共查询到20条相似文献，搜索用时 15 毫秒
1.
G. C. Hegerl P. A. Stott M. R. Allen J. F. B. Mitchell S. F. B. Tett U. Cubasch 《Climate Dynamics》2000,16(10-11):737-754
Fingerprint techniques for the detection of anthropogenic climate change aim to distinguish the climate response to anthropogenic forcing from responses to other external influences and from internal climate variability. All these responses and the characteristics of internal variability are typically estimated from climate model data. We evaluate the sensitivity of detection and attribution results to the use of response and variability estimates from two different coupled ocean atmosphere general circulation models (HadCM2, developed at the Hadley Centre, and ECHAM3/LSG from the MPI für Meteorologie and Deutsches Klimarechenzentrum). The models differ in their response to greenhouse gas and direct sulfate aerosol forcing and also in the structure of their internal variability. This leads to differences in the estimated amplitude and the significance level of anthropogenic signals in observed 50-year summer (June, July, August) surface temperature trends. While the detection of anthropogenic influence on climate is robust to intermodel differences, our ability to discriminate between the greenhouse gas and the sulfate aerosol signals is not. An analysis of the recent warming, and the warming that occurred in the first half of the twentieth century, suggests that simulations forced with combined changes in natural (solar and volcanic) and anthropogenic (greenhouse gas and sulfate aerosol) forcings agree best with the observations. 相似文献
2.
Signal analysis of the atmospheric mean 500/1000 hPa temperature north of 55°N between 1949 and 1994
The lower tropospheric mean temperature 500/1000 hPa is examined in the Northern Hemisphere high-latitude region north of
55°N with regard to a climate change signal due to anthropogenic climate forcing as a supplement to previous studies which
concentrated on near surface temperatures. An observational data set of the German Weather Service is compared with several
model simulations including different scenarios of greenhouse gas and sulfate aerosol forcing derived from the two recent
versions of the coupled climate model in Hamburg, ECHAM-3/LSG and ECHAM-4/OPYC. The signal analysis is based on the optimal fingerprint method, which supplies a detection variable with optimal signal-to-noise ratio. The natural variability measures are derived
from the corresponding long-term control experiments. From 1970 onward, we find high trend pattern analogies between the observational
data and the greenhouse-gas induced model simulations. The fingerprint of this common temperature signal consists of a predominate
warming with maximum over Siberia and a weak cooling over the North Atlantic reaching an estimated significance level of about
1%. A non-optimized approach has also been examined, leading to even closer trend pattern correlations. The additional forcing
by sulfate aerosols decreases the correlation of this climate change simulation with the observations. The natural variability
constitutes about 50% of the conforming trend patterns. The signal-to-noise ratio is best over the oceans while the tropospheric
temperatures over the land masses are contaminated by strong noise. The trend pattern correlations look the same for both
model versions and several ensemble members with different noise realizations.
Received: 4 January 1999 / Accepted: 11 April 2001 相似文献
3.
DJ Karoly JA Cohen GA Meehl JFB Mitchell AH Oort RJ Stouffer RT Wetherald 《Climate Dynamics》1994,10(1-2):97-105
As an example of the technique of fingerprint detection of greenhouse climate change, a multivariate signal or fingerprint of the enhanced greenhouse effect is defined using the zonal mean atmospheric temperature change as a function of height and latitude between equilibrium climate model simulations with control and doubled CO2 concentrations. This signal is compared with observed atmospheric temperature variations over the period 1963 to 1988 from radiosonde-based global analyses. There is a significant increase of this greenhouse signal in the observational data over this period.These results must be treated with caution. Upper air data are available for a short period only, possibly too short to be able to resolve any real greenhouse climate change. The greenhouse fingerprint used in this study may not be unique to the enhanced greenhouse effect and may be due to other forcing mechanisms. However, it is shown that the patterns of atmospheric temperature change associated with uniform global increases of sea surface temperature, with El NinoSouthern Oscillation events and with decreases of stratospheric ozone concentrations individually are different from the greenhouse fingerprint used here. 相似文献
4.
