Zonal Sea Surface Temperature Gradient Research Articles

Influence of Indian Ocean warming on rainfall of Sri Lanka

AbstractRecent studies have pointed out an increased warming over the tropical Indian Ocean (IO) and how such warming could alter the convection and rainfall in the region. In this study, using observational/reanalysis datasets from 1981 to 2020, we show that the early Maha rainfall of Sri Lanka (SL) has been increasing, and it is considerably influenced by the North‐western IO sea surface temperature (SST) increase in the second inter‐monsoon (SIM). A significant warming in the North‐western IO alters the zonal SST gradient and strengthens the low‐level circulation, which induces large‐scale convergence over the western IO during SIM, contributing to the enhancement of rainfall over SL. However, despite the substantial impact of IO warming, the moderate correlation suggests the importance of examining other factors, which may influence the rainfall variability of SL.

Biases and improvements of the boreal winter–spring equatorial undercurrent in the Indian Ocean in the CMIP5 and CMIP6 models

We assessed the performance of state-of-the-art coupled models in reproducing the equatorial undercurrent (EUC) in the Indian Ocean based on the outputs of the Coupled Model Intercomparison Project Phase 6 (CMIP6) models and compared with the Phase 5 (CMIP5) models. Our results showed that the CMIP6 models reproduced the boreal winter–spring Indian Ocean EUC more realistically than the CMIP5 models, although both generations of models underestimated the strength of the Indian Ocean EUC compared with the observations. This underestimation of the Indian Ocean EUC can be attributed to the excessively strong and westward-extended cold tongue in the equatorial Pacific. In the CMIP models, a stronger winter-mean cold tongue favors a stronger zonal sea surface temperature gradient, which forces a strong easterly wind bias over the equatorial western Pacific. This, in turn, contributes to an acceleration of the Walker circulation. This enhanced Walker circulation over the Indo-Pacific Ocean directly causes a lower level westerly wind bias over the equatorial Indian Ocean and drives a shallow west–deep east thermocline tilt bias, ultimately leading to an excessively weak EUC in the Indian Ocean via wind-induced thermocline processes. Compared with the CMIP5 models, the overall improvement in the strength of the winter–spring Indian Ocean EUC in the CMIP6 models can be traced back to the improvement in the degree of the strong and westward-extended cold tongue bias. Our results suggest that efforts should be made to reduce the bias in the mean-state equatorial Pacific sea surface temperature to further improve the simulation and projection of the atmospheric and oceanic circulations in the Indian Ocean.

The future of the El Niño–Southern Oscillation: using large ensembles to illuminate time-varying responses and inter-model differences

Abstract. Future changes in the El Niño–Southern Oscillation (ENSO) are uncertain, both because future projections differ between climate models and because the large internal variability of ENSO clouds the diagnosis of forced changes in observations and individual climate model simulations. By leveraging 14 single model initial-condition large ensembles (SMILEs), we robustly isolate the time-evolving response of ENSO sea surface temperature (SST) variability to anthropogenic forcing from internal variability in each SMILE. We find nonlinear changes in time in many models and considerable inter-model differences in projected changes in ENSO and the mean-state tropical Pacific zonal SST gradient. We demonstrate a linear relationship between the change in ENSO SST variability and the tropical Pacific zonal SST gradient, although forced changes in the tropical Pacific SST gradient often occur later in the 21st century than changes in ENSO SST variability, which can lead to departures from the linear relationship. Single-forcing SMILEs show a potential contribution of anthropogenic forcing (aerosols and greenhouse gases) to historical changes in ENSO SST variability, while the observed historical strengthening of the tropical Pacific SST gradient sits on the edge of the model spread for those models for which single-forcing SMILEs are available. Our results highlight the value of SMILEs for investigating time-dependent forced responses and inter-model differences in ENSO projections. The nonlinear changes in ENSO SST variability found in many models demonstrate the importance of characterizing this time-dependent behavior, as it implies that ENSO impacts may vary dramatically throughout the 21st century.

Accelerated mafic weathering in Southeast Asia linked to late Neogene cooling.

