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1.
T. M. Lenton M. S. Williamson N. R. Edwards R. Marsh A. R. Price A. J. Ridgwell J. G. Shepherd S. J. Cox 《Climate Dynamics》2006,26(7-8):687-711
A new Earth system model, GENIE-1, is presented which comprises a 3-D frictional geostrophic ocean, phosphate-restoring marine biogeochemistry, dynamic and thermodynamic sea-ice, land surface physics and carbon cycling, and a seasonal 2-D energy-moisture balance atmosphere. Three sets of model climate parameters are used to explore the robustness of the results and for traceability to earlier work. The model versions have climate sensitivity of 2.8–3.3°C and predict atmospheric CO2 close to present observations. Six idealized total fossil fuel CO2 emissions scenarios are used to explore a range of 1,100–15,000 GtC total emissions and the effect of rate of emissions. Atmospheric CO2 approaches equilibrium in year 3000 at 420–5,660 ppmv, giving 1.5–12.5°C global warming. The ocean is a robust carbon sink of up to 6.5 GtC year−1. Under ‘business as usual’, the land becomes a carbon source around year 2100 which peaks at up to 2.5 GtC year−1. Soil carbon is lost globally, boreal vegetation generally increases, whilst under extreme forcing, dieback of some tropical and sub-tropical vegetation occurs. Average ocean surface pH drops by up to 1.15 units. A Greenland ice sheet melt threshold of 2.6°C local warming is only briefly exceeded if total emissions are limited to 1,100 GtC, whilst 15,000 GtC emissions cause complete Greenland melt by year 3000, contributing 7 m to sea level rise. Total sea-level rise, including thermal expansion, is 0.4–10 m in year 3000 and ongoing. The Atlantic meridional overturning circulation shuts down in two out of three model versions, but only under extreme emissions including exotic fossil fuel resources. 相似文献
2.
《Climate Dynamics》2008,30(7-8):887-907
Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in
global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary
charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices
during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong
broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North
America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial
period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present
fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire
activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene
with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from
11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present.
Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex
patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel
load.
The readers are requested to refer to the section “List of contributors” for the complete list of author affiliation details. 相似文献
3.
Understanding public complacency about climate change: adults’ mental models of climate change violate conservation of matter 总被引:1,自引:2,他引:1
Public attitudes about climate change reveal a contradiction. Surveys show most Americans believe climate change poses serious
risks but also that reductions in greenhouse gas (GHG) emissions sufficient to stabilize atmospheric GHG concentrations can
be deferred until there is greater evidence that climate change is harmful. US policymakers likewise argue it is prudent to
wait and see whether climate change will cause substantial economic harm before undertaking policies to reduce emissions.
Such wait-and-see policies erroneously presume climate change can be reversed quickly should harm become evident, underestimating
substantial delays in the climate’s response to anthropogenic forcing. We report experiments with highly educated adults –
graduate students at MIT – showing widespread misunderstanding of the fundamental stock and flow relationships, including
mass balance principles, that lead to long response delays. GHG emissions are now about twice the rate of GHG removal from
the atmosphere. GHG concentrations will therefore continue to rise even if emissions fall, stabilizing only when emissions
equal removal. In contrast, most subjects believe atmospheric GHG concentrations can be stabilized while emissions into the
atmosphere continuously exceed the removal of GHGs from it. These beliefs – analogous to arguing a bathtub filled faster than
it drains will never overflow – support wait-and-see policies but violate conservation of matter. Low public support for mitigation
policies may arise from misconceptions of climate dynamics rather than high discount rates or uncertainty about the impact
of climate change. Implications for education and communication between scientists and nonscientists (the public and policymakers)
are discussed. 相似文献
4.
