Aim: This research investigates drought in Iran and evaluates its relationship with global CO₂ (GCO2) concentration and monthly sunspot frequency (MSSF). It examines the interplay between natural factors and human influences on this climatic phenomenon.
Materials & Methods:
Data were obtained from 31 synoptic stations across Iran for the period 1961–2023. The 12‑month Standardized Precipitation Evapotranspiration Index (SPEI‑12) was used as the drought metric. Relationships among SPEI‑12, GCO2, and MSSF were examined using Pearson’s correlation and Cross Wavelet Transform (XWT).
Findings: The study found that minimum SPEI‑12 values occurred at Bushehr (airport), Bandarabbas, Arak, Abadan, and Orumiyeh; maximum values were recorded at Bushehr (airport), Isfahan, Kermanshah, Torbat-e-Heydariyeh, and Khoy. All stations, except Shahrekord, exhibited a significant downward trend in SPEI‑12, confirmed by trend tests such as Mann‑Kendall, Sen’s slope, and Mann‑Kendall mutation test. Shahrekord uniquely experienced an upward shift around 1970. Pearson’s analysis revealed a strong negative correlation between SPEI‑12 and GCO2. Although the correlation with MSSF was less pronounced, the XWT results highlight the out-of-phase patterns, especially in the 128-month periods.
Conclusion: Based on the findings, the persistent decline in SPEI‑12 indicates intensifying drought conditions across Iran. The inverse relationship with GCO2 underscores the impact of climate change on water resources and calls for updated water management policies to address shifting precipitation patterns.
Innovation: By integrating time series trend analysis, XWT, and correlation tests, the study introduces an innovative methodology for refining climate models and guiding strategic water management. Its findings offer a valuable reference for similar research in other arid regions.