The Influence of Regional SSTs on the Interdecadal Shift of the East Asian Summer Monsoon

East Asia has experienced a significant interdecadal climate shift since the late 1970s. This shift was accompanied by a decadal change of global SST. Previous studies have suggested that the decadal shift of global SST background status played a substantial role in such a climatic shift. However, the individual roles of different regional SSTs remain unclear. In this study, we investigated these roles using ensemble experiments of an atmospheric general circulation model, GFDL (Geophysical Fluid Dynamics Laboratory) AM2. Two kinds of ensembles were performed. The first was a control ensemble in which the model was driven with the observed climatological SSTs. The second was an experimental ensemble in which the model was driven with the observed climatological SSTs plus interdecadal SST background shifts in separate ocean regions. The results suggest that the SST shift in the tropics exerted more important influence than those in the extratropics, although the latter contribute to the shift modestly. The variations of summer monsoonal circulation systems, including the South Asian High, the West Pacific Subtropical High, and the lower-level air flow, were analyzed. The results show that, in comparison with those induced by extratropical SSTs, the shifts induced by tropical SSTs bear more similarity to the observations and to the simulations with global SSTs prescribed. In particular, the observed SST shift in the tropical Pacific Ocean, rather than the Indian Ocean, contributed significantly to the shift of East Asian summer monsoon since the 1970s.     

Tropical pacific forcing of a 1998–1999 climate shift: observational analysis and climate model results for the boreal spring season

Observational data and climate model simulations and experiments are utilized to document an abrupt shift in Pacific sea surface temperatures (SSTs) and associated atmospheric conditions, which occurred in 1998–1999. Emphasis is placed on the March–May (MAM) season, as the motivation for the work is to extend a recent study that reported an abrupt decline in East African MAM rainfall at that time. An empirical orthogonal function analysis of MAM SSTs over the last century following the removal of the concurrent influence of the El Niño-Southern Oscillation and global warming trend by linear regression reveals a pattern of multidecadal variability in the Pacific similar to the Pacific Decadal Oscillation. Examination of MAM precipitation variations since 1940 indicates, among other findings, that recurrent drought events since 1999 in East Africa, central-southwest Asia, parts of eastern Australia and the southwestern US are all regional manifestations of a global scale multidecadal pattern. Associated shifts in the low-level wind field and upper-level stationary waves are discussed. Simulations using an atmospheric climate model forced with observed, global SSTs capture many of the salient precipitation and atmospheric circulation features associated with the observed shift. Further, when the model is forced only with observed SSTs from the tropical Pacific it also captures many of the observed atmospheric changes, including the abrupt shift in 1999. The results point to the fundamental role played by the tropical Pacific in driving the response to multidecadal variability of SSTs in the basin and provide important context for recent seasonal climate extremes in several regions of the globe.     

Interdecadal Variability of the East Asian Summer Monsoon in an AGCM

It is well known that significant interdecadal variation of the East Asian summer monsoon （EASM） occurred around the end of the 1970s. Whether these variations can be attributed to the evolution of global sea surface temperature （SST） and sea ice concentration distribution is investigated with an atmospheric general circulation model （AGCM）. The model is forced with observed monthly global SST and sea ice evolution through 1958-1999. A total of four integrations starting from different initial conditions are carried out. It is found that only one of these reproduces the observed interdecadal changes of the EASM after the 1970s, including weakened low-level meridional wind, decreased surface air temperature and increased sea level pressure in central China, as well as the southwestward shift of the western Pacific subtropical high ridge and the strengthened 200-hPa westerlies. This discrepancy among these simulated results suggests that the interdecadal variation of the EASM cannot be accounted for by historical global SST and sea ice evolution. Thus, the possibility that the interdecadal timescale change of monsoon is a natural variability of the coupled climate system evolution cannot be excluded.     

大气环流的年代际变化 II.GCM数值模拟研究

类似大气环流模式比较计划（AMIP）的数值模拟,将实际观测的海表水温（SST）资料引入模式进行40多年的数值积分,得到长时间的大气环流模拟结果。分析数值模拟结果发现,无论是大气中的主要涛动和遥相关型,还是重要大气环流系统都极为清楚地存在着年代际变化特征,包括10～20年准周期振荡和可能的30年以上的准周期振荡;而且上述主要环流系统的形势及其年代际变化大都与实际观测资料所给出的结果相一致。顺便分析中国东部气候的模拟结果,年代际变化特征（包括60年代的气候突变）也很清楚,并同大气环流变化配合十分合理。结果也表明,同研究季节和年际变化一样,大气环流模式（AGCM）数值模拟也是研究大气环流和气候年代际变化的有效方法。     

