NASA Earth Observatory · Nov 18, 2008 corroborates
Fires in California
NASA satellite imagery for November 16 shows Southern California wildfires around the Los Angeles metropolitan area and smoke spreading far west over the Pacific.
Wildfire smoke Corroborated
2008-11-16 wildfire smoke episode affecting Los Angeles-Long Beach-Anaheim, CA
Daily PM2.5 peaked at 78.3 µg/m³ near Los Angeles across 1 covered metro home to 13 million people.
Counting the extra PM2.5 above each metro's typical day, this event handed the average affected resident ≈ 2.9 cigarettes. Across everyone living in the affected metros, that is the collective equivalent of ≈ 37 million cigarettes. An awareness illustration of outdoor exposure at 22 µg/m³ per cigarette (Berkeley Earth), counting only the event's ranked days; not a medical dose.
Why we think this happened
The basis for “Wildfire smoke”
Qualified frozen evidence supports wildfire smoke as the broad root cause.
Corroborated Independent reporting agrees on the cause, with no agency determination, monitor flag, or published assessment behind it.
CBS News / Associated Press · Nov 16, 2008 corroborates
Calif. Fires Rage Despite Calmer Winds
Contemporaneous wire reporting said Southern California wildfires blanketed much of the region with choking smoke.
Evidence path
From source to city
A cause is more convincing when the record connects three things: something happened, the air mass moved toward the region, and local instruments responded. Here is how much of that chain is documented for this event.
- 1Documented
Source or mechanism
Wildfire smoke
Contemporaneous reporting and NASA imagery explicitly connected the Los Angeles-region smoke episode to Southern California wildfires.
View supporting source ↗ - 2Documented
Air-mass movement
Transport into the affected region is documented
NASA satellite imagery for November 16 shows Southern California wildfires around the Los Angeles metropolitan area and smoke spreading far west over the Pacific.
View transport source ↗ - 3Documented
Local response
78.3 µg/m³ near Los Angeles
Contemporaneous wire reporting said Southern California wildfires blanketed much of the region with choking smoke.
Inspect the pollutant and weather signals ↓
Event autopsy
What the instruments saw
Before, during, and after the episode: nearby pollutant monitors and surface-weather stations show what changed. This context tests the “Wildfire smoke” explanation; it does not assign the cause by itself.
Los Angeles-Long Beach-Anaheim, CA
Monitor comparison window 2008-11-13 to 2008-11-19 · PM2.5 target: Los Angeles-North Main Street
118% above nearby days
About the same as surrounding days
104% higher than surrounding days
Pollution fingerprint
Metro-wide median of reporting monitors PM2.5 60.9 µg/m³
118% higher than surrounding days
Before27.9 µg/m³ Event60.9 µg/m³ After25.9 µg/m³
PM10 99 µg/m³
104% higher than surrounding days
Before48 µg/m³ Event99 µg/m³ After48.5 µg/m³
Carbon monoxide 1.03 ppm
5% higher than surrounding days
Before1.15 ppm Event1.03 ppm After0.963 ppm
Nitrogen dioxide 33.2 ppb
24% lower than surrounding days
Before45.9 ppb Event33.2 ppb After43.4 ppb
Sulfur dioxide 2.65 ppb
30% higher than surrounding days
Before2.13 ppb Event2.65 ppb After1.91 ppb
Ozone 0.025 ppm
113% higher than surrounding days
Before0.011 ppm Event0.025 ppm After0.010 ppm
Atmospheric conditions
Nearby EPA weather observations33% lower than surrounding days
About the same as surrounding days
About the same as surrounding days
About the same as surrounding days
Source: U.S. EPA AirData daily observations and, where available, nearby ASOS/AWOS surface observations. Values are descriptive medians over the retained monitor set; missing measurements remain missing. Transport and source evidence remain separate layers because this instrument pattern does not assign a cause by itself.
Measured daily PM2.5 at EPA monitors, as cigarette-equivalents
EPA monitors sit in metro areas, so the colour clusters there. Land between and beyond
them is unmeasured, not clean: this map shows where IAQng has readings, not the extent
of the smoke.
—
Episode peak
-- cigarettes
The smoke map's scale, replayed over this event: the surface interpolates between covered metros' daily records, framed to the affected region. Hover for a reading, click a metro to pin it to the card. Days a monitor did not report draw nothing.
Affected metros
| Metro | Peak PM2.5 | Cigarettes, whole event | Peak day | All-time standing |
|---|---|---|---|---|
| Los Angeles-Long Beach-Anaheim, CA | 78.3 µg/m³ | 3.6 | Nov 16, 2008 | #23 of its top days |
"Cigarettes, whole event" totals a metro's ranked event days at 22 µg/m³ per cigarette: what a person outdoors there breathed across the event, as the illustration. "All-time standing" is where this episode's days sit in each metro's ranked record (worst-area measure, since 1999). Full local context is on each metro's Air Records page.
Public evidence library
What supports this account
Each card states what a source supports—and what it does not. Official records, research, reporting, community observations, and transparent inferences remain visibly different kinds of evidence.
Agency and publisher pages 2
-
Calif. Fires Rage Despite Calmer Winds
Contemporaneous wire reporting said Southern California wildfires blanketed much of the region with choking smoke.
-
NASA satellite imagery for November 16 shows Southern California wildfires around the Los Angeles metropolitan area and smoke spreading far west over the Pacific.
What remains uncertain
- The evidence supports regional influence or transport but does not quantify the contribution to observed PM2.5.
Status and provenance
Corroborated Independent reporting agrees on the cause, with no agency determination, monitor flag, or published assessment behind it.
This episode was grouped from the monitor record by the catalog pipeline and given its cause from the evidence listed above. It has not been individually reviewed and signed off, so its boundaries, cause, and name may change as evidence accumulates. Grouping policy common_sense_root_cause_grouping.v2. The cause label reflects the assembled evidence above, not an IAQng detection formula. If it is wrong, tell us.