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1.
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
2.
Shifts of means are not a proxy for changes in extreme winter temperatures in climate projections 总被引:1,自引:0,他引:1
Changes in the severity of extreme weather events under the influence of the enhanced greenhouse effect could have disproportionally
large effects compared to changes in the mean climate. Here, we explored the meteorological circumstances of extremes and
changes therein using two 49-member climate model ensembles for reference (1961–1990) and scenario (2051–2080) greenhouse-gas
concentrations. We have focused on daily-mean surface-air temperatures over the Northern Hemisphere in January. Over large
parts of the continents, changes in the one-in-10-year temperature events are influenced at least as much by changes in the
shape of the probability distribution functions (PDFs) as by shifts in the mean. In coastal areas, this is largely attributable
to changes in the large-scale circulation, for those types of extremes linked to infrequent wind directions. In other areas,
the inhomogeneous mean warming, increasing inland and polewards, affects the tails of the local temperature PDFs. Temperature
extremes in widely different regions were found to be linked by a large-scale circulation anomaly pattern, which resembles
the Arctic Oscillation. In the scenario ensemble, this anomaly pattern favors its positive phase, leading to enhanced probabilities
of westerly winds in a belt around the Northern Hemisphere. 相似文献
3.
Bayesian multi-model projection of climate: bias assumptions and interannual variability 总被引:1,自引:0,他引:1
Current climate change projections are based on comprehensive multi-model ensembles of global and regional climate simulations.
Application of this information to impact studies requires a combined probabilistic estimate taking into account the different
models and their performance under current climatic conditions. Here we present a Bayesian statistical model for the distribution
of seasonal mean surface temperatures for control and scenario periods. The model combines observational data for the control
period with the output of regional climate models (RCMs) driven by different global climate models (GCMs). The proposed Bayesian
methodology addresses seasonal mean temperatures and considers both changes in mean temperature and interannual variability.
In addition, unlike previous studies, our methodology explicitly considers model biases that are allowed to be time-dependent
(i.e. change between control and scenario period). More specifically, the model considers additive and multiplicative model
biases for each RCM and introduces two plausible assumptions (“constant bias” and “constant relationship”) about extrapolating
the biases from the control to the scenario period. The resulting identifiability problem is resolved by using informative
priors for the bias changes. A sensitivity analysis illustrates the role of the informative prior. As an example, we present
results for Alpine winter and summer temperatures for control (1961–1990) and scenario periods (2071–2100) under the SRES
A2 greenhouse gas scenario. For winter, both bias assumptions yield a comparable mean warming of 3.5–3.6°C. For summer, the
two different assumptions have a strong influence on the probabilistic prediction of mean warming, which amounts to 5.4°C
and 3.4°C for the “constant bias” and “constant relation” assumptions, respectively. Analysis shows that the underlying reason
for this large uncertainty is due to the overestimation of summer interannual variability in all models considered. Our results
show the necessity to consider potential bias changes when projecting climate under an emission scenario. Further work is
needed to determine how bias information can be exploited for this task. 相似文献
4.
Recent global-scale analyses of the CMIP3 model projections for the twenty-first century indicate a strong, coherent decreased
precipitation response over Central America and the Intra-America Seas region. We explore this regional response and examine
the models’ skill in representing present-day climate over this region. For much of Central America, the annual cycle of precipitation
is characterized by a rainy season that extends from May to October with a period of reduced precipitation in July and August
called the mid-summer drought. A comparison of the climate of the twentieth century simulations (20c3m) with observations
over the period 1961–1990 shows that nearly all models underestimate precipitation over Central America, due in part to an
underestimation of sea surface temperatures over the tropical North Atlantic and an excessively smooth representation of regional
topographical features. However, many of the models capture the mid-summer drought. Differences between the A1B scenario (2061–2090)
and 20c3m (1961–1990) simulations show decreased precipitation in the future climate scenario, mostly in June and July, just
before and during the onset of the mid-summer drought. We thus hypothesize that the simulated twenty-first century drying
over Central America represents an early onset and intensification of the mid-summer drought. An analysis of circulation changes
indicates that the westward expansion and intensification of the North Atlantic subtropical high associated with the mid-summer
drought occurs earlier in the A1B simulations, along with stronger low-level easterlies. The eastern Pacific inter-tropical
convergence zone is also located further southward in the scenario simulations. There are some indications that these changes
could be forced by ENSO-like warming of the tropical eastern Pacific and increased land–ocean heating contrasts over the North
American continent. 相似文献
5.
