Over in the Australia Is On Fire thread, Sheldrake wanted some details on why the current fire season is being attributed to climate change. I don't have much appetite for chasing down a thousand rabbit holes about a genuinely complex area of science but for anyone who's interested, here are a few pieces aimed at the general public that try to pull together the general picture. If there's a particular piece of the puzzle where the data are lacking, then perhaps we could discuss that piece.
In brief, any clear understanding of causality for fires probably needs to incorporate the following:
* Long term mean temperature change (~1C over the past century)
* Long term variability in temperatures (especially extremes, like the set of temperature records that tumbled over Christmas)
* Long term changes in rainfall over various seasons (autumn and winter rainfall drive veg growth and capacity for fuel reduction burns, while summer rain can help control existing fires)
* The temperature and rainfall interact to lengthen fire seasons, largely by drying out forests. Our fire season "should" just be getting underway now, not be into its fifth month.
* A lot of the weather in Australia is driven by a few big ocean/climate systems that play together to drive seasonal conditions - El Nino (which is neutral this year), the Indian Ocean Dipole (in a positive phase this year), and the Southern Annual Mode (in a negative phase this year)
* Increased CO2 can, where CO2 availability is the limiting factor, increase plant growth rates, potentially increasing the fuel load for fires
* Long term patterns in fire size, intensity, and frequency (ash layers in soil, charred tree rings, and age of fire-vulnerable species mean that we can, in some places, push this back thousands of years, though obviously with less detail than modern fires)
* Vegetation patterns (including land clearing, spread of fire-obligate and fire-vulnerable species)
* Water patterns (including extraction for intensive agriculture)
* Variations in fire management practices (I remember, in a previous career, reporting on an accidental bushfire in a cool season that the local fire authorities let burn through half the park (maybe 1000km2?), on the grounds that it would help in a bad year. So that fire had a huge footprint but in a good way. Hectares are therefore a limited proxy for tracking changes in fire patterns)
* Patterns in where and how people build infrastructure (tree changers and population increase make the peri-urban areas more vulnerable, so it's another limited measure of "how bad" the fires are)
* Changes in prediction and communication technologies (improving these tends to help people get out of the way,Modern communication systems and modern technology would generally tend to save lives, so death tolls are another limited measure).
There are a lot of interlocking pieces of the puzzle of understanding and assigning causality for changing patterns in the geographic extent, intensity, and temporal extent of Australia's severe bushfires. The data for some of these pieces is patchy, though it's excellent for other pieces. I am not a climate scientist, nor a fire ecologist, nor a fire manager, so I take my lead in understanding the patterns by listening to the people who spend their career investigating those patterns, unless I can see an obvious error in their working.
The links below are for media explainers and policy briefings, since they're handy ways to find the big picture conclusions. If anyone wants to discuss one particular piece of the puzzle, these will at least provide search terms and context.
Vox Explainer
Climate Council Briefing Paper
Guardian Explainer
Conversation article from November about modelling that predicts an increase in pyrocumulus clouds, thanks to climate change
More Conversation articles on bushfires. A decent starting place