3D simulations of the Archean Earth including photochemical haze profiles

TL;DR

This study uses 3D simulations to explore how photochemical haze layers, formed under different methane to carbon dioxide ratios, influence the climate and atmospheric structure of the Archean Earth.

Contribution

It introduces a novel integration of 3D climate modeling with prescribed photochemical haze profiles to assess their climatic effects.

Findings

Thin haze causes ~10.6 K warming.

Thick haze results in up to ~65 K cooling.

Haze optical thickness reaches a threshold at CH4/CO2 ~ 0.175.

Abstract

We present results from 3D simulations of the Archean Earth including a prescribed (non-interactive) spherical haze generated through a 1D photochemical model. Our simulations suggest that a thin haze layer, formed when CH4/CO2 = 0.1, leads to global warming of ~10.6 K due to the change of water vapour and cloud feedback, compared to the simulation without any haze. However, a thicker haze layer, formed when CH4/CO2 > 0.1, leads to global cooling of up to ~65 K as the scattering and absorption of shortwave radiation from the haze reduces the radiation from reaching the planetary surface. A thermal inversion is formed with a lower tropopause as the CH4/CO2 ratio increases. The haze reaches an optical threshold thickness when CH4/CO2 ~ 0.175 beyond which the atmospheric structure and the global surface temperature do not vary much.