Greenhouse Gas Trends in the Central Himalayas: New High-Altitude Data Unveils Climate Challenges

In a landmark study, Indian scientists have, for the first time, captured high-resolution, continuous online measurements of key greenhouse gases in the Central Himalayas, shedding new light on how environmental factors and human activities together influence atmospheric composition in this ecologically sensitive region.

These measurements were conducted over a span of five years at a high-altitude research site in Nainital, Uttarakhand, by the Aryabhatta Research Institute of Observational Sciences (ARIES)—an autonomous institute under the Department of Science & Technology (DST), Government of India.

The ARIES research team focused on three critical greenhouse gases: carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO).

Their findings address a long-standing data gap in ground-based atmospheric observations in South Asia’s mountainous regions, which have traditionally been underrepresented in global climate monitoring efforts.

The unique geographic vantage point of the Himalayan site in Nainital provides an exceptional opportunity to disentangle (separate and analyze individually) the effects of biospheric uptake (absorption of gases like CO₂ by vegetation), regional emissions, and complex meteorological patterns. These dynamics collectively shape the region’s air quality and contribute to broader climate change processes.

Trend in CO2, CH4, and CO at Nainital (NTL) and Mauna Loa, a background site, during 2014–2018.

Monthly variation in excess CO/CO2, ppb/ppm with CO from fossil fuel combustion (COff) and from biomass burning (CObb), fire events over the Northern Indian region (24-35° N, 70-89° E) and boundary layer height at the site location. The yellow highlighted region denotes the emission ratios reported for fossil fuel emissions and biomass emissions.

One of the key observations from the study is that greenhouse gas concentrations in the Central Himalayas are generally higher than those at remote background sites (such as Mauna Loa in Hawaii, which is often used as a global benchmark for atmospheric gases). However, they remain lower than concentrations typically observed in urban and semi-urban areas, indicating a mixed influence of local emissions and pollutant transport from distant upwind regions.

The research highlights pronounced diurnal (daily) and seasonal cycles in gas concentrations. During daylight hours, carbon dioxide levels drop due to active photosynthesis, wherein plants absorb CO₂ for energy production. In contrast, both methane and carbon monoxide levels peak during the day, driven by mountain winds that transport pollutants from lower elevations to higher altitudes.

Seasonal variability is also significant. Carbon dioxide concentrations increase during spring, primarily due to biomass burning (the burning of crop residues and forests) and reduced vegetation cover, which limits natural CO₂ absorption. Methane levels peak in autumn, likely associated with agricultural practices, particularly rice cultivation, which releases methane during paddy field flooding. Carbon monoxide peaks in late spring, suggesting a substantial contribution from regional pollution transport, possibly due to wind-borne pollutants from the Indo-Gangetic Plain.

More concerning are the long-term trends: CO₂ levels are rising at a rate of 2.66 parts per million (ppm) per year, while CH₄ is increasing by 9.53 parts per billion (ppb) per year—both figures exceeding those recorded at Mauna Loa. This indicates a growing influence of anthropogenic (human-induced) emissions in the region. On the other hand, carbon monoxide is gradually declining at 3.15 ppb per year, which could be attributed to improvements in combustion efficiency (better burning techniques in vehicles or stoves) or shifting emission sources.

The study emphasizes the role of environmental variables such as solar radiation, temperature, and the atmospheric boundary layer—the lower part of the atmosphere where most weather phenomena and pollution dispersion occur. This layer acts as a cap that limits how high pollutants can rise and therefore has a critical impact on greenhouse gas dynamics. These factors are just as influential as human activities like agriculture and urban emissions in shaping regional air quality.

Such comprehensive, high-resolution observations are invaluable for multiple purposes: they help validate satellite-based climate data, refine emission inventories, and enhance the accuracy of atmospheric models. These improvements are crucial for both climate forecasting and climate policy planning.

Ultimately, this research offers localized, real-time data—a powerful tool for policymakers and climate scientists seeking to develop effective climate mitigation strategies. By uncovering how both natural processes and human activities shape the air we breathe, especially in such a complex terrain, the study sets a new benchmark for climate monitoring and response in South Asia and similar mountainous ecosystems worldwide.

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