The possible changes in the frequency of extreme temperature events in Hong Kong in the 21st century were investigated by statistically downscaling 26 sets of the daily global climate model projections (a combination of 11 models and 3 greenhouse gas emission scenarios, namely A2, A1B, and B1) of the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. The models’ performance in simulating the past climate during 1971–2000 has also been verified and discussed. The verification revealed that the models in general have an acceptable skill in reproducing past statistics of extreme temperature events. Moreover, the models are more skillful in simulating the past climate of the hot nights and cold days than that of the very hot days. The projection results suggested that, in the 21st century, the frequency of occurrence of extremely high temperature events in Hong Kong would increase significantly while that of the extremely low temperature events is expected to drop significantly. Based on the multi-model scenario ensemble mean, the average annual numbers of very hot days and hot nights in Hong Kong are expected to increase significantly from 9 days and 16 nights in 1980–1999 to 89 days and 137 nights respectively in 2090–2099. On the other hand, the average annual number of cold days will drop from 17 days in 1980–1999 to about 1 day in 2090–2099. About 65 percent of the model-scenario combinations indicate that there will be on average less than one cold day in 2090–2099. While all the model-emission scenarios in general have projected consistent trends in the change of temperature extremes in the 21st century, there is a large divergence in the projections between difierent model/emission scenarios. This reflects that there are still large uncertainties in the model simulation of the future climate of extreme temperature events. 相似文献
6.
Daniel Steiner Andreas Pauling Samuel U. Nussbaumer Atle Nesje Jürg Luterbacher Heinz Wanner Heinz J. Zumbühl 《Climatic change》2008,90(4):413-441
A nonlinear backpropagation network (BPN) has been trained with high-resolution multiproxy reconstructions of temperature
and precipitation (input data) and glacier length variations of the Alpine Lower Grindelwald Glacier, Switzerland (output
data). The model was then forced with two regional climate scenarios of temperature and precipitation derived from a probabilistic
approach: The first scenario (“no change”) assumes no changes in temperature and precipitation for the 2000–2050 period compared
to the 1970–2000 mean. In the second scenario (“combined forcing”) linear warming rates of 0.036–0.054°C per year and changing
precipitation rates between −17% and +8% compared to the 1970–2000 mean have been used for the 2000–2050 period. In the first
case the Lower Grindelwald Glacier shows a continuous retreat until the 2020s when it reaches an equilibrium followed by a
minor advance. For the second scenario a strong and continuous retreat of approximately −30 m/year since the 1990s has been
modelled. By processing the used climate parameters with a sensitivity analysis based on neural networks we investigate the
relative importance of different climate configurations for the Lower Grindelwald Glacier during four well-documented historical
advance (1590–1610, 1690–1720, 1760–1780, 1810–1820) and retreat periods (1640–1665, 1780–1810, 1860–1880, 1945–1970). It
is shown that different combinations of seasonal temperature and precipitation have led to glacier variations. In a similar
manner, we establish the significance of precipitation and temperature for the well-known early eighteenth century advance
and the twentieth century retreat of Nigardsbreen, a glacier in western Norway. We show that the maritime Nigardsbreen Glacier
is more influenced by winter and/or spring precipitation than the Lower Grindelwald Glacier. 相似文献
7.
Unlike many other environmental problems, the terms used to describe the phenomenon of increasing atmospheric concentrations
of anthropogenic greenhouse gases are many, with multiple and sometimes conflicting meanings. Whether there are meaningful
distinctions in public perceptions of “global warming,” “climate change,” and “global climate change” has been a topic of
research over the past decade. This study examines public preferences for these terms based on respondent characteristics,
including climate change beliefs, political affiliation, and audience segment status derived from the “Global Warming’s Six
Americas” classification. Certainty of belief in global warming, political affiliation and audience segment status were found
to be the strongest predictors of preference, although “I have no preference” was the modal response. Global warming appears
to be a more polarizing term than climate change, preferred most by people already concerned about the issue, and least by
people who don’t believe climate change is occurring. Further research is needed to identify which of these two names promotes
the engagement of people across the spectrum of climate change beliefs in constructive dialogue about the issue. 相似文献
8.