The Canadian Centre for Climate Modelling and Analysis (CCCma) global coupled model is used to investigate the potential
climate effects of increasing greenhouse gas (GHG) concentrations and changes in sulfate aerosol loadings. The forcing scenario
adopted closely resembles that of Mitchell et al. for both the greenhouse gas and aerosol components. Its implementation in
the model and the resulting changes in forcing are described. Five simulations of 200 years in length, nominally for the years
1900 to 2100, are available for analysis. They consist of a control simulation without change in forcing, three independent
simulations with the same greenhouse gas and aerosol changes, and a single simulation with greenhouse gas only forcing. Simulations
of the evolution of temperature and precipitation from 1900 to the present are compared with available observations. Temperature
and precipitation are primary climate variables with reasonable temporal and spatial coverage in the observational record
for the period. The simulation of potential climate change from the present to the end of the twenty-first century, based
on projected GHG and aerosol forcing changes, is discussed in a companion paper. For the historical period dealt with here,
the GHG and aerosol forcing has changed relatively little compared to the forcing changes projected to the end of the twenty-first
century. Nevertheless, the forced climate signal for temperature in the model is reasonably consistent with the observed global
mean temperature from the instrumental record. This is true also for the trend in zonally averaged temperature as a function
of latitude and for some aspects of the geographical and regional distributions of temperature. Despite the modest change
in overall forcing, the difference between GHG+aerosol and GHG-only forcing is discernible in the temperature response for
this period. Changes in precipitation, on the other hand, are much less evident in both the instrumental and simulated record.
There is an apparent increasing trend in average precipitation in both the observations and the model results over that part
of the land for which observations are available. Regional and geographical changes and trends (which are less affected by
sampling considerations), if they exist, are masked by the large natural variability of precipitation in both model and observations.
Received: 24 September 1998 / Accepted: 8 October 1999 相似文献
5.
K. Hasselmann 《Climate Dynamics》1997,13(9):601-611
The multi-variate optimal fingerprint method for the detection of an externally forced climate change signal in the presence
of natural internal variability is extended to the attribution problem. To determine whether a climate change signal which
has been detected in observed climate data can be attributed to a particular climate forcing mechanism, or combination of
mechanisms, the predicted space–time dependent climate change signal patterns for the candidate climate forcings must be specified.
In addition to the signal patterns, the method requires input information on the space–time dependent covariance matrices
of the natural climate variability and of the errors of the predicted signal patterns. The detection and attribution problem
is treated as a sequence of individual consistency tests applied to all candidate forcing mechanisms, as well as to the null
hypothesis that no climate change has taken place, within the phase space spanned by the predicted climate change patterns.
As output the method yields a significance level for the detection of a climate change signal in the observed data and individual
confidence levels for the consistency of the retrieved climate change signal with each of the forcing mechanisms. A statistically
significant climate change signal is regarded as consistent with a given forcing mechanism if the statistical confidence level
exceeds a given critical value, but is attributed to that forcing only if all other candidate climate change mechanisms (from
a finite set of proposed mechanisms) are rejected at that confidence level. Although all relations can be readily expressed
in standard matrix notation, the analysis is carried out using tensor notation, with a metric given by the natural-variability
covariance matrix. This simplifies the derivations and clarifies the invariant relation between the covariant signal patterns
and their contravariant fingerprint counterparts. The signal patterns define the reduced vector space in which the climate
trajectories are analyzed, while the fingerprints are needed to project the climate trajectories onto this reduced space.
Received: 19 April 1996/Accepted: 21 April 1997 相似文献
6.