东亚冬季风的年代际变化及其与全球气候变化的可能联系

对近年来中外关于东亚冬季风(EAWM)年代际变化问题研究进展做了回顾和评述,主要包括以下3个方面内容:(1)东亚冬季风明显受到全球气候变化的影响,从20世纪50年代开始,中国冬季气温经历了一次冷期(从20世纪50年代延续到80年代初中期),一次暖期(从20世纪80年代初中后期延续到21世纪初)和近10-15年(约从1998年开始)出现的气候变暖趋缓期(也称气候变暖停顿期)。(2)东亚冬季风主要表现出强-弱-强3阶段的特征,即从1950年到1986/1987年,明显偏强;从1986/1987年冬季开始,东亚冬季风减弱;约2005年之后,东亚冬季风开始由弱转强。与东亚冬季风的年代际变化特征相对应,东亚冬季大气环流以及中国冬季气温和寒潮都表现出一致的年代际变化。(3)东亚冬季风的年代际变化与大气环流和太平洋海表温度(SST)的区域模态变化密切相关。当北半球环状模/北极涛动(NAM/AO)和太平洋年代际振荡(PDO)处于负(正)位相,东亚冬季风偏强(弱),中国冬季气温偏低(高)。此外,北大西洋年代尺度振荡(AMO)对东亚冬季风也有重要影响,在AMO负位相时,对应东亚冷期(强冬季风),正位相对应暖期(弱冬季风)。因而海洋的年代际变化是造成东亚冬季风气候脉动的主要自然原因,而全球气候变暖对东亚冬季风强度的减弱也有明显影响。     

Numerical Simulation of the Effect of the SST Anomalies in the Tropical Western Pacific on the Blocking Highs over the Northeastern Asia

The effects of the sea surface temperature (SST) anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are simulated by the IAP-GCM with an observed and idealized distributions of the SST anomalies in the tropical western Pacific,respectively.Firstly,the atmospheric circulation anomalies during July and August,1980 are simulated by three anomalous experiments including the global SST anomaly experiment,the tropical SST anomaly experiment and the extratropical SST anomaly experiment,using the observed SST anomalies in 1980.It is shown that the SST anomalies in the tropical ocean greatly influence the formation and maintenance of the blocking high over the northeastern Asia,and may play a more important role than the SST anomalies in the extratropical ocean in the influence on the atmospheric circulation anomalies.Secondly,the effects of the SST anomalies in the tropical western Pacific on the atmospheric circulation anomalies over East Asia are also simulated w     

Variability and predictability of Northeast China climate during 1948–2012

In this work, authors examine the variabilities of precipitation and surface air temperature (T2m) in Northeast China during 1948–2012, and their global connection, as well as the predictability. It is noted that both the precipitation and T2m variations in Northeast China are dominated by interannual and higher frequency variations. However, on interdecadal time scales, T2m is shifted significantly from below normal to above normal around 1987/1988. Statistically, the seasonal mean precipitation and T2m are largely driven by local internal atmospheric variability rather than remote forcing. For the precipitation variation, circulation anomalies in the low latitudes play a more important role in spring and summer than in autumn and winter. For T2m variations, the associated sea surface pressure (SLP) and 850-hPa wind (uv850) anomalies are similar for all seasons in high latitudes with significantly negative correlations for SLP and westerly wind anomaly for uv850, suggesting that a strong zonal circulation in the high latitudes favors warming in Northeast China. The predictability of precipitation and T2m in Northeast China is assessed by using the Atmospheric Model Inter-comparison Project type experiments which are forced by observed sea surface temperature (SST) and time-evolving greenhouse gas (GHG) concentrations. Results suggest that T2m has slightly higher predictability than precipitation in Northeast China. To some extent, the model simulates the interdecadal shift of T2m around 1987/1988, implying a possible connection between SST (and/or GHG forcing) and surface air temperature variation in Northeast China on interdecadal time scales. Nevertheless, the precipitation and T2m variations are mainly determined by the unpredictable components which are caused by the atmospheric internal dynamic processes, suggesting low predictability for the climate variation in Northeast China.     