L. D. Danny Harvey 《Climatic change》2007,82(1-2):1-25
Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC) calls for stabilization of greenhouse gas
(GHG) concentrations at levels that prevent dangerous anthropogenic interference (DAI) in the climate system. However, some
of the recent policy literature has focused on dangerous climatic change (DCC) rather than on DAI. DAI is a set of increases
in GHGs concentrations that has a non-negligible possibility of provoking changes in climate that in turn have a non-negligible
possibility of causing unacceptable harm, including harm to one or more of ecosystems, food production systems, and sustainable
socio-economic systems, whereas DCC is a change of climate that has actually occurred or is assumed to occur and that has
a non-negligible possibility of causing unacceptable harm. If the goal of climate policy is to prevent DAI, then the determination
of allowable GHG concentrations requires three inputs: the probability distribution function (pdf) for climate sensitivity,
the pdf for the temperature change at which significant harm occurs, and the allowed probability (“risk”) of incurring harm
previously deemed to be unacceptable. If the goal of climate policy is to prevent DCC, then one must know what the correct
climate sensitivity is (along with the harm pdf and risk tolerance) in order to determine allowable GHG concentrations. DAI
from elevated atmospheric CO2 also arises through its impact on ocean chemistry as the ocean absorbs CO2. The primary chemical impact is a reduction in the degree of supersaturation of ocean water with respect to calcium carbonate,
the structural building material for coral and for calcareous phytoplankton at the base of the marine food chain. Here, the
probability of significant harm (in particular, impacts violating the subsidiary conditions in Article 2 of the UNFCCC) is
computed as a function of the ratio of total GHG radiative forcing to the radiative forcing for a CO2 doubling, using two alternative pdfs for climate sensitivity and three alternative pdfs for the harm temperature threshold.
The allowable radiative forcing ratio depends on the probability of significant harm that is tolerated, and can be translated
into allowable CO2 concentrations given some assumption concerning the future change in total non-CO2 GHG radiative forcing. If future non-CO2 GHG forcing is reduced to half of the present non-CO2 GHG forcing, then the allowable CO2 concentration is 290–430 ppmv for a 10% risk tolerance (depending on the chosen pdfs) and 300–500 ppmv for a 25% risk tolerance
(assuming a pre-industrial CO2 concentration of 280 ppmv). For future non-CO2 GHG forcing frozen at the present value, and for a 10% risk threshold, the allowable CO2 concentration is 257–384 ppmv. The implications of these results are that (1) emissions of GHGs need to be reduced as quickly
as possible, not in order to comply with the UNFCCC, but in order to minimize the extent and duration of non-compliance; (2)
we do not have the luxury of trading off reductions in emissions of non-CO2 GHGs against smaller reductions in CO2 emissions, and (3) preparations should begin soon for the creation of negative CO2 emissions through the sequestration of biomass carbon. 相似文献
5.
Ulrike Löptien Olga Zolina Sergey Gulev Mojib Latif Vladimir Soloviov 《Climate Dynamics》2008,31(5):507-532
Cyclone activity and life cycle are analysed in the coupled GCMs ECHAM5/OM and ECHAM4/OPYC3. First, the results for the present
climate (1978–1999) are compared with ERA-40 and NCEP/NCAR reanalyses, showing a drastic improvement in the representation
of cyclone activity in ECHAM5/OM compared to ECHAM4/OPYC3. The total number of cyclones, cyclone intensity, propagation velocity
and deepening rates are found to be much more realistic in ECHAM5/OM relative to ECHAM4/OPYC3. Then, changes in extra tropical
cyclone characteristics are compared between present day climate and future climate under the emission-scenario A1B using
ECHAM5/OM. This comparison is performed using the 20-year time slices 1978–1999, 2070–2090 and 2170–2190, which were considered
to be representative for the various climate conditions. The total number of cyclones does not undergo significant changes
in a warmer climate. However, regional changes in cyclone numbers and frequencies are evident. One example is the Mediterranean
region where the number of cyclones in summer increases almost by factor 2. Some noticeable changes are also found in cyclone
life cycle characteristics (deepening rate and propagation velocity). Cyclones in the future climate scenario tend to move
slower and their deepening rate becomes stronger, while cyclone intensity does not undergo significant change in a warmer
climate. Generally, our results do not support the hypothesis of enhanced storminess under future climate conditions. 相似文献
6.
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
7.
Lucas da Costa Santos Jefferson Vieira Jos Fabiani Denise Bender Daniel Soares Alves Pablo Ricardo Nitsche Elton Fialho dos Reis Rubens Duarte Coelho 《Theoretical and Applied Climatology》2020,140(1):55-68
The hydrological variable evapotranspiration (ET) is challenging to estimate because it cannot be measured directly in natural environments (except in small plots). The uncertainties associated with the models used for its prediction have increased under climate change conditions. We studied the influence of stomatal resistance on ET estimates using the Penman-Monteith method as projected by three general circulation models in two emission scenarios (RCP4.5 and RCP8.5) for future climates throughout the twenty-first century (2010–2039, 2040–2069, and 2070–2099). We also investigated the probable ET rate changes in relation to the current (30 years average, 1980–2009) climate conditions for the Paraná state in the southern region of Brazil. The results were regionalized to help policymakers assess climate change impacts and design adaptation measures. ET increases of up to 15% were found in future climate conditions, which may lead to a significant increase in the water demand for agricultural crops. However, we believe that plant morphophysiological changes may occur under atmospheric CO2 enrichment conditions and that a possible reduction in stomatal conductance will result in lower ET increases than those obtained with the traditional Penman-Monteith method. When considering future climate scenarios, we propose the equation be adjusted to consider stomatal resistance as a function of CO2 concentrations. 相似文献
8.