The spatial and temporal variability of land carbon flux over the past one hundred years was investigated based on an empirical
model directly calculating soil respiration rate. Our model shows that during 1901–1995, about 44-89 PgC (equals to 0.5, 0.9
PgC/yr respectively) were absorbed by terrestrial biosphere. The simulated net ecosystem productivity (NEP) after the 1930s
was close to the estimated value of “ missing C sink” from deconvolution analysis. Most of the total carbon sink happened
during 1951–1985 with the estimated value of 33–50 PgC. Three major sinks were located in the tropics (10°S–10°N), Northern
mid-latitudes (30°–60°N) and Southern subtropics (10°–40°S). During 1940s-mid-1970s, carbon sinks by terrestrial ecosystem
increased with time, and decreased after the mid-1970s. These may be due to the changing of climate condition, as during the
1940s–1970s, temperature decreased and precipitation increased, while after the mid-1970s, an opposite climate situation occurred
with evident increasing in temperature and decreasing in precipitation. Usually, warmer and dryer climate condition is not
favor for carbon absorption by biosphere and even induces net carbon release from soil, while cooler and wetter condition
may induce more carbon sink. Our model results show that the net carbon flux is particularly dependent on moisture / precipitation
effect despite of temperature effect. The changing of climate in the past century may be a possible factor inducing increases
in carbon sink in addition to CO2 and N fertilizer.
This research was funded by CAS One Hundred Talents project and Knowledge Innovation Project of CAS(KZCX2-201). 相似文献
9.
Future change of climate in South America in the late twenty-first century: intercomparison of scenarios from three regional climate models 总被引:2,自引:1,他引:1
Jose A. Marengo Tercio Ambrizzi Rosmeri P. da Rocha Lincoln M. Alves Santiago V. Cuadra Maria C. Valverde Roger R. Torres Daniel C. Santos Simone E. T. Ferraz 《Climate Dynamics》2010,35(6):1073-1097
Regional climate change projections for the last half of the twenty-first century have been produced for South America, as
part of the CREAS (Cenarios REgionalizados de Clima Futuro da America do Sul) regional project. Three regional climate models
RCMs (Eta CCS, RegCM3 and HadRM3P) were nested within the HadAM3P global model. The simulations cover a 30-year period representing
present climate (1961–1990) and projections for the IPCC A2 high emission scenario for 2071–2100. The focus was on the changes
in the mean circulation and surface variables, in particular, surface air temperature and precipitation. There is a consistent
pattern of changes in circulation, rainfall and temperatures as depicted by the three models. The HadRM3P shows intensification
and a more southward position of the subtropical Pacific high, while a pattern of intensification/weakening during summer/winter
is projected by the Eta CCS/RegCM3. There is a tendency for a weakening of the subtropical westerly jet from the Eta CCS and
HadRM3P, consistent with other studies. There are indications that regions such of Northeast Brazil and central-eastern and
southern Amazonia may experience rainfall deficiency in the future, while the Northwest coast of Peru-Ecuador and northern
Argentina may experience rainfall excesses in a warmer future, and these changes may vary with the seasons. The three models
show warming in the A2 scenario stronger in the tropical region, especially in the 5°N–15°S band, both in summer and especially
in winter, reaching up to 6–8°C warmer than in the present. In southern South America, the warming in summer varies between
2 and 4°C and in winter between 3 and 5°C in the same region from the 3 models. These changes are consistent with changes
in low level circulation from the models, and they are comparable with changes in rainfall and temperature extremes reported
elsewhere. In summary, some aspects of projected future climate change are quite robust across this set of model runs for
some regions, as the Northwest coast of Peru-Ecuador, northern Argentina, Eastern Amazonia and Northeast Brazil, whereas for
other regions they are less robust as in Pantanal region of West Central and southeastern Brazil. 相似文献
10.
