A 26-year, long-term record of atmospheric methane (CH₄) measured in situ at the Mount Waliguan (WLG) station, the only World Meteorological Organization (WMO) and Global Atmosphere Watch (GAW) global station in inland Eurasia, is presented. Overall, a nearly continuous increase in atmospheric CH₄ was observed at WLG, with a yearly growth rate of 5.1±0.1 parts per billion (ppb) per year during 1994–2019, except for some particular periods with near-zero or negative values, e.g., 1999–2000 and 2004–2006. The average CH₄ mole fraction was only 1799.0±0.4 ppb in 1994 but increased to about 133 ppb and reached a historic level of 1932.0±0.1 ppb in 2019. The case study in the Tibetan Plateau showed that the atmospheric CH₄ increased rapidly. During some special periods, it is even larger than that of city regions (e.g., 6.7±0.2 ppb yr⁻¹ in 2003–2007). Generally, the characteristics of CH₄ varied in different observing periods as follows: (i) the diurnal cycle has become apparent and the amplitudes of the diurnal or seasonal cycles increased over time; (ii) the wind sectors with elevated CH₄ mole fractions switched from ENE-E-ESE-SE-SSE sectors (wind directions) in early periods to NNE-NE-ENE-E sectors in later years; (iii) the area of source regions increased as the years progressed, and strong sources shifted from northeast (city regions) to southwest (northern India); and (iv) the annual growth rates in recent years (e.g., 2008–2019) were significantly larger than those in the early periods (e.g., 1994–2007).

The research of greenhouse gases on the Tibetan Plateau is of great importance since its unique topography as the third pole of our planet and profound response on the climate change. In this study, we compared the concurrent observations of atmospheric carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO) during 2010–2016 from two stations located on the Tibetan Plateau, which are Mt. Waliguan station (WLG), the only World Meteorological Organization/Global Atmosphere Watch global station in the inland of Eurasia, and Shangri‐La station, a Chinese national station (XGLL). Although both stations are located at remote area, the atmospheric CO₂, CH₄, and CO concentrations are frequently influenced by regional sources, especially for XGLL throughout the year and WLG in summer. Due to the unique topography and regional conditions, the atmospheric CH₄ and CO at both stations display different trends with other sites in China, with higher values in summer. The atmospheric CO₂, CH₄, and CO at the XGLL mainly represent the conditions in regional scale. As the only World Meteorological Organization/Global Atmosphere Watch global station in the inland of Eurasia, the observation results at WLG can be used to represent the conditions on the Tibetan Plateau, but some of them are frequently influenced by the emissions from the cities located on the east or north east, and some even can be affect by emissions from the Ganges basin in autumn and winter, which should be treated with caution. By subtracting the influences of the cities, we updated the growth rate of 2.45 ± 0.02 ppm yr⁻¹ for CO₂, 8.2 ± 0.1 ppb yr⁻¹ for CH₄, and −0.4 ± 0.1 ppb yr⁻¹ for CO, compared to the prior estimation of 2.31 ± 0.02 ppm yr⁻¹ for CO₂, 8.1 ± 0.1 ppb yr⁻¹ for CH₄, and −0.6 ± 0.1 ppb yr⁻¹ for CO on the Tibetan Plateau.

The importance of carbon neutrality and green development rose sharply in the post‐pandemic era in China. This study investigated the long‐term variability of atmospheric carbon dioxide (CO₂) in China using CO₂ records from Mount Waliguan (WLG), the only global station of World Meteorological Organization/Global Atmosphere Watch in Eurasia, covering a 26‐year period (1994–2019). Overall, the atmospheric CO₂ mole fraction increased continuously and steadily with a growth rate of 2.15 ± 0.01 ppm yr⁻¹ over 1994–2019 at WLG. The average CO₂ mole fraction was only 359.9 ± 0.04 ppm in 1994, but reached a historic level of 414.9 ± 0.04 ppm by 2019. The mean growth rates in city sectors (data from the city regions) were slightly higher than that in the Tibetan Plateau. The seasonal amplitude of atmospheric CO₂ at WLG was lower than those at adjacent regional stations, such as Lin'an, and Shangdianzi, but larger those at global stations Mauna Loa and Minamitorishima. Potential strong source regions moved from urban areas to the southwest region away from WLG, suggesting the potential emergence of Northern India as a strong CO₂ source region. The area of potential CO₂ sources at WLG prominently expanded with time, reflecting the effect of more intensifying anthropogenic emissions in recent decades. Although numerous measures for carbon emission reduction have already been implemented, it is clear that much work, e.g., carbon emission estimation, sources/sinks tracing, cleaner energy technologies, remains to be done in order to achieve carbon emission peak and carbon neutrality set by the Chinese government.

Observation of atmospheric CO 2 and CO at Shangri-La station: results from the only regional station located at southwestern China