Decadal/Interdecadal Variations of the Ocean Temperature and its Impacts on Climate

Decadal/interdecadal climate variability is an important research focus of the CLIVAR Program and has been paid more attention. Over recent years, a lot of studies in relation to interdecadal climate variations have been also completed by Chinese scientists. This paper presents an overview of some advances in the study of decadal/interdecadal variations of the ocean temperature and its climate impacts, which includes interdecadal climate variability in China, the interdecadal modes of sea surface temperature (SST) anomalies in the North Pacific, and in particular, the impacts of interdecadal SST variations on the Asian monsoon rainfall. As summarized in this paper, some results have been achieved by using climate diagnostic studies of historical climatic datasets. Two fundamental interdecadal SST variability modes (7– 10-years mode and 25–35-years mode) have been identified over the North Pacific associated with different anomalous patterns of atmospheric circulation. The southern Indian Ocean dipole (SIOD) shows a major feature of interdecadal variation, with a positive (negative) phase favoring a weakened (enhanced) Asian summer monsoon in the following summer. It is also found that the China monsoon rainfall exhibits interdecadal variations with more wet (dry) monsoon years in the Yangtze River (South China and North China) before 1976, but vice versa after 1976. The weakened relationship between the Indian summer rainfall and ENSO is a feature of interdecadal variations, suggesting an important role of the interdecadal variation of the SIOD in the climate over the south Asia and southeast Asia. In addition, evidence indicates that the climate shift in the 1960s may be related to the anomalies of the North Atlantic Oscillation (NAO) and North Pacific Oscillation (NPO). Overall, the present research has improved our understanding of the decadal/interdecadal variations of SST and their impacts on the Asian monsoon rainfall. However, the research also highlights a number of problems for future research, in particular the mechanisms responsible for the monsoon long-term predictability, which is a great challenge in climate research.     

A possible role of solar radiation and ocean in the mid-Holocene East Asian monsoon climate

An atmospheric general circulation model (AGCM) and an oceanic general circulation model (OGCM) are asynchronously coupled to simulate the climate of the mid-Holocene period. The role of the solar radiation and ocean in the mid-Holocene East Asian monsoon climate is analyzed and some mechanisms are revealed. At the forcing of changed solar radiation induced by the changed orbital parameters and the changed SST simulated by the OGCM, compared with when there is orbital forcing alone, there is more precipitation and the monsoon is stronger in the summer of East Asia, and the winter temperature increases over China. These agree better with the reconstructed data. It is revealed that the change of solar radiation can displace northward the ITCZ and the East Asia subtropical jet, which bring more precipitation over the south of Tibet and North and Northeast China. By analyzing the summer meridional latent heat transport, it is found that the influence of solar radiation change is mainly to increase the convergence of atmosphere toward the land, and the influence of SST change is mainly to transport more moisture to the sea surface atmosphere. Their synergistic effect on East Asian precipitation is much stronger than the sum of their respective effects.     

东亚和西北太平洋地区气候的准10年尺度振荡及其可能机制

本文基于对气候、大气环流和海表水温的资料分析以及简单的理想化海气耦合模式的分析,研究了东亚和西北太平洋地区气候的准１０年振荡及其可能机制。研究表明,东亚和西北太平洋地区的气候（降水和地面气温等）和大气环流（环流指数和副高活动等）的演变都有明显的准１０年振荡;同赤道太平洋ＳＳＴＡ主要为ＥＮＳＯ循环不同,西北太平洋ＳＳＴＡ主要表现为准１０年尺度的振荡,且同气候和大气环流的准１０年变化密切相关;中纬度海－气相互作用可产生一种甚低频耦合波（１０年左右周期）,它可能是海气系统准１０年振荡的重要机制之一     

An Introduction to the Integrated Climate Model of the Center for Monsoon System Research and its simulated influence of El Niño on East Asian-western North Pacific climate

This study introduces a new global climate model--the Integrated Climate Model （ICM）--developed for the seasonal prediction of East Asian-western North Pacific （EA-WNP） climate by the Center for Monsoon System Research at the Institute of Atmospheric Physics （CMSR, IAP）, Chinese Academy of Sciences. ICM integrates ECHAM5 and NEMO2.3 as its atmospheric and oceanic components, respectively, using OASIS3 as the coupler. The simulation skill of ICM is evaluated here, including the simulated climatology, interannual variation, and the influence of E1 Nifio as one of the most important factors on EA-WNP climate. ICM successfully reproduces the distribution of sea surface temperature （SST） and precipitation without climate shift, the seasonal cycle of equatorial Pacific SST, and the precipitation and circulation of East Asian summer monsoon. The most prominent biases of ICM are the excessive cold tongue and unrealistic westward phase propagation of equatorial Pacific SST. The main interannual variation of the tropical Pacific SST and EA-WNP climate E1 Nifio and the East Asia-Pacific Pattern--are also well simulated in ICM, with realistic spatial pattern and period. The simulated E1 Nifio has significant impact on EA-WNP climate, as in other models. The assessment shows ICM should be a reliable model for the seasonal prediction of EA-WNP climate.     