We use a frame-based simulation model to estimate future rate of advance of the arctic treeline in response to scenarios of transient changes in temperature, precipitation, and fire regime. The model is simple enough to capture both the short-term direct response of vegetation to climate and the longer-term interactions among vegetation, fire, and insects that are important features of dynamic vegetation models. We estimate a 150–250 yr time lag in forestation of Alaskan tundra following climatic warming and suggest that, with rapid warming under dry conditions, there would be significant development of boreal grassland-steppe, a novel ecosystem type that was common during the late Pleistocene and today occurs south of the boreal forest in continental regions. Together, the time lag and grassland development would delay the positive feedback of vegetation change to climatic warming, providing a window of opportunity to control fossil fuel emissions, the primary cause of this warming. 相似文献
9.
Weather services base their operational definitions of “present” climate on past observations, using a 30-year normal period
such as 1961–1990 or 1971–2000. In a world with ongoing global warming, however, past data give a biased estimate of the actual
present-day climate. Here we propose to correct this bias with a “delta change” method, in which model-simulated climate changes
and observed global mean temperature changes are used to extrapolate past observations forward in time, to make them representative
of present or future climate conditions. In a hindcast test for the years 1991–2002, the method works well for temperature,
with a clear improvement in verification statistics compared to the case in which the hindcast is formed directly from the
observations for 1961–1990. However, no improvement is found for precipitation, for which the signal-to-noise ratio between
expected anthropogenic changes and interannual variability is much lower than for temperature. An application of the method
to the present (around the year 2007) climate suggests that, as a geographical average over land areas excluding Antarctica,
8–9 months per year and 8–9 years per decade can be expected to be warmer than the median for 1971–2000. Along with the overall
warming, a substantial increase in the frequency of warm extremes at the expense of cold extremes of monthly-to-annual temperature
is expected. 相似文献
10.
With the continuing warming due to greenhouse gases concentration, it is important to examine the potential impacts on regional
crop production spatially and temporally. We assessed China’s potential maize production at 50 × 50 km grid scale under climate
change scenarios using modelling approach. Two climate changes scenarios (A2 and B2) and three time slices (2011–2040, 2041–2070,
2071–2100) produced by the PRECIS Regional Climate Model were used. Rain-fed and irrigated maize yields were simulated with
the CERES-Maize model, with present optimum management practices. The model was run for 30 years of baseline climate and three
time slices for the two climate change scenarios, without and with simulation of direct CO2 fertilization effects. Crop simulation results under climate change scenarios varied considerably between regions and years.
Without the CO2 fertilization effect, China’s maize production was predicted to suffer a negative effect under both A2 and B2 scenarios for
all time slices, with greatest production decreases in today’s major maize planting areas. When the CO2 fertilization effect is taken into account, production was predicted to increase for rain-fed maize but decrease for irrigated
maize, under both A2 and B2 scenarios for most time periods. 相似文献
11.
Changing growing season observed in Canada 总被引:1,自引:1,他引:0
It is theoretically interesting for climate change detection and practically important for agricultural producers to know
whether climate change has influenced agroclimatic conditions and, if so, what the potential impacts are. We present analyses
on statistical differences in means and variances of agroclimatic indices between three 30-year periods in the 20th century
(i.e., 1911–1940, 1941–1970 and 1971–2000). We found many occurrences of statistically significant changes in means between
pairs of the three 30-year periods. The findings consistently support agroclimatic trends identified from trend analysis as
an earlier growing season start and an earlier end to spring frost (SF), together with an extended growing season, more frost-free
days (FFD) and more available heat units were often found in the later 30-year periods as compared to the earlier ones. In
addition, this study provides more detailed quantitative information than the trend signals for the practical interests of
agricultural applications. Significant changes were detected for SF and FFD at a much larger percentage of stations between
the latter two 30-year periods (1941–1970 vs. 1971–2000) as compared to the earlier two periods (1911–1940 vs. 1941–1970).
