Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next generation of fire science and provide guidance for investment in future research. We synthesize insights needed to better address the long-standing challenges of innovation across disciplines to (i) promote coordinated research efforts; (ii) embrace different ways of knowing and knowledge generation; (iii) promote exploration of fundamental science; (iv) capitalize on the “firehose” of data for societal benefit; and (v) integrate human and natural systems into models across multiple scales. Fire science is thus at a critical transitional moment. We need to shift from observation and modeled representations of varying components of climate, people, vegetation, and fire to more integrative and predictive approaches that support pathways toward mitigating and adapting to our increasingly flammable world, including the utilization of fire for human safety and benefit. Only through overcoming institutional silos and accessing knowledge across diverse communities can we effectively undertake research that improves outcomes in our more fiery future.

Lasers and laser spectroscopic techniques have been extensively used in several applications since their advent, and the subject has been reviewed extensively in the last several decades. This review is focused on three areas of laser spectroscopic applications in atmospheric and environmental sensing; namely laser-induced fluorescence (LIF), cavity ring-down spectroscopy (CRDS), and photoluminescence (PL) techniques used in the detection of solids, liquids, aerosols, trace gases, and volatile organic compounds (VOCs).

The study of biomass burning particle density provides information on aging, new particle formation, transport properties, and is an important parameter in aerosol impacts modeling. Density is used in mass closure techniques to estimate the temporal resolution of particulate mass concentrations. However, the study of BB particle density as a function of burning conditions is still limited. Laboratory measurement of six sub-Saharan African biomass fuels burned under a range of conditions: from pure smoldering to pure flaming conditions is presented. Smoldering-dominated burning (modified combustion efficiency (MCE) < 0.9) particles has a very narrow range of effective density ( ${\rho }_{\mathit{eff}}$) 1.03 g cm⁻³ to 1.21 g cm⁻³ and a mass mobility exponent ( $D_{fm}$) of ∼3 (2.97 ± 0.05), indicating that they are spherical particles. For the flaming-dominated burning (MCE >0.95) particles, show a size dependent ${\rho }_{\mathit{eff}}$ for all six different fuels. In this case, the mean and standard deviation of the ${\rho }_{\mathit{eff}}$ decreased with increasing size, from (0.94 ± 0.21) g cm⁻³ at a mobility diameter of 80 nm to (0.31 ± 0.07) g cm⁻³ at a mobility diameter of 400 nm. The size-dependent ${\rho }_{\mathit{eff}}$ of flaming-dominated aerosol suggests the fractal nature of freshly emitted particles. The relationship between $D_{fm}$ and the MCE shows three distinct morphology regimes, which we define as the spherical particle, the transition, and the fractal regime. Our proposed relationship of $D_{fm}$ with the MCE can be used as a tool to assess the applicability of Mie theory for optical closure calculations in the absence of particle morphological information.

Long‐term exposure to ambient fine particulate matter (PM_2.5) is the second leading risk factor of premature death in Sub‐Saharan Africa. We use GEOS‐Chem to quantify the effects of (a) trash burning, (b) residential solid‐fuel burning, and (c) open biomass burning (BB) (i.e., landscape fires) on ambient PM_2.5 and PM_2.5‐attributable mortality in Africa. Using a series of sensitivity simulations, we excluded each of the three combustion sources in each of five African regions. We estimate that in 2017 emissions from these three combustion sources within Africa increased global ambient PM_2.5 by 2%, leading to 203,000 (95% confidence interval: 133,000–259,000) premature mortalities yr⁻¹ globally and 167,000 premature mortalities yr⁻¹ in Africa. BB contributes more ambient PM_2.5‐related premature mortalities per year (63%) than residential solid‐fuel burning (29%) and trash burning (8%). Open BB in Central Africa leads to the largest number of PM_2.5‐attributed mortalities inside the region, while trash burning in North Africa and residential solid‐fuel burning in West Africa contribute the most regional mortalities for each source. Overall, Africa has a unique ambient air pollution profile because natural sources, such as windblown dust and BB, contribute strongly to ambient PM_2.5 levels and PM_2.5‐related mortality. Air pollution policies may need to focus on taking preventative measures to avoid exposure to ambient PM_2.5 from these less‐controllable sources.

Biomass burning (BB) is a major source of pollutants that impact local, regional, and global climate, air quality, and public health. However, the influence of burning conditions and fuel type on the emission factors of pollutants is still not well understood. Here, we present the results from a laboratory study of emission factors (EFs) of pollutants from six different sub‐Saharan African biomass fuels combusted under a wide range of burning conditions, ranging from smoldering to flaming. We found that particulate matter (PM) and carbon monoxide (CO) EFs (g (kg wood)⁻¹) are highly sensitive to the burning conditions, with an order of magnitude variation between flaming and smoldering burning conditions. Nitric oxide (NO) EF shows a fuel type dependence, with higher NO EFs for fuels with larger nitrogen content. While CO is not generally a proxy for PM_2.5 emissions, in this work a correlation was found between CO and PM emissions generated by combustion of seven wood fuels with moisture content (dry basis) <10% in a tube furnace and measured from a laboratory smog chamber with a temperature of ∼21–24°C and an RH below 5%. Unlike total PM, EFs of inorganic particle‐phase species do not show dependence on burning conditions. Finally, we showed that burning biomass fuels in a tube furnace would be a useful experimental approach to study BB emission under controlled burning conditions.

Sub-Saharan Africa is a hotspot for biomass burning (BB)-derived carbonaceous aerosols, including light-absorbing organic (brown) carbon (BrC). However, the chemically complex nature of BrC in BB aerosols from this region is not fully understood. We generated smoke in a chamber through smoldering combustion of common sub-Saharan African biomass fuels (hardwoods, cow dung, savanna grass, and leaves). We quantified aethalometer-based, real-time light-absorption properties of BrC-containing organic-rich BB aerosols, accounting for variations in wavelength, fuel type, relative humidity, and photochemical aging conditions. In filter samples collected from the chamber and Botswana in the winter, we identified 182 BrC species, classified into lignin pyrolysis products, nitroaromatics, coumarins, stilbenes, and flavonoids. Using an extensive set of standards, we determined species-specific mass and emission factors. Our analysis revealed a linear relationship between the combined BrC species contribution to chamber-measured BB aerosol mass (0.4-14%) and the mass-absorption cross-section at 370 nm (0.2-2.2 m² g^-1). Hierarchical clustering resolved key molecular-level components from the BrC matrix, with photochemically aged emissions from leaf and cow-dung burning showing BrC fingerprints similar to those found in Botswana aerosols. These quantitative findings could potentially help refine climate model predictions, aid in source apportionment, and inform effective air quality management policies for human health and the global climate.