Responses of East Asian summer monsoon to historical SST and atmospheric forcing during 1950–2000

The East Asian summer monsoon (EASM) circulation and summer rainfall over East China have experienced large decadal changes during the latter half of the 20th century. To investigate the potential causes behind these changes, a series of simulations using the national center for atmospheric research (NCAR) community atmospheric model version 3 (CAM3) and the geophysical fluid dynamics laboratory (GFDL) atmospheric model version 2.1 (AM2.1) are analyzed. These simulations are forced separately with different historical forcing, namely tropical sea surface temperature (SSTs), global SSTs, greenhouse gases plus aerosols, and a combination of global SSTs and greenhouse gases plus aerosols. This study focuses on the relative roles of these individual forcings in causing the observed monsoon and rainfall changes over East Asia during 1950–2000. The simulations from both models show that the SST forcing, primarily from the Tropics, is able to induce most of the observed weakening of the EASM circulation, while the greenhouse gas plus (direct) aerosol forcing increases the land-sea thermal contrast and thus enhances the EASM circulation. The results suggest that the recent warming in the Tropics, especially the warming associated with the tropical interdecadal variability centered over the central and eastern Pacific, is a primary cause for the weakening of the EASM since the late 1970s. However, a realistic simulation of the relatively small-scale rainfall change pattern over East China remains a challenge for the global models.     

初夏东亚环流对厄尔尼诺的两种响应过程及其对中国降水的影响

利用NCEP/NCAR提供的月平均850、500 hPa位势高度场和风矢量场资料及NOAA气候诊断中心的海温扩展重建资料,同时利用NCEP的CAM3.0模式对厄尔尼诺气候效应进行了分析。外强迫为赤道东太平洋的异常海温,从9月积分至次年6月,对此进行了模拟,结果表明:(1)冬季厄尔尼诺达到强盛后对次年东亚初夏的环流有明显的影响,表现在低层菲律宾附近反气旋环流的增强和中高纬度OKJ类波列(主要为鄂霍次克海—日本东部—日期变更线以西副热带高压北部的波列)的活跃,而后者更容易被模拟,这两种环流方面的影响都能在资料中检测出来。当这两种异常环流的发展被模拟出来时,长江以南地区的多雨状态也能够被模拟,表明厄尔尼诺发生后,其对夏季风的发生、发展有滞后作用,从而加强向中国南方的水汽输送,但至6月由于OKJ波列的发展使波活动通量在北太平洋中西部产生大面积强烈散射使副热带高压偏南,因而又抑制了夏季风的进一步向北推进,从而只停留在长江及其以南地区,这可能是致使降水南多北少的原因之一;(2)中国南方降水多寡受到鄂霍次克海高压及菲律宾反气旋的共同影响,两者任何一方加强时南方降水增多,反之亦然。近年来受鄂霍次克海高压的影响更为突出,鄂霍次克海高压、南北方降水、厄尔尼诺事件以及菲律宾反气旋都存在相近似但又各自不同的年代际变化规律,其共同影响与中国南涝北旱的年代际降水格局变化有密切关系。     

The coherent interdecadal changes of East Asia climate in mid-summer simulated by BCC_AGCM 2.0.1

This study proposes primary diagnostic metrics to evaluate the integrated structure of interdecadal changes of East Asian climate in mid-summer (July–August) over the recent half-century (1955–2000) in numerical models. The metrics are applied to comprehensively examine the performance of BCC_AGCM (Beijing Climate Center atmospheric general circulation model) version 2.0.1. When forced by historical sea surface temperatures (SST), the ensemble simulation with the BCC_AGCM reasonably reproduced the coherent interdecadal changes of rainfall, temperature and circulation. The main feature of the “southern-flooding-and-northern-drought” rainfall change is captured by the model. Correspondingly, the tropospheric cooling in the upper and middle troposphere, the southward shift of upper level westerly jet and weakening of the low-level southwesterly monsoon flow are also reproduced, as well as their relationships with rainfall changes. One of the main deficiencies of the simulation is that the amplitudes of the changes of tropospheric cooling and large-scale circulation are both much weaker than those in reanalysis, and they are consistent with the rainfall deficiency. Also, the upper and middle troposphere cooling center and decreasing of upper-level westerly jet axis shift westward in the model simulations compared with that in the observations. Overall, although BCC_AGCM shows problems in simulating the interdecadal changes of East Asia climate, especially the amplitude and locations of change centers, it reasonably represents the observed configuration of rainfall variation and the associated coherent temperature and circulation changes. Therefore, it could be further used to discuss the mechanisms of the interdecadal variation in East Asia. Meanwhile, the reasonably reproduced configuration of rainfall and its associated large-scale circulation by SST-forced runs indicate that the interdecadal variations in East Asia could mostly arise from the regional response to the global climate change.     

