Abstract
The hydrological cycle has a significant impact on human activities and ecosystems, so understanding its mechanisms with respect to a changing climate is essential. In particular, a more detailed understanding of hydrological cycle response to transient climate change is required for successful adaptation and mitigation policies. In this study, we exploit large ensemble model experiments using the Community Earth System Model version 1.2.2 (CESM1) in which CO2 concentrations increase steadily and then decrease along the same path. Our results show that precipitation changes in the CO2 increasing and decreasing phases are nearly symmetrical over land but asymmetric over oceans. After CO2 concentrations peak, the ocean continues to uptake heat from the atmosphere, which is a key process leading the hydrological cycle’s contrasting response over land and ocean. The symmetrical hydrological cycle response over land involves a complex interplay between rapid responses to CO2 and slower responses to ensuing warming. Therefore, the surface energy constraints lead to the contrasting hydrological response over land and ocean to CO2 forcing that needs to be verified and considered in climate change mitigation and adaption actions.
Highlights
The global hydrological cycle’s responses to rising temperatures driven by increasing greenhouse gas concentration significantly impact human activities and Earth’s ecosystems[1,2,3,4,5,6,7,8]
The changes in global mean precipitation are almost identical to the changes in ocean precipitation, land precipitation changes are almost symmetric in a changing CO2 pathway (Fig. 1b)
Neither the global mean precipitation nor ocean and land precipitation returns to the present climate conditions, as the adjustment back to the PD simulation is likely to be slow after 280 continuous years of excess heating, much of which is stored in the deep ocean
Summary
The global hydrological cycle’s responses to rising temperatures driven by increasing greenhouse gas concentration significantly impact human activities and Earth’s ecosystems[1,2,3,4,5,6,7,8]. The magnitude and rate of changes for regional hydrological events directly impact infrastructure, agriculture, and health[15,16,17]. Previous studies examined precipitation changes in warmer climates by analyzing Coupled Model Intercomparison Projection. These climate change simulations are characterized by a wet-get-wetter/dry-get-drier pattern[18,19,20] or a warmer-get-wetter pattern[21,22] over the oceans. Water vapor content at typical lower troposphere temperatures is constrained to increase by no more than 7% K−1 18, which is the limit set by the Clausius–Clapeyron equation for saturation vapor pressure
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