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1.
In order to improve the reliability of climate reconstruction, especially the climatologies outside the modern observed climate
space, an improved inverse vegetation model using a recent version of BIOME4 has been designed to quantitatively reconstruct
past climates, based on pollen biome scores from the BIOME6000 project. The method has been validated with surface pollen
spectra from Eurasia and Africa, and applied to palaeoclimate reconstruction. At 6 cal ka BP (calendar years), the climate
was generally wetter than today in southern Europe and northern Africa, especially in the summer. Winter temperatures were
higher (1–5°C) than present in southern Scandinavia, northeastern Europe, and southern Africa, but cooler in southern Eurasia
and in tropical Africa, especially in Mediterranean regions. Summer temperatures were generally higher than today in most
of Eurasia and Africa, with a significant warming from ∼3 to 5°C over northwestern and southern Europe, southern Africa, and
eastern Africa. In contrast, summers were 1–3°C cooler than present in the Mediterranean lowlands and in a band from the eastern
Black Sea to Siberia. At 21 cal ka BP, a marked hydrological change can be seen in the tropical zone, where annual precipitation
was ∼200–1,000 mm/year lower than today in equatorial East Africa compared to the present. A robust inverse relationship is
shown between precipitation change and elevation in Africa. This relationship indicates that precipitation likely had an important
role in controlling equilibrium-line altitudes (ELA) changes in the tropics during the LGM period. In Eurasia, hydrological
decreases follow a longitudinal gradient from Europe to Siberia. Winter temperatures were ∼10–17°C lower than today in Eurasia
with a more significant decrease in northern regions. In Africa, winter temperature was ∼10–15°C lower than present in the
south, while it was only reduced by ∼0–3°C in the tropical zone. Comparison of palaeoclimate reconstructions using LGM and
modern CO2 concentrations reveals that the effect of CO2 on pollen-based LGM reconstructions differs by vegetation type. Reconstructions for pollen sites in steppic vegetation in
Europe show warmer winter temperatures under LGM CO2 concentrations than under modern concentrations, and reconstructions for sites in xerophytic woods/scrub in tropical high
altitude regions of Africa are wetter for LGM CO2 concentrations than for modern concentrations, because our reconstructions account for decreased plant water use efficiency. 相似文献
2.
Influence of vegetation changes during the Last Glacial Maximum using the BMRC atmospheric general circulation model 总被引:3,自引:0,他引:3
The influence of different vegetation distributions on the atmospheric circulation during the Last Glacial Maximum (LGM,
21 000 years before present) is investigated. The atmospheric general circulation model of the Bureau of Meteorology Research
Center was run using a modern vegetation and in a second experiment with a vegetation reconstruction for the LGM. It is found
that a change from conifer to desert and tundra causes an additional LGM cooling of 1–2 °C in Western Europe, up to −4 °C
in North America and −6 °C in Siberia. An expansion of dryland vegetation causes an additional annual cooling of 1–2 °C for
Australia and northern Africa. On the other hand, an increase of temperature (2 °C) is found in Alaska due to changes in circulation.
In the equatorial region the LGM vegetation leads to an increased modelled temperature of 0.5–1.5 °C and decreased precipitation
(30%) over land due to a reduction of the tropical rainforest, mainly in Indonesia, where the reduction of precipitation over
land is associated with an increase of precipitation of 30% over the western Pacific.
Received: 15 December 1999 / Accepted: 10 January 2001 相似文献
3.
A comparison of PMIP2 model simulations and the MARGO proxy reconstruction for tropical sea surface temperatures at last glacial maximum 总被引:2,自引:1,他引:1
Bette L. Otto-Bliesner Ralph Schneider E. C. Brady M. Kucera A. Abe-Ouchi E. Bard P. Braconnot M. Crucifix C. D. Hewitt M. Kageyama O. Marti A. Paul A. Rosell-Melé C. Waelbroeck S. L. Weber M. Weinelt Y. Yu 《Climate Dynamics》2009,32(6):799-815
Results from multiple model simulations are used to understand the tropical sea surface temperature (SST) response to the
reduced greenhouse gas concentrations and large continental ice sheets of the last glacial maximum (LGM). We present LGM simulations
from the Paleoclimate Modelling Intercomparison Project, Phase 2 (PMIP2) and compare these simulations to proxy data collated
and harmonized within the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface Project (MARGO). Five atmosphere–ocean
coupled climate models (AOGCMs) and one coupled model of intermediate complexity have PMIP2 ocean results available for LGM.