Interdecadal Variability of the East Asian Winter Monsoon and Its Possible Links to Global Climate Change

This paper presents a concise summary of the studies on interdecadal variability of the East Asian winter monsoon (EAWM) from three main perspectives. (1) The EAWM has been significantly affected by global climate change. Winter temperature in China has experienced three stages of variations from the beginning of the 1950s: a cold period (from the beginning of the 1950s to the early or mid 1980s), a warm period (from the early or mid 1980s to the early 2000s), and a hiatus period in recent 10 years (starting from 1998). The strength of the EAWM has also varied in three stages: a stronger winter monsoon period (1950 to 1986/87), a weaker period (1986/87 to 2004/05), and a strengthening period (from 2005). (2) Corresponding to the interdecadal variations of the EAWM, the East Asian atmospheric circulation, winter temperature of China, and the occurrence of cold waves over China have all exhibited coherent interdecadal variability. The upper-level zonal circulation was stronger, the mid-tropospheric trough over East Asia was deeper with stronger downdrafts behind the trough, and the Siberian high was stronger during the cold period than during the warm period. (3) The interdecadal variations of the EAWM seem closely related to major modes of variability in the atmospheric circulation and the Pacific sea surface temperature. When the Northern Hemisphere annular mode/Arctic Oscillation and the Pacific decadal oscillation were in negative (positive) phase, the EAWM was stronger (weaker), leading to colder (warmer) temperatures in China. In addition, the negative (positive) phase of the Atlantic multi decadal oscillation coincided with relatively cold (warm) temperatures and stronger (weaker) EAWMs. It is thus inferred that the interdecadal variations in the ocean may be one of the most important natural factors influencing long-term variability in the EAWM, although global warming may have also played a significant role in weakening the EAWM.     

Influence of the Atlantic Multidecadal Oscillation on the Winter Climate of East China

The Atlantic Multidecadal Oscillation （AMO）, the multidecadal variation of North Atlantic sea surface temperature （SST）, exhibits an oscillation with a period of 65-80 years and an amplitude of 0.4℃. Observational composite analyses reveal that the warm phase AMO is linked to warmer winters in East China, with enhanced precipitation in the north of this region and reduced precipitation in the south, on multidecadal time scales. The pattern is reversed during the cold phase AMO. Whether the AMO acts as a forcing of the multidecadal winter climate of East China is explored by investigating the atmospheric response to warm AMO SST anomalies in a large ensemble of atmospheric general circulation model （AGCM） experiments. The results from three AGCMs are consistent and suggest that the AMO warmth favors warmer winters in East China. This influence is realized through inducing negative surface air pressure anomalies in the hemispheric-wide domain extending from the midlatitude North Atlantic to midlatitude Eurasia. These negative surface anomalies favor the weakening of the Mongolian Cold High, and thus induce a weaker East Asian Winter Monsoon.     

A Numerical Simulation of the Impact of Tropical Western Pacific SST Anomalies on the Decadal Shift of the Meiyu Belt

The sea surface temperature (SST) of the tropical western Pacific Ocean (TWPO) showed a pronounced warming in the late 1990s. Using numerical experiments of a regional climate model (RegCM), we analyzed the impact of this warming on rainfall over the Yangtze-Huaihe River valley of China during the Meiyu period (June-July). The model results revealed that the observed decadal changes in Meiyu rainfall since the late 1990s can be reproduced by a control experiment forced by the observed SST. Additionally, the sensitivity experiments suggested that the warming trend in the TWPO played a substantial role in the northward shift of the Meiyu belt in the late 1990s.     

