Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor

Abstract

The sensitivity of Earth's climate to an external radiative forcing depends critically on the response of water vapor. We use the global cooling and drying of the atmosphere that was observed after the eruption of Mount Pinatubo to test model predictions of the climate feedback from water vapor. Here, we first highlight the success of the model in reproducing the observed drying after the volcanic eruption. Then, by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling. These results provide quantitative evidence of the reliability of water vapor feedback in current climate models, which is crucial to their use for global warming projections.

Water‐vapor climate feedback inferred from climate fluctuations, 2003–2008

“…The close correspondence between average l q RH and l q arises despite the fact that the atmosphere does not actually keep RH fixed, but displays a complex pattern of increases and decreases. Soden et al [2002Soden et al [ , 2005 analyzed the LW feedback and concluded that it has a magnitude close to that of a constant-RH feedback, and Soden and Held [2006] concluded that l q and l q RH differed in climate models by just a few percent. [19] Figures 4a-4d show that the LW water-vapor feedback arises primarily from changes in q in the tropical upper troposphere, while the SW feedback arises from changes in the lower troposphere.…”

Change of precipitation intensity spectra at different spatial scales under warming conditions

“…A theoretically well-determined value is the change in waterholding capacity of the atmosphere of 7%/K, governed by the Clausius-Clapeyron equation [1]. This equation indicates an increase of precipitable water (column-integrated water) in relation to the constant relative humidity on the global scale [12]. This value is at odds with the model-predicted increase of 2%/K in precipitation intensity proposed in a study using an ensemble of 17 latest-generation climate models [13].…”

The Role of Volcanic Activity in Climate and Global Change

“…Heat Content Anomaly/10 22 J f0055 FIGURE 10 The global and ensemble mean ocean heat content (10 22 J) anomaly for 300 m and whole depth ocean for the Pinatubo ensemble calculated with respect to ensemble control.…”

“…Volcanically induced changes in interior ocean temperature, the meridional overturning circulation and steric height have even longer relaxation times, from several decades to a century. Because of their various impacts on climate systems, volcanic eruptions play a role of natural tests, providing an independent means of assessing multiple climate feedback mechanisms and climate sensitivity [7][8][9][10][11]. p0030…”