Summary Climatic changes of summer temperature and precipitation in the greater Alpine region are assessed by using statistical-dynamical
downscaling. The downscaling procedure is applied to two 30-year periods (1971–2000 and 2071–2100, summer months only) taken
from the results of a transient coupled ocean/atmosphere climate scenario simulation with increasing greenhouse gas concentrations.
The downscaling results for the present-day climate are compared with observations. The estimated regional climate change
during the next 100 years shows a general warming. The mean summer temperatures increase by 3 to 5 Kelvin. The most intense
climatic warming is predicted in the western parts of the Alps. The amount of summer precipitation decreases in most parts
of central Europe by more than 20 percent. Increasing precipitation is simulated only over the Adriatic area and parts of
eastern central Europe.
The results are compared with observed climate trends for the last decades and results of other regional climate change estimations.
The observed trends and the majority of the simulated trends (including ours) have a number of common features. However, there
are also climate change estimates of other groups which completely contradict our results.
Received April 8, 1999 Revised November 16, 1999 相似文献
11.
A version of the National Centre for Atmospheric Research (NCAR) coupled climate model is integrated under current climate
conditions and in a series of experiments with climate forcings ranging from modest to very strong. The purpose of the experiments
is to investigate the nature and behaviour of the climate feedback/sensitivity of the model, its evolution with time and climate
state, the robustness of model parameterizations as forcing levels increase, and the possibility of a “runaway” warming under
strong forcing. The model is integrated for 50 years, or to failure, after increasing the solar constant by 2.5, 10, 15, 25,
35, and 45% of its control value. The model successfully completes 50 years of integration for the 2.5, 10, 15, and 25% solar
constant increases but fails for increases of 35% and 45%. The effective global climate sensitivity evolves with time and
analysis indicates that a new equilibrium will be obtained for the 2.5, 10, and 15% cases but that runaway warming is underway
for the 25% increase in solar constant. Feedback processes are analysed both locally and globally in terms of longwave and
shortwave, clear-sky/surface, and cloud forcing components. Feedbacks in the system must be negative overall and of sufficient
strength to balance the positive forcing if the system is to attain a new equilibrium. Longwave negative feedback processes
strengthen in a reasonably linear fashion as temperature increases but shortwave feedback processes do not. In particular,
solar cloud feedback becomes less negative and, for the 25% forcing case, eventually becomes positive, resulting in temperatures
that “run away”. The conditions under which a runaway climate warming might occur have previously been investigated using
simpler models. For sufficiently strong forcing, the greenhouse effect of increasing water vapour in a warmer atmosphere is
expected to overwhelm the negative feedback of the longwave cooling to space as temperature increases. This is not, however,
the reason for the climate instability experienced in the GCM. Instead, the model experiences a “cloud feedback” warming whereby
the decrease in cloudiness that occurs when temperature increases beyond a critical value results in an increased absorption
of solar radiation by the system, leading to the runaway warming. 相似文献
12.
Z. Yan P. D. Jones T. D. Davies A. Moberg H. Bergström D. Camuffo C. Cocheo M. Maugeri G. R. Demarée T. Verhoeve E. Thoen M. Barriendos R. Rodríguez J. Martín-Vide C. Yang 《Climatic change》2002,53(1-3):355-392
Ten of the longest daily temperature series presently available in Europe and China are analysed, focusing on changes in extremes since pre-industrial times. We consider extremes in both a relative (with respect to the time of year) and an absolute sense. To distinguish changes in extremes from changes affecting the main part of the temperature distribution, a percentile smaller than 10 (and/or larger than 90) is recommended for defining an extreme. Three periods of changes in temperature extremes are identified: decreasing warm extremes before the late 19th century; decreasing cold extremes since then and increasing warm extremes since the 1960s. The early decreases and recent increases of warm extremes dominate in summer, while the decrease of cold extremes for winter persists throughout the whole period. There were more frequent combined (warm plus cold) extremes during the 18th century and the recent warming period since 1961 at most of the ten stations, especially for summer. Since 1961, the annual frequency of cold extremes has decreased by about 7% per century with warm extremes increasing by more than 10% per century but with large spatial variability. Compared with recent annual mean warming of about 2–3 ° C/century, the coldest winter temperatures have increased atthree times this rate, causing a reduced within-season range and therefore less variable winters. Changes in the warmest summer temperatures since 1961 exhibit large spatial variability, with rates of change ranging from slightly negative to 6 ° C/century. More extensive station observations since 1961 indicate that the single site results are representative of larger regions, implying also that the extremes studied are the result of large-scale changes. Recent circulation changes in daily gridded pressure data, used as an indicator of wind speed changes, support the results by explaining some of the trends. 相似文献
13.
