at the surface, and because colder air is denser, it sinks and increases the air pressure at the surface, while decreasing the pressure aloft causing a trough to form in the jet stream flow (Abatzoglou et al., 2013).⁴ The stronger the radiative cooling is, the stronger the surface high [pressure] will be, and the stronger the high is, the tighter the pressure gradient will be between the high and surrounding areas of lower pressure. The tighter the pressure gradient is at any given location, the stronger the winds will be as they attempt to equalize the pressure differences.

Winds around high pressure systems flow anticyclonically (clockwise) in the Northern Hemisphere, thus when high pressure is situated over the Rockies or Great Basin, the winds blow from the north or northeast towards the Pacific Ocean. If there’s a low pressure area over the Four Corners region, the cyclonic (counterclockwise) flow will aid in reinforcing the north, northeast winds towards the Pacific. As yesterday’s 00z run of the GFS model shows, this is exactly the case currently causing the Santa Ana Winds (Figure 3)

As per the usual setup, a cold air mass migrated southeast out of Western Canada over the weekend and has since settled into the Rocky Mountains. Temperatures this week in the Rockies are some record 30 to 40°F BELOW AVERAGE (Figure 4), and because, once again, cold air is denser than warm air, the cold air has sunk to the surface therefore increasing the atmospheric pressure at the surface and has decreased it aloft (denoted by an upper level trough). Because cold air is sinking, convective cloud development has been shut off leading to clear skies thereby enhancing overnight radiational cooling, which consequently increases the air pressure at the surface, tightening the pressure gradient, leading to stronger north, northeast winds.

As the winds flow from the Great Basin and desert regions over the mountains of California, they then begin to downslope down the mountains towards the coastline.⁵ Downsloping winds decrease the relative humidity of the air and warm the air temperature through adiabatic pressure increases, thereby creating a warm and very dry wind.⁵ Occasionally, these winds can reach hurricane-force strength (at least 74 miles per hour).⁵

With the addition of the fact that we are on the tail end of the dry season in California, the Santa Ana Winds can further dry out vegetation making them more vulnerable to catch fire.⁵ These winds may also spread existing fires, which is what we are currently seeing.⁵

The fact that we are seeing fires exactly right now is not surprising considering I was forecasting them days before most of the fires broke out and escalated.

Has Climate Change Played A Role?

While there is a clear and concise explanation for how the fires started and a solid meteorological explanation for the worsening of the ongoing wildfires, as I stated above, one can certainly ask the question, “has climate change, man-made or natural, played a role?”

While the U.S. National Climate Assessment (NCA4, Chapter 6) shows that the area burned (by million acres) has increased since 1985⁶ (Figure 5), one must look at the entire record (1926-present) and natural climate variability to see why we’ve observed an increase in forest fires over the last four decades.

The National Interagency Fire Center (NIFC) has a large table listing the annual wildfire statistics for the United States; both the number of fires, and the acreage burned by such fires.⁷ Using the data provided from them, I made two graphs, both of which are shown below.

The first graph (Figure 6) shows the acreage burned by wildfires in the United States from 1926 to the present.⁷ As you can see, prior to the early 1980s, wildfires were far more common in the United States.

With regards to the amount of acreage that has been burned by wildfires, that too has declined substantially since 1926 (Figure 7).⁷

While the National Interagency Fire Center (NIFC) warns that data prior to 1983 may be too high or too low⁷, it can be safely assumed (based on peer-reviewed and non peer-reviewed studies) that the historical record is sufficient.

