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Numerical simulation of global temperature change during the 20th century with the IAP/LASG GOALS model
Abstract
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°C over the century; additionally, the effect of solar variability
is not negligible in the simulation of climate change over the 20th century.
... La simulation numérique instationnaire s'impose progressivement comme un moyen efficace pour la compréhension des phénomènes complexes et fortement dépendants du temps. Des simulations instationnaires sont par exemple utilisées pour tenter de prédire les changements climatiques futurs [1], pour comprendre la propagation des tsunamis [2] ou bien le fonctionnement du champ magnétique terrestre [3]. Dans le domaine de l'aéronautique, ces simulations peuvent par exemple être utilisées pour la prédiction du phénomène de décrochage, responsable de la perte des performances aérodynamiques d'un avion [4], ou bien pour l'étude de la propagation acoustique du bruit généré par les aéronefs [5]. ...
... Afin d'accroître la précision du schéma de Roe à l'ordre deux, les états gauche et droit U i+ 1 2 ,G et U i+ 1 2 ,D sont reconstruits à l'aide de la méthode MUSCL. Ce choix conduit à une solution précise au second ordre en espace mais elle amène des oscillations numériques dans les régions de forts gradients. ...
... Si ∆t ≤ ∆t z , alors ∆t z prend la valeur ∆t ∀k ∈ [1,3], si ∆t/2 k ≤ ∆t z ≤ ∆t/2 k−1 alors ∆t z prend la valeur ∆t/2 k La figure 5.7 montre les pas de temps corrigés associés aux différentes zones. ...
La simulation instationnaire d'écoulements turbulents (LES : Large Eddy Simulation, par exemple) reste à l'heure actuelle coûteuse en terme de temps de calcul. Un travail sur les méthodes numériques d'intégration temporelle des équations de la mécanique des fluides peut rendre de type de simulation plus accessible. Les méthodes d'intégration temporelle explicites présentent des propriétés intéressantes telles qu'une bonne précision et une bonne compatibilité avec les techniques HPC (parallélisation, vectorisation...). Néanmoins, le pas de temps de ces méthodes est fortement limité : il est choisi de manière à respecter la contrainte CFL la plus restrictive sur le maillage. Ceci rend ces méthodes généralement très coûteuses. Dans le cas des méthodes explicites à pas de temps local, le pas de temps varie sur le maillage en s'adaptant à différentes contraintes CFL locales. Le pas de temps est plus optimal sur l'ensemble du maillage, ce qui réduit les temps de simulation par rapport à une méthode explicite à pas de temps global (uniforme). Les schémas à pas de temps local de la littérature sont essentiellement utilisés sur des cas-test académiques, et on recense peu d'applications de ces schémas en CFD. L'objectif de cette thèse est de montrer que ce type de schéma peut être utilisé de manière efficace pour la LES. Pour atteindre cet objectif, deux nouveaux schémas à pas de temps local ont d'abord été mis en place. Deux simulations LES ont ensuite été réalisées à l'aide de notre schéma à pas de temps local le plus performant. Ces deux simulations ont démontré la bonne précision et l'efficacité de notre schéma à pas de temps local pour la simulation d'écoulements turbulents.
... Over the last century, the average temperature of the Earth has increased by 0.8ºC [1]. ...
Environment-friendly pigments based on AFeO3 (A = La, Pr, Nd, Sm, Gd, Tb, Y or Yb) with high near-infrared (NIR) reflectance were synthesised by a coprecipitation method at 1200ºC. The Rietveld refinement analysis showed single-phase orthorhombic perovskite for all compositions. All pigments, which showed reddish hues, offered good colour stability after mixing these pigments in powder form with siloxane transparent paint and two different glazes. The powder–paint mixtures produced with GdFeO3, TbFeO3 and YFeO3 pigments have the highest NIR solar reflectance, reaching values of R = 50%. The temperature shielding studies conducted using TbFeO3 pigment–paint mixture for a roof coating yielded a reduction of 3.2ºC in comparison to a commercial pigment. Moreover, the glazes that were pigmented using GdFeO3, TbFeO3 and YFeO3 compositions also presented the most intense reddish colours. A study of the thermal and chemical stability of the pigment with the highest NIR solar reflectance showed good stability in both cases. The reddish pigments that were prepared can therefore be good candidates for use in different applications such as cool pigments or pigments for ceramic glazes at high temperatures.
... However, there are some different voices that have questioned the conclusions of the IPCC (Singers, 2008) To address these disparate viewpoints of global climate change, many studies have been conducted by the scientific community using various modes and methods. The results indicate that only when the atmospheric system is coupled with both natural systems and human activities do climate models could reasonably simulate the evolution of the global average temperature in the 20th century (Barnett et al., 1999;Braganza et al., 2004;Ma et al., 2004;Man et al., 2012;Shi et al., 2016). Hence, there is no doubt that GHGs represent the key factor affecting climate change. ...
