Murujuga report blames sulfur emissions that stopped decades ago, not today's LNG plants

A gradient is a statement about space, and the sites it points at have not moved. Proximity on its own cannot say whether the acid fell in 1985 or last month, so the weight of this year's conclusion rests on chemistry and on a timing argument.

The chemistry is settled ground. Sulfur dioxide converts to sulfuric acid in the atmosphere or on the rock itself, and that acid dissolves the manganese and iron oxides which give the rock varnish its dark colour; what it leaves behind is pore space ^[12]. The timing is where the real work happens. Sulfur dioxide emissions have fallen sharply since the 1980s, at Murujuga and globally, so the authors read the measured porosity as the residue of historic peaks rather than of anything a current stack contributes ^[13]. They apply the same logic to ammonia: experiments suggest it may influence chemical and biological processes on the surfaces, but the researchers say industrial ammonia emissions are too recent to explain a pattern this old ^[15].

Elimination by age is a legitimate method and also the softest joint in the report, and it sits against the program's own record. Nitrogen dioxide is the most abundant pollutant gas at Murujuga and was the earlier candidate, until last year's data could not separate its effects from those of sulfur dioxide ^[10]. Last year's finding was narrower too: raised porosity on surfaces near industrial areas, with a risk of fading or flaking if it continued ^[8]. Between the second report and the third, the named agent changed. The fourth and final report, due next year, is meant to establish how sulfur chemistry and microbial activity on the rock surface interact, an interaction the authors already believe was involved ^[14]. On the program's own schedule, that leaves one report to go ^[19].

The researchers are more careful than the fight around them will be. They say the work does not resolve every question, and that understanding a system as complex as Murujuga takes time ^[7]. They also name current air pollution as the thing they are asked about most ^[18]. The report carries more than 30 researchers, government funding and independent international peer review, and states that it was written solely by the researchers ^[6]. That last point is load-bearing rather than decorative. A peer-reviewed finding that points away from present-day operations, on a landscape spanning the Burrup Peninsula and the Dampier Archipelago that holds an estimated one to two million petroglyphs recording at least 50,000 years of Ngarda-Ngarli relationship to Country ^[1][2], will be quoted by parties who neither funded it nor wrote it. The test for each of them is whether they engage the dating argument or only the map.