Atmospheric Study Reveals Greenhouse Gases Strengthen East Asian Westerly Jet Despite Rising Global Temperatures

New atmospheric research reveals that greenhouse gases strengthen the East Asian westerly jet, countering the weakening effects of historical orbital forcing.

By: AXL Media

Published: Apr 25, 2026, 6:27 AM EDT

Source: Information for this report was sourced from EurekAlert!

The Dual Nature of Atmospheric Transitions

A comprehensive analysis of the last deglaciation, spanning roughly 19,000 to 11,500 years ago, has revealed that the East Asian subtropical westerly jet (EASWJ) does not follow a uniform response to global warming. Researchers from the State Key Laboratory of Climate System Prediction and Risk Management found that the jet exhibited millennial-scale fluctuations layered over a long-term weakening trend. This period of Earth's history, marked by rapid thermal shifts and atmospheric variability, serves as a critical baseline for scientists attempting to forecast how midlatitude climates will react to modern anthropogenic forcing.

Contradictory Forcing Mechanisms Identified

The study identifies a fundamental divergence in how different climate drivers manipulate the jet stream's intensity and position. While orbital forcing historically initiated a weakening trend, the rise in greenhouse gases (GHGs) during the deglaciation period actually exerted a strengthening effect. According to the research team, this finding is significant because it proves that two different warming agents can push the same atmospheric feature in opposite directions, depending on how they distribute heat across the planet's latitudes and altitudes.

Structural Warming and the Temperature Gradient

Dr. Yan, the corresponding author of the study, explained that the spatial structure of warming is more influential than the absolute increase in temperature. Orbital forcing typically results in amplified warming at higher latitudes, which reduces the temperature gap between the equator and the poles, thereby slowing the jet. Conversely, greenhouse gases induce more intense warming in the upper troposphere at low to mid latitudes. This specific heating pattern sharpens the meridional temperature gradient, which acts as a thermal engine to accelerate and strengthen the westerly jet.