1.
Chen, Deliang, 1961, et al.
(författare)
Recent Recovery of the Siberian High Intensity
2011
Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116
Tidskriftsartikel (refereegranskat) abstract
This study highlights the fast recovery of the wintertime Siberian High intensity (SHI) over the last two decades. The SHI showed a marked weakening trend from the 1970s to 1980s, leading to unprecedented low SHI in the early 1990s according to most observational data sets. This salient declining SHI trend, however, was sharply replaced by a fast recovery over the last two decades. Since the declining SHI trend has been considered as one of the plausible consequences of climate warming, the recent SHI recovery seemingly contradicts the continuous progression of climate warming in the Northern Hemisphere. We suggest that alleviated surface warming and decreased atmospheric stability in the central Siberia region, associated with an increase in Eurasian snow cover, in the recent two decades contributed to this rather unexpected SHI recovery. The prominent SHI change, however, is not reproduced by general circulation model (GCM) simulations used in the IPCC AR4. The GCMs indicate the steady weakening of the SHI for the entire 21st century, which is found to be associated with a decreasing Eurasian snow cover in the simulations. An improvement in predicting the future climate change in regional scale is desirable.
2.
Chen, Deliang, 1961, et al.
(författare)
Summary of a workshop on extreme weather events in a warming world organized by the Royal Swedish Academy of Sciences
2020
Ingår i: Tellus Series B-Chemical and Physical Meteorology. - : Stockholm University Press. - 1600-0889 .- 0280-6509. ; 72:1
Tidskriftsartikel (refereegranskat) abstract
Climate change is not only about changes in means of climatic variables such as temperature, precipitation and wind, but also their extreme values which are of critical importance to human society and ecosystems. To inspire the Swedish climate research community and to promote assessments of international research on past and future changes in extreme weather events against the global climate change background, the Earth Science Class of the Royal Swedish Academy of Sciences organized a workshop entitled 'Extreme weather events in a warming world' in 2019. This article summarizes and synthesizes the key points from the presentations and discussions of the workshop on changes in floods, droughts, heat waves, as well as on tropical cyclones and extratropical storms. In addition to reviewing past achievements in these research fields and identifying research gaps with a focus on Sweden, future challenges and opportunities for the Swedish climate research community are highlighted.
3.
4.
Gunnarson, Björn, et al.
(författare)
Improving a tree-ring reconstruction from west-central Scandinavia : 900 years of warm-season temperatures
2011
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 36:1-2, s. 97-108:36, s. 97-108
Tidskriftsartikel (refereegranskat) abstract
Dendroclimatological sampling of Scots pine (Pinus sylvestris L.) has been made in the province of Jamtland, in the west-central Scandinavian mountains, since the 1970s. The tree-ring width (TRW) chronology spans several thousand years and has been used to reconstruct June August temperatures back to 1632 BC. A maximum latewood density (MXD) dataset, covering the period AD 1107-1827 (with gap 1292-1315) was presented in the 1980s by Fritz Schweingruber. Here we combine these historical MXD data with recently collected MXD data covering AD 1292-2006 into a single reconstruction of April September temperatures for the period AD 1107 2006. Regional curve standardization (RCS) provides more low-frequency variability than non-RCS and stronger correlation with local seasonal temperatures (51% variance explained). The MXD chronology shows a stronger relationship with temperatures than the TRW data, but the two chronologies show similar multi-decadal variations back to AD 1500. According to the MXD chronology, the period since AD 1930 and around AD 1150-1200 were the warmest during the last 900 years. Due to large uncertainties in the early part of the combined MXD chronology, it is not possible to conclude which period was the warmest. More sampling of trees growing near the tree-line is needed to further improve the MXD chronology.
5.
Jeong, Jee-Hoon, 1976, et al.
(författare)
Greening in the circumpolar high-latitude may amplify warming in the growing season
2012
Ingår i: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 38:7-8, s. 1421-1431
Tidskriftsartikel (refereegranskat) abstract
We present a study that suggests greening in the circumpolar high-latitude regions amplifies surface warming in the growing season (May–September) under enhanced greenhouse conditions. The investigation used a series of climate simulations with the Community Atmospheric Model version 3—which incorporates a coupled, dynamic global vegetation model—with and without vegetation feedback, under both present and doubled CO2 concentrations. Results indicate that climate warming and associated changes promote circumpolar greening with northward expansion and enhanced greenness of both the Arctic tundra and boreal forest regions. This leads to additional surface warming in the high-latitudes in the growing season, primarily through more absorption of incoming solar radiation. The resulting surface and tropospheric warming in the high-latitude and Arctic regions weakens prevailing tropospheric westerlies over 45–70N, leading to the formation of anticyclonic pressure anomalies in the Arctic regions. These pressure anomalies resemble the anomalous circulation pattern during the negative phase of winter Arctic Oscillation. It is suggested that these circulation anomalies reinforce the high-latitude and Arctic warming in the growing season.
