Unveiling shifts in Eurasian annual temperature cycles under anthropogenic warming.

The annual temperature cycle (ATC) is an essential component of Earth's ecological and climate systems, driving prominent oscillations in many organic and climate variables outside the tropics. Significant decreases in ATC amplitude have been evident across most extratropical Eurasian land areas over the last 70 years, particularly in Western Siberia. However, the long-term trend in the ATC phase yields substantial uncertainty, with its dominant change being a phase advance in Eastern Europe. The state-of-the-art climate models underestimate the amplitude decrease due to inadequate modeling of the ATC amplitude's response to anthropogenic surface warming, manifesting as a robust linear constraint across multiple models. The preliminary attribution analysis also indicates that the ATC amplitude decrease in Western Siberia is primarily related to anthropogenic forcings. Greenhouse gas emissions are the primary contributor, further suggesting the robustness of this long-term trend under anthropogenic warming. Nevertheless, most climate models exhibit erroneous estimates of long-term changes in the ATC phase, highlighting the necessity for future model improvement to achieve robust climate detection and attribution.