The models give a range of tropical (defined for this paper as 15°S–15°N) SST cooling of 1.0–2.4°C, comparable to the MARGO
estimate of annual cooling of 1.7 ± 1°C. The models simulate greater SST cooling in the tropical Atlantic than tropical Pacific,
but interbasin and intrabasin variations of cooling are much smaller than those found in the MARGO reconstruction. The simulated
tropical coolings are relatively insensitive to season, a feature also present in the MARGO transferred-based estimates calculated
from planktonic foraminiferal assemblages for the Indian and Pacific Oceans. These assemblages indicate seasonality in cooling
in the Atlantic basin, with greater cooling in northern summer than northern winter, not captured by the model simulations.
Biases in the simulations of the tropical upwelling and thermocline found in the preindustrial control simulations remain
for the LGM simulations and are partly responsible for the more homogeneous spatial and temporal LGM tropical cooling simulated
by the models. The PMIP2 LGM simulations give estimates for the climate sensitivity parameter of 0.67°–0.83°C per Wm−2, which translates to equilibrium climate sensitivity for doubling of atmospheric CO2 of 2.6–3.1°C. 相似文献
4.
Philip B. Holden N. R. Edwards K. I. C. Oliver T. M. Lenton R. D. Wilkinson 《Climate Dynamics》2010,35(5):785-806
In order to investigate Last Glacial Maximum and future climate, we “precalibrate” the intermediate complexity model GENIE-1
by applying a rejection sampling approach to deterministic emulations of the model. We develop ~1,000 parameter sets which
reproduce the main features of modern climate, but not precise observations. This allows a wide range of large-scale feedback
response strengths which generally encompass the range of GCM behaviour. We build a deterministic emulator of climate sensitivity
and quantify the contributions of atmospheric (±0.93°C, 1σ) vegetation (±0.32°C), ocean (±0.24°C) and sea–ice (±0.14°C) parameterisations to the total uncertainty. We then perform
an LGM-constrained Bayesian calibration, incorporating data-driven priors and formally accounting for structural error. We
estimate climate sensitivity as likely (66% confidence) to lie in the range 2.6–4.4°C, with a peak probability at 3.6°C. We estimate LGM cooling likely to lie in
the range 5.3–7.5°C, with a peak probability at 6.2°C. In addition to estimates of global temperature change, we apply our
ensembles to derive LGM and 2xCO2 probability distributions for land carbon storage, Atlantic overturning and sea–ice coverage. Notably, under 2xCO2 we calculate a probability of 37% that equilibrium terrestrial carbon storage is reduced from modern values, so the land
sink has become a net source of atmospheric CO2. 相似文献
5.
Quantitative reconstruction of the last interglacial vegetation and climate based on the pollen record from Lake Baikal, Russia 总被引:1,自引:0,他引:1
P. Tarasov W. Granoszewski E. Bezrukova S. Brewer M. Nita A. Abzaeva H. Oberhänsli 《Climate Dynamics》2005,25(6):625-637
Changes in mean temperature of the coldest (T
c) and warmest month (T
w), annual precipitation (P
ann) and moisture index (α) were reconstructed from a continuous pollen record from Lake Baikal, Russia. The pollen sequence
CON01-603-2 (53°57′N, 108°54′E) was recovered from a 386 m water depth in the Continent Ridge and dated to ca. 130–114.8 ky
BP. This time interval covers the complete last interglacial (LI), corresponding to MIS 5e. Results of pollen analysis and
pollen-based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record. Shrubby
tundra covered the area at the beginning of MIS 5e (ca. 130–128 ky), consistent with the end of the Middle Pleistocene glaciation.
