Preprint shows accelerating tropospheric warming

Cheng-Zhi Zou and three co-authors posted a preprint on Research Square this week arguing that global warming in the lower troposphere has accelerated in satellite records since 2015. The paper, titled “Global warming acceleration in satellite observed lower-tropospheric temperature,” is labeled Version 1 and says it has not been peer reviewed by a journal. (researchsquare.com) The authors are Cheng-Zhi Zou, Xianjun Hao, John J. Qu and Satya Kalluri. Zou and Qu are listed by George Mason University’s Environmental Science and Technology Center, while Kalluri is identified in NOAA-affiliated biographies as chief of cooperative research programs at NOAA/NESDIS STAR. ### What exactly does the preprint say changed? The preprint says satellite-derived lower-tropospheric temperature, or TLT, shows statistically significant acceleration over 1981-2025, with the sharpest recent warming centered on the post-2015 period. In the abstract, the authors say adjusted TLT trends reach as high as 0.482 ± 0.113 degrees Celsius per decade from 2015 onward across the satellite and reanalysis datasets they examined. They say that is roughly four to five times larger than the pre-2015 period. A second headline figure in the paper is an inferred acceleration rate of up to 0.48 ± 0.12 degrees Celsius per decade squared near 2024. (researchsquare.com) The abstract says the authors interpret the 2023-2024 temperature jump as part of an ongoing acceleration that was amplified by El Niño. It also says projections based on those accelerated trends imply another 0.5 to 1.0 degree Celsius of warming within the next decade. ### What data are they using when they say “lower troposphere”? NOAA and Remote Sensing Systems describe TLT as a satellite-derived measure of lower-tropospheric temperature built from microwave sounding instruments flown on polar-orbiting satellites. (researchsquare.com) NOAA’s Version 5 climate data record covers November 1978 to the present and merges observations from 16 satellites. RSS says its TLT product is built by combining measurements at different viewing angles to shift sensitivity lower in the atmosphere. The preprint says it uses multiple lower-tropospheric satellite datasets processed with different homogenization methods, along with reanalysis datasets, to assess acceleration. (researchsquare.com) That matters because satellite temperature records are not direct thermometer readings; they are long climate records assembled from successive instruments and adjusted for calibration, orbital drift and other changes over time. ### How did the authors try to separate long-term warming from short-term noise? The authors say they constructed an “adjusted TLT” record by removing variability linked to ENSO and aerosols. The abstract says that step reduced annual variability by nearly 50%, which they say improved the robustness of acceleration detection. (ncei.noaa.gov) They recommend using the ENSO-aerosol-adjusted record for long-term trend and acceleration analysis. The paper places particular weight on the 2023-2024 spike in global temperatures. Its introduction says those years produced the highest global temperatures observed and that the margin over previous records reached about 0.2 to 0.4 degrees Celsius during late 2023 and early 2024. (researchsquare.com) The authors say that unusually large jump prompted a closer look at whether the recent rise was a short-lived anomaly or part of a faster long-term trend. ### How should readers treat this result right now? Research Square says the manuscript is a preprint and “has not been peer reviewed by a journal.” That means the paper is public and citable, but it has not yet gone through formal external review. (researchsquare.com) The platform lists it as posted Version 1. The authors are not working from an unfamiliar data stream. Zou and Hao are associated with NOAA’s mean-layer temperature climate data record, and NOAA describes that record as a vetted long-term satellite dataset for tracking atmospheric temperature from the lower troposphere to the lower stratosphere. But the acceleration claim itself is new and, as of Tuesday, is being presented in preprint form rather than in a peer-reviewed journal article. (researchsquare.com) ### Where can the next step be checked? Research Square hosts the current manuscript under DOI 10.21203/rs.3.rs-9283491/v1 and labels it as the latest posted version. Any revision, journal submission, peer-review discussion or linked commentary would appear through that record or through a later journal publication by Zou, Hao, Qu and Kalluri. (researchsquare.com) (orcid.org)