Severe climate-induced water shortage and extremes in Crete 总被引:1,自引:0,他引:1
Ioannis K. Tsanis Aristeidis G. Koutroulis Ioannis N. Daliakopoulos Daniela Jacob 《Climatic change》2011,106(4):667-677
Climate change is expected to have a significant impact on the hydrologic cycle, creating changes in freshwater resources.
The Intergovernmental Panel on Climate Change (IPCC) predicts that, as a result, floods and prolonged droughts will take place
at increasingly frequent periods. The Mediterranean has been described as one of the main climate change “hot-spots”, with
recent simulations showing a collective picture of substantial drying and warming. This effect appears more pronounced during
warm periods, when the seasonal decrease of precipitation can exceed control climatology by 25–30%. Despite the decreasing
annual rainfall trend, an increase in the amount and intensity of wintertime rainfall is evident. However, the scientific
question on the quantitative impact of these signals to small scale coastal watersheds and Mediterranean islands has not been
answered. The state-of-the-art Ensembles dataset was employed to assess the impact of the changing climate on the water availability
of the island of Crete at basin scale. Here, the Ensembles precipitation and temperature data is used as input for a rainfall–runoff
model previous calibrated for the whole island with the principle of regionalization. Data analysis for the period 1970–2100
reveals an overall decreasing precipitation trend which, combined with a temperature rise, leads to substantial reduction
of water availability. Quantitative results of hydrological change provide the data required to improve knowledge and adaptation
policy to water shortages. 相似文献
14.
This is the second part of the authors’ analysis on the output of 24 coupled climate models from the Twentieth-Century Climate in Coupled Models (20C3M) experiment and 1% per year CO 2 increase experiment (to doubling) (1pctto2x) of phase 3 of the Coupled Model Inter-comparison Project (CMIP3). The study focuses on the potential changes of July–August temperature extremes over China. The pattern correlation coefficients of the simulated temperature with the observations are 0.6–0.9, which are higher than the results for precipitation. However, most models have cold bias compared to observation, with a larger cold bias over western China (>5°C) than over eastern China (<2°C). The multi-model ensemble (MME) exhibits a significant increase of temperature under the 1pctto2x scenario. The amplitude of the MME warming shows a northwest–southeast decreasing gradient. The warming spread among the models (~1°C– 2°C) is less than MME warming (~2°C–4°C), indicating a relatively robust temperature change under CO 2 doubling. Further analysis of Geophysical Fluid Dynamics Laboratory coupled climate model version 2.1 (GFDL-CM2.1) simulations suggests that the warming pattern may be related to heat transport by summer monsoons. The contrast of cloud effects also has contributions. The different vertical structures of warming over northwestern China and southeastern China may be attributed to the different natures of vertical circulations. The deep, moist convection over southeastern China is an effective mechanism for "transporting" the warming upward, leading to more upper-level warming. In northwestern China, the warming is more surface-orientated, possibly due to the shallow, dry convection. 相似文献
15.
Scenarios with daily time resolution are frequently used in research on the impacts of climate change. These are traditionally
developed by regional climate models (RCMs). The spatial resolution, however, is usually too coarse for local climate change
analysis, especially in regions with complex topography, such as Norway. The RCM used, HIRHAM, is run with lateral boundary
forcing provided from two global medium resolution models; the ECHAM4/OPYC3 from MPI and the HadAM3H from the Hadley centre.