The late glacial climate was characterised by low winter and summer temperatures (T
c ~ −38 to −35°C and T
w~11–13°C) and low annual precipitation (P
ann~300 mm). However, the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures
and evaporation (reconstructed α~1). Tundra was replaced by boreal conifer forest (taiga) by ca. 128 ky BP, suggesting a transition
to the interglacial. Taiga-dominant phase lasted until ca. 117.4 ky BP, e.g. about 10 ky. The most favourable climate conditions
occurred during the first half of the LI. P
ann reached 500 mm soon after 128 ky BP. However, temperature changed more gradually. Maximum values of T
c ~ −20°C and T
w~16–17°C are reconstructed from about 126 ky BP. Conditions became gradually colder after ca. 121 ky BP. T
c dropped to ~ −27°C and T
w to ~15°C by 119.5 ky BP. The reconstructed increase in continentality was accompanied by a decrease in P
ann to ~400–420 mm. However, the climate was still humid enough (α~0.9) to support growth of boreal evergreen conifers. A sharp
turn towards a dry climate is reconstructed after ca. 118 ky BP, causing retreat of forest and spread of cool grass-shrub
communities. Cool steppe dominated the vegetation in the area between ca. 117.5 ky and 114.8 ky BP, suggesting the end of
the interglacial and transition to the last glacial (MIS 5d). Shift to the new glaciation was characterised by cool and very
dry conditions with T
c ~ −28 to −30°C, T
w~14–15°C, P
ann~250 mm and α~0.5. 相似文献
6.
Raphael E. Okoola 《Meteorology and Atmospheric Physics》2000,73(3-4):177-187
Summary Climatological statistics of extreme temperature events over Kenya are established from the analysis of daily and monthly
maximum temperatures for a representative station (Nairobi Dagoretti Corner) over the period 1956–1997.
The months of June to August were shown to be the coldest with a mean monthly maximum temperature of less than 22 °C. Seasonal
(June to August) mean maximum temperature was 21.5 °C. Using this seasonal mean temperature for the period 1967–1997 delineated
1968 as the coldest year in this series and 1983 as the warmest year.
Spectral analysis of the seasonal data, for both the coldest and the warmest years, revealed that the major periods were the
quasi-biweekly (10 days) and the Intraseasonal Oscillations (23 days). Secondary peaks occurred at periods of 4–6 and 2.5–3.5
days.
A temperature threshold of 16.7 °C during July was used to define cold air outbreaks over Nairobi. This threshold temperature
of 16.7 °C was obtained from the mean July maximum temperature (20.9 °C) minus two standard deviations. Notable trends include
a decrease in the frequency of station-days, between 1956 and 1997, with temperatures less than 16.7 °C during July.
Surface pressure patterns indicate that the origin of the cold air is near latitude 25° S and to the east of mainland South
Africa. The cold air near 25° S is advected northwards ahead of the surface pressure ridge.
Received July 19, 1999 Revised January 11, 2000 相似文献
7.
Summary The Siberian High is the most important atmospheric centre of action in Eurasia during the winter months. Here its variability
and relationship with temperature and precipitation is investigated for the period 1922 to 2000. The pronounced weakening
of the Siberian High during the last ∼ 20 years is its most remarkable feature. Mean temperature, averaged over middle to
high latitude Asia (30° E–140° E, 30° N–70° N), is correlated with the Siberian High central intensity (SHCI) with correlation
coefficient of − 0.58 (1922–1999), and for precipitation, the correlation coefficient is − 0.44 (1922–1998). Taking the Arctic
Oscillation (AO), the SHCI, the Eurasian teleconnection pattern (EU), and the Southern Oscillation (SO) index into account,
72 percent of the variance in temperature can be explained for the period 1949–1997 (for precipitation the variance is 26
percent), with the AO alone explaining 30 percent of the variance, and the Siberian High contributing 24 percent. The precipitation
variance explained by the Siberian High is only 9.8 percent of the total.
Received January 2, 2001 Revised November 24, 2001 相似文献
8.
Summary Spatial-temporal characteristics of temperature variations were analyzed from China daily temperature based on 486 stations
during the period 1960–2000. The method of hierarchical cluster analysis was used to divide the territory into sub-regional
areas with a coherent evolution, both annually and seasonally. Areas numbering 7–9 are chosen to describe the regional features
of air temperature in mainland China.