In this study, we conducted a literature review of relevant research and then statistically analyzed global greenhouse gas (GHG) emissions from natural systems, including forest fires, oceans, wetlands, permafrost, mud volcanoes, volcanoes, and earthquakes. Drawing on the Global Carbon Project (GCP) report, we also summarized the global anthropogenic GHG emissions. We then compared the global annual GHG emissions from natural systems with those generated by human activity. The results indicate that the global annual GHG emissions range approximately between 54.33 and 75.50 Gt CO2-eq, of which natural emissions account for 18.13–39.30 Gt CO2-eq, with the most likely value being approximately 29.07 Gt CO2-eq. According to the GCP report, the global anthropogenic emissions have increased from 22 Gt CO2-eq in 1990 to 36.2 Gt CO2-eq in 2016. The amounts of natural and anthropogenic GHGs emissions are roughly of the same order of magnitude. Anthropogenic emissions account for approximately 55.46% of the total global GHGs emissions (2016 value), i.e., the ratio of natural to anthropogenic emissions is approximately 0.8. In addition, the annual amount of GHGs absorbed by Earth systems (ocean and terrestrial ecosystems) ranges between approximately 14.4 Gt CO2-eq and 26.5 Gt CO2-eq, with natural system GHG emissions and sinks also having roughly the same order of magnitude. This finding indicates that the GHG emissions generated by human activity exert extra pressure on what is otherwise a self-balancing Earth system. © 2018 National Climate Center (China Meteorological Administration)
... ". Brojni znanstvenici[3]smatraju da je zagrijavanje tijekom 20. stoljeća glavninom uzrokovano povećanjem koncentracije stakleničkih plinova, te da je posebno intenzivirano tijekom kasnih osamdesetih godina prošlog stoljeća. ...
The analysis ofmean annual air temperature series, as measured on 26 weather stations in Croatia, is presented. In this paper, the objective was to study changes In the mean annual air temperature regimen during the available measurement time at individual stations in Croatia. Statistically significant changes, i.e. cases of sudden increase in temperature, first occurred In 1988 on 57.7 percent of stations, and in 1992 on 34.6 percent of the stations. On an average, mean annual air temperatures increased by 0.844°C.
... " . Brojni znanstvenici [3] smatraju da je zagrijavanje tijekom 20. stoljeća glavninom uzrokovano povećanjem koncentracije stakleničkih plinova, te da je posebno intenzivirano tijekom kasnih osamdesetih godina prošlog stoljeća. ...
Ključne riječi srednja godišnja temperatura zraka, promjena klime, varijacija klime, Hrvatska, nagli porast srednje godišnje temperature zraka O. Bonacci Izvorni znanstveni rad Analiza nizova srednjih godišnjih temperatura zraka u Hrvatskoj te 1992. na 34,6 % stanica. Srednje godišnje temperature zraka povećane su prosječno za 0,844 ºC. Key words mean annual air temperature, climate change, climate variation, Croatia, sudden increase in mean annual air temperature O. Bonacci Original scientific paper Analysis of mean annual air temperature series in Croatia The analysis of mean annual air temperature series, as measured on 26 weather stations in Croatia, is presented. In this paper, the objective was to study changes in the mean annual air temperature regimen during the available measurement time at individual stations in Croatia. Statistically significant changes, i.e. cases of sudden increase in temperature, first occurred in 1988 on 57.7 percent of stations, and in 1992 on 34.6 percent of the stations. On an average, mean annual air temperatures increased by 0.844°C.
... This CO 2 was maintained in the atmosphere via volcanic and biological activities (Gaetano 2006). Global warming is becoming an important social issue in addition to being of scientific interest (Ma et al. 2004). On 17 December 2009, the 'Climate Change Summit' held in Copenhagen renewed interest in GHG research worldwide. ...
In Asia, sand dust storms (SDSs) occur nearly every year, especially in northern China. However, there is little research about the relationship between SDSs and greenhouse gases (GHGs). In this article, we selected four SDSs that occurred in Asia in the spring of 2009 and 2010. We monitored the areas covered by these SDSs using Moderate Resolution Imaging Spectroradiometer (MODIS) data, then we used Greenhouse Gases Observing Satellite (GOSAT) data to check how the SDSs affected the concentrations of CO2 and CH4. We then compared the concentrations of CO2 and CH4 on SDS days with the monthly mean values of the months in which SDSs occurred. We also compared the concentrations of CO2 and CH4 on SDS days with the values before and after the SDSs. After analysis, we found that SDSs had increased the concentrations of CO2 and CH4 in the atmosphere. When the SDSs occurred, the concentrations of CO2 and CH4 increased and reached peak values on the last or penultimate days of the storms and then decreased to their normal values. Atmospheric flow is the main reason for the increase in concentration of CO2, and the lack of the free radical (OH) during SDSs and the presence of CH4 sources in southeast China are the main reasons for the increase in concentration of CH4. We also found that in arid and semi-arid areas, SDSs had little effect on the concentration of these two GHGs.
... It has a clear physical interpretation and precise results compareed to traditional line-by-line integration, which is utilized commonly to calculate atmospheric transmittance. The model includes a suitable method for cloud and aerosol radiation parameterization, and reasonably simulates radiative forcing and climate effects of global sulfate and soot aerosols [14][15][16]. Wang et al. [17,18] coupled the dust radiation parameterization scheme including instant dust forecasting concentration and latest dust optical performance into the model, which rapalces the climate values of key radiative parameters including optical thickness, single scattering albedo and dust asymmetry factors with temporal and special changing values on-line calculated by the dust model. It successfully calculated the radiative forcing of aerosols in the East Asia-North Pacific region in northern spring 2001, and evaluated the impact of optical performance of east Asian dust particles on direct radiative forcing and radiative heating rates. ...
