LAUSR

We welcome the letter from Wang et al. (1) regarding the uncertainty in eddy covariance (EC) measurements on the Tibetan Plateau (TP) and appreciate the opportunity to clarify our thinking. Our study focuses on the CO2 exchange between the air and plants/soil on the TP (2), rather than the carbon (C) balance of the whole region; for instance, we did not measure the C sources/sinks in water bodies (3). Furthermore, different approaches tend to yield inconsistent results regarding the CO2 sink of a region—for example, in the Arctic (4, 5). Our estimate, based upon 32 EC towers, which challenges previous estimates in this region, is not necessarily an overestimation. The EC technique provides the scientific community with an almost ideal approach to measuring the CO2 exchange, although it still has limitations. For example, EC will occasionally yield a CO2 sink in winter, and the imputation models used for day/night are different, so it is necessary to artificially determine the growing/nongrowing season and day/ night to make the result reasonable (6). Taking the division of day/night as an example, given the phenomenon of A