All regions in mainland China experienced increasing trends of annual mean temperature. The trend of increasing temperature
was about 0.2–0.3 °C/10 yr in northern China and less than 0.1 °C/10 yr in southern China. In the winter season, the increasing
trend of temperature was about 0.5–0.7 °C/10 yr in northern China and about 0.2–0.3 °C/10 yr in southern China. The increasing
trend of autumn temperature was mainly located in northwestern China and southwestern China including the Tibetan Plateau.
In spring, the rising trend of temperature was concentrated in Northeast China and North China while there was a declining
temperature trend of −0.13 °C/10 yr in the upper Yangtze River. In summer, the declining trend of temperature was only concentrated
in the mid-low valley of the Yangtze and Yellow Rivers while surrounding this valley there were increasing trends in South
China, Southwest China, Northwest China, and Northeast China.
Rapid changes in temperature in various regions were detected by the multiple timescale t-test method. The year 1969 was a rapid change point from a high temperature to a low temperature along the Yangtze River
and South China. In the years 1977–1979, temperature significantly increased from a lower level to a higher level in many
places except for regions in North China and the Yangtze River. Another rapid increasing temperature trend was observed in
1987. In the years 1976–1979, a positive rapid change of summer temperature occurred in northwestern China and southwestern
China while a decreasing temperature was found between the Yellow River and the Yangtze River. A rapid increase of winter
temperature was found for 1977–1979 and 1985–1986 in many places.
There were increasing events of extreme temperature in broad areas except in the north part of Northeast China and the north
part of the Xinjiang region. In winter, increasing temperature of the climate state and weakening temperature extremes are
observed in northern China. In summer, both increasing temperature of the climate state and enhancing temperature extremes
were commonly exhibited in northern China.
Present address: Linfen Meteorological Office, Linfen 041000, Shanxi Province, China. 相似文献
9.
Palaeoclimates across Europe for 6000 y BP were estimated from pollen data using the modern pollen analogue technique constrained
with lake-level data. The constraint consists of restricting the set of modern pollen samples considered as analogues of the
fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration (P–E) is consistent with the regional change in moisture balance as indicated by lakes. An artificial neural network was used
for the spatial interpolation of lake-level changes to the pollen sites, and for mapping palaeoclimate anomalies. The climate
variables reconstructed were mean temperature of the coldest month (T
c
), growing degree days above 5 °C (GDD), moisture availability expressed as the ratio of actual to equilibrium evapotranspiration (α), and P–E. The constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies, especially for P–E. The reconstructions indicate clear spatial and seasonal patterns of Holocene climate change, which can provide a quantitative
benchmark for the evaluation of palaeoclimate model simulations. Winter temperatures (T
c
) were 1–3 K greater than present in the far N and NE of Europe, but 2–4 K less than present in the Mediterranean region.
Summer warmth (GDD) was greater than present in NW Europe (by 400–800 K day at the highest elevations) and in the Alps, but >400 K day less
than present at lower elevations in S Europe. P–E was 50–250 mm less than present in NW Europe and the Alps, but α was 10–15% greater than present in S Europe and P–E was 50–200 mm greater than present in S and E Europe.
Received: 3 January 1996 / Accepted: 15 July 1996 相似文献
10.
Annual precipitation, July and January temperatures were reconstructed from a continuous Holocene pollen sequence from the
Middle Atlas, Morocco, using the best modern analogues method. The reconstructions show a clear difference between the early
and late Holocene: from ∼10 ka to ∼6.5 ka the climate was drier and warmer than during the period since 6.5 ka. The average
value of annual precipitation was ∼870 mm until 6.5 ka, then rose to ∼940 mm. Between 10 ka and 6.5 ka January and July temperatures
were about 4 °C higher than the present. Both temperatures show a marked decrease between 7 ka and 6 ka. After 6.5 ka July
and January temperatures fluctuated between 21 and 23 °C, and 2.5 and 5 °C respectively. January temperatures show a period
of intermediate values (∼3.5 °C) between 4 ka and 5.5 ka. The reconstructed climate values generally match palaeolimnological
data from the same core, which show five intervals of low lake level during the Holocene. They are also consistent with regional-scale
COHMAP simulated palaeoclimate that shows contrasting patterns of rainfall variation between the northwesternmost part of
Africa and the intertropical band.
Received: 7 July 1997 / Accepted: 28 May 1998 相似文献
11.
