Indonesia's Anak Krakatau SO2 Scare: Why Satellite Maps Overstate the Risk to Malaysia

As Malaysia grapples with hazardous transboundary haze from Indonesian wildfires, viral social media posts have claimed that toxic sulphur dioxide (SO2) from the Anak Krakatau eruption is now entering Malaysian airspace. Volcanology experts and official monitoring data, however, indicate these claims are unfounded, underscoring the need for data literacy in regional environmental governance.

What triggered the false SO2 claims?

In early September 2026, a continuous explosive eruption at Mount Anak Krakatau, located in the Sunda Strait between Java and Sumatra, coincided with severe haze from forest and peatland fires in Borneo and Sumatra. The convergence of these events fueled public anxiety across Malaysia, Singapore, and Brunei, where air quality had already deteriorated significantly.

A Facebook post shared on September 8, 2026, overlaid Malay-language text warning that SO2 had begun entering Malaysian airspace. The accompanying graphic, apparently sourced from weather visualization platform Windy.com, showed high SO2 concentrations over Indonesia. The caption urged the public to wear masks, claiming the haze was now mixed with dangerous acidic gas. Similar claims spread across Facebook, Threads, and TikTok.

Why satellite SO2 readings do not reflect ground-level risk

Experts emphasize a critical distinction between satellite measurements and ground-level air quality. Nurzulaifa Shaheera Erne Mohd Yasim from Universiti Teknologi MARA's faculty of applied science explained that satellite instruments measure SO2 within a vertical atmospheric column above a location, rather than directly measuring concentration at ground level.

Therefore, a high SO2 signal on the satellite map does not necessarily mean that people at the surface are being exposed to a high or harmful concentration of SO2, said Nurzulaifa.

Suraya Hilmi Hazim of Universiti Kebangsaan Malaysia's department of earth sciences and environment echoed this assessment, stating that satellite readings are not representative of the air quality people are breathing. She added there was no evidence of a health risk posed by SO2 emissions from Anak Krakatau, noting that the Ministry of Health would have issued timely statements if a threat existed.

Official data confirms no SO2 health risk

Ground-level air quality monitoring from Malaysia's Department of Environment (DOE) shows no confirmed evidence of harmful SO2 concentrations from the eruption. Data from Kuala Lumpur and Kuching on Borneo island indicate SO2 levels did not breach WHO air quality guidelines at any point in September 2026.

Nurzulaifa also noted uncertainty regarding other sources of SO2 hotspots on circulating maps. Some detected SO2 could potentially be associated with biomass burning, but satellite SO2 maps alone cannot establish the origin of specific hotspots near Malaysia.

MetMalaysia's director-general, Dr Mohd Hisham Mohd Anip, confirmed in a September 10 Bernama report that volcanic ash from Anak Krakatau is moving toward the Indian Ocean northwest of Sumatra, not toward Malaysian airspace.

What are the governance implications for ASEAN?

The episode highlights a recurring challenge in ASEAN environmental governance: the rapid spread of misleading information during transboundary crises. Both experts stressed the importance of relying on official monitoring agencies rather than uncontextualized satellite maps circulating on social media.

For regional policymakers, the incident reinforces the value of investing in public data literacy and transparent communication channels. As Southeast Asia faces increasingly frequent environmental stress events, from haze to volcanic activity, the ability to distinguish between atmospheric measurements and ground-level health impacts becomes a matter of public trust and effective governance.

The Singaporean model of integrated environmental monitoring and proactive public communication offers a reference point for regional best practices. Strengthening these institutional capacities across ASEAN would help mitigate both the environmental and informational risks that accompany such crises.

Frequently asked questions

Is sulphur dioxide from Anak Krakatau affecting Malaysia's air quality?

No. Ground-level monitoring data from Malaysia's Department of Environment shows no confirmed evidence of harmful SO2 concentrations from the eruption. Satellite maps showing high SO2 levels measure the vertical atmospheric column, not the air people breathe at ground level.

Why did satellite maps show high SO2 levels near Malaysia?

The maps, sourced from Windy.com, display satellite measurements of SO2 within a vertical column of the atmosphere. These readings do not represent ground-level concentrations and may also capture SO2 from biomass burning rather than volcanic emissions.

What should the public rely on during transboundary haze events?

Experts recommend relying on official monitoring agencies such as Malaysia's Department of Environment and MetMalaysia, which provide validated ground-level data and timely public health advisories. Social media maps without context can be misleading.