The first is run with IPCC SRES emission scenario B2, the latter is run with IPCC SRES emission scenarios A2 and B2. All three
scenarios represent the future time period 2071–2100. Both models have a control run, representing the present climate (1961–1990).
Daily temperature scenarios are interpolated from HIRHAM to Norwegian temperature stations. The at-site HIRHAM-temperatures,
both for the control and scenario runs, are adjusted to be locally representative. Mean monthly values and standard deviations
based on daily values of the adjusted HIRHAM-temperatures, as well as the cumulative distribution curve of daily seasonal
temperatures, are conclusive with observations for the control period. Residual kriging are used on the adjusted daily HIRHAM-temperatures
to obtain high spatial temperature scenarios. Mean seasonal temperature grids are obtained. By adjusting the control runs
and scenarios and improving the spatial resolution of the scenarios, the absolute temperature values are representative at
a local scale. The scenarios indicate larger warming in winter than in summer in the Scandinavian regions. A marked west–east
and south–north gradient is projected for Norway, where the largest increase is in eastern and northern regions. The temperature
of the coldest winter days is projected to increase more than the warmer temperatures. 相似文献
16.
Climatic impacts of historical wetland drainage in Switzerland 总被引:1,自引:0,他引:1
The effects of historical land-use and land-cover changes on the climate of the Swiss Plateau in the different seasons were
investigated. In the 19th century, a civil engineering project was initiated to reshape the lake and river system on the Swiss
Plateau in order to ban the frequent flooding during extreme weather events. The landscape modifications consisted primarily
of a conversion of wetlands with extended peat soils into a highly productive agricultural landscape. Historical maps (1800–1850)
served as a basis for the reconstruction of the past land use. The “Lokal-Modell” of the Consortium for Small-Scale Modelling
was used to conduct eight one-month long high-resolution simulations (1.5 × 1.5 km2) with present and past landscape conditions. The modified soil and surface properties led to distinctly altered energy and
moisture exchanges at the surface and as a consequence affected the local and regional climate. The climatic changes show
different characteristics and magnitudes in the cold (October – March) as compared to the warm season (April – September).
The landscape modifications led to an average daytime cooling between −0.12 °C (January) and −0.61 °C (April) and a night-time
warming of 0.19 °C−0.34 °C. The differences in the mean monthly temperatures show a warming of 0.1 °C−0.2 °C in the cold season
and a cooling of similar magnitude in most of the study area in the warm season. The modification of the radiation budget
and the surface energy balance distinctly affected the convective activity in the study area in the warm season, but had only
a weak effect on convectivity in the cold season. The cloud coverage in the warm season is therefore distinctly reduced compared
to the past. 相似文献
17.
Haiyan Teng Warren M. Washington Gerald A. Meehl Lawrence E. Buja Gary W. Strand 《Climate Dynamics》2006,26(6):601-616
Arctic climate change in the Twenty-first century is simulated by the Community Climate System Model version 3.0 (CCSM3).
The simulations from three emission scenarios (A2, A1B and B1) are analyzed using eight (A1B and B1) or five (A2) ensemble
members. The model simulates a reasonable present-day climate and historical climate trend. The model projects a decline of
sea-ice extent in the range of 1.4–3.9% per decade and 4.8–22.2% per decade in winter and summer, respectively, corresponding
to the range of forcings that span the scenarios. At the end of the Twenty-first century, the winter and summer Arctic mean
surface air temperature increases in a range of 4–14°C (B1 and A2) and 0.7–5°C (B1 and A2) relative to the end of the Twentieth
century. The Arctic becomes ice-free during summer at the end of the Twenty-first century in the A2 scenario. Similar to the
observations, the Arctic Oscillation (AO) is the dominant factor in explaining the variability of the atmosphere and sea ice
in the 1870–1999 historical runs. The AO shifts to the positive phase in response to greenhouse gas forcings in the Twenty-first
century. But the simulated trends in both Arctic mean sea-level pressure and the AO index are smaller than what has been observed.