Simulating the winter North Atlantic Oscillation: the roles of internal variability and greenhouse gas forcing 总被引：5，自引：2，他引：5
T. J. Osborn 《Climate Dynamics》2004,22(6-7):605-623
Analysis of simulations with seven coupled climate models demonstrates that the observed variations in the winter North Atlantic Oscillation (NAO), particularly the increase from the 1960s to the 1990s, are not compatible with either the internally generated variability nor the response to increasing greenhouse gas forcing simulated by these models. The observed NAO record can be explained by a combination of internal variability and greenhouse gas forcing, though only by the models that simulate the strongest variability and the strongest response. These models simulate inter-annual variability of the NAO index that is significantly greater than that observed, and can no longer explain the observed record if the simulated NAO indices are scaled so that they have the same high-frequency variance as that observed. It is likely, therefore, that other external forcings also contributed to the observed NAO index increase, unless the climate models are deficient in their simulation of inter-decadal NAO variability or their simulation of the response to greenhouse gas forcing. These conclusions are based on a comprehensive analysis of the control runs and transient greenhouse-gas-forced simulations of the seven climate models. The simulations of mean winter circulation and its pattern of inter-annual variability are very similar to the observations in the Atlantic half of the Northern Hemisphere. The winter atmospheric circulation response to increasing greenhouse gas forcing shows little inter-model similarity at the regional scale, and the NAO response is model-dependent and sensitive to the index used to measure it. At the largest scales, however, sea level pressure decreases over the Arctic Ocean in all models and increases over the Mediterranean Sea in six of the seven models, so that there is an increase of the NAO in all models when measured using a pattern-based index. 相似文献
7.
A transient climate change simulation with greenhouse gas and aerosol forcing: projected climate to the twenty-first century 总被引：3，自引：0，他引：3
The potential climatic consequences of increasing atmospheric greenhouse gas (GHG) concentration and sulfate aerosol loading
are investigated for the years 1900 to 2100 based on five simulations with the CCCma coupled climate model. The five simulations
comprise a control experiment without change in GHG or aerosol amount, three independent simulations with increasing GHG and
aerosol forcing, and a simulation with increasing GHG forcing only. Climate warming accelerates from the present with global
mean temperatures simulated to increase by 1.7 °C to the year 2050 and by a further 2.7 °C by the year 2100. The warming is
non-uniform as to hemisphere, season, and underlying surface. Changes in interannual variability of temperature show considerable
structure and seasonal dependence. The effect of the comparatively localized negative radiative forcing associated with the
aerosol is to retard and reduce the warming by about 0.9 °C at 2050 and 1.2 °C at 2100. Its primary effect on temperature
is to counteract the global pattern of GHG-induced warming and only secondarily to affect local temperatures suggesting that
the first order transient climate response of the system is determined by feedback processes and only secondarily by the local
pattern of radiative forcing. The warming is accompanied by a more active hydrological cycle with increases in precipitation
and evaporation rates that are delayed by comparison with temperature increases. There is an “El Nino-like” shift in precipitation
and an overall increase in the interannual variability of precipitation. The effect of the aerosol forcing is again primarily
to delay and counteract the GHG-induced increase. Decreases in soil moisture are common but regionally dependent and interannual
variability changes show considerable structure. Snow cover and sea-ice retreat. A PNA-like anomaly in mean sea-level pressure
with an enhanced Aleutian low in northern winter is associated with the tropical shift in precipitation regime. The interannual
variability of mean sea-level pressure generally decreases with largest decreases in the tropical Indian ocean region. Changes
to the ocean thermal structure are associated with a spin-down of the Atlantic thermohaline circulation together with a decrease
in its variability. The effect of aerosol forcing, although modest, differs from that for most other quantities in that it
does not act primarily to counteract the GHG forcing effect. The barotropic stream function in the ocean exhibits modest change
in the north Pacific but accelerating changes in much of the Southern Ocean and particularly in the north Atlantic where the
gyre spins down in conjunction with the decrease in the thermohaline circulation. The results differ in non-trivial ways from
earlier equilibrium 2 × CO2 results with the CCCma model as a consequence of the coupling to a fully three-dimensional ocean model and the evolving nature
of the forcing.