Arc-continent collision in Southeast Asia during the Neogene may have driven global cooling through chemical weathering of freshly exposed ophiolites resulting in atmospheric CO2 removal. Yet, little is known about the cause-and-effect relationships between erosion and the long-term evolution of tectonics and climate in this region. Here, we present an 8-million-year record of seawater chemistry and sediment provenance from the eastern Indian Ocean, near the outflow of Indonesian Throughflow waters. Using geochemical analyses of foraminiferal shells and grain size-specific detrital fractions, we show that erosion and chemical weathering of ophiolitic rocks markedly increased after 4 million years (Ma), coincident with widespread island emergence and gradual strengthening of Pacific zonal sea-surface temperature gradients. Together with supportive evidence for enhanced mafic weathering at that time from re-analysis of the seawater 87Sr/86Sr curve, this finding suggests that island uplift and hydroclimate change in the western Pacific contributed to maintaining high atmospheric CO2 consumption throughout the late Neogene.

Future Indian Ocean warming patterns

Most future projections conducted with coupled general circulation models simulate a non-uniform Indian Ocean warming, with warming hotspots occurring in the Arabian Sea (AS) and the southeastern Indian Ocean (SEIO). But little is known about the underlying physical drivers. Here, we are using a suite of large ensemble simulations of the Community Earth System Model 2 to elucidate the causes of non-uniform Indian Ocean warming. Strong negative air-sea interactions in the Eastern Indian Ocean are responsible for a future weakening of the zonal sea surface temperature gradient, resulting in a slowdown of the Indian Ocean Walker circulation and the generation of southeasterly wind anomalies over the AS. These contribute to anomalous northward ocean heat transport, reduced evaporative cooling, a weakening in upper ocean vertical mixing and an enhanced AS future warming. In contrast, the projected warming in the SEIO is related to a reduction of low-cloud cover and an associated increase in shortwave radiation. Therefore, the regional character of air-sea interactions plays a key role in promoting future large-scale tropical atmospheric circulation anomalies with implications for society and ecosystems far outside the Indian Ocean realm.

Record-breaking 2020 summer marine heatwaves in the western North Pacific

Record-breaking marine heatwaves (MHWs) occurred in the western North Pacific during the summer of 2020. These unprecedented MHWs were consistent with favorable large-scale conditions that are linked to an anomalous western North Pacific subtropical high (WNPSH), resulting mainly from sea surface temperature (SST) anomalies across the tropical oceans. In addition, a moderate La Niña-like pattern was also conducive to transporting warm seawater to the western North Pacific. Mixed-layer heat budgets suggest that surface heat flux contributed to the SST anomaly in the western subtropical Pacific. In contrast, oceanic heat advection dominanted in the South China Sea and the western equatorial Pacific. Numerical model experiments indicated that the tropical Indian Ocean SST anomalies were responsible for the enhanced WNPSH. The increased zonal SST gradient across the tropical Pacific also played an important role. Inter-ocean interactions can modulate climate variability through ocean-atmospheric coupling and deserve more attention when predicting MHWs within the context of global warming. In addition, it is critical to consider MHWs as a powerful tool in detecting acute, intense thermal stress events in the coral bleaching pre-warning system.

Storylines of Maritime Continent dry period precipitation changes under global warming

The dry half of the year from May to October over the Maritime Continent (MC) has experienced unprecedented damages from forest fires in recent decades. The observed interannual rainfall variability during this period is closely tied to sea surface temperature (SST) variability over the equatorial Pacific (EP). Therefore, the future evolution of EP SST can be expected to influence the climatological precipitation over the MC. Whilst multi-model means (MMMs) suggest a future drying trend over the south-western part of the MC, there is considerable model uncertainty. Here, using a storyline approach with the 38 climate models from Coupled Model Intercomparison Project Phase 6, we distinguish the model uncertainty associated with changes in the zonal EP SST gradient from that associated with the basin-wide EP (BEP) warming. We find that an increase in east-to-west EP SST gradient would bring more rainfall over the north-eastern regions including northern Borneo, Sulawesi and New Guinea. In contrast, the intensity of the basin-wide warming of EP SST is directly linked with the drying response seen over the south-western MC in the MMM. This drying affects the highly vulnerable regions of Sumatra and Kalimantan for forest fires. Our results suggest that a storyline under higher BEP warming accompanied by an El-Niño like change in zonal SST gradient would lead to even drier climatic conditions over these key regions. However, the observed record of more than one hundred years favours a storyline of lower BEP warming accompanied by a La-Niña like change in zonal SST gradient, which would lead to minimal drying over the south-western MC and wetter conditions over the north-eastern parts of the MC.