We demonstrate that a hemispherically averaged upwelling-diffusion energy-balance climate model (UD/EBM) can emulate the
surface air temperature change and sea-level rise due to thermal expansion, predicted by the HadCM2 coupled atmosphere-ocean
general circulation model, for various scenarios of anthropogenic radiative forcing over 1860–2100. A climate sensitivity
of 2.6 °C is assumed, and a representation of the effect of sea-ice retreat on surface air temperature is required. In an
extended experiment, with CO2 concentration held constant at twice the control run value, the HadCM2 effective climate sensitivity is found to increase
from about 2.0 °C at the beginning of the integration to 3.85 °C after 900 years. The sea-level rise by this time is almost
1.0 m and the rate of rise fairly steady, implying that the final equilibrium value (the `commitment') is large. The base
UD/EBM can fit the 900-year simulation of surface temperature change and thermal expansion provided that the time-dependent
climate sensitivity is specified, but the vertical profile of warming in the ocean is not well reproduced. The main discrepancy
is the relatively large mid-depth warming in the HadCM2 ocean, that can be emulated by (1) diagnosing depth-dependent diffusivities
that increase through time; (2) diagnosing depth-dependent diffusivities for a pure-diffusion (zero upwelling) model; or (3)
diagnosing higher depth-dependent diffusivities that are applied to temperature perturbations only. The latter two models can be run to equilibrium, and with a climate sensitivity of 3.85 °C, they give sea-level rise
commitments of 1.7 m and 1.3 m, respectively.
Received: 27 April 1999 / Accepted: 13 September 2000 相似文献
12.
Summary Near surface climate was observed through temperature profiling from the surface to 2.47 m height in an urban vegetated park
and its surroundings in central Stockholm, Sweden. Measurements were conducted during three summer days by mobile traverses.
Air temperature differences between the built-up area and the park were in the range of 0.5–0.8 °C during the day and reached
a maximum of 2 °C at sunset. The thermal stratification of the air was mainly stable in the park and unstable in the built-up
area. Inverse air temperature profiles in the park were less stable in open than in shady areas, and close to neutral at midday.
The most unstable air was found in the north–south orientated canyons in the early afternoon. Possible heat advection from
the surroundings, and thus uncoupling between the surface and the air, was identified through temperature gradients pointing
at different directions within the 2.47 m profile. Examples at midday indicated that warm air advected as far as 150 m into
the park. 相似文献
13.
Jan Esper Lara Klippel Paul J. Krusic Oliver Konter Christoph C. Raible Elena Xoplaki Jrg Luterbacher Ulf Bntgen 《Climate Dynamics》2020,54(3):1367-1382
The Mediterranean has been identified as particularly vulnerable to climate change, yet a high-resolution temperature reconstruction extending back into the Medieval Warm Period is still lacking. Here we present such a record from a high-elevation site on Mt. Smolikas in northern Greece, where some of Europe’s oldest trees provide evidence of warm season temperature variability back to 730 CE. The reconstruction is derived from 192 annually resolved, latewood density series from ancient living and relict Pinus heldreichii trees calibrating at r1911–2015 = 0.73 against regional July–September (JAS) temperatures. Although the recent 1985–2014 period was the warmest 30-year interval (JAS Twrt.1961–1990 = + 0.71 °C) since the eleventh century, temperatures during the ninth to tenth centuries were even warmer, including the warmest reconstructed 30-year period from 876–905 (+ 0.78 °C). These differences between warm periods are statistically insignificant though. Several distinct cold episodes punctuate the Little Ice Age, albeit the coldest 30-year period is centered during high medieval times from 997–1026 (− 1.63 °C). Comparison with reconstructions from the Alps and Scandinavia shows that a similar cold episode occurred in central Europe but was absent at northern latitudes. The reconstructions also reveal different millennial-scale temperature trends (NEur = − 0.73 °C/1000 years, CEur = − 0.13 °C, SEur = + 0.23 °C) potentially triggered by latitudinal changes in summer insolation due to orbital forcing. These features, the opposing millennial-scale temperature trends and the medieval multi-decadal cooling recorded in Central Europe and the Mediterranean, are not well captured in state-of-the-art climate model simulations. 相似文献
14.
