Pyrocumulonimbus (pyroCb) wildfires cause devastation in many regions globally. Given that fire‐atmosphere coupling is associated with pyroCbs, future changes in coincident high index values of atmospheric instability and dryness (C‐Haines) and near‐surface fire weather are assessed for southeastern Australia using a regional climate projection ensemble. We show that observed pyroCb events occur predominantly on forested, rugged landscapes during extreme C‐Haines conditions, but over a wide range of surface fire weather conditions. Statistically significant increases in the number of days where both C‐Haines and near‐surface fire weather values are conducive to pyroCb development are projected across southeastern Australia, predominantly for November (spring), and less strongly for December (summer) in 2060‐2079 versus 1990‐2009, with future C‐Haines increases linked to increased 850‐hPa dewpoint depression. The increased future occurrence of conditions conducive to pyroCb development and their extension into spring have implications for mitigating these dangerous wildfires and urbanizing fire‐prone landscapes.

Extreme wildfires have recently caused disastrous impacts in Australia and other regions of the world, including events with strong convective processes in their plumes (i.e., strong pyroconvection). Dangerous wildfire events such as these could potentially be influenced by anthropogenic climate change, however, there are large knowledge gaps on how these events might change in the future. The McArthur Forest Fire Danger Index (FFDI) is used to represent near-surface weather conditions and the Continuous Haines index (CH) is used here to represent lower to mid-tropospheric vertical atmospheric stability and humidity measures relevant to dangerous wildfires and pyroconvective processes. Projected changes in extreme measures of CH and FFDI are examined using a multi-method approach, including an ensemble of global climate models together with two ensembles of regional climate models. The projections show a clear trend towards more dangerous near-surface fire weather conditions for Australia based on the FFDI, as well as increased pyroconvection risk factors for some regions of southern Australia based on the CH. These results have implications for fields such as disaster risk reduction, climate adaptation, ecology, policy and planning, noting that improved knowledge on how climate change can influence extreme wildfires can help reduce future impacts of these events.

Summary Understanding changes of biodiversity across the landscape underlies biogeography and ecology and is important in land management and conservation. Measures of species and phylogenetic turnover used to estimate the rate of change of assemblages between sets of locations are more often influenced by wide‐ranging taxa. Transition zones between regions that are associated with range‐restricted taxa can be obscured by wide‐ranging taxa that span them. We present a set of new range‐weighted metrics of taxon and phylogenetic turnover, as modifications of conventional metrics, where the range‐restricted components of the assemblages are assigned greater weight in the calculations. We show how these metrics are derived from weighted endemism and phylogenetic endemism and demonstrate their properties using a continent‐wide data set of Australian Acacia. The range‐weighted metrics result in better delineated transition zones between regions, in that the rate of turnover is steeper than with conventional turnover measures. These metrics provide important complementary information for the interpretation of spatial turnover patterns derived from conventional turnover metrics. Additionally, the phylogenetic variant incorporates information about phylogenetic relatedness while also not saturating at high values of turnover, thus remaining useful for comparisons over greater distances than conventional turnover metrics.

Key Points Spatial variability in the land‐atmosphere coupling defines local heatwave sensitivity to antecedent land surface conditions Land‐driven coupling regions experience a higher heatwave day frequency with temperatures sensitive to prior soil moisture conditions Antecedent soil moisture anomaly rather than drying rate 2 weeks prior to a heatwave has a longer impact on heatwave temperatures

No abstract