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Wednesday, November 25, 2020

California Wildfires, Climate Change, and Lisa Murkowski Message #12


Alaska Senator Lisa Murkowski and James Hubbard, USDA Undersecretary for Natural Resources and the Environment, recently produced a session of the Senator’s podcast, talking about the extraordinary wildfire season in the Western US.  These public servants failed to acknowledge man-made climate change as the ultimate cause of the fire intensity.  Increased fire size and intensity were clearly forecast in the IPCC (Intergovernmental Panel on Climate Change) Impacts report in 1990, thirty years ago.  The causes of increased fire intensity were clearly identified in that report: higher temperatures and drought, leading to low soil moisture, dry plants and deadwood, increased fuel loading and increased lightning strikes.  Every contributing factor identified in the 1990 report has been realized and today’s wildfires are larger and more intense as predicted.  To neglect the explanation for that intensification is irresponsible.  Murkowski and Hubbard failed to inform the public, not only about what happened in 2020, but to warn the public of future risks as CO2 emissions and climate change continue unchecked.

Murkowski’s Message #12

In September of 2020, California was wracked by some of the largest and most destructive wildfires in its history.  Senator Lisa Murkowski, in her role as chair of the Senate Committee on Energy and Natural Resources, met with James Hubbard, USDA Undersecretary for Natural Resources and the Environment, to discuss the crisis.  Senator Murkowski posted audio of the twenty-minute interview as #12 in her series of Murkowski’s Messages, available here: 

I listened to the entire discussion. There is practically no mention of climate change, although Murkowski and Hubbard danced around the topic, with Murkowski making a passing reference to “the changing climate”.  However, they quickly brushed that idea aside and focused instead on overstocked fuel conditions in the forests.

Undersecretary Hubbard noted the persistence of abnormal fire conditions in the western states, with Hubbard saying, “…it has been developing for a long time, and it’s certainly going to be with us for a long time….We can expect this kind of fire behavior for some time to come.”  Hubbard also noted the significance of high heat and low humidity in intensifying the fires, and stated “This is unusual, but I think we will see more of it.” 

For her part, Murkowski dismissed the idea of seeking causes for the intense fires.  The Senator said that others were asking, “Why are we seeing so much?  What can be done?  Who is responsible, and who is to blame?”, but these were not questions she wanted to pursue.  In my view, this is deeply flawed.  On the contrary, these are exactly the questions we must answer if we want to avoid even worse wildfires in the future.

Incredibly, this talk by the Senator and the Undersecretary avoided all mention of human-caused climate change, which is the most significant factor in causing the disastrous Western wildfires.  Let me be clear – the dry and hot weather conditions of recent years in the West are due to the accumulation of greenhouse gases in the atmosphere, principally CO2 from human use of fossil fuels.  Hot and dry weather cause low soil moisture, dry plants, and more deadwood.  Low soil moisture causes excess fuel in the forest, and causes fires to burn hotter and faster.  As Undersecretary Hubbard acknowledged, these conditions are strikingly different from the past and will persist a long time.  In fact, these conditions will persist as long as elevated CO2 in the atmosphere persists.  Levels of atmospheric CO2 will inevitably increase in coming decades, worsening the wildfire problem in the West.  We are not likely to return to the CO2 levels and climate conditions of the 20th century for another century or more. 

Forecast of Increased Wildfires, 1990 IPPC Impacts Assessment

For thirty years, we’ve been warned repeatedly that human-caused climate change will result in more destructive wildfires.  Beginning in 1990, each report of the ICPP (Intergovernmental Committee on Climate Change, a UN agency) has warned about the increasing danger of wildfires.  The series of National Climate Assessments produced by the United States have also highlighted the danger. 

The 1990 IPCC Impacts Assessment lays out in explicit detail how and why wildfires are becoming worse, depending on geography.  Temperatures are higher, and some areas are subject to drought; these cause a number of second-order changes that intensify wildfires.  Later IPCC reports provide even more area-specific forecasts.  Here are a few quotes from IPCC 1990 Impact Assessment:

  • "Losses from wild-fire will be increasingly extensive" (Policy-Makers Summary, p. 2)
  • “Fire damage is expected to increase with the susceptibility of forests.  Even if precipitation remains roughly the same, increased temperatures will lead to increased evapotranspiration and thus drier sites.  Warmer drier sites could have a higher incidence of severe fires, especially where stands are in a state of decline because of climatic changes” (p. 2-25).
  • “…blocking high pressure patterns, more lightning strikes and increased fuel loadings are a dangerous combination causing more and larger fires" (p. 2-25).
  • “Wildfire frequency and severity is expected to increase throughout most of the unmanaged lands because of the projected increases in available fuel as primary productivity increases and because of the increased amount of dead fuel accumulating as a result of increased mortality” (p. 3-19).
  • “In those forested areas where there is a decrease in soil moisture, drying of forest fuels will be enhanced, thereby increasing the amount of available fuel”  (p. 3-20).
  • Increased fuel loading resulting from climate change was forecast to cause a three-fold increase in the number of fires greater than 1000 hectares in the Sierra Nevada (p. 3-20). 

Temperature, Precipitation and Fires in California, 2000 – 2020

Dr. Robert Rohde of Berkeley Earth compiled temperature and precipitation data for the California fire season from 1895 to 2020.  The animation of the data can be found on Dr. Rohde’s Twitter page, and is quite striking.  The trend of increasing temperatures and decreasing precipitation across the decades is quite evident in his chart, with 19 of the years from 2000 to 2020 occurring above the midpoint in temperature, and 12 of those 20 years occurring in the hot and dry quadrant of the chart.  The last two decades have also seen the largest deviations from normal conditions of the preceding century. 