Focusing on three dust storms occurring in spring 2001, we developed a detailed aerosol parameterization scheme and integrated
it in a radiative transfer model to characterize possible impacts of solar altitude angle on dust direct radiative effects
over China desert regions and the North Pacific, using actual daily solar altitude angles. Increasing solar altitude angle
from early spring (or winter) to late spring (or summer) leads to increase of positive clear sky radiative forcing, and decrease
of negative radiative forcing due to dust aerosols at the top of the atmosphere. Because solar altitude angle increases from
early to late spring, dust-clear sky radiative forcing may change from negative to positive at the top of atmosphere, showing
a change from cooling to heating of the earth-atmosphere system over high-albedo deserts and nearby regions. Over low-albedo
ocean negative clear sky radiative forcing by dust may decrease, suggesting a change from strong to weak cooling on the earth-atmosphere
system. The impacts of solar altitude angle on cloudy sky radiative forcing due to dust are similar to those of clear sky.
Impacts of low cloud on dust radiative forcing are the same as increasing surface albedo. This causes the transition of dust
cooling effects into heating effects over deserts to occur earlier, and causes decrease of negative radiative forcing over
the ocean and even cause a change from weak negative radiative forcing to weak positive forcing over local areas. Even in
the same East Asian desert regions and nearby areas, the strength and sign of the radiative forcings depend on storm dates
and thus solar altitude angle. The nearer to early spring (or winter) a dust storm occurs, the easier it leads to negative
radiative forcing at the top of atmosphere, which indicates cooling effects on the earth-atmosphere system. In contrast, the
nearer to late spring (or summer) a dust storm occurs, the easier it leads to positive radiative forcing at the top of atmosphere,
showing heating effects. Over East Asian deserts and nearby regions, dust layers may be regarded as cooling sources in early
spring (winter) and warming sources in late spring (summer).
... Chinese scientists have paid considerable effort in the recent several years to address global and East Asian climate changes related to human activities. Ma et al. (2004) employed the IAP/LASG GOALS coupled model, created and developed by the Institute of Atmospheric Physics of the Chinese Academy of Sciences (IAP/CAS) (Zhang et al., 2000;, to simulate 20th century climate changes forced by atmospheric greenhouse gasses, sulfate aerosols, and solar variability. examined the response of the Atlantic thermohaline circulation (THC) to global warming as simulated by the model. ...
The Climate Variability and Predictability (CLIVAR) program is one of the sub-programs of the World Climate Research Program
(WCRP). In this paper, CLIVAR related research in China (2003–2006) is briefly reviewed, including four major components,
namely, low-frequency intraseasonal oscillations, interannual variability, decadal variations in East Asia, and global warming
simulations.
... odel analyses reveal that there exists a time-dependence in the relationship between the East Asian monsoon and SST. The anomalous winter monsoon may have significant correlations with the succeeding summer monsoon, but this relationship may disappear in a different time period. The GOALS model has also been a useful tool in climate change studies. Ma et al. (2004) drove the GOALS model by using historical greenhouse gases concentrations , the mass mixing ratio of sulfate aerosols, and reconstructed solar variations spanning 1900–1997. The model reproduced reasonable temporal and spatial distributions of the temperature change. The global warming during the 20th century is caused mainly by increas ...
A review is presented about the development and application of climate ocean models and oceanatmosphere coupled models developed
in China as well as a review of climate variability and climate change studies performed with these models. While the history
of model development is briefly reviewed, emphasis has been put on the achievements made in the last five years. Advances
in model development are described along with a summary on scientific issues addressed by using these models. The focus of
the review is the climate ocean models and the associated coupled models, including both global and regional models, developed
at the Institute of Atmospheric Physics, Chinese Academy of Sciences. The progress of either coupled model development made
by other institutions or climate modeling using internationally developed models also is reviewed.
This paper gives a definition of earth system model and shows three development phases of it, including physical climate system model, earth climate system model, and earth system model, based on an investigation of climate system models in the world. It provides an expatiation on the strategic significance of future development of earth system model, an introduction of some representative scientific research plans on development of earth system model home and abroad, and a review of its status and trends based on the models of the fourth assessment report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). Some suggestions on future development of earth system model in China are given, which are expected to be helpful to advance the development.
In this paper, the first-ever measurements of the wake of a full-scale wind turbine using an instrumented uninhabited aerial vehicle (UAV) are reported. The key enabler for this novel measurement approach is the integration of fast response aerodynamic probe technology with miniaturized hardware and software for UAVs that enable autonomous UAV operation. The measurements, made to support the development of advanced wind simulation tools, are made in the near-wake (0.5D-3D, where D is rotor diameter) region of a 2 MW wind turbine that is located in a topography of complex terrain and varied vegetation. Downwind of the wind turbine, profiles of the wind speed show that there is strong three-dimensional shear in the near-wake flow. Along the centerline of the wake, the deficit in wind speed is a consequence of wakes from the rotor, nacelle, and tower. By comparison with the profiles away from the centerline, the shadowing effects of nacelle and tower diminish downstream of 2.5D. Away from the centerline, the deficit in wind speed is approximately constant ≈ 25. However, along the centerline, the deficit is ≈ 65 near to the rotor, 0.5D-1.75D, and only decreases to ≈ 25 downstream of 2.5D.
