Contribution of Shorter-term Radiative Forcings of Aerosols and Ozone to Global Warming in the Last Two Decades

Abstract: This paper reports observations of regional and global upper stratosphere temperature (UST) and surface temperature, as well as various climate drivers including greenhouse gases (GHGs), ozone, aerosols, solar variability, snow cover extent, and sea ice extent (SIE). We strikingly found warming trends of 0.77(+/-0.57) and 0.69(+/-0.22) K/decade in UST at altitudes of 35-40 km in the Arctic and Antarctic respectively and no significant trends over non-polar regions since 2002. These UST trends provide fingerprints of decreasing and no significant trends in total GHG effect in polar and non-polar regions respectively. Correspondingly, we made the first observation of surface cooling trends in both the Antarctic since 2005 and the Arctic since 2016 once the SIE started to recover. But surface warming remains at mid-latitudes, which causes the recent rise in global mean surface temperature (GMST). These temperature changing patterns are consistent with the characteristics of the cosmic-ray-driven electron reaction (CRE) mechanism of halogen-containing GHGs (halo-GHGs) with larger destruction rates at higher latitudes. Moreover, the no-parameter physics model of warming caused by halo-GHGs reproduces closely the observed GMSTs from 2000 to 2024, including the almost no warming during 2000-2012 and the significant warming by 0.2-0.3 deg C during 2013-2023, of which 0.27 deg C was calculated to arise from the net radiative forcing of aerosols and ozone due to improved air quality. The results also show that the physics model captures 76% of the variance in the observed GMSTs, exhibiting a warming peak in October 2023 and predicting a gradual GMST reversal thereafter. The results from this study may greatly improve our understanding of global climate change and lead to the identifying of the correct major culprit for human contribution to changing the climate.

• The paper demonstrates that aerosols and ozone significantly contribute to global warming, challenging traditional CO2-centric climate models.
• It identifies contrasting temperature trends with mid-latitude warming alongside polar cooling, supported by detailed UST and GMST analyses.
• The study shows that improved air quality and declining halogenated GHGs may lead to a long-term reversal of global mean surface temperatures.

Analysis of Global Surface Warming from Shorter-term Radiative Forcings of Aerosols and Ozone

The study by Qing-Bin Lu offers a comprehensive examination of global and regional temperature trends, with a focus on the unique impacts of aerosols, ozone, and halogenated GHGs over the past two decades. This paper scrutinizes the conventional understanding of climate drivers and presents critical observations regarding upper stratosphere temperature (UST) and global mean surface temperature (GMST) trends.

Key Observations and Findings

• Upper Stratosphere Temperature Trends: The paper reveals warming trends of 0.8(±0.6) K/decade and 0.7(±0.2) K/decade in the UST at altitudes of 35-40 km in the Arctic and Antarctic, respectively. These trends are contrasted with insignificant changes in non-polar regions. The author suggests this as evidence of a decreasing total GHG effect in polar areas, yet a constant GHG effect in other global regions.
• Surface Temperature Trends: Surface cooling is observed in the Antarctic since 2002 and in the Arctic since 2016, coinciding with signs of stabilization in sea-ice extent (SIE). Conversely, surface warming continues in mid-latitudes, aligning with the general rise in GMST attributed to positive short-term radiative forcings from aerosols and improved air quality.
• Role of Aerosols and Ozone: The data underscores the significant influence of aerosols and ozone on GMST, accounting for recent warming trends alongside pollutants' improvements. The paper challenges the continued dominance of CO2 as the main driver of radiative forcing, instead implicating short-term agents as crucial contributors in the current era.
• Decreasing Halogenated GHGs: Lu emphasizes the decline in halo-GHGs since regulations enacted by the Montreal Protocol, aligning with models predicting long-term GMST reversal, potentially commencing by the end of 2023.

Theoretical and Practical Implications

1. Contradictions with Conventional Climate Models: Lu points out contradictions to CO2-centric climate models by demonstrating different UST trends than those predicted. This challenges the notion of a consistent inverse relationship between tropospheric warming and stratospheric cooling.
2. Regional Variations and Polar Focus: With the anticipation of long-term GMST reversal, the study highlights polar regions as critical observation sites for understanding GHG impacts due to the diminished confounding effects of aerosols and SIE-induced surface albedo feedback.
3. CFC-Warming Model: The conceptual physics model proposed, termed the CFC-warming model, contrasts the conventional GCM approaches by eschewing tunable parameters. This model fortifies the argument of aerosols and ozone as substantial, emergent factors in climate dynamics.
4. Data Discrepancies and Calibration Challenges: The discrepancy between ROM SAF data and NOAA STAR reprocessed datasets is concerning, raising questions on the reliability of SSU/AMSU data, which are traditionally corrected based on GCM assumptions.

Future Outlook in Climate Research

Future investigations could explore quantifying the nuanced contributions of stratospheric temperature changes to GMST prediction accuracy. The contrasting predictions between different climate models necessitate deeper exploration into the role of improved air quality and policy interventions affecting radiative forcing. Given Lu's critical findings, the study signals a pivotal point for climate science, prompting a reevaluation of predominant paradigms driving climate action strategies.

Overall, Qing-Bin Lu's work prompts an important dialogue about common assumptions in climate modeling, advocating for refined methodologies sensitive to both halogenated compounds and short-term climatic agents. This paper encourages researchers to further investigate the layered, multi-faceted influences governing climate change beyond traditional CO2 emissions narratives.