Greenhouse warming and internal variability increase extreme and central Pacific El Niño frequency since 1980

El Niño has been recorded to change its properties since the 1980s, characterized by more common extreme El Niño and Central Pacific (CP) El Niño events. However, it is still unclear whether such change is externally forced or part of the natural variability. Here, we find that the frequency of the extreme and CP El Niño events also increased during the period 1875–1905, when the anthropogenic CO2 concentration was relatively lower, but with a positive phase of the Atlantic Multidecadal Oscillation (AMO). Models and palaeoclimate proxies reveal that a positive AMO enhances the zonal sea surface temperature gradient in the CP, which strengthens zonal advective feedback, favoring extreme and CP El Niño development. Moreover, we estimate that internal variability contributed to ~65% of the increasingly extreme and CP El Niño events, while anthropogenic forcing has made our globe experience ~1 more extreme and ~2 more CP events over the past four decades.

Effect of anthropogenic forcing on increased winter precipitation in Southeast Asia from 1979 to 2014

Observations indicate that the winter precipitation over Southeast Asia (SEAP) shows significantly increased trends from 1979 to 2014, which can be partly reproduced under the historical all-forcing simulations from the 12 Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models. By analyzing separate external forcings run with the Detection and Attribution experiments, we find that the effects of anthropogenic forcing rather than natural variation play a primary role in driving the increasing of SEAP trends simulated in the historical all-forcing experiments. Further analysis indicate that the observed increasing trend is closely associated with the decadal shift of the Southeast Asian precipitation after the mid-1990s, which could be also driven by anthropogenic forcing to some extent. Anthropogenic forcing can favor a La Niña-like pattern of sea surface temperature (SST) warming in the tropical Pacific and result in the decadal increase of SEAP via the enhanced zonal SST gradient and the Pacific Walker circulation. This study thus provides some evidence of the impacts of anthropogenic forcing to drive recent changes in the winter SEAP.

Understanding CMIP6 biases in the representation of the Greater Horn of Africa long and short rains

The societies of the Greater Horn of Africa (GHA) are vulnerable to variability in two distinct rainy seasons, the March–May ‘long’ rains and the October–December ‘short’ rains. Recent trends in both rainy seasons, possibly related to patterns of low-frequency variability, have increased interest in future climate projections from General Circulation Models (GCMs). However, previous generations of GCMs historically have poorly simulated the regional hydroclimate. This study conducts a process-based evaluation of simulations of the long and short rains in CMIP6, the latest generation of GCMs. Key biases in CMIP5 remain or are worsened, including long rains that are too short and weak and short rains that are too long and strong. Model biases are driven by a complex set of related oceanic and atmospheric factors, including simulations of the Walker Circulation. Biased wet short rains in models are connected with Indian Ocean zonal sea surface temperature (SST) gradients that are too warm in the west and convection that is too deep. Models connect equatorial African winds with the strength of the short rains, though in observations a robust connection is primarily found in the long rains. Model mean state biases in the timing of the western Indian Ocean SST seasonal cycle are associated with certain rainfall timing biases, though both biases may be due to a common source. Simulations driven by historical SSTs (AMIP runs) often have larger biases than fully coupled runs. A path towards using biases to better understand uncertainty in projections of GHA rainfall is suggested.

Present-day warm pool constrains future tropical precipitation

Future changes in tropical precipitation affect the livelihood of the world’s human population and ecosystems. Climate models project an increased rainfall intensification under anthropogenic warming, but uncertainties in the distribution and magnitude of the changes remain large. Here, we identify a strong positive relationship between the present-day Indo-Pacific warm pool size and projected precipitation changes in the central-to-eastern tropical Pacific using multi-model simulations. Models with larger present-day warm pool size project excessive future warming in the eastern tropical Pacific due to intensified ocean stratification which reduces the zonal sea surface temperature gradient of the tropical Pacific, resulting in the weakening of Walker circulation and precipitation increases in the central-to-eastern tropical Pacific. Based on this relationship, uncertainty in the projected precipitation in the central-to-eastern tropical Pacific can be reduced by approximately 25%, which demonstrates that an improved simulation of present-day Indo-Pacific warm pool size is important for reliable tropical precipitation projections.

A Pliocene Precipitation Isotope Proxy-Model Comparison Assessing the Hydrological Fingerprints of Sea Surface Temperature Gradients.