Based on the data of 600 years global above class 5 volcanic explosion index (VEI) and the comparison of the northern hemispheric ground temperature, the western pacific high, the northern Atlantic high and the sea surface temperature anomaly (SSTA) in the northern Atlantic westerly region, it is showed that: (1) The global strong volcano activities have obvious century timescale cycles about 88 and 100 years, accounting for about 21.65% of total variance for VEI, an about 33-year interdecadal timescale cycle, and an 11-year cycle associated with solar activity. (2) The western Pacific subtropical high in July has a 33-year period oscillation accordant to the volcanic activity, which is considered to be the response to the 33-year periodic volcanic activity. (3) In the North Atlantic, the volcanic activities inspire the summer North Atlantic sub-tropical high with 88-year cycle oscillation, winter (January) northern Atlantic westerly region SSTA with 100-year oscillation and summer (July) SSTA 88-year cycle oscillation. (4) Analysis shows that the 88-year periodic variation of northern hemispheric ground temperature is the response to the 88-year cycle of volcanic activity.
This paper gives a definition of earth system model and shows three development phases of it, including physical climate system model, earth climate system model, and earth system model, based on an investigation of climate system models in the world. It provides an expatiation on the strategic significance of future development of earth system model, an introduction of some representative scientific research plans on development of earth system model home and abroad, and a review of its status and trends based on the models of the fourth assessment report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). Some suggestions on future development of earth system model in China are given, which are expected to be helpful to advance the development.
Monthly mean values of climate at Bet Dagan in the central coastal plain
of Israel, downwind of Tel Aviv, were analyzed to yield seasonal and
annual values of long- and short wave irradiance which were then related
to changes in air temperature measured between 1964 and 2010. Over half
the large inter-annual variation and significant increase in atmospheric
long-wave radiation, which averaged 0.7 Wm-2 per decade, was associated
with concurrent changes measured in specific humidity; the remaining
changes, by increases in concentrations of carbon dioxide and other
anthropogenic radiatively active gases. Large decadal variations and a
significant overall reduction in short-wave solar radiation were
measured averaging 3.6 W m-2 per decade which were, in part, attributed
to urban pollution. The resulting strong negative all-wave radiative
forcing averaged 2.9 Wm-2 per decade. Changes in down -welling long and
short wave irradiances together accounted for 58% of inter-annual
variation in the mean annual temperature. Climate sensitivity to
short-wave radiation forcing was very low, 0.0004 0 C per W m-2,
compared with that of long-wave, 0.253 0 C per W m-2, resolving the
paradox of the sharp rise in temperature accompanying negative radiative
forcing. Possible physical mechanisms explaining the decoupling between
annual values of solar irradiance and air temperature are discussed. A
significant, inverse correlation between temperature and the annual
number of rain days was found, accounting for 21 % of the inter-annual
variation in air temperature unexplained by surface radiative forcing.
During the last 45 years changes in annual temperature at Bet Dagan, a
near-coastal site with a strong urban influence situated in the
semi-arid Mediterranean climate, were associated, in the following order
of importance, with changes in water vapor, rainfall and solar
radiation.
We present a simple but effective small unmanned aerial vehicle design that is able to make high-resolution temperature and humidity measurements of the atmospheric boundary layer. The air model used is an adapted commercial design, and is able to carry all the instrumentation (barometer, temperature and humidity sensor, and datalogger) required for such measurements. It is fitted with an autopilot that controls the plane’s ascent and descent in a spiral to 1800 m above ground. We describe the results obtained on three different days when the plane, called Aerolemma-3, flew continuously throughout the day. Surface measurements of the sensible virtual heat flux made simultaneously allowed the calculation of all standard convective turbulence scales for the boundary layer, as well as a rigorous test of existing models for the entrainment flux at the top of the boundary layer, and for its growth. A novel approach to calculate the entrainment flux from the top-down, bottom-up model of Wynagaard and Brost is used. We also calculated temperature fluctuations by means of a spectral high-pass filter, and calculated their spectra. Although the time series are small, tapering proved ineffective in this case. The spectra from the untapered series displayed a consistent −5/3 behaviour, and from them it was possible to calculate a dimensionless dissipation function, which exhibited the expected similarity behaviour against boundary-layer bulk stability. The simplicity, ease of use and economy of such small aircraft make us optimistic about their usefulness in boundary-layer research.
Changes in the mean annual air temperature measured at 67 meteorological
stations in the Balkans during the last 48 (from 1961 to 2008) to 158
(from 1851 to 2008) years were investigated. This presentation is an
attempt to show variability of regional climate using available
relatively long-term time series of mean annual air temperature. The
problem of causes (anthropogenic or natural) of the air temperature
increase in the analysed region will not be discussed. The main purpose
is to analyse records of air temperature during the 20th century in
order to identify timing and magnitude of increase of air temperature
observed in last twentieth years. Methods of rescaled adjusted partial
sums (RAPS), regression and correlation analyses as well as F- and
t-tests are used in order to describe changes in air temperature
regimes. The analyses indicated that the most frequently statistically
significant changes started in 1988 (at 34 gauging station or 50.7 %)
and in 1992 (at 16 gauging station or 23.9 %). It was calculated that
the increases of average mean annual air temperatures in period before
and after warming is 0.807 °C ranging from the minimum value of
-0.11 °C (decreasing) to the maximum value of 1.56 °C
(increasing).