6.
Jeong, Jee-Hoon, 1976, et al.
(författare)
Impact of urban warming on earlier spring flowering in Korea
2011
Ingår i: International Journal of Climatology. - : Wiley. - 1097-0088 .- 0899-8418. ; :31, s. 1488-1497
Tidskriftsartikel (refereegranskat) abstract
Using long-term (1954-2004) observations of four selected species in South Korea: goldenbell (Forsythia koreana), azalea (Rhododendron mucronulatum), cherry (Prunus yedoensis), and peach (Prunus persica), the impact of urban warming on spring flowering was investigated. Trends of early spring temperatures and first-flowering dates (FFDs) of the four plants were cross-compared among nine differently urbanized cities. It was clearly observed that urban warming has led to an advance in the timing of first-flowering of several days to weeks during recent decades, while the intrinsic physiology of plants to sense thermal energy has not been changed. The degree of advancement of the FFD was observed to be roughly proportional to degree of urbanization. Moreover, the sensitivity of the FFD to urban warming was estimated to be higher for the shrub species (-9.07 and -6.64 days °C-1 for goldenbell and azalea, respectively) than the tree species (-2.46 and -2.90 days °C-1 for peach and cherry, respectively). Our results suggest that the impact of urban warming should be considered as an influential factor which drives changes in the regional natural environment, especially in regions of rapid urbanization. Copyright © 2010 Royal Meteorological Society
7.
Seftigen, Kristina, 1985, et al.
(författare)
Reconstructed drought variability in southeastern Sweden since the 1650s
2013
Ingår i: International Journal of Climatology. - : Wiley. - 0899-8418 .- 1097-0088. ; 33:11, s. 2449-2458
Tidskriftsartikel (refereegranskat) abstract
In this study, we present the first regional reconstruction of summer drought for southeastern Sweden. The June–July standardized precipitation index (SPI) was reconstructed over the period 1650–2002 based on Pinus sylvestris L. tree-ring width data, where the reconstruction could account for 41.6% of the total variance in the instrumental record over 1901–2002. Our reconstruction suggests an overall wet 18th century and a dry 19th century. The most outstanding pluvial phase in the pre-instrumental period took place in the mid-1720s and lasted over 50 years, while multi-decadal periods of below average moisture conditions were reconstructed in the 1660s–1720s, 1800s-early 30s, and in the 1840s–50s. Several of these dry spells have previously been found in reconstructions from Sweden and Finland, indicating that our reconstruction reflects large-scale moisture anomalies across eastern Fennoscandia. Comparison of the SPI estimates with mid-tropospheric pressure patterns suggests that summertime drought is associated with positive pressure anomalies over British Isles and the North Sea, while an eastward movement of the Icelandic low-pressure systems over the western part of central Fennoscandia results in wetter than normal June–July conditions over the region of interest. Copyright 2012 Royal Meteorological Society
8.
9.
Jansson, Peter, et al.
(författare)
Editorial
2018
Ingår i: Geografiska Annaler. - 0435-3676 .- 1468-0459. ; 100:1, s. 1-3
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
10.
Ou, Tinghai, et al.
(författare)
Evaluation of global climate models in simulating extreme precipitation in China
2013
Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 65
Tidskriftsartikel (refereegranskat) abstract
Variations in extreme precipitation can be described by various indices. In order to evaluate a climate model’s ability to simulate extreme precipitation, gridded extreme precipitation indices from observations are needed. There are two ways to obtain gridded extreme precipitation indices from station-based observations: either through interpolation of station-based extreme indices (EISTA) or estimated from gridded precipitation datasets (EIGRID). In this work, we evaluated these two methods and compared observational extreme precipitation indices in China to those obtained from a set of widely used global climate models. Results show that the difference between the two methods is quite large; and in some cases it is even larger than the difference between model simulations and observed gridded EISTA. Based on the sensitivity of the indices to horizontal resolution, it was suggested that EIGRID is more appropriate for evaluating extreme indices simulated by models. Subsequently, historic simulations of extreme precipitation from 21 CMIP5 (Coupled Model Intercomparison Project Phase 5) global climate models were evaluated against two reanalysis datasets during 1961-2000. It was found that most models overestimate extreme precipitation in the mountain regions in western China and northern China and underestimate extreme precipitation in southern China. In eastern China, these models simulate mean extreme precipitation fairly well. Despite this bias, the temporal trend in extreme precipitation for western China is well captured by most models. However, in eastern China, the trend of extreme precipitation is poorly captured by most models, especially for the so-called southern flood and northern drought pattern. Overall, our results suggest that the dynamics of inter-decadal summer monsoon variability should be improved for better prediction of extreme precipitation by the global climate models
