Scaling of Central England Temperature Fluctuations?

Climate Dynamics, 2013

A monthly index based on the persistence of the westerly winds over the English Chanel is constructed for 1685-2008 using daily data from ships' logbooks and comprehensive marine meteorological datasets. The socalled Westerly Index (WI) provides the longest instrumental record of atmospheric circulation currently available. Anomalous WI values are associated with spatially coherent climatic signals in temperature and precipitation over large areas of Europe, which are stronger for precipitation than for temperature and in winter and summer than in transitional seasons. Overall, the WI series accord with the known European climatic history, and reveal that the frequency of the westerlies in the eastern Atlantic during the twentieth century and the Late Maunder Minimum was not exceptional in the context of the last three centuries. It is shown that the WI provides additional and complementary information to the North Atlantic Oscillation (NAO) indices. The analysis of WI series during the industrial era indicates an overall good agreement with the winter and high-summer NAO, with the exception of several multidecadal periods of weakened correlation. These decoupled periods between the frequency and the intensity of the zonal flow are interpreted on the basis of several sources of non-stationarity affecting the centres of the variability of the North Atlantic and their teleconnections. Comparisons with NAO reconstructions and long instrumental indices extending back to the seventeenth century suggest that similar situations have occurred in the past, which call for caution when reconstructing the past atmospheric circulation from climatic proxies. The robustness and extension of its climatic signal, the length of the series and its instrumental nature make the WI an excellent benchmark for proxy calibration in Europe and Greenland.

Science, 1995

2010

Sea surface temperatures (SSTs) in the North Atlantic Ocean show multidecadal fluctuations known as the Atlantic Multidecadal Oscillation (AMO) . The AMO has been related to the thermohaline circulation, which implies a strong association to large-scale climate variability. Indeed, the variability of a wide range of climate parameters in the North Atlantic region has been related to the AMO, e.g. temperatures, precipitation, drought and hurricanes. Moreover, the AMO seems to influence the Asian summer monsoon, and South American precipitation. Most of these relationships have been established analyzing the short observational records or from experiments with climate models. In order to establish the stability of the multidecadal oscillation in the AMO as well as the association with climate, it is necessary to extend the record further back in time. Using tree-ring data from the Northern Hemisphere a reconstruction of the AMO, spanning AD 800 to 2000 is presented. The reconstruction suggests anomalously warm North Atlantic SSTs from ca. AD 900 to 1050, coinciding with the "Medieval Warm Period", as well as a phase between 1100 and 1400 with relatively little interdecadal variability. There is a prolonged negative phase of AMO from ca. 1600-1860, i.e. during the "Little Ice Age" (LIA). The multidecadal variability of approximately 40-80 years remains constant throughout the record, except around ca 1500-1700, i.e. during the LIA, when it breaks down.

Climate Dynamics, 2011

August Sea Surface Temperatures (aSSTs) based on fossil diatom assemblages are generated with 2 year average resolution from a 230-year-long sediment core (Rapid 21-12B), from the Reykjanes Ridge in the subpolar North Atlantic. The results indicate a warming trend of *0.5°C of the surface waters at the Reykjanes Ridge for the last 230 years. Superimposed on this warming trend there is a multidecadal to decadal aSST variability of up to 1°C. The interval from the 1770s to the 1830s represents the coldest period, whereas *1860-1880 represents the warmest period during the last 230 years. The last 25 years is characterized by a warming trend showing strong decadal aSST variability with several warm years, but also the coldest years since the 1820s. The time of these cold years in the mid-1970s, -1980s and -1990s correspond with the documented great salinity anomalies (GSA) in the North Atlantic suggesting increased fluxes of cold, low-salinity waters from the Arctic during the last decades. The aSST record and the August North Atlantic Oscillation (aNAO) index show similar multidecadal-scale variability indicating a close coupling between the oceanic and atmospheric patterns. The aSST record shows a negative correlation with the aNAO indicating cold aSST during the positive aNAO trend and vice versa. Results suggest that the wind driven variation in volume fluxes of the North Atlantic surface waters could be the major mechanism behind the observed relationship.

International Geophysics, 2002

This paper summarizes an invited presentation given at the historic "Meteorology at the Millennium" Conference in July 2000, which marked the 150 th anniversary of the Royal Meteorological Society. It begins with a broad review of the North Atlantic Oscillation (NAO) and the mechanisms that might influence its phase and amplitude on decadal and longer time scales. New results are presented which suggest an important role for tropical ocean forcing of the unprecedented trend in the wintertime NAO index over the past several decades. We conclude with a brief discussion of a recent significant change in the pattern of the summertime atmospheric circulation over the North Atlantic.