This volume of IOP Conference Series: Earth and Environmental Science presents a selection of papers that were given at the 24th Conference of the Danube Countries. Within the framework of the International Hydrological Program IHP of UNESCO. Since 1961 the Danube countries have successfully co-operated in organizing conferences on Hydrological Forecasting and Hydrological Water Management Issues. The 24th Conference of the Danube Countries took place between 2–4 June 2008 in Bled, Slovenia and was organized by the National Committee of Slovenia for the International Hydrological Program of UNESCO, under the auspices of the President of Republic of Slovenia. It was organized jointly by the Slovenian National Commission for UNESCO and the Environmental Agency of the Republic of Slovenia, under the support of UNESCO, WMO, and IAHS. Support for the attendance of some participants was provided by UNESCO. Additional support for the symposium was provided by the Slovene Commission for UNESCO, Environmental Agency of Slovenia, Karst Research Institute, Hydropower plants on the lower Sava River and Chair of Hydraulics Engineering FGG University of Ljubljana. All participants expressed great interest and enthusiasm in presenting the latest research results and sharing practical experiences in the Hydrology of the Danube River basin. The Editorial Board, who were nominated at the Conference, initially selected 80 full papers for publication from 210 submitted extended abstracts and papers provided by authors from twenty countries. Altogether 51 revised papers were accepted for publishing in this volume. Papers are divided by conference topics: Hydrological forecasting Hydro-meteorological extremes, floods and droughts Global climate change and antropogenic impacts on hydrological processes Water management Floods, morphological processes, erosion, sediment transport and sedimentation Developments in hydrology Mitja Brilly, Ognjen Bonacci, Peter Hans Nachtnebel, Ján Szolgay and Gabor Balint Editorial Board International Scientific Committee: P Hubert: Centre d'Informatique Géologique, France H P Nachtnebel: Universität für Bodenkultur Wien, Austria H Weber: Bavarian Water Management Administration, Germany H Moser: Federal Institute of Hydrology, Germany M Domokos: VITUKI, Hungary P Stanciu: National Institute of Meteorology and Hydrology, Romania O Bonacci: University of Split, Croatia S Prohaska: Institute Jaroslav Černi, Belgrade, Serbia J Szolgay: Faculty of Civil Engineering, Bratislava, Slovak Republic K Tzankov: Institute of Meteorology and Hydrology, Sofia, Bulgaria E Soukalová: Czech Hydrometeorological Institute, Czech Republic B Matičič: National Committee on Irrigation and Drainage, Slovenia M Mikoš: University of Ljubljana, Ljubljana, Slovenia J Rakovec: University of Ljubljana, Ljubljana, Slovenia M Brilly: University of Ljubljana, Ljubljana, Slovenia M Veselič: ARAO, Slovenia
The meteorological mini unmanned aerial vehicle (M2AV) was used for measuring the meteorological wind. The wind is the vector difference between the aircraft speed relative to the earth (inertial velocity) and relative to the airflow (true airspeed). The latter was computed from five-hole-probe pressure measurements in combination with calibration–coefficient polynomials obtained during wind tunnel calibration. The aircraft inertial velocity, position, and attitude were calculated using a Kalman filter that combined data from a global positioning system (GPS) and an inertial navigation system (INS). The temporal (and spatial) resolution of the M2AV wind measurement is remarkably fine. An inertial subrange of locally isotropic turbulence can be measured up to 40 Hz (or 0.55 m at 22 m s−1 airspeed).
The first M2AV wind estimation showed some systematic deviations compared to the expected values (like a constant mean wind in every flight direction). Therefore, an in-flight wind calibration technique was developed that corrects for the inaccuracy of the true heading, the constant offset of the pitch angle, and the underestimation of the true airspeed. The final adjusted wind measurements were verified during a field experiment at the measurement field of the German Meteorological Service, southeast of Berlin. The mean horizontal and vertical wind measured by the M2AV agreed well with simultaneous sodar and tower measurements.
The structure parameter of temperature, CT2{C_{T}^{2}} , in the lower convective boundary layer was measured using the unmanned mini aerial vehicle M2AV. The measurements were carried out on two hot summer days in July 2010 over a heterogeneous land surface around the boundary-layer
field site of the Lindenberg Meteorological Observatory—Richard-Aßmann-Observatory of the German Meteorological Service. The
spatial series of CT2{C_{T}^{2}} showed considerable variability along the flight path that was caused by both temporal variations and surface heterogeneity.
Comparison of the aircraft data with CT2{C_{T}^{2}} values derived from tower-based in situ turbulence measurements showed good agreement with respect to the diurnal variability. The decrease of CT2{C_{T}^{2}} with height as predicted by free-convection scaling could be confirmed for the morning and afternoon flights while the flights
around noon suggest a different behaviour.
KeywordsHeterogeneous surface–Spatial averaging–Temperature structure parameter–Unmanned aerial vehicle
Coupled ocean-atmospheric general circulation models are the only tools to quantitatively simulate the climate system. Since
the end of the 1980s, a group of scientists in the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and
Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), have been working
to develop a global OGCM and a global coupled ocean-atmosphere general circulation model (CGCM). From the original flux anomaly-coupling
model developed in the beginning of the 1990s to the latest directly-coupling model, LASG scientists have developed four global
coupled GCMs. This study summarizes the development history of these models and describes the third and fourth coupled GCMs
and selected applications. Strengths and weaknesses of these models are highlighted.
