Weekly cycles of global fires—Associations with religion, wealth and culture, and insights into anthropogenic influences on global climate

Abstract

One approach to quantifying anthropogenic influences on the environment and the consequences of those is to examine weekly cycles (WCs). No long‐term natural process occurs on a WC so any such signal can be considered anthropogenic. There is much ongoing scientific debate as to whether regional‐scale WCs exist above the statistical noise level, with most significant studies claiming that anthropogenic aerosols and their interaction with solar radiation and clouds (direct/indirect effect) is the controlling factor. A major source of anthropogenic aerosol, underrepresented in the literature, is active fire (AF) from anthropogenic burning for land clearance/management. WCs in AF have not been analyzed heretofore, and these can provide a mechanism for observed regional‐scale WCs in several meteorological variables. We show that WCs in AFs are highly pronounced for many parts of the world, strongly influenced by the working week and particularly the day(s) of rest, associated with religious practices.

Spatial and Temporal Variability and Trends in 2001–2016 Global Fire Activity

“…Figure shows the global distribution of fires that have occurred over the period 2001–2016 (representing an extension of the period along with the updated Collection 6 data, from Collection 5 presented by Earl et al, ) and split into four seasons. The broad global fire distribution seen in the 0.1° AF data is similar to coarser global AF and BA maps (see Andela et al, ; Chuvieco et al, ; Giglio et al, , ; Krawchuk et al, ; Oom & Pereira, ).…”

“…This indicates that anthropogenic factors are not the main influence in the African fire regime and may not have an impact on the overall decreasing trend. However, Earl et al () note that this may be due to NH part of Africa containing both Muslim and Christian populations, so the weekly cycle may not be the best indicator of anthropogenic activity over this area. As mentioned, the NH African decline is linked to the NPP increase observed in NH Africa from 2000 to 2009 (Zhao & Running, ); therefore, the African decline in fires is associated with both anthropogenic fire management and changes in NPP.…”

“…However, as seen in Africa, in the season where the decline is strongest (June‐July‐August (JJA)), this cycle is less apparent (Figure ). This could indicate a natural response, though it has to do with fire management practices being more reactive than proactive during this fire‐abundant part of the year (see Earl et al, ). Zhao and Running () found NPP increases over this area, which acts as another contributor to the decline.…”

“…If the original weekly cycle range of a region is larger than, for example, 9,900 of the simulated ranges for that region, the p value of the AF weekly cycle would be 0.01 (1%). Figure 1 shows the global distribution of fires that have occurred over the period 2001-2016 (representing an extension of the period along with the updated Collection 6 data, from Collection 5 presented by Earl et al, 2015) and split into four seasons. The broad global fire distribution seen in the 0.1°AF data is similar to coarser global AF and BA maps (see Andela et al, 2017;Chuvieco et al, 2008;Giglio et al, 2006Giglio et al, , 2013Krawchuk et al, 2009;Oom & Pereira, 2013).…”

“…Humans have always influenced the fire regime and today are the main source of ignition in many different ecosystems including tropical forests and savannas. Fire activity in many regions over the globe has been shown to follow a weekly cycle (Earl et al, ), highlighting the anthropogenic influence on their behavior. In a changing climate and with population increasing, it is important to monitor fire activity throughout the world to diagnose how it varies temporally and spatially and determine what drives these variations.…”