B. Alijani 《Theoretical and Applied Climatology》2002,72(1-2):41-54
Summary In order to explore the spatial and temporal variations of 500 hPa flow patterns and their relationship with the climate
of Iran, monthly mean geopotential heights for the region 0° E to 70° E and 20° N to 50° N, at 5 degree resolution, were analysed.
The study period covered the winter months October to March during the period 1961–90. The monthly height of the 500 hPa level
was averaged along each meridian from 25° N to 45° N. The height of the mean monthly pressure pattern was mapped against the
study years. The results showed that the characteristics of the 500 hPa flow pattern varied over monthly and annual time scales.
Principal Component Analysis, with S-mode and Varimax rotation, was also used to reduce the gridded data to 5 (6 in October)
significant factors. The factor scores for each month were then correlated with monthly Z-scores of precipitation and temperature
anomalies over Iran. The results showed that troughs and ridges located close to Iran had more influence on the climate of
Iran. Two troughs were identified and named the Caspian and Syrian troughs.
Received April 12, 2001 Revised July 24, 2001 相似文献
15.
Seong-Joong Kim Thomas J. Crowley David J. Erickson Bala Govindasamy Phillip B. Duffy Bang Yong Lee 《Climate Dynamics》2008,31(1):1-16
The climate of the last glacial maximum (LGM) is simulated with a high-resolution atmospheric general circulation model, the
NCAR CCM3 at spectral truncation of T170, corresponding to a grid cell size of roughly 75 km. The purpose of the study is
to assess whether there are significant benefits from the higher resolution simulation compared to the lower resolution simulation
associated with the role of topography. The LGM simulations were forced with modified CLIMAP sea ice distribution and sea
surface temperatures (SST) reduced by 1°C, ice sheet topography, reduced CO2, and 21,000 BP orbital parameters. The high-resolution model captures modern climate reasonably well, in particular the distribution
of heavy precipitation in the tropical Pacific. For the ice age case, surface temperature simulated by the high-resolution
model agrees better with those of proxy estimates than does the low-resolution model. Despite the fact that tropical SSTs
were only 2.1°C less than the control run, there are many lowland tropical land areas 4–6°C colder than present. Comparison
of T170 model results with the best constrained proxy temperature estimates (noble gas concentrations in groundwater) now
yield no significant differences between model and observations. There are also significant upland temperature changes in
the best resolved tropical mountain belt (the Andes). We provisionally attribute this result in part as resulting from decreased
lateral mixing between ocean and land in a model with more model grid cells. A longstanding model-data discrepancy therefore
appears to be resolved without invoking any unusual model physics. The response of the Asian summer monsoon can also be more
clearly linked to local geography in the high-resolution model than in the low-resolution model; this distinction should enable
more confident validation of climate proxy data with the high-resolution model. Elsewhere, an inferred salinity increase in
the subtropical North Atlantic may have significant implications for ocean circulation changes during the LGM. A large part
of the Amazon and Congo Basins are simulated to be substantially drier in the ice age—consistent with many (but not all) paleo
data. These results suggest that there are considerable benefits derived from high-resolution model regarding regional climate
responses, and that observationalists can now compare their results with models that resolve geography at a resolution comparable
to that which the proxy data represent. 相似文献
16.
Paleo-data suggest that East African mountain treelines underwent an altitudinal shift during the Last Glacial Maximum (LGM). Understanding the ecological and physiological processes underlying treeline response to such past climate change will help to improve forecasts of treeline change under future global warming. In spite of significant improvements in paleoclimatic reconstruction, the climatic conditions explaining this migration are still debated and important factors such as atmospheric CO2 concentration, the impact of lapse rate decreasing temperature along altitudinal gradients and rainfall modifications due to elevation have often been neglected or simplified. Here, we assess the effects of these different factors and estimate the influence of the most dominant factors controlling changes in past treeline position using a multi-proxy approach based on simulations from BIOME4, a coupled biogeography and biogeochemistry model, modified to account for the effect of elevation on vegetation, compared with pollen, and isotopic data. The results indicate a shift in mountain vegetation at the LGM was controlled by low pCO2 and low temperatures promoting species morphologically and physiologically better adapted to LGM conditions than many trees composing the forest belt limit. Our estimate that the LGM climate was cooler than today’s by ?4.5 °C (range: ?4.3 to ?4.6 °C) at the upper limit of the treeline, whereas at 831 m it was cooler by ?1.4 °C (range: ?2.6 to ?0.6 °C), suggests that a possible lapse rate modification strongly constrained the upper limit of treeline, which may limit its potential extension under future global warming. 相似文献
17.