Several scenario experiments of the IPCC 4th Assessment Report (AR4) are performed by version g1.0 of a Flexible coupled Ocean-Atmosphere-Land
System Model (FGOALS) developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS), including
the “Climate of the 20th century experiment”, “CO2 1% increase per year to doubling experiment” and two separate IPCC greenhouse gases emission scenarios A1B and B1 experiments.
To distinguish between the different impacts of natural variations and human activities on the climate change, three-member
ensemble runs are performed for each scenario experiment. The coupled model simulations show: (1) from 1900 to 2000, the global
mean temperature increases about 0.5°C and the major increase occurs during the later half of the 20th century, which is in
consistent with the observations that highlights the coupled model’s ability to reproduce the climate changes since the industrial
revolution; (2) the global mean surface air temperature increases about 1.6°C in the CO2 doubling experiment and 1.5°C and 2.4°C in the A1B and B1 scenarios, respectively. The global warming is indicated by not
only the changes of the surface temperature and precipitation but also the temperature increase in the deep ocean. The thermal
expansion of the sea water would induce the rise of the global mean sea level. Both the control run and the 20th century climate
change run are carried out again with version g1.1 of FGOALS, in which the cold biases in the high latitudes were removed.
They are then compared with those from version g1.0 of FGOALS in order to distinguish the effect of the model biases on the
simulation of global warming.
The analysis of mean annual air temperature series, as measured on 26 weather stations in Croatia, is presented. In this paper, the objective was to study changes in the mean annual air temperature regimen during the available measurement time at individual stations in Croatia. Statistically significant changes, i.e. cases of sudden increase in temperature, first occurred in 1988 on 57.7 percent of stations, and in 1992 on 34.6 percent of the stations. On an average, mean annual air temperatures increased by 0.844°C.
In a recent paper, Han et al. analyzed satellite data radiances to retrieve cloud droplet effective radii and reported significant interhemispheric differences for both maritime and continental clouds. The mean cloud droplet radius in the Northern Hemisphere is smaller than in the Southern Hemisphere by about 0.7 [mgr]m. This hemispheric contrast suggests the presence of an aerosol effect on cloud droplet size and is consistent with higher cloud condensation nuclei number concentration in the Northern Hemisphere due to anthropogenic production of aerosol precursors. In the present study, we constrain a climate model with the satellite retrievals of Han et al. and discuss the climate forcing that can be inferred from the observed distribution of cloud droplet radius. Based on two sets of experiments, this sensitivity study suggests that the indirect radiative forcing by anthropogenic aerosols could he about 0.6 or 1 W m2 averaged in the 0°-50°N latitude band. The uncertainty of these estimates is difficult to a assess but is at least 50%.
Solar total and ultraviolet (UV) irradiances are reconstructed annually from 1610 to the present. This epoch includes the Maunder Minimum of anomalously low solar activity (circa 1645-1715) and the subsequent increase to the high levels of the present Modern Maximum. In this reconstruction, the Schwabe (11-year) irradiance cycle and a longer term variability component are determined separately, based on contemporary solar and stellar monitoring. The correlation of reconstructed solar irradiance and Northern Hemisphere (NH) surface temperature is 0.86 in the pre-industrial period from 1610 to 1800, implying a predominant solar influence. Extending this correlation to the present suggests that solar forcing may have contributed about half of the observed 0.55°C surface warming since 1860 and one third of the warming since 1970.
Spatially resolved global reconstructions of annual surface temperature
patterns over the past six centuries are based on the multivariate calibration
of widely distributed high-resolution proxy climate indicators. Time-dependent
correlations of the reconstructions with time-series records representing
changes in greenhouse-gas concentrations, solar irradiance, and volcanic aerosols
suggest that each of these factors has contributed to the climate variability
of the past 400 years, with greenhouse gases emerging as the dominant forcing
during the twentieth century. Northern Hemisphere mean annual temperatures
for three of the past eight years are warmer than any other year since (at
least) ad 1400.
Abstract. We review the surface air temperature
record of the past 150 years, considering the homogeneity
of the basic data and the standard errors of estimation
of the average hemispheric and global estimates.
We present global fields of surface temperature change
over the two 20-year periods of greatest warming this
century, 1925–1944 and 1978–1997. Over these periods,
global temperatures rose by 0.378 and 0.328C, respectively.
The twentieth-century warming has been accompanied
by a decrease in those areas of the world affected
by exceptionally cool temperatures and to a lesser extent
by increases in areas affected by exceptionally warm
temperatures. In recent decades there have been much
greater increases in night minimum temperatures than
in day maximum temperatures, so that over 1950–1993
the diurnal temperature range has decreased by 0.088C
per decade. We discuss the recent divergence of surface
and satellite temperature measurements of the lower
troposphere and consider the last 150 years in the context
of the last millennium. We then provide a globally
complete absolute surface air temperature climatology
on a 18 3 18 grid. This is primarily based on data for
1961–1990. Extensive interpolation had to be undertaken
over both polar regions and in a few other regions
where basic data are scarce, but we believe the climatology
is the most consistent and reliable of absolute surface
air temperature conditions over the world. The
climatology indicates that the annual average surface
temperature of the world is 14.08C (14.68C in the Northern
Hemisphere (NH) and 13.48C for the Southern
Hemisphere). The annual cycle of global mean temperatures
follows that of the land-dominated NH, with a
maximum in July of 15.98C and a minimum in January of
12.28C.