The Pliocene offers insights into future climate, with near-modern atmospheric pCO2 and global mean surface temperature estimated to be 3-4°C above pre-industrial. However, the hydrological response differs between future global warming and early Pliocene climate model simulations. This discrepancy results from the use of reduced meridional and zonal sea surface temperature (SST) gradients, based on foraminiferal Mg/Ca and Alkenone proxy evidence, to force the early Pliocene simulation. Subsequent, SST reconstructions based on the organic proxy TEX86, have found warmer temperatures in the warm pool, bringing the magnitude of the gradient reductions into dispute. We design an independent test of Pliocene SST scenarios and their hydrological cycle "fingerprints." We use an isotope-enabled General Circulation Model, iCAM5, to model the distribution of water isotopes in precipitation in response to four climatological SST and sea-ice fields representing modern, abrupt 4×CO2, late Pliocene and early Pliocene climates. We conduct a proxy-model comparison with all the available precipitation isotope proxy data, and we identify target regions that carry precipitation isotopic fingerprints of SST gradients as priorities for additional proxy reconstructions. We identify two regions with distinct precipitation isotope (D/H) fingerprints resulting from reduced SST gradients: the Maritime Continent (D-enriched due to reduced convective rainfall) and the Sahel (wetter, more deep convection, D-depleted). The proxy-model comparison using available plant wax reconstructions, mostly from Africa, is promising but inconclusive. Additional proxy reconstructions are needed in both target regions and in much of the world for significant tests of SST scenarios and dynamical linkages to the hydrological cycle.

Orbital-scale thermocline temperature variability in the western equatorial Pacific during the last 370 kyr

Tropical subsurface circulation plays a key role in regulating heat and salt transport between the hemispheres, and in ocean–atmosphere interactions (e.g., El Niño-Southern Oscillation; ENSO). Therefore, understanding the past behavior of tropical thermoclines is important for predicting long-term global climate change. Here, we provide an orbital-scale thermocline temperature (TT) record based on Mg/Ca measurements of planktonic foraminifer Pulleniatina obliquiloculata in sediment cores obtained from the western equatorial Pacific (WEP) for the last 370 kyr. The vertical temperature gradient between sea surface temperature (SST) and TT in WEP showed weak positive correlations with the tropical Pacific zonal SST gradient in long-term trend and obliquity signal. The relationship of the two gradients does not coincide with modern ENSO variability, suggesting that the long-term TT variation depend primarily on another mechanism. Spectral analysis indicated that TT variability has strong signals in both the obliquity and precession bands. Since the obliquity signal is very weak in local insolation, the significant obliquity in TT variability implies an extratropical influence on tropical thermocline circulation. Therefore, our findings suggest that the subsurface circulation connecting the tropics and extratropics plays an essential role in orbital-scale tropical thermocline variability.

Recognizing the Role of Tropical Seaways in Modulating the Pacific Circulation

AbstractVarious modeling studies have examined the climatic effects of either the Central American Seaway or the Indonesian seaway. The co‐existence of these two tropical seaways may have a greater influence than the existence of a single seaway. Although the dual seaway situation is closer to that reconstructed during Miocene/Pliocene, relevant studies remain scarce. Here, we investigate the co‐effects of dual tropical seaway changes on the Pacific circulation through a set of sensitivity experiments. Our results show that the combined shallow opening of tropical seaways can generate an active Pacific meridional overturning circulation and maintain strong upwelling conditions along the equatorial Pacific, which may have helped favor a “biogenic bloom” during the late Miocene and early Pliocene. Moreover, the logically successive closure of the tropical seaways can provide patterns of zonal sea surface temperature gradients that are similar to those recorded in the equatorial Pacific from the late Miocene to the Pliocene.

Large-scale climate response to regionally confined extratropical cooling: effect of ocean dynamics

