CLIMATE CHANGE. Long-term climate forcing by atmospheric oxygen concentrations

Area of Science:

• Paleoclimatology
• Geochemistry
• Atmospheric Science

Background:

• Atmospheric oxygen (O2) levels fluctuated significantly (10-35%) during the Phanerozoic Eon.
• These O2 variations have been primarily linked to biological evolution and have not been previously considered a driver of climate change.

Purpose of the Study:

• To investigate the impact of varying partial pressure of oxygen (pO2) on Earth's climate dynamics.
• To determine if O2 levels can act as a significant climate forcing factor throughout geologic time.

Main Methods:

• Climate modeling simulations were employed to assess the effects of different pO2 levels.
• The simulations analyzed how pO2 influences atmospheric mass, density, and optical depth.

Main Results:

• Reduced atmospheric density under low pO2 conditions led to less frequent shortwave scattering, increasing surface shortwave forcing.
• Feedbacks involving latent heat, marine stratus clouds, and water vapor amplified warming.
• Increased pO2 was shown to enhance greenhouse forcing and global surface temperatures.

Conclusions:

• The partial pressure of oxygen (pO2) is identified as a critical factor in regulating Earth's climate over geologic timescales.
• O2's influence on atmospheric density and optical properties directly impacts climate forcing.
• This study necessitates a re-evaluation of past climate dynamics, incorporating O2 levels as a key variable.