A comprehensive analysis of the simple biosphere model (SIB) of Sellers et al. (1986) is performed in an effort to bridge the gap between the typical hydrological treatment of the land surface biosphere and the conventional general circulation model treatment, which is specified through a single parameter. Approximations are developed that stimulate the effects of reduced soil moisture more simply, maintaining the essence of the biophysical concepts utilized in SIB. Comparing the reduced parameter biosphere with those from the original formulation in a GCM and a zero-dimensional model shows the simplified version to reproduce the original results quite closely.
From satellite observations the solar total irradiance is known to vary. Sunspot blocking, facular emission, and network emission are three identified causes for the variations. In this paper we examine several different solar indices measured over the past century that are potential proxy measures for the Sun's irradiance. These indices are (1) the equatorial solar rotation rate, (2) the sunspot structure, the decay rate of individual sunspots, and the number of sunspots without umbrae, and (3) the length and decay rate of the sunspot cycle. Each index can be used to develop a model for the Sun's total irradiance as seen at the Earth. Three solar indices allow the irradiance to be modeled back to the mid-1700s. The indices are (1) the length of the solar cycle, (2) the normalized decay rate of the solar cycle, and (3) the mean level of solar activity. All the indices are well correlated, and one possible explanation for their nearly simultaneous variations is changes in the Sun's convective energy transport. Although changes in the Sun's convective energy transport are outside the realm of normal stellar structure theory (e.g., mixing length theory), one can imagine variations arising from even the simplest view of sunspots as vertical tubes of magnetic flux, which would serve as rigid pillas affecting the energy flow patterns by ensuring larger-scale eddies. A composite solar irradiance model, based upon these proxies, is compared to the northern hemisphere temperature depatures for 1700-1992. Approximately 71% of the decadal variance in the last century can be modeled with these solar indices, although this analysis does not include anthropogenic or other variations which would affect the results. Over the entire three centuries, approx. 50% of the variance is modeled. Both this analysis and previous similar analyses have correlations of model solar irradiances and measured Earth surface temperatures that are significant at better than the 95% confidence level. To understand our present climate variations, we must place the anthropogenic variations in the context of natural variability from solar, volcanic, oceanic, and other sources.
A global coupled ocean-atmosphere general circulation model without flux
correction is integrated in a set of 75 year sensitivity experiments
where the indirect forcing effect of sulfate aerosols is included for
the first time in combination with transient greenhouse gas forcing and
the direct effect of sulfate aerosols. Sulfate aerosol forcing increases
from zero to present-day estimates in the first 30 years of the
integrations while equivalent CO2 forcing increases by 1% per
year relative to the control experiment, similar to the rate of increase
of observed greenhouse gas forcing over the period 1960-1990.
Annual mean averages around year 30, analogous to present-day
conditions, indicate better agreement with recent observed geographic
and zonal mean temperature anomaly patterns in the sulfate aerosol
experiments and less warming in northern summer than winter. Sulfate
aerosols then are increased following the IS92a scenario, while
CO2 continues to increase at 1% per year. Averages around
year 65, analogous to conditions roughly 35 years in the future,
indicate warming almost everywhere in the troposphere over the globe as
the CO2 forcing overwhelms the negative radiative forcing
from the sulfate aerosols. There is also a general indication of
weakening of the south Asian monsoon in the sulfate aerosol experiments.
There is qualitative agreement in the patterns of the temperature
changes, both geographic and zonal, between the different sulfate
aerosol experiments, with the magnitude of the changes a function of the
size of the forcing.
Using a coupled atmosphere/ocean general circulation model, we have simulated the climatic response to natural and anthropogenic forcings from 1860 to 1997. The model, HadCM3, requires no flux adjustment and has an interactive sulphur cycle, a simple parameterization of the effect of aerosols on cloud albedo (first indirect effect), and a radiation scheme that allows explicit representation of well-mixed greenhouse gases. Simulations were carried out in which the model was forced with changes in natural forcings (solar irradiance and stratospheric aerosol due to explosive volcanic eruptions), well-mixed greenhouse gases alone, tropospheric anthropogenic forcings (tropospheric ozone, well-mixed greenhouse gases, and the direct and first indirect effects of sulphate aerosol), and anthropogenic forcings (tropospheric anthropogenic forcings and stratospheric ozone decline). Using an ``optimal detection'' methodology to examine temperature changes near the surface and throughout the free atmosphere, we find that we can detect the effects of changes in well-mixed greenhouse gases, other anthropogenic forcings (mainly the effects of sulphate aerosols on cloud albedo), and natural forcings. Thus these have all had a significant impact on temperature. We estimate the linear trend in global mean near-surface temperature from well-mixed greenhouse gases to be 0.9 +/- 0.24 K/century, offset by cooling from other anthropogenic forcings of 0.4 +/- 0.26 K/century, giving a total anthropogenic warming trend of 0.5 +/- 0.15 K/century. Over the entire century, natural forcings give a linear trend close to zero. We found no evidence that simulated changes in near-surface temperature due to anthropogenic forcings were in error. However, the simulated tropospheric response, since the 1960s, is ~50% too large. Our analysis suggests that the early twentieth century warming can best be explained by a combination of warming due to increases in greenhouse gases and natural forcing, some cooling due to other anthropogenic forcings, and a substantial, but not implausible, contribution from internal variability. In the second half of the century we find that the warming is largely caused by changes in greenhouse gases, with changes in sulphates and, perhaps, volcanic aerosol offsetting approximately one third of the warming. Warming in the troposphere, since the 1960s, is probably mainly due to anthropogenic forcings, with a negligible contribution from natural forcings.