In contrast, changes in variances of the selected agroclimatic indices were less evident than changes in their means, based
on the percentage of stations showing significant differences. We also present new climate averages of the selected agroclimatic
indices that can be useful for agricultural planning and management. 相似文献
12.
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
13.
This study examines the role of vegetation dynamics in regional predictions of future climate change in western Africa using
a dynamic vegetation model asynchronously coupled to a regional climate model. Two experiments, one for present day and one
for future, are conducted with the linked regional climate-vegetation model, and the third with the regional climate model
standing alone that predicts future climate based on present-day vegetation. These simulations are so designed in order to
tease out the impact of structural vegetation feedback on simulated climate and hydrological processes. According to future
predictions by the regional climate-vegetation model, increase in LAI is widespread, with significant shift in vegetation
type. Over the Guinean Coast in 2084–2093, evergreen tree coverage decreases by 49% compared to 1984–1993, while drought deciduous
tree coverage increases by 56%. Over the Sahel region in the same period, grass cover increases by 31%. Such vegetation changes
are accompanied by a decrease of JJA rainfall by 2% over the Guinean Coast and an increase by 23% over the Sahel. This rather
small decrease or large increase of precipitation is largely attributable to the role of vegetation feedback. Without the
feedback effect from vegetation, the regional climate model would have predicted a 5% decrease of JJA rainfall in both the
Guinean Coast and the Sahel as a result of the radiative and physiological effects of higher atmospheric CO2 concentration. These results demonstrate that climate- and CO2-induced changes in vegetation structure modify hydrological processes and climate at magnitudes comparable to or even higher
than the radiative and physiological effects, thus evincing the importance of including vegetation feedback in future climate
predictions. 相似文献
14.
Northern African climate at the end of the twenty-first century: an integrated application of regional and global climate models 总被引:1,自引:1,他引:0
A method for simulating future climate on regional space scales is developed and applied to northern Africa. Simulation with
a regional model allows for the horizontal resolution needed to resolve the region’s strong meridional gradients and the optimization
of parameterizations and land-surface model. The control simulation is constrained by reanalysis data, and realistically represents
the present day climate. Atmosphere–ocean general circulation model (AOGCM) output provides SST and lateral boundary condition
anomalies for 2081–2100 under a business-as-usual emissions scenario, and the atmospheric CO2 concentration is increased to 757 ppmv. A nine-member ensemble of future climate projections is generated by using output
from nine AOGCMs. The consistency of precipitation projections for the end of the twenty-first century is much greater for
the regional model ensemble than among the AOGCMs. More than 77% of ensemble members produce the same sign rainfall anomaly
over much of northern Africa. For West Africa, the regional model projects wetter conditions in spring, but a mid-summer drought
develops during June and July, and the heat stoke risk increases across the Sahel. Wetter conditions resume in late summer,
and the likelihood of flooding increases. The regional model generally projects wetter conditions over eastern Central Africa
in June and drying during August through September. Severe drought impacts parts of East Africa in late summer. Conditions
become wetter in October, but the enhanced rainfall does not compensate for the summertime deficit. The risk of heat stroke
increases over this region, although the threat is not projected to be as great as in the Sahel. 相似文献
15.
In a warming climate, atmospheric wave activity and associated weather patterns may change, although conflicting results have been reported on this topic. Additionally, atmospheric wave changes in a future climate have mainly focused on waves of a specified spatial scale, rather than a particular spatiotemporal scale. Here, changes in the variability of Rossby waves of multiple spatiotemporal scales are analyzed using the wavenumber-frequency power spectrum, a tool commonly applied to analyze atmospheric equatorial waves. Daily 500 hPa geopotential height data over 40°–60°N from historical (1950–2005) and future (2006–2099) simulations from 20 models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) under the RCP8.5 scenario were analyzed. When compared to the historical period, the late 21st century climate projections showed a decline in spectral power for both eastward and westward propagating waves with wavenumbers greater than 8 that spanned over all frequencies in all seasons, but an increase in mean power for eastward propagating waves with wavenumbers 1–7 over all frequencies was shown in winter and spring. This increase in power was accompanied by increased variance, i.e., an increased meridional extent of 500 hPa ridges and troughs, and was the result of increases in the mean number of high amplitude events and duration of activity within this wave band. These results indicate that large-scale (~ 104 km) eastward propagating weather systems may intensify with higher amplitudes for ridges and troughs, while short-scale (102–103 km) weather systems may decrease in their intensity due to reduced variability in the late 21st century under the high emissions scenario. Potential mechanisms for these changes are discussed, including enhanced Arctic warming and midlatitude-tropical interactions. 相似文献
16.