Received: 24 September 1998 / Accepted: 8 October 1999 相似文献
8.
There are many indicators that human activity may change climate conditions all around the globe through emissions of greenhouse
gases. In addition, aerosol particles are emitted from various natural and anthropogenic sources. One important source of
aerosols arises from biomass burning, particularly in low latitudes where shifting cultivation and land degradation lead to
enhanced aerosol burden. In this study the counteracting effects of greenhouse gases and aerosols on African climate are compared
using climate model experiments with fully interactive aerosols from different sources. The consideration of aerosol emissions
induces a remarkable decrease in short-wave solar irradiation near the surface, especially in winter and autumn in tropical
West Africa and the Congo Basin where biomass burning is mainly prevailing. This directly leads to a modification of the surface
energy budget with reduced sensible heat fluxes. As a consequence, temperature decreases, compensating the strong warming
signal due to enhanced trace gas concentrations. While precipitation in tropical Africa is less sensitive to the greenhouse
warming, it tends to decrease, if the effect of aerosols from biomass burning is taken into account. This is partly due to
the local impact of enhanced aerosol burden and partly to modifications of the large-scale monsoon circulation in the lower
troposphere, usually lagging behind the season with maximum aerosol emissions. In the model equilibrium experiments, the greenhouse
gas impact on temperature stands out from internal variability at various time scales from daily to decadaland the same holds
for precipitation under the additional aerosol forcing. Greenhouse gases and aerosols exhibit an opposite effect on daily
temperature extremes, resulting in an compensation of the individual responses under the combined forcing. In terms of precipitation,
daily extreme events tend to be reduced under aerosol forcing, particularly over the tropical Atlantic and the Congo basin.
These results suggest that the simulation of the multiple aerosol effects from anthropogenic sources represents an important
factor in tropical climate change, hence, requiring more attention in climate modelling attempts. 相似文献
9.
Numerical Simulation of Global Temperature Change during the 20th Century with the IAP／LASG GOALS Model 总被引：1，自引：0，他引：1
The IAP/LASG GOALS coupled model is used to simulate the climate change during the 20th century using historical greenhouse gases concentrations, the mass mixing ratio of sulfate aerosols simulated by a CTM model, and reconstruction of solar variability spanning the period 1900 to 1997. Four simulations, including a control simulation and three forcing simulations, are conducted. Comparison with the observational record for the period indicates that the three forcing experiments simulate reasonable temporal and spatial distributions of the temperature change. The global warming during the 20th century is caused mainly by increasing greenhouse gas concentration especially since the late 1980s; sulfate aerosols offset a portion of the global warming and the reduction of global temperature is up to about 0.11℃ over the century; additionally, the effect of solar variability is not negligible in the simulation of climate change over the 20th century. 相似文献
10.
Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model 总被引：9，自引：4，他引：9
Two simulations with a global coupled ocean-atmosphere circulation model have been carried out to study the potential impact
of solar variability on climate. The Hoyt and Schatten estimate of solar variability from 1700 to 1992 has been used to force
the model. Results indicate that the near-surface temperature simulated by the model is dominated by the long periodic solar
fluctuations (Gleissberg cycle), with global mean temperatures varying by about 0.5 K. Further results indicate that solar
variability and an increase in greenhouse gases both induce to a first approximation a comparable pattern of surface temperature
change, i.e., an increase of the land-sea contrast. However, the solar-induced warming pattern in annual means and summer
is more centered over the subtropics, compared to a more uniform warming associated with the increase in greenhouse gases.
The observed temperature rise over the most recent 30 and 100 years is larger than the trend in the solar forcing simulation
during the same period, indicating a strong likelihood that, if the model forcing and response is realistic, other factors
have contributed to the observed warming. Since the pattern of the recent observed warming agrees better with the greenhouse
warming pattern than with the solar variability response, it is likely that one of these factors is the increase of the atmospheric
greenhouse gas concentration.
Received: 14 October 1996 / Accepted: 9 May 1997 相似文献
11.