CLIMATE models suggest that increases in greenhouse-gas concentrations in the atmosphere should have produced a larger global mean warming than has been observed in recent decades, unless the climate is less sensitive than is predicted by the present generation of coupled general circulation models1,2. After greenhouse gases, sulphate aerosols probably exert the next largest anthropogenic radiative forcing of the atmosphere3, but their influence on global mean warming has not been assessed using such models. Here we use a coupled oceaná¤-atmosphere general circulation model to simulate past and future climate since the beginning of the near-global instrumental surface-temperature record4, and include the effects of the scattering of radiation by sulphate aerosols. The inclusion of sulphate aerosols significantly improves the agreement with observed global mean and large-scale patterns of temperature in recent decades, although the improvement in simulations of specific regions is equivocal. We predict a future global mean warming of 0.3 K per decade for greenhouse gases alone, or 0.2 K per decade with sulphate aerosol forcing included. By 2050, all land areas have warmed in our simulations, despite strong negative radiative forcing in some regions. These model results suggest that global warming could accelerate as greenhouse-gas forcing begins to dominate over sulphate aerosol forcing.
This study investigates changes in surface air temperature (SAT), hydrology and the thermohaline circulation due to the the radiative forcing of anthropogenic greenhouse gases and the direct radiative forcing (DRF) of sulfate aerosols in the GFDL coupled ocean-atmosphere model. Three 300-year model integrations are performed with increasing greenhouse gas concentrations only, increasing sulfate aerosol concentrations only and increasing greenhouse gas and sulfate aerosol concentrations. A control integration is also performed keeping concentrations of sulfate and carbon dioxide fixed. The global annual mean SAT change when both greenhouse gases and sulfate aerosols are included is in better agreement with observations than when greenhouse gases alone are included. When the global annual mean SAT change from a model integration that includes only increases in greenhouse gases is added to that from a model integration that includes only increases in sulfate, the resulting global SAT change is approximately equal to that from a model integration that includes increases in both greenhouse gases and sulfate aerosol throughout the integration period. Similar results are found for global annual mean precipitation changes and for the geographical distribution of both SAT and precipitation changes indicating that the climate response is linearly additive for the two types of forcing considered here. Changes in the mid-continental summer dryness and thermohaline circulation are also briefly discussed.
We evaluate aerosol indirect radiative forcing simulated by the Model for Integrated Research on Atmospheric Global Exchange (MIRAGE). Although explicit measurements of aerosol indirect radiative forcing do not exist, measurements of many of the links between aerosols and indirect radiative forcing are available and can be used for evaluation. These links include the cloud condensation nuclei concentration, the ratio of droplet number to aerosol number, the droplet number concentration, the column droplet number, the column cloud water, the droplet effective radius, the cloud optical depth, the correlation between cloud albedo and droplet effective radius, and the cloud radiative forcing. The CCN concentration simulated by MIRAGE agrees with measurements for supersaturations larger than 0.1% but not for smaller supersaturations. Simulated droplet number concentrations are too low in most but not all locations with available measurements, even when normalized by aerosol number. MIRAGE correctly simulates the higher droplet numbers and smaller droplet sizes over continents and in the Northern Hemisphere. Biases in column cloud water, cloud optical depth, and shortwave cloud radiative forcing are evident in the Intertropical Convergence Zone and in the subtropical oceans. MIRAGE correctly simulates a negative correlation between cloud albedo and droplet size over remote oceans for cloud optical depths greater than 15 and a positive correlation for cloud optical depths less than 15 but fails to simulate a negative correlation over land.
A variety of measurements have been used to evaluate the treatment of aerosol radiative properties and radiative impacts of aerosols simulated by the Model for Integrated Research on Atmospheric Global Exchange (MIRAGE). The treatment of water uptake in MIRAGE agrees with laboratory measurements, and the growth of aerosol extinction with relative humidity in MIRAGE simulations agrees with field measurements. The simulated frequency of relative humidity near 100% is about twice that of analyzed relative humidity. When the analyzed relative humidity is used to calculate aerosol water uptake in MIRAGE, the simulated aerosol optical depth agrees with most surface measurements after cloudy conditions are filtered out and differences between model and station elevations are accounted for, but simulated optical depths are too low over Brazil and central Canada. Simulated optical depths are mostly within a factor of 2 of satellite estimates, but are too high off the east coasts of the United States and China and too low off the coast of West Africa and in the Arabian Sea. The simulated single-scatter albedo is consistent with surface measurements. MIRAGE correctly simulates a larger Ångström exponent near regions with emissions of submicron particles and aerosol precursor gases, and a smaller exponent near