Climate changes, associated with accumulation of greenhouse gases, are expected to have a profound influence on agricultural
sustainability in Israel, a semi-arid area characterized by a cold wet winter and a dry warm summer. Accordingly this study
explored economic aspects of agricultural production under projected climate-change scenarios by the “production function”
approach, as applied to two representative crops: wheat, as the major crop grown in Israel’s dry southern region, and cotton,
representing the more humid climate in the north. Adjusting outputs of the global climate model HadCM3 to the specific research
locations, we generated projections for 2070–2100 temperatures and precipitations for two climate change scenarios. Results
for wheat vary among climate scenarios; net revenues become negative under the severe scenario (change from −145 to −273%),
but may increase under the moderate one (−43 to +35%), depending on nitrogen applied to the crop. Distribution of rain events
was found to play a major role in determining yields. By contrast, under both scenarios cotton experiences a considerable
decrease in yield with significant economic losses (−240 and −173% in A2 and B2 scenarios, respectively). Additional irrigation
and nitrogen may reduce farming losses, unlike changes in seeding dates. 相似文献
17.
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
18.
The UN Framework Convention on Climate Change calls for the avoidance of “dangerous anthropogenic interference with the climate
system”. Among the many plausible choices, dangerous interference with the climate system may be interpreted as anthropogenic
radiative forcing causing distinct and widespread climate change impacts such as a widespread demise of coral reefs or a disintegration
of the West Antarctic ice sheet. The geological record and numerical models suggest that limiting global warming below critical
temperature thresholds significantly reduces the likelihood of these eventualities. Here we analyze economically optimal policies
that may ensure this risk-reduction. Reducing the risk of a widespread coral reef demise implies drastic reductions in greenhouse
gas emissions within decades. Virtually unchecked greenhouse gas emissions to date (combined with the inertia of the coupled
natural and human systems) may have already committed future societies to a widespread demise of coral reefs. Policies to
reduce the risk of a West Antarctic ice sheet disintegration allow for a smoother decarbonization of the economy within a
century and may well increase consumption in the long run. 相似文献
19.
We assessed the potential effects of a greenhouse gas-induced global climate change on the hydrology and vegetation of a semi-permanent prairie wetland using a spatially-defined, rule-based simulation model. An 11-yr simulation was run using current versus enhanced greenhouse gas climates. Projections of climatic change were from the Goddard Institute for Space Studies (GISS) general circulation model. Simulations were also run using a range of temperature (+2 and +4 °C) and precipitation change values (–20, –10, 0, +10, +20%) to determine the responsiveness of wetland vegetation and hydrology to a variety of climate scenarios.Maximum water depths were significantly less under the enhanced greenhouse gas scenario than under the current climate. The wetland dried in most years with increased temperature and changes in precipitation. Simulations also revealed a significant change in the vegetation, from a nearly balanced emergent cover to open water ratio to a completely closed basin with no open water areas. Simulations over a range of climate change scenarios showed that precipitation changes (particularly increases) had a greater impact on water levels and cover ratios when the temperature increase was moderate (+2 °C).These potential changes in wetland hydrology and vegetation could result in a dramatic decline in the quality of habitat for breeding birds, particularly waterfowl. Continued research on climate and wetland modeling is needed. 相似文献
20.
To begin exploring the underlying mechanisms that couple vegetation to cloud formation processes, we derive the lifting condensation
level (LCL) to estimate cumulus cloud base height. Using a fully coupled land–ocean–atmosphere general circulation model (HadCM3LC),
we investigate Amazonian forest feedbacks on cloud formation over three geological periods; modern-day (a.d. 1970–1990), the last glacial maximum (LGM; 21 kya), and under a future climate scenario (IS92a; a.d. 2070–2090). Results indicate that for both past and future climate scenarios, LCL is higher relative to modern-day. Statistical
analyses indicate that the 800 m increase in LCL during the LGM is related primarily to the drier atmosphere promoted by lower
tropical sea surface temperatures. In contrast, the predicted 1,000 m increase in LCL in the future scenario is the result
of a large increase in surface temperature and reduced vegetation cover. 相似文献