Solar activity and the mean global temperature (0901.0515v1)

Abstract: The variation with time from 1956-2002 of the globally averaged rate of ionization produced by cosmic rays in the atmosphere is deduced and shown to have a cyclic component of period roughly twice the 11 year solar cycle period. Long term variations in the global average surface temperature as a function of time since 1956 are found to have a similar cyclic component. The cyclic variations are also observed in the solar irradiance and in the mean daily sun spot number. The cyclic variation in the cosmic ray rate is observed to be delayed by 2-4 years relative to the temperature, the solar irradiance and daily sun spot variations suggesting that the origin of the correlation is more likely to be direct solar activity than cosmic rays. Assuming that the correlation is caused by such solar activity, we deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is $\lesssim14%$ of the observed global warming.

• The paper demonstrates that cosmic ray ionization rates follow an 11-year cycle with a 2-4 year delay in temperature response.
• The paper validates strong correlations between solar irradiance, sunspot numbers, and mean global temperature anomalies using advanced simulation models.
• The paper quantitatively bounds the natural impact on warming, attributing no more than 14% of the temperature increase to solar and cosmic ray activity.

Analysis of Solar Activity and its Impact on Global Temperature

The paper "Solar Activity and the Mean Global Temperature" by Erlykin, Sloan, and Wolfendale offers a quantitative investigation into the influence of solar activity on global temperature variations from 1956 to 2002. This paper examines the correlation between the globally averaged rate of ionization produced by cosmic rays (CR) in the atmosphere and long-term variations in global mean surface temperature. By analyzing cyclic components, the authors assess the impacts of direct solar irradiance (SI), sunspot numbers (SSN), and cosmic rays on climate variability.

Study Overview

The authors present data demonstrating a cyclic component in cosmic ray ionization rates with a period approximately twice that of the 11-year solar cycle. They establish parallels between similar cyclic variations observed in solar irradiance, daily sunspot numbers, and mean global surface temperatures over decades. Notably, the paper highlights a 2-4 year delay in the correlation between cosmic ray variations and temperature/irradiance patterns, suggesting a direct influence from solar activity rather than indirect effects through cosmic rays.

Key Findings

1. Cosmic Ray Ionization: Simulations of ionization rates from cosmic rays using sophisticated models like CORSIKA and GEANT4 reveal an 11-year modulation, with longer-term cyclic variations correlated with global temperature and solar phenomena. These simulations match with available long-term observational data, reinforcing the hypothesis of solar-modulated ionization.
2. Solar Activity and Temperature Correlation: A substantial correlation emerges between solar cycle variations (SSN and SI) and deviations in global surface temperature. The alignment of temperature anomalies with solar activity, rather than the ionization delay, indicates direct solar drivers.
3. Limits on Global Warming Attribution: Statistical analyses reveal that, even if CR or SI were affecting climatic trends, their contribution to the observed global warming since 1956 would not exceed 14%. This finding challenges claims assigning significant climate change impact to cosmic ray-induced mechanisms.

Implications and Future Prospects

The findings put into context the limitations of attributing significant portions of global warming to fluctuations in cosmic radiation and solar activity. By quantitatively bounding their contributions, the paper narrows the search for other dominant anthropogenic or natural factors driving climate change.

• Practical Implications: The role of solar cycle variations in climate metrics should be considered in climate models, but their quantifiable influence compared to human-related factors appears limited.
• Theoretical Implications: The recognized delay in ionization impact adds complexities to the causal understanding of solar-climatic interconnections, encouraging further examination into distinct solar cycle mechanisms affecting climate.

This paper advances the discourse on climatic implications of cosmic rays and solar activity, emphasizing the necessity for comprehensive models that incorporate multiple contributing factors. Future investigations in climate science should continue refining the accuracy of long-term predictions, acknowledging the modest role identified for cosmic rays and solar irradiance in climate dynamics.