This study investigates the effect of ocean dynamics on the tropical climate response to localized radiative cooling over three northern extratropical land regions using hierarchical model simulations that vary in the degree of ocean coupling. Without ocean dynamics, the tropical climate response is independent of the extratropical forcing location, characterized by a southward tropical precipitation shift with a high degree of zonal symmetry, a reduced zonal sea surface temperature gradient along the equatorial Pacific, and the eastward-shifted Walker circulation. When ocean dynamical adjustments are allowed, the zonal-mean tropical precipitation shift is damped primarily via Eulerian-mean ocean heat transport. The oceanic damping effect is strongest (weakest) for North Asian (American) cooling, associated with the largest (smallest) Eulerian-mean ocean heat transport across the equatorial Pacific. The cross-equatorial ocean heat transport in the Pacific is anchored to the North Pacific subtropical high, the response of which can be inferred from the corresponding slab ocean simulations. Hence, the slab ocean simulations provide useful a priori prediction for oceanic damping efficiency. Ocean dynamics also modulates the spatial pattern of climate response in a distinct manner depending on the zonal distribution of imposed forcing. North Asian forcing induces a pronounced eastern equatorial Pacific cooling extending to the western basin, accompanying the westward shifted Walker circulation. European forcing causes cooling confined to the eastern equatorial Pacific and strengthens the Walker circulation. The tropical precipitation response in these two cases exhibits large zonal variations with a high degree of equatorial symmetry, being essentially uncorrelated with the corresponding slab ocean simulations. By contrast, North American forcing induces a sufficiently strong inter-hemispheric contrast in the tropical Pacific SST response, due to the relatively weak oceanic damping effect, producing a weaker but spatially similar tropical response to that in the slab ocean simulation. This study demonstrates that the effect of ocean dynamics in modulating the tropical climate response depends on the extratropical forcing location. The results are relevant for understanding the distinct climate response induced by aerosols from different continental sites.

Investigating Extratropical Influence on the Equatorial Atlantic Zonal Bias with Regional Data Assimilation

Abstract A reversal of zonal sea surface temperature (SST) gradient in the equatorial Atlantic is a common bias in climate models. Studies to investigate the origin of this bias mainly focused on the tropics itself. Applying the regional data assimilation method in the GFDL CM2.1 model, we investigate the combined and respective influences of the northern and southern extratropics on this bias. It is found that the reversed zonal SST gradient bias is caused to a considerable extent by the extratropical atmosphere, especially by the northern extratropics. This extratropical impact on the equator occurs mainly through influencing the Hadley circulation. Therefore, the ITCZ position in boreal spring in this model most likely determines the dominant role of northern extratropics in the spring equatorial westerly bias and additionally the zonal SST gradient bias. Due to the cold bias in the extratropical atmosphere, the northward shift of the ITCZ coupled with the increased meridional SST gradient caused by assimilating the northern extratropics strengthens the cross-equatorial southeasterly wind, thus correcting the spring equatorial westerly bias. The strengthened spring equatorial easterlies further steepen the thermocline slope and enhance the eastern upwelling, thus reproducing the summer cold tongue and finally improving the annual-mean zonal SST gradient bias.

Western and Central Tropical Pacific Rainfall Response to Climate Change: Sensitivity to Projected Sea Surface Temperature Patterns

Abstract Rainfall projections from the Coupled Model Intercomparison Project (CMIP) models are strongly tied to projected sea surface temperature (SST) spatial patterns through the “warmer-gets-wetter” mechanism. While these models consistently project an enhanced equatorial warming, they, however, indicate much more uncertain changes in zonal SST gradients. That translates into large uncertainties on rainfall projections. Here, we force an atmospheric model with synthetic SSTs whose zonal SST gradient changes span the range of CMIP5 uncertainties in the presence and in the absence of the robust equatorially enhanced warming. Our results confirm that projected rainfall changes are dominated by the effect of circulation changes, which are tied to SST through the “warmer-gets-wetter” mechanism. We show that SPCZ rainfall changes are entirely driven by the uncertain zonal SST gradient changes. The western equatorial Pacific rainfall increase is largely controlled by the robust enhanced equatorial warming for modest zonal SST gradient changes. However, for larger values, the effect of the zonal SST gradient change on rainfall projections becomes dominant due to nonlinear interactions with the enhanced equatorial warming. Overall, our study demonstrates that uncertainties in the zonal SST gradient changes strongly contribute to uncertainties in rainfall projections over both the South Pacific convergence zone and western equatorial Pacific. It is thus critical to reduce these uncertainties to produce more robust precipitation estimates.

Why was South China extremely wet during January–February 2022 despite La Niña?

