Northern winter climate change: Assessment of uncertainty in CMIP5 projections related to stratosphere-troposphere coupling

Abstract

Future changes in the stratospheric circulation could have an important impact on northern winter tropospheric climate change, given that sea level pressure (SLP) responds not only to tropospheric circulation variations but also to vertically coherent variations in troposphere-stratosphere circulation. Here we assess northern winter stratospheric change and its potential to influence surface climate change in the Coupled Model Intercomparison Project-Phase 5 (CMIP5) multimodel ensemble. In the stratosphere at high latitudes, an easterly change in zonally averaged zonal wind is found for the majority of the CMIP5 models, under the Representative Concentration Pathway 8.5 scenario. Comparable results are also found in the 1% CO 2 increase per year projections, indicating that the stratospheric easterly change is common feature in future climate projections. This stratospheric wind change, however, shows a significant spread among the models. By using linear regression, we quantify the impact of tropical upper troposphere warming, polar amplification, and the stratospheric wind change on SLP. We find that the intermodel spread in stratospheric wind change contributes substantially to the intermodel spread in Arctic SLP change. The role of the stratosphere in determining part of the spread in SLP change is supported by the fact that the SLP change lags the stratospheric zonally averaged wind change. Taken together, these findings provide further support for the importance of simulating the coupling between the stratosphere and the troposphere, to narrow the uncertainty in the future projection of tropospheric circulation changes.

Remarkable link between projected uncertainties of Arctic sea-ice decline and winter Eurasian climate

“…4d). This is consistent with other studies (e.g., Screen and Simmonds, 2010;Manzini et al, 2014;Blackport and Kushner, 2017;Ogawa et al, 2017 a ). Models with more pronounced lower-tropospheric warming in the Arctic than in the low-latitude region exhibit weakening of the equator-to-pole temperature gradient and midlatitude westerlies (Fig.…”

“…The strengthening of the midlatitude zonal-mean zonal wind in the MME response appears to be linked to the stratospheric signals, whereas the weakening of the zonal-mean zonal wind in the SVD1 is due to SIC-related signals. The former is consistent with Manzini et al (2014), who highlighted the importance of stratospheric forcing in future surface circulation changes.…”

Using Causal Effect Networks to Analyze Different Arctic Drivers of Midlatitude Winter Circulation

“…However, conclusions are strictly limited to the extent of the physical realism of the climate model used. It remains questionable whether models capture important processes like ocean-ice feedbacks (Tremblay et al 2007), land-snow interactions (Furtado et al 2015), troposphere-stratosphere interactions (Manzini et al 2014), and Rossby wave propagation (Gray et al 2014) accurately. Thus, both climate model experiments and correlation analysis of observational data are restricted in their interpretability (Barnes and Screen 2015).…”

Can we trust climate models to realistically represent severe European windstorms?

“…This low confidence is related to concerns over the skill of many models in realistically representing large-scale features such as the stratosphere (Scaife et al 2012;Manzini et al 2014) and ocean circulation as well as the dynamics of individual storm systems, for example due to insufficient horizontal resolution (Willison et al 2013). Consequently, the consensus between different models on a climate change signal remains rather low (Harvey et al 2012;Zappa et al 2013b).…”