The Twenty-first century Arctic warming mainly results from the radiative forcing of greenhouse gases. The 1st empirical orthogonal
function (explains 72.2–51.7% of the total variance) of the wintertime surface air temperature during 1870–2099 is characterized
by a strong warming trend and a “polar amplification”-type of spatial pattern. The AO, which plays a secondary role, contributes
to less than 10% of the total variance in both surface temperature and sea-ice concentration. 相似文献
18.
The modification of greenhouse gas warming by the direct effect of sulphate aerosols 总被引:1,自引:0,他引:1
The Canadian Centre for Climate Modelling and Analysis (CCCma) second generation climate model (GCMII) consists of an atmospheric
GCM coupled to mixed layer ocean. It is used to investigate the climate response to a doubling of the CO2 concentration together with the direct effect of scattering by sulphate aerosols. As expected, the aerosols offset some of
the greenhouse gas (GHG) warming; the global annual mean screen temperature change due to doubled CO2 is 3.4 °C in this model and this is reduced to 2.7 °C when an estimate of the direct effect of anthropogenic sulphate aerosols
is included. The pattern of climate response to the comparatively localized aerosol forcing is not itself localized, and it
bears a striking resemblance to the response pattern that arises from the globally distributed change in GHG forcing. This
“non-local” response to “localized” forcing indicates that the pattern of climate response is determined, to first order,
by the overall magnitude of the change in forcing rather than its detailed nature or structure. Feedback processes operating
in the system apparently determine this pattern by locally amplifying and suppressing the response to the magnitude of the
change in forcing. The influence of the location of the change in forcing is relatively small. These “non-local” and “local”
effects of aerosol forcing are characterized and displayed and some of their consequences discussed. Effects on the moisture
budget and on the energetics of the global climate are also examined.
Received: 10 June 1997 / Accepted: 8 January 1998 相似文献
19.
This paper reports a comprehensive study on the observed and projected spatiotemporal changes in mean and extreme climate over the arid region of northwestern China, based on gridded observation data and CMIP5 simulations under the RCP4.5 and RCP8.5 scenarios. The observational results reveal an increase in annual mean temperature since 1961, largely attributable to the increase in minimum temperature. The annual mean precipitation also exhibits a significant increasing tendency. The precipitation amount in the most recent decade was greater than in any preceding decade since 1961. Seasonally,the greatest increase in temperature and precipitation appears in winter and in summer, respectively. Widespread significant changes in temperature-related extremes are consistent with warming, with decreases in cold extremes and increases in warm extremes. The warming of the coldest night is greater than that of the warmest day, and changes in cold and warm nights are more evident than for cold and warm days. Extreme precipitation and wet days exhibit an increasing trend, and the maximum number of consecutive dry days shows a tendency toward shorter duration. Multi-model ensemble mean projections indicate an overall continual increase in temperature and precipitation during the 21 st century. Decreases in cold extremes, increases in warm extremes, intensification of extreme precipitation, increases in wet days, and decreases in consecutive dry days, are expected under both emissions scenarios, with larger changes corresponding to stronger radiative forcing. 相似文献
20.
Empirical-statistical downscaling and error correction of regional climate models and its impact on the climate change signal 总被引:7,自引:3,他引:4
Realizing the error characteristics of regional climate models (RCMs) and the consequent limitations in their direct utilization
in climate change impact research, this study analyzes a quantile-based empirical-statistical error correction method (quantile
mapping, QM) for RCMs in the context of climate change. In particular the success of QM in mitigating systematic RCM errors,
its ability to generate “new extremes” (values outside the calibration range), and its impact on the climate change signal
(CCS) are investigated. In a cross-validation framework based on a RCM control simulation over Europe, QM reduces the bias
of daily mean, minimum, and maximum temperature, precipitation amount, and derived indices of extremes by about one order
of magnitude and strongly improves the shapes of the related frequency distributions. In addition, a simple extrapolation
of the error correction function enables QM to reproduce “new extremes” without deterioration and mostly with improvement
of the original RCM quality. QM only moderately modifies the CCS of the corrected parameters. The changes are related to trends
in the scenarios and magnitude-dependent error characteristics. Additionally, QM has a large impact on CCSs of non-linearly
derived indices of extremes, such as threshold indices. 相似文献