Summary The possibility of climate change in the Korean Peninsula has been examined in view of the general increase in greenhouse
gases. Analyses include changes in annual temperature and precipitation. These analyses are supplemented with our observations
regarding the apparent decrease of forest areas.
It was found that there was a 0.96 °C (0.42 °C per decade) increase in annual mean temperature between 1974 and 1997. The
increase in large cities was 1.5 °C but only 0.58 °C at rural and marine stations. The difference in the mean temperature
between large cities and rural stations was small from 1974 to 1981. However, the difference increased from 1982 to 1997.
In particular, the warming appears most significant in winter. Prior to 1982, the lowest temperatures were often −18 °C in
central Korea, and since then the lowest temperatures have been only −12∼−14 °C. Recently, the minimum January temperature
has increased at a rate of 1.5 °C per decade. It is estimated that the increase of1 °C in annual mean temperature corresponds
to about a 250 km northward shift of the subtropical zone boundary.
The analysis of data from 1906 to 1997 indicates a trend of increasing annual precipitation, an increase of 182 mm during
the 92-year peirod, with large year-to-year variations. More than half of the annual mean amount, 1,274 mm, occurred from
June to September.
Meteorological data and satellite observations suggest that changes have occurred in the characteristics of the quasi-stationary
fronts that produce summer rain. In recent years scattered local heavy showers usually occur with an inactive showery front,
in comparison with the classical steady rain for more than three weeks. For instance, local heavy rainfall, on 6 August 1998
was in the range of 123–481 mm. The scattered convective storms resulted in flooding with a heavy toll of approx. 500 people.
The northward shift of the inactive showery front over Korea, and of a convergence zone in central China, correlate with the
increase in temperature. It has been suggested that the decrease in forest areas and the change in ground cover also contribute
to the warming of the Korean Peninsula.
Received March 16, 2000 相似文献
18.
Tropical climates at the Last Glacial Maximum: a new synthesis of terrestrial palaeoclimate data. I. Vegetation, lake-levels and geochemistry 总被引:1,自引:1,他引:0
I. Farrera S. P. Harrison I. C. Prentice G. Ramstein J. Guiot P. J. Bartlein R. Bonnefille M. Bush W. Cramer U. von Grafenstein K. Holmgren H. Hooghiemstra G. Hope D. Jolly S.-E. Lauritzen Y. Ono S. Pinot M. Stute G. Yu 《Climate Dynamics》1999,15(11):823-856
Palaeodata in synthesis form are needed as benchmarks for the Palaeoclimate Modelling Intercomparison Project (PMIP). Advances
since the last synthesis of terrestrial palaeodata from the last glacial maximum (LGM) call for a new evaluation, especially
of data from the tropics. Here pollen, plant-macrofossil, lake-level, noble gas (from groundwater) and δ18O (from speleothems) data are compiled for 18±2 ka (14C), 32 °N–33 °S. The reliability of the data was evaluated using explicit criteria and some types of data were re-analysed
using consistent methods in order to derive a set of mutually consistent palaeoclimate estimates of mean temperature of the
coldest month (MTCO), mean annual temperature (MAT), plant available moisture (PAM) and runoff (P-E). Cold-month temperature
(MAT) anomalies from plant data range from −1 to −2 K near sea level in Indonesia and the S Pacific, through −6 to −8 K at
many high-elevation sites to −8 to −15 K in S China and the SE USA. MAT anomalies from groundwater or speleothems seem more
uniform (−4 to −6 K), but the data are as yet sparse; a clear divergence between MAT and cold-month estimates from the same
region is seen only in the SE USA, where cold-air advection is expected to have enhanced cooling in winter. Regression of
all cold-month anomalies against site elevation yielded an estimated average cooling of −2.5 to −3 K at modern sea level,
increasing to ≈−6 K by 3000 m. However, Neotropical sites showed larger than the average sea-level cooling (−5 to −6 K) and
a non-significant elevation effect, whereas W and S Pacific sites showed much less sea-level cooling (−1 K) and a stronger
elevation effect. These findings support the inference that tropical sea-surface temperatures (SSTs) were lower than the CLIMAP
estimates, but they limit the plausible average tropical sea-surface cooling, and they support the existence of CLIMAP-like
geographic patterns in SST anomalies. Trends of PAM and lake levels indicate wet LGM conditions in the W USA, and at the highest
elevations, with generally dry conditions elsewhere. These results suggest a colder-than-present ocean surface producing a
weaker hydrological cycle, more arid continents, and arguably steeper-than-present terrestrial lapse rates. Such linkages
are supported by recent observations on freezing-level height and tropical SSTs; moreover, simulations of “greenhouse” and
LGM climates point to several possible feedback processes by which low-level temperature anomalies might be amplified aloft.