Studies like Littell et al. (2009) concluded that wildfire burn acreage was just as high, if not higher during the period 1916 through the Dust Bowl Era in eleven western U.S. states.⁸ During the 1950s through the 1970s, wildfire burn acreage was lower, and since 1985, has been elevated.⁸ The study also concluded that while forest management and fire suppression practices have been implemented nearly half of the variations in wildfire activity is directly linked to natural variations in the climate.⁸ (See Figure 8)

While annual variations in wildfire frequency and intensity are primarily driven by changes in the Pacific Decadal Oscillation (PDO), El Nino Southern Oscillation (ENSO), and the frequency of Santa Ana Wind events, studies, including Kitzberger et al. (2007) showed that the Atlantic Multidecadal Oscillation (AMO) drives multidecadal changes in wildfire activity.⁹

The study showed that periods when the AMO is positive (warm), droughts tend to occur from northern Mexico to the Rocky Mountains in the U.S., the Great Plains, and Pacific Northwest, whereas California observes above average moisture.⁹ The negative (cool) phase of the AMO tends to result in less fire activity in California.⁹

Moreover, Kitzberger et al. (2007) found that when the AMO and PDO are both in their positive phases, the northwestern U.S. is drier leading to increased wildfire activity and potential.⁹ During coincident negative phases of these two oscillations, the southwestern United States tended to by dry and hot/warm.⁹

As far as Santa Ana Wind events go (because they enhance and spread fires as already stated), Abatzogoul et al. (2013) found no such increase in the frequency of both extreme and total wind event days from 1948 to 2010 (Figure 9b).⁴

As far as the scientific community’s confidence in attributing individual wildfires to climate change, confidence remains low and results have been inconclusive, as the National Academy of Sciences shows in the chart below.¹⁰

To blame the fires in California on climate change is pure superstition, utter nonsense, and has no basis on reality. Mother nature, not global warming, causes wildfires .

REFERENCES

[1] “Brown: California fires show ‘the horror’ world will face from climate change.” Politico. October 28, 2019. Accessed October 28, 2019. https://www.politico.com/states/california/story/2019/10/28/brown-california-fires-show-the-horror-world-will-face-from-climate-change-1226036.

[2] Raphael, M. N., et al. “The Santa Ana Winds of California.” March 17, 2003. Accessed October 29, 2019. https://journals.ametsoc.org/doi/pdf/10.1175/1087-3562%282003%29007%3C0001%3ATSAWOC%3E2.0.CO%3B2.

[3] Haby, Jeff. “FIRE WEATHER.” Weather Prediction Education. Accessed October 29, 2019. http://www.theweatherprediction.com/habyhints2/549/.

[4] Abatzogoul, John T., et al. “Diagnosing Santa Ana Winds in Southern California with Synoptic-Scale Analysis.” March 6, 2013. Accessed October 29, 2019. https://journals.ametsoc.org/doi/pdf/10.1175/WAF-D-13-00002.1.

[5] Erdman, Jonathan. “The Science Behind Santa Ana Winds.” The Weather Channel. October 16, 2018. Accessed October 29, 2019. https://weather.com/science/weather-explainers/news/2018-10-15-santa-ana-winds.

[6] “Forests” Fourth National Climate Assessment Vol I + II. 2018. Accessed October 29, 2019. https://nca2018.globalchange.gov/downloads/NCA4_Ch06_Forests_Full.pdf.

[7] “Total Wildland Fires and Acres (1926-2018).” National Interagency Fire Center. 2018. Accessed October 29, 2019. https://www.nifc.gov/fireInfo/fireInfo_stats_totalFires.html.

[8] Litell, Jeremy S., et al. “Climate and wildfire area burned in western U.S. ecoprovinces, 1916–2003.” 2009. Accessed October 29, 2019. https://pdfs.semanticscholar.org/4af3/67682e73d0f2a2d45592baa571bf5332bfe3.pdf

[9] Kitzberger, Thomas, et al. “Contingent Pacific–Atlantic Ocean influence on multi century wildfire synchrony over western North America.” 2007. Accessed October 29, 2019. https://www.researchgate.net/publication/6604237_Contigent_Pacific-Atlantic_Ocean_influence_on_multicentury_wildfire_synchrony_over_western_North_America.

[10] “Climate Change and Extreme Weather.” Penn State University. 2016. Accessed October 29, 2019. https://www.e-education.psu.edu/meteo3/l10_p9.html.

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