Climate Dynamics, 2016

representation of the NAO and the utility of this approach. Finally, we note that the interannual statistics of the NAO and associated surface climate impacts are subject to uncertainty due to sampling fluctuations, even when based on a century of data.

Journal of Geophysical Research: Atmospheres, 2013

1] Knowledge of the variability of climate in the past is essential for understanding current climatic changes. Therefore, we investigated two temperature indices and seven rainfall time series of northwestern Europe since the 17th century. Trends and multidecadal to interdecadal variability are similar in England and northern France for temperature, whereas a strong regional contrast is evident between the two regions for rainfall. Multidecadal and interdecadal variability displays several periods of enhanced amplitude for both temperature and rainfall that may be related to large-scale climate control. On these scales, temperatures in both England and France display phase opposition with the Atlantic Multidecadal Oscillation (AMO) before 1800, while they are in-phase afterward, as determined by wavelet coherence. On the other hand, the relationships between temperature and the North Atlantic Oscillation (NAO) are weak across multidecadal and interdecadal scales for the whole period under study. For rainfall, coherence with the AMO is observed for scales at around 30-60 years, whereas coherence with the NAO is detected on 50-80 year scales and interdecadal 16-23 year scales. However, relationships between rainfall variability and North Atlantic climate indices are highly contrasted depending on the region considered. Finally, the results of a mixed spectral/empirical orthogonal function analysis of mean sea level pressure on these co-oscillation time scales highlight not only NAO regimes but also other patterns, explaining a nonnegligible amount of variance during certain time periods.

Journal of Climate, 2008

CITATIONS 17 READS 35 7 authors, including: Some of the authors of this publication are also working on these related projects: Influence of summer Arctic sea ice reductions on Northern Hemisphere summer climate View project Predictability of Tropical Rainfall View project Adam A. Scaife

Wiley Interdisciplinary Reviews: Climate Change, 2011

The North Atlantic oscillation (NAO) is under current climate conditions the leading mode of atmospheric circulation variability over the North Atlantic region. While the pattern is present during the entire year, it is most important during winter, explaining a large part of the variability of the large-scale pressure field, being thus largely determinant for the weather conditions over the North Atlantic basin and over Western Europe. In this study, a review of recent literature on the basic understanding of the NAO, its variability on different time scales and driving physical mechanisms is presented. In particular, the observed NAO variations and long-term trends are put into a long term perspective by considering paleo-proxy evidence. A representative number of recently released NAO reconstructions are discussed. While the reconstructions agree reasonably well with observations during the instrumental overlapping period, there is a rather high uncertainty between the different reconstructions for the pre-instrumental period, which leads to partially incoherent results, that is, periods where the NAO reconstructions do not agree even in sign. Finally, we highlight the future need of a broader definition of the NAO, the assessment of the stability of the teleconnection centers over time, the analysis of the relations to other relevant variables like temperature and precipitation, as well as on the relevant processes involved.

Journal of Climate, 2009

Summer climate in the North Atlantic-European sector possesses a principal pattern of year-to-year variability that is the parallel to the well-known North Atlantic Oscillation in winter. This summer North Atlantic Oscillation (SNAO) is defined here as the first empirical orthogonal function (EOF) of observed summertime extratropical North Atlantic pressure at mean sea level. It is shown to be characterized by a more northerly location and smaller spatial scale than its winter counterpart. The SNAO is also detected by cluster analysis and has a near-equivalent barotropic structure on daily and monthly time scales. Although of lesser amplitude than its wintertime counterpart, the SNAO exerts a strong influence on northern European rainfall, temperature, and cloudiness through changes in the position of the North Atlantic storm track. It is, therefore, of key importance in generating summer climate extremes, including flooding, drought, and heat stress in northwestern Europe. The El Niñ o-Southern Oscillation (ENSO) phenomenon is known to influence summertime European climate; however, interannual variations of the SNAO are only weakly influenced by ENSO. On interdecadal time scales, both modeling and observational results indicate that SNAO variations are partly related to the Atlantic multidecadal oscillation. It is shown that SNAO variations extend far back in time, as evidenced by reconstructions of SNAO variations back to 1706 using tree-ring records. Very long instrumental records, such as central England temperature, are used to validate the reconstruction. Finally, two climate models are shown to simulate the present-day SNAO and predict a trend toward a more positive index phase in the future under increasing greenhouse gas concentrations. This implies the long-term likelihood of increased summer drought for northwestern Europe.