Considerable controversy has been generated by the observation that the Earth's climate has warmed over the last century. Public policy decisions hinge on the question of whether this trend is natural climate variability or the result of the increase in atmospheric concentrations of greenhouse gases. The strength of the enhanced greenhouse effect depends, in large part, on the uncertain value of climate sensitivity. In this paper climate sensitivity is estimated from the global temperature record by assuming models for greenhouse forcing, climate response to forcing, and climate variability. We find optimal estimates of climate sensitivity are remarkably insensitive to assumptions, at least for forcing excluding the effect of aerosols, and these values are considerably less than most predictions arising from General Circulation Models (GCM's). It is, however, the statistical significance of these estimates that is sensitive to assumptions about climate variability. Assuming climate variability with a time scale of a decade or less, climate sensitivity is estimated to be significantly greater than zero, but also significantly lower than that predicted by GCM's. Climate variability with a century time scale is consistent with both the recent temperature record and the pre-instrumental record for the last millenium; if this type of variability is assumed, the estimate of climate sensitivity has a confidence band wide enough to encompass both zero and typical values obtained by GCM's. With century time-scale variability it will be several decades before confident estimates can be made. 相似文献
12.
Five simple indices of surface temperature are used to investigate the influence of anthropogenic and natural (solar irradiance and volcanic aerosol) forcing on observed climate change during the twentieth century. These indices are based on spatial fingerprints of climate change and include the global-mean surface temperature, the land-ocean temperature contrast, the magnitude of the annual cycle in surface temperature over land, the Northern Hemisphere meridional temperature gradient and the hemispheric temperature contrast. The indices contain information independent of variations in global-mean temperature for unforced climate variations and hence, considered collectively, they are more useful in an attribution study than global mean surface temperature alone. Observed linear trends over 1950–1999 in all the indices except the hemispheric temperature contrast are significantly larger than simulated changes due to internal variability or natural (solar and volcanic aerosol) forcings and are consistent with simulated changes due to anthropogenic (greenhouse gas and sulfate aerosol) forcing. The combined, relative influence of these different forcings on observed trends during the twentieth century is investigated using linear regression of the observed and simulated responses of the indices. It is found that anthropogenic forcing accounts for almost all of the observed changes in surface temperature during 1946–1995. We found that early twentieth century changes (1896–1945) in global mean temperature can be explained by a combination of anthropogenic and natural forcing, as well as internal climate variability. Estimates of scaling factors that weight the amplitude of model simulated signals to corresponding observed changes using a combined normalized index are similar to those calculated using more complex, optimal fingerprint techniques. 相似文献
13.
Hyung-Gyu Lim Sang-Wook Yeh Ji-Won Kim Rokjin Park Chang-Keun Song 《Meteorology and Atmospheric Physics》2014,126(1-2):71-79
Due to the dramatic increase in the global mean surface temperature (GMST) during the twentieth century, the climate science community has endeavored to determine which mechanisms are responsible for global warming. By analyzing a millennium simulation (the period of 1000–1990 ad) of a global climate model and global climate proxy network dataset, we estimate the contribution of solar and greenhouse gas forcings on the increase in GMST during the present warm period (1891–1990 ad). Linear regression analysis reveals that both solar and greenhouse gas forcing considerably explain the increase in global mean temperature during the present warm period, respectively, in the global climate model. Using the global climate proxy network dataset, on the other hand, statistical approach suggests that the contribution of greenhouse gas forcing is slightly larger than that of solar forcing to the increase in global mean temperature during the present warm period. Overall, our result indicates that the solar forcing as well as the anthropogenic greenhouse gas forcing plays an important role to increase the global mean temperature during the present warm period. 相似文献
14.