The boreal winter climate of 2022 was characterized by the occurrence of La Niña, which is one of the most predictable drivers of South China precipitation (SCP) deficit. However, surprisingly, South China (SC) received abnormal high precipitation in January–February (JF) 2022. Possible causes of the deviation of JF 2022 SCP from its historical response to La Niña are explored with observational and reanalysis data. Results suggest that the La Niña event in winter 2022 features an eastern Pacific (EP) type, which corresponds to a weaker zonal sea surface temperature (SST) gradient between the equatorial central and western Pacific than those of the historical La Niña events, leading to a weaker western North Pacific (WNP) cyclone (WNPC) anomaly. Meanwhile, the SST warming over the tropical Indian Ocean (TIO) would also weaken the La Niña-associated WNP circulation anomaly. Therefore, the flavor of La Niña and the TIO warming act in concert to dampen the La Niña-associated WNPC anomaly and the SCP deficit. But these tropical SST anomalies are still insufficient to explain the extremely high SCP. Furthermore, the investigation identifies two extra-tropical circulation patterns over Eurasia that dominate the SCP anomalies in JF 2022. One is the wave train propagating along the South Asian jet that intensifies the India–Burma trough. It enhances the SCP through exciting anomalous strong moisture transport from the Bay of Bengal and ascending motion. The other is the positive geopotential height anomaly over eastern Siberia that prompts southward cold air intrusion and convergence over the SC region. These two dynamical drivers can account for approximately 75% of the observed SCP anomaly in JF 2022. However, they may be largely attributed to the atmospheric internal dynamical processes, which implies limited seasonal predictability of this extreme wet event.

Interdecadal Increase in Summertime Extreme Precipitation over East China in the Late 1990’s

This study focuses on the interdecadal increase of summertime extreme precipitation over East China in the late 1990s and physical mechanisms behind. The results show that summer extreme precipitation over East China during 1979–2020 demonstrates an upward trend and a significant interdecadal increase occurs around 1997/1998. Since 1997, extreme precipitation anomalies turn from less than normal to more than normal, corresponding to a strong upward movement in the lower troposphere over East China. A cyclonic circulation with positive vorticity controlled by a strong southeasterly flow appears in the lower level over South China. The reasons for the interdecadal increase of summer extreme precipitation over East China are analyzed from the perspective of the abnormally strong South Asian subtropical high (SAH) and the atmospheric circulation anomalies caused by zonal sea surface temperature (SST) gradient in the tropical oceans. After 1997, positive sensible heat anomalies appear over the Tibetan Plateau in spring, which is the major factor that maintains the intensity of the SAH. Besides, the SST of the tropical oceans presents an obvious “high-low-high” zonal gradient distribution with positive sea surface temperature anomaly (SSTA) in the Indian Ocean and western Pacific, and negative SSTA over the Maritime Continent. The zonal SST gradient results in an anomalous downdraft and boundary layer divergence over the Maritime Continent. The tropical zonal SST gradient triggers a local Hadley circulation, and its ascending branch is located in East China. This is a circulation condition favorable for the development of extreme precipitation. In addition, since the late 1990s, the SAH has strengthened in the upper troposphere above the southeastern China. The anomalous divergence at the upper level effectively maintains the upward movement, which in turn facilitates the occurrence of extreme precipitation. As a result, the sensible heat changes in the Tibetan Plateau in spring and the tropical SST zonal gradient jointly affect summer extreme precipitation over East China, leading to the interdecadal increase of extreme precipitation in the late 1990s.

Roman Warm Period and Late Antique Little Ice Age in an Earth System Model Large Ensemble

AbstractChanges in climate during the Roman Warm Period (RWP, 1–250 CE) and Late Antique Little Ice Age (LALIA, 536–660 CE) play a critical role in early societal evolution, but the climate differences between these two periods and the possible causes of the changes remain poorly explored. Here we use the LOch–Vecode‐Ecbilt‐CLio‐agIsM model Large Common Era Ensemble with 70 members to examine the climate change over these two intervals and compare the results of this ensemble with the latest temperature reconstructions from the Past Global Changes 2k network and the transient simulation for the past 2,000 years from the Community Earth System Model. Results from both proxy reconstructions and climate model simulations show warming in mid‐to‐high latitudes of the Northern Hemisphere (NH) during the RWP compared with the LALIA. This is likely linked with the increased radiative forcing associated with weaker volcanic eruptions in the RWP, which results in reduced sea ice area and pronounced high‐latitude warming through surface albedo and lapse‐rate feedbacks. This increases the upper ocean heat content over centennial time scales to maintain warming over the NH high‐latitude regions. Moreover, the RWP has drier (wetter) conditions in the eastern (western) equatorial Pacific than the LALIA, and this is related to the zonal sea surface temperature gradient in the equatorial Pacific through modification of the zonal circulation.