Dr. Rohde also posted the ten largest fires and ten most damaging fires in California’s history on the chart, by year.  The year with the farthest excursion from normal temperature and precipitation, 2020, also had the worst fire record.  Other years with bad fire records, 2017 & 2018, were among the years with the farthest excursion from normal.  It’s worth noting that all of the large and destructive fires occurred in the hot and dry quadrant of the chart.

Figure 1.  California temperature and precipitation, 1895 – 2020, with the ten largest fires and ten most damaging fires.  Chart created by Robert Rohde, Berkeley Earth, and used by permission.

Low soil moisture is a consequence of high temperature and low precipitation.  Most of the years since 2000 have been marked by persistent drought conditions in the west.  The USDA published nationwide maps of drought conditions, which have been seasonally persistent in the American West since the year 2000.   National Centers for Environmental Prediction (NCEP), a department of NOAA, publishes maps of soil moisture over the lower 48 states.  Relative soil moisture is shown as a percentile map with respect to historical conditions.  Maps of drought conditions and soil moisture show persistent conditions that predispose the West to high fire activity since the year 2000. 

Figure 2.  Drought conditions, week of September 15, 2020, USDA map.

Figure 3.  Soil Moisture Percentile (relative to history) September, 2020, map from NCEP, NOAA.

Of course, California was not the only place on earth to experience severe fires in recent years.  Dr. Rohde also prepared a similar chart of temperature and precipitation for New South Wales, Australia.  Although Dr. Rohde did not include fire statistics on this chart, the decadal shift in temperature and precipitation is clearly apparent on this chart. 

Figure 4.  New South Wales temperature and precipitation, January – October, 1900 – 2019.   Chart created by Robert Rohde, Berkeley Earth, and used by permission.

In Alaska, Senator Murkowski’s home state, wildfires have also been larger and more damaging.  Lightning initiates most of the wildfires in the state.  It follows that increased thunderstorm activity results in more fires.  The location of the state’s largest recent fires, generally north and east of Fairbanks, corresponds with the highest summer temperatures and increased thunderstorm activity.  This information is documented in communications by Rick Thoman, climatologist with the International Arctic Research Center (IARC), Fairbanks. 

Figure 5.  Alaska Wildfire Acreage, Season Total, 1950 – 2019.  Chart by Rick Thoman, IARC.

Figure 6.  Fairbanks Alaska, Annual Days with Thunder, 1952 – 2020.  Chart by Rick Thoman, IARC.


It’s clear that the scientific forecasts of wildfire intensity in 1990 were correct.  The processes causing more intense wildfires are higher temperatures and lower precipitation, which lead to low soil moisture, dry plants and more deadwood.  Higher temperatures and low precipitation in California and Australia are predictable consequences of human emissions of greenhouse gases, which continue to accumulate in the atmosphere.  The conditions which lead to large, fast-moving and destructive wildfires didn’t “just happen”, and will worsen in coming decades. 

Senator Murkowski and Undersecretary Hubbard failed the public by not discussing the actual causes of the wildfires in their public communications.  Explanations matter, and causes matter.  Senator Murkowski’s questions -- “What can be done?  Who is responsible, and who is to blame?” – are pertinent questions.  Human emissions of CO2 are responsible; consumers of energy are to blame.  And the best thing to do is to reduce emissions of greenhouse gases, significantly and quickly.   

The physical processes of climate change are well-established, proven science.  We’ve known how it works for over 120 years.  We’ve had pretty good estimates for how much temperatures would change, depending on how much CO2 was in the air, for almost as long.  The forecasts of more intense wildfires, made 30 years ago, have been entirely accurate.  At this point, in 2020, it is important for our public leaders to acknowledge man-made climate change as the ultimate cause of intense wildfires, and to give a credible warning that the situation will only get worse as temperatures continue to rise.  Senator Murkowkski and Undersecretary Hubbard have done the public a disservice by neglecting to address the cause of 2020’s extraordinary fire season, and to give a warning for the future.  It’s time for them to address the public truthfully.


Murkowski's Message #12

Arrhenius, 1896, On the Influence of Carbonic Acid in the Air upon the Temperature on the Ground

Arrhenius, 1906, The Probable Cause of Climate Fluctuations,%20final.pdf

Climate Change, The IPCC Impacts Assessment, 1990

Forest Fuels   

California Department of Forestry and Fire Protection

University of California Cooperative Extension

California chapter of the Society of American Foresters

Soil Moisture maps

Drought Maps

Australia's Climate in 2019

Australia’s climate in 2019

  • Australia's warmest year on record, with the annual national mean temperature 1.52 °C above average
  • Both mean annual maximum and minimum temperatures above average for all States and the Northern Territory
  • Annual national mean maximum temperature warmest on record (2.09 °C above average)
  • Widespread warmth throughout the year; January, February, March, April, July, October, and December all amongst the ten warmest on record for Australian mean temperature for their respective months
  • Significant heatwaves in January and in December
  • Australia's driest year on record
  • Nationally-averaged rainfall 40% below average for the year at 277.6 mm
  • Rainfall below average for most of Australia
  • Rainfall above average for parts of Queensland's northwest and northern tropics
  • Much of Australia affected by drought, which was especially severe in New South Wales and southern Queensland
  • Widespread severe fire weather throughout the year; national annual accumulated Forest Fire Danger Index highest since 1950, when national records began