Neutral Mode Dominates the Forced Global and Regional Surface Temperature Response in the Past and Future

Abstract

Barring the broadest spatial features, confidence in the regional details of climate change projections is still lacking (Neelin et al., 2006), which has been a longstanding challenge to the climate community (Beniston, 2013;Mlawer et al., 1997). The projected increase in heat waves and extreme precipitation has been largely premised on the thermodynamics-regulated temperature and moisture changes (Fischer et al., 2021;Madakumbura et al., 2021;Mantua & Hare, 2002), whereas the lack of robustness in the projected regional precipitation response by climate models has been blamed on the dynamics-regulated atmospheric and oceanic circulation changes (Biasutti et al., 2018;Hall, 2014;Xie et al., 2015). Since no one lives in the global mean climate, improving the confidence in regional-scale climate change projections is critical for adaptation and mitigation planning at national and state (provincial) levels. As astutely pointed out by Xie et al. (2015), the challenge of unreliable regional climate change information cannot be addressed solely by increasing model resolution or regional downscaling; advancing understanding of the large-scale coupled dynamics between the ocean and atmospheric circulation might be foundational to narrowing the uncertainties on scales greater than 100s km.A promising way forward to address the challenge above may be through the lens of the intrinsic dynamical modes of the climate system. The rationale behind the mode approach is that the slow, large-scale evolution/ response of the Earth climate is governed by sparse dynamics , although climate is a complex, nonlinear, and high-dimensional system. Moreover, dynamical mode manifests the deterministic

Asymmetric response of cross-equatorial ocean heat transport to latitudinal thermal forcing in CESM

“…The linear response is calculated as 𝑅 𝑙𝑖𝑛𝑒𝑎𝑟 = (𝑅 + − 𝑅 − )/2 , where 𝑅 + and 𝑅 − represent the positive and negative TOA flux perturbation, respectively. More details on the experiments can be found in Liu et al (2022).…”

“…9c). The AMOC strength is closely related to the buoyancy flux change in the North Atlantic Deep Water (NADW) formation region (e.g., Danabasoglu et al 2019;Liu et al 2022). The main NADW formation region in CESM used in this study is located in the Irminger Sea (Fig.…”