Received: 7 September 1998 / Accepted: 18 March 1999 相似文献
19.
Wyoming provides more fossil fuels to the remainder of the United States than any other state or country, and its citizens
remain skeptical of anthropogenic influences on their climate. However, much of the state including Yellowstone National Park
and the headwaters of several major river systems, may have already been affected by rising temperatures. This paper examines
the historic climate record from Wyoming in the context of ∼14,000-year temperature reconstructions based on fossil pollen
data. The analysis shows that 24 of 30 U.S. Historical Climatology Network records from the state show an increase in the
frequency of unusually warm years since 1978. Statewide temperatures have included 15 years (50%) from 1978 to 2007 that were
greater than 1σ above the mean annual temperature for 1895–1978. The frequent warm years coincide with a reduction in the
frequency of extremely low (<−20°C) January temperatures, and are not well explained by factors such as solar irradiance and
the Pacific Decadal Oscillation. Linear regressions require inclusion of atmospheric greenhouse gas concentrations to explain
the multi-decadal temperature trends. The observed warming is large in Yellowstone National Park where 21 years (70%) from
1978 to 2007 were greater than 1σ above the 1895–1978 mean; the deviation from the mean (>1°C) is greater than any time in
the past 6,000 years. Recent temperatures have become as high as those experienced from 11,000 to 6,000 years ago when summer
insolation was >6% higher than today and when regional ecosystems experienced frequent severe disturbances. 相似文献
20.
Observed and projected climate change in Taiwan 总被引:1,自引:0,他引:1
Summary
This study examined the secular climate change characteristics in Taiwan over the past 100 years and the relationship with
the global climate change. Estimates for the likelihood of future climate changes in Taiwan were made based on the projection
from the IPCC climate models.
In the past 100 years, Taiwan experienced an island-wide warming trend (1.0–1.4 °C/100 years). Both the annual and daily temperature
ranges have also increased. The warming in Taiwan is closely connected to a large-scale circulation and SAT fluctuations,
such as the “cool ocean warm land” phenomenon. The water vapor pressure has increased significantly and could have resulted
in a larger temperature increase in summer. The probability for the occurrence of high temperatures has increased and the
result suggests that both the mean and variance in the SAT in Taiwan have changed significantly since the beginning of the
20th century. Although, as a whole, the precipitation in Taiwan has shown a tendency to increase in northern Taiwan and to
decrease in southern Taiwan in the past 100 years, it exhibits a more complicated spatial pattern. The changes occur mainly
in either the dry or rainy season and result in an enhanced seasonal cycle. The changes in temperature and precipitation are
consistent with the weakening of the East Asian monsoon.
Under consideration of both the warming effect from greenhouse gases and the cooling effect from aerosols, all projections
from climate models indicated a warmer climate near Taiwan in the future. The projected increase in the area-mean temperature
near Taiwan ranged from 0.9–2.7 °C relative to the 1961–1990 averaged temperature, when the CO2 concentration increased to 1.9 times the 1961–1990 level. These simulated temperature increases were statistically significant
and can be attributed to the radiative forcing associated with the increased concentration of greenhouse gases and aerosols.
The projected changes in precipitation were within the range of natural variability for all five models. There is no evidence
supporting the possibility of precipitation changes near Taiwan based on the simulations from five IPCC climate models.
Received February 5, 2001 Revised July 30, 2001 相似文献