Abstract
Radiation management (RM) has been proposed as a conceivable climate engineering (CE) intervention to mitigate global warming. In this study, we used a coupled climate model (MPI-ESM) with a very idealized setup to investigate the efficacy and risks of CE at a local scale in space and time (regional radiation management, RRM) assuming that cloud modification is technically possible. RM is implemented in the climate model by the brightening of low-level clouds (solar radiation management, SRM) and thinning of cirrus (terrestrial radiation management, TRM). The region chosen is North America, and we simulated a period of 30 years. The implemented sustained RM resulted in a net local radiative forcing of −9.8 Wm−2 and a local cooling of −0.8 K. Surface temperature (SAT) extremes (90th and 10th percentiles) show negative anomalies in the target region. However, substantial climate impacts were also simulated outside the target area, with warming in the Arctic and pronounced precipitation change in the eastern Pacific. As a variant of RRM, a targeted intervention to suppress heat waves (HW) was investigated in further simulations by implementing intermittent cloud modification locally, prior to the simulated HW situations. In most cases, the intermittent RRM results in a successful reduction of temperatures locally, with substantially smaller impacts outside the target area compared to the sustained RRM.
Highlights
Climate engineering (CE), referred to as geoengineering, encompasses a set of technologies and methods to deliberately intervene in the climate system to counteract global warming [1]
Here we demonstrate that regional RM (RRM) may lead to non-local responses which are modulated by the atmospheric circulation, and subsequently we demonstrate that limiting RRM in time substantially reduces these side-effects
The implemented Radiation management (RM) in the climate model increases the reflection of solar radiation by liquid-water clouds and reduces the cirrus greenhouse effect by allowing more terrestrial radiation to escape to space
Summary
Climate engineering (CE), referred to as geoengineering, encompasses a set of technologies and methods to deliberately intervene in the climate system to counteract global warming [1]. The response of climate to stratospheric aerosol injection (SAI) has been investigated in many modeling studies (e.g., [10,18,19,24,25,34,35,36,37]) These suggest that SAI could possibly stabilize the global mean surface temperature. The suggestion is to modify low-level marine clouds by injecting aerosols into the marine boundary layer and so increase cloud albedo Such modification would produce a negative RF, which implies a cooling of surface temperature [46]. It is essential to identify the regional response to climate change [60] In this context, Quaas et al (2016) [21] pointed out that RRM could further be limited by implementing them only “on demand” to target certain climate extreme events, in particular, heat waves (HW).
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