California fires -- a legitimate example of climate change in action

Wasn't sure if this should go in the politics or weather section, so went with the former. @jamie feel free to move this. 

As of the time of writing, historically devastating wildfires have overtaken much of southern California, including Malibu. Unlike many other natural disasters (re: Hurricanes, winter storms), this event is a good example of the impact that climate change is already having on our planet. While climate change itself is not a cause of these fires, there is fairly undeniable evidence that it is the reason that they are so devastating. Let me explain:

Believe it or not, the National Weather Service Storm Prediction Center has an entire forecasting division devoted to predicting "fire weather". This forecasting division is charged with creating forecasts for "critical fire weather", in which atmospheric conditions conducive to extreme fire behavior are present. We understand these conditions to occur in the presence of low relative humidity and high wind. One can find forecasts such as these here: SPC fire weather forecast. I've attached a screenshot of today's forecast, in which you can see that the fire risk in southern California is designated as being "extreme". 

So you might be asking where does climate change fit into this, and how does an event like this differ from a hurricane? Simply put, it has to do with time-scale. A big issue that often arises when making attributions to climate change is the time-scale over which an event occurs. Within the weather-climate umbrella, we typically bin events as follows: short-term events that last on the order of minutes to hours are known as mesoscale, longer-term daily to weekly events are known as synoptic scale and monthly and longer events are typically though of as climate scale. These types of events are binned similarly by their spatial scales, where you can imagine something like thunderstorm would be considered mesoscale, a hurricane synoptic scale and a drought or monsoon climate scale. 

With this in mind, let's first consider seasonal precipitation. Seasonal precipitation is a feature that is measured over an extensive region over the course of several months and falls squarely into the climate-scale bin. When considering the impact on large-scale precipitation patterns, we typically look to Held and Soden (2006), which more or less asserts that in a warmed climate, areas that are typically wet will get wetter, and areas that are dry will get dryer. We know that southern California is, under normal climatological circumstances, a dry area. With the results of Held and Soden in mind, consider that the area near Paradise, CA (the initial ignition point of the fire) is currently at about 20% of its autumnal rainfall expectation compared to climatology. This works out to about a 5 inch precipitation deficit in the area (images also below). The dry area is drier than normal. 

Once you consider that we start with exceptionally dry air, as well as a now exceptionally dry ground, the stage is set for extreme fire weather. This is especially the case in autumn, when leaves are falling off of trees and drying on the ground. To make matters worse, California experiences Santa Ana winds, an event unique to areas in the lee of large mountain ranges. When air is blown up a mountain, it is forced to expand and therefore cool. This cooling leads to any water vapor in the air condensing into clouds on the windward side of the mountain. This phenomenon is why regions like western Washington state (west of the Cascades) are very wet, while just to the east of the mountains it is very dry (rain shadow). Due to the molecular weight of air vs. water, it can be shown that dry air is more dense than moist air. Given this fact, once we condense the water out of the air, it becomes more dense and therefore slightly heavier. If air makes its way over a mountain and in the process is forced to dry and become more dense, it will often accelerate downward faster on the leeward side of the mountain. In doing so, the already strong wind is made even stronger, allowing for fire to spread rapidly. While changes to the Santa Ana winds are something I'm not particularly comfortable making climate change attributions to, when climate change sets the stage for fire, the wind can make it that much worse. 

Now let's compare this type of event to something like a Hurricane. There's an argument that using the precedent set forth in Held and Soden that wet hurricanes will get wetter. There's also an argument that rising sea surface temperatures (SSTs) will increase hurricane intensity. Both of these arguments fall somewhere in line with what I described above with regards to fire: climate change doesn't necessarily cause these events, but may impact their evolution. The difference here however is subtle yet important. Hurricanes (and winter storms, etc.) are incredibly complex beasts that rely on a confluence of events within the atmosphere to occur. Fires like that which we are seeing in California are largely simple: if its anomalously dry, they will happen. Given a spark, dry air and dry fuel is a necessary and sufficient condition. The same can't necessarily be said about hurricanes, where warmer SSTs are a necessary but not sufficient condition alone for growth.

So to TL;DR this, climate change, while not the cause of these fires, has made them exponentially worse and will continue to do so in the future. Hurricanes are a tougher thing to explain through climate change.


Wow. Thanks. This photo was over N. California earlier this year...

-s.


soda said:
Wow. Thanks. This photo was over N. California earlier this year...
-s.

I hate to be the bearer of bad news, but that picture is a fake -- or rather, not associated with fire. It's actually a deck of marine stratocumulus off the coast of Hawaii. You can tell by how flat it is. Compare that with this pic, taken the other day (credit unkown to me) near the fire.


Two alarming dangers: climate change, and the increasingly easy proliferation of false information.


Thanks for this analysis. I've been thinking that the intensity and extent of the fires seemed more closely correlated with climate change, but didn't know specifics.


Thanks WxNut, great post.


somehow this landed up in the wrong thread...


All I can say is, thanks for the explanation - makes it easier to understand why we nearly lost Canberra in recent weeks with a scary fire in close-by mountains. 

We've had an early start to what we've been told will be an extreme fire season nationally, and they've already told us to expect it to last well after Easter. Remember those shocking fires a few years back? Apparently nothing compared to what could happen this year. 

Makes me fearful for your fire-prone areas after this past week. 



Clarification  much appreciated...

-s.


My President assures me that the problem is mismanagement by California forestry experts.  That and letting rivers flow into the sea.


This is a compelling argument for the "100 by 50" bill, a real, comprehensive plan to address the climate crisis.

There is no excuse for the House not to pass it:

Texts of the Senate version and the House flyer:

https://www.congress.gov/bill/115th-congress/senate-bill/987/text

https://polis.house.gov/uploadedfiles/100_by_50_one_pager.pdf


have just been reading the latest accounts here, with so many hundreds missing, and so many confirmed dead. Even though point of origin seems confirmed, and the utility company is being as cooperative as possible (under the circumstances; we've had similar legal nightmares here, where almost half the continent seemed to be burning), it just sickens me that the next few months will be filled with political point-scoring out of this tragedy. Instead of really speedy clearing and rebuilding. 

All those communities broken, businesses lost; and the impacts on school students...  

I really hope the insurance industry will be reasonable this time round, and that government support is supplied with receivers' dignity left intact. They don't have much else left. 


Ahh ... - but the Republicans are doing a lot.  Thoughts and Prayers, what more could you ask for???


*wry smiles*

My knowledge of the State geography is hazy. The fire damage is so huge and the agricultural areas impacted are so extensive; we’re getting the reports about various farm and agisted animals that need rescuing as well as wildlife and pets. 

I’m also wondering about the famous vineyards, though. Have they been affected? Or just smoke-affected? The smoke tainted our wines for the best part of two vintages (from memory), and pretty much the resulting wines couldn’t even be used for vinegar.



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