Impact of anthropogenic climate change on wildfire

I designed and developed my Fire Weather Index (FWI) for Personal Weather stations (PWSs) starting with basic logic reasoning (wet wood does not burn), with scientific background and made it usable in the context of PWSs. I found a very interesting and confirming article from October 2016: Impact of anthropogenic climate change on wildfire across western US forests [1].

The article examines

The strong interannual correlation between forest fire activity and fire-season fuel aridity, as well as observed increases in vapor pressure deficit (VPD) (9), fire danger indices (10), and climatic water deficit (CWD) (11) over the past several decades […] (my emphasis).

As described in my background blog on pwsFWI, I use the VPD as indicator, modified by qualitative characteristics of vegetation such as reaction time of absorption and evaporation speeds in relation to the occurrence of rain. Anthropogenic Climate Change (ACC) appears to be a major factor in an increase of Vapour Pressure Deficiency (VPD) as an indicator of fuel aridity.

Burned Area versus Fuel Aridity

Burned Area versus Fuel Aridity (from 1)

They write:

Increased forest fire activity across the western United States in recent decades has contributed to widespread forest mortality, carbon emissions, periods of degraded air quality, and substantial fire suppression expenditures. Although numerous factors aided the recent rise in fire activity, observed warming and drying have significantly increased fire-season fuel aridity, fostering a more favorable fire environment across forested systems. We demonstrate that human-caused climate change caused over half of the documented increases in fuel aridity since the 1970s and doubled the cumulative forest fire area since 1984. This analysis suggests that anthropogenic climate change will continue to chronically enhance the potential for western US forest fire activity while fuels are not limiting.

This states, that the increasing fuel aridity will increase the forest fire area (as long as there are forests). The pwsFWI proves currently in Australia that it does indicate long and extreme warning levels while New South Wales (NSW) experiences extreme fire events. See accompanying figures of December 7 2019 from the pwsFWI on the testsite of Phil’s Backyard and the map of the NSW Rural Fire Service.

My assumption for Europe is, that while the warming is creeping north from the Mediterranean, in the coming decade(s) we will see an increase in burned areas in forests where forest fires were rarely seen in the past. For example, one might want to watch out for the Ardennes (Belgium) Perigord-Limousin or even the Morvan (France), but certainly also the forests in Eastern Europe and north of the Alps. These regions are not  traditional forest fire regions, but are susceptible to become one.

pwsFWI as such is only an indicator but we better be prepared.


[1]  Abatzoglou, JT and Williams AP, (2015) Contribution of anthropogenic warming to California drought during 2012–2014. Geophys Res Lett 42(16):68196828. (local copy here).

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