In the conventional approach to the detection of an anthropogenic or other externally forced climate change signal, optimal filters (fingerprints) are used to maximize the ratio of the observed climate change signal to the natural variability noise. If detection is successful, attribution of the observed climate change to the hypothesized forcing mechanism is carried out in a second step by comparing the observed and predicted climate change signals. In contrast, the Bayesian approach to detection and attribution makes no distinction between detection and attribution. The purpose of filtering in this case is to maximize the impact of the evidence, the observed climate change, on the prior probability that the hypothesis of an anthropogenic origin of the observed signal is true. Whereas in the conventional approach model uncertainties have no direct impact on the definition of the optimal detection fingerprint, in optimal Bayesian filtering they play a central role. The number of patterns retained is governed by the magnitude of the predicted signal relative to the model uncertainties, defined in a pattern space normalized by the natural climate variability. Although this results in some reduction of the original phase space, this is not the primary objective of Bayesian filtering, in contrast to the conventional approach, in which dimensional reduction is a necessary prerequisite for enhancing the signal-to-noise ratio. The Bayesian filtering method is illustrated for two anthropogenic forcing hypotheses: greenhouse gases alone, and a combination of greenhouse gases plus sulfate aerosols. The hypotheses are tested against 31-year trends for near-surface temperature, summer and winter diurnal temperature range, and precipitation. Between six and thirteen response patterns can be retained, as compared with the one or two response patterns normally used in the conventional approach. Strong evidence is found for the detection of an anthropogenic climate change in temperature, with some preference given to the combined forcing hypothesis. Detection of recent anthropogenic trends in diurnal temperature range and precipitation is not successful, but there remains strong net evidence for anthropogenic climate change if all data are considered jointly.
相似文献
| R. SchnurEmail: |
15.
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
16.
The aim of this paper is to evaluate current knowledge and uncertainties associated with the impact of increasing greenhouse
gas and aerosol concentrations on the West African monsoon. For this purpose, coupled and time-slice simulations are used.
A global measure of the monsoon changes is defined in order to avoid regional biases and to try and obtain significant results.
The position and width of the monsoon in latitude are the main focuses. There is almost no agreement between the Coupled General
Circulation models from the Coupled models Inter-Comparison project—Phase II in regard to the impact of climate change on
the monsoon. Moreover, very simple discriminations between the models seem inappropriate to get a better signal. The role
of the different forcings in time-slice simulations is then investigated. The sea surface temperature (SST) and particularly
the pattern of the SST are shown to be the most important forcing. This accounts for the diversity of the results either from
the coupled or the forced simulations with different SST changes. With a fixed SST, but of a smaller magnitude in AMJ, there
are still uncertainties, coming first from the Atmospheric General Circulation models and the way they balance greenhouse
gas and global SST increase. Finally the uncertainty due to the Land Surface models (LSMs) is not negligible. The greenhouse
gas and the LSMs are shown to have more impact in August, when the monsoon is at its highest latitude on the continent. 相似文献
17.
L. D. Danny Harvey 《Climatic change》1989,15(1-2):15-30
The physical factors governing the transient climatic response to an increase of greenhouse gases are discussed, reasons for remaining uncertainties are identified, and recent climate modelling results are briefly summarized. The relevance of the transient response, and of uncertainties in the transient response, to questions such as the applicability of equilibrium climate model simulations to a gradual greenhouse gas increase, the verification of model projections, rates of climatic change, and the impacts of preventative strategies for dealing with the buildup of greenhouse gases is also discussed. 相似文献
18.
