NASA researchers retract Nature paper on climate change and evapotranspiration

The authors of a 2021 Nature paper on how climate change might affect the amount of evaporation from the earth’s land surface have retracted the article after learning of a crucial error in their analysis. 

The crux of the paper, titled “A 10 per cent increase in global land evapotranspiration from 2003 to 2019,”  was the finding that:

Variability in global land evapotranspiration is positively correlated with El Niño–Southern Oscillation. The main driver of the trend, however, is increasing land temperature. Our findings provide an observational constraint on global land evapotranspiration, and are consistent with the hypothesis that global evapotranspiration should increase in a warming climate.

In other words, according to the authors – from a pair of NASA labs in California and Maryland – the rate of evapotranspiration over that 17-year-period was twice as high as previous estimates. As the lead author, Madeleine Pascolini-Campbell, said in this press release (Wayback Machine link) from NASA:  

Images of melting glaciers and shrinking ice sheets are a palpable way for us to understand the impacts of global warming … But dramatic changes are also happening to other key components of our planet’s water cycle that aren’t so visible, such as when water evaporates from the land before it can enter the rivers as runoff.

The study garnered some attention, with articles in the trade press, such as this one in Phys.org and this coverage in CarbonBrief.

But as the retraction notice explains, that conclusion was incorrect: 

In this article, we calculated global land evapotranspiration for 2003 to 2019 using a mass-balance approach. To do this, we calculated evapotranspiration as the residual of the water balance, using an ensemble of datasets for precipitation, discharge and total water storage change. We made an error in calculating the global mean precipitation: we used arithmetic averaging to calculate the mean, instead of calculating a spatially weighted mean to account for the changing grid box size with latitude. As a result, the magnitudes of the global mean precipitation time series were underestimated. This impacted the subsequent calculation of global mean evapotranspiration, resulting in the mean evapotranspiration values being underestimated and altering some results. We are therefore retracting this article. We thank Ning Ma and others for bringing this error to our attention.

Ma is a climate researcher with the Chinese Academy of Sciences in Beijing. 

Pascolini-Campbell has not responded to a request for comment.

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