Mechanisms of the atmospheric response to North Atlantic multidecadal variability: a model study

The atmospheric circulation response to decadal fluctuations of the Atlantic meridional overturning circulation (MOC) in the IPSL climate model is investigated using the associated sea surface temperature signature. A SST anomaly is prescribed in sensitivity experiments with the atmospheric component of the IPSL model coupled to a slab ocean. The prescribed SST anomaly in the North Atlantic is the surface signature of the MOC influence on the atmosphere detected in the coupled simulation. It follows a maximum of the MOC by a few years and resembles the model Atlantic multidecadal oscillation. It is mainly characterized by a warming of the North Atlantic south of Iceland, and a cooling of the Nordic Seas. There are substantial seasonal variations in the geopotential height response to the prescribed SST anomaly, with an East Atlantic Pattern-like response in summer and a North Atlantic oscillation-like signal in winter. In summer, the response of the atmosphere is global in scale, resembling the climatic impact detected in the coupled simulation, albeit with a weaker amplitude. The zonally asymmetric or eddy part of the response is characterized by a trough over warm SST associated with changes in the stationary waves. A diagnostic analysis with daily data emphasizes the role of transient-eddy forcing in shaping and maintaining the equilibrium response. We show that in response to an intensified MOC, the North Atlantic storm tracks are enhanced and shifted northward during summer, consistent with a strengthening of the westerlies. However the anomalous response is weak, which suggests a statistically significant but rather modest influence of the extratropical SST on the atmosphere. The winter response to the MOC-induced North Atlantic warming is an intensification of the subtropical jet and a southward shift of the Atlantic storm track activity, resulting in an equatorward shift of the polar jet. Although the SST anomaly is only prescribed in the Atlantic ocean, significant impacts are found globally, indicating that the Atlantic ocean can drive a large scale atmospheric variability at decadal timescales. The atmospheric response is highly non-linear in both seasons and is consistent with the strong interaction between transient eddies and the mean flow. This study emphasizes that decadal fluctuations of the MOC can affect the storm tracks in both seasons and lead to weak but significant dynamical changes in the atmosphere.     

有关南半球大气环流与东亚气候的关系研究的若干新进展

南半球大气环流是全球大气环流的重要组成部分,也是影响气候变化和亚洲季风系统的一个重要因素.中国气象学家很早就注意到南半球大气环流对东亚夏季风降水的影响.近年来,有关南半球气候变率的研究目前正受到世界气象学家越来越多的关注.南半球中高纬大气资料的丰富及南极涛动的确定,使得认识南半球高中纬环流的年际变动规律及其与东亚气候关系成为可能.本文主要介绍近年来有关南极涛动的年际变化与沙尘天气发生频次及东亚冬春季气候的关系,古气候资料揭示的南极涛动与华北降水的关系,以及南半球大气环流与长江中下游夏季降水的关系和南极涛动变率的可预测性等方面的研究进展.并对未来研究方向作了初步的展望.     

Natural forcing of climate during the last millennium: fingerprint of solar variability

The variability of the climate during the last millennium is partly forced by changes in total solar irradiance (TSI). Nevertheless, the amplitude of these TSI changes is very small so that recent reconstruction data suggest that low frequency variations in the North Atlantic Oscillation (NAO) and in the thermohaline circulation may have amplified, in the North Atlantic sector and mostly in winter, the radiative changes due to TSI variations. In this study we use a state-of-the-art climate model to simulate the last millennium. We find that modelled variations of surface temperature in the Northern Hemisphere are coherent with existing reconstructions. Moreover, in the model, the low frequency variability of this mean hemispheric temperature is found to be correlated at 0.74 with the solar forcing for the period 1001?C1860. Then, we focus on the regional climatic fingerprint of solar forcing in winter and find a significant relationship between the low frequency TSI forcing and the NAO with a time lag of more than 40?years for the response of the NAO. Such a lag is larger than the around 20-year lag suggested in other studies. We argue that this lag is due, in the model, to a northward shift of the tropical atmospheric convection in the Pacific Ocean, which is maximum more than four decades after the solar forcing increase. This shift then forces a positive NAO through an atmospheric wave connection related to the jet-stream wave guide. The shift of the tropical convection is due to the persistence of anomalous warm SST forcing the anomalous precipitation, associated with the advection of warm SST by the North Pacific subtropical gyre in a few decades. Finally, we analyse the response of the Atlantic meridional overturning circulation to solar forcing and find that the former is weakened when the latter increases. Changes in wind stress, notably due to the NAO, modify the barotropic streamfunction in the Atlantic 50?years after solar variations. This implies a wind-driven modification of the oceanic circulation in the Atlantic sector in response to changes in solar forcing, in addition to the variations of the thermohaline circulation.