In this study we assess the role of anthropogenic forcing (greenhouse gases and sulphate aerosols, GS) in recently observed precipitation trends over the Mediterranean region. We investigate whether the observed precipitation trends (1966–2005 and 1979–2008) are consistent with what 22 models project as response of precipitation to GS forcing. Significance is estimated using 9,000-year control runs derived from the CMIP3 archive. The results indicate that externally forced changes are detectable in observed precipitation trends in winter, late summer and in autumn. Natural internal climate variability cannot explain these changes. However, the observed trends (derived from 3 sources) are markedly inconsistent with expected changes due to GS forcing. While the influence of GS signal is detectable in winter and early spring, observed changes are several times larger than the projected response to GS forcing. The most striking inconsistency, however, is the contradiction between projected drying and the observed increase in precipitation in late summer and autumn, irrespective of the data set used. Natural (internal) variability as estimated from the models cannot account for these inconsistencies, which are already present in the large scale circulation patterns (Geopotential height at 500 hPa). The obtained results are robust to the removal of the fingerprint of the North Atlantic Oscillation. The detection of an outright sign mismatch of observed and projected trends in autumn and late summer, leads us to conclude that the recently observed trends can not be used as an illustration of plausible future expected change in the Mediterranean region. These significant shortcomings in our understanding of recent observed changes complicate communication of future expected changes in Mediterranean precipitation. 相似文献
19.
The economics (or lack thereof) of aerosol geoengineering 总被引：1，自引：0，他引：1
Anthropogenic greenhouse gas emissions are changing the Earth’s climate and impose substantial risks for current and future generations. What are scientifically sound, economically viable, and ethically defendable strategies to manage these climate risks? Ratified international agreements call for a reduction of greenhouse gas emissions to avoid dangerous anthropogenic interference with the climate system. Recent proposals, however, call for a different approach: to geoengineer climate by injecting aerosol precursors into the stratosphere. Published economic studies typically neglect the risks of aerosol geoengineering due to (i) the potential for a failure to sustain the aerosol forcing and (ii) the negative impacts associated with the aerosol forcing. Here we use a simple integrated assessment model of climate change to analyze potential economic impacts of aerosol geoengineering strategies over a wide range of uncertain parameters such as climate sensitivity, the economic damages due to climate change, and the economic damages due to aerosol geoengineering forcing. The simplicity of the model provides the advantages of parsimony and transparency, but it also imposes severe caveats on the interpretation of the results. For example, the analysis is based on a globally aggregated model and is hence silent on intragenerational distribution of costs and benefits. In addition, the analysis neglects the effects of learning and has a very simplistic representation of climate change impacts. Our analysis suggests three main conclusions. First, substituting aerosol geoengineering for CO2 abatement can be an economically ineffective strategy. One key to this finding is that a failure to sustain the aerosol forcing can lead to sizeable and abrupt climatic changes. The monetary damages due to such a discontinuous aerosol geoengineering can dominate the cost-benefit analysis because the monetary damages of climate change are expected to increase with the rate of change. Second, the relative contribution of aerosol geoengineering to an economically optimal portfolio hinges critically on, thus far, deeply uncertain estimates of the damages due to aerosol forcing. Even if we assume that aerosol forcing could be deployed continuously, the aerosol geoengineering does not considerably displace CO2 abatement in the simple economic optimal growth model until the damages due to the aerosol forcing are rather low. Third, substituting aerosol geoengineering for greenhouse gas emission abatement can fail an ethical test regarding intergenerational justice. Substituting aerosol geoengineering for greenhouse gas emissions abatements constitutes a conscious risk transfer to future generations, in violation of principles of intergenerational justice which demands that present generations should not create benefits for themselves in exchange for burdens on future generations. 相似文献
20.
Mode water is a distinct water mass characterized by a near vertical homogeneous layer or low potential vorticity, and is considered essential for understanding ocean climate variability. Based on the output of GFDL CM3, this study investigates the response of eastern subtropical mode water(ESTMW) in the North Pacific to two different single forcings: greenhouse gases(GHGs) and aerosol. Under GHG forcing, ESTMW is produced on lighter isopycnal surfaces and is decreased in volume. Under aerosol forcing, in sharp contrast, it is produced on denser isopycnal surfaces and is increased in volume.The main reason for the opposite response is because surface ocean-to-atmosphere latent heat flux change over the ESTMW formation region shoals the mixed layer and thus weakens the lateral induction under GHG forcing, but deepens the mixed layer and thus strengthens the lateral induction under aerosol forcing. In addition, local wind changes are also favorable to the opposite response of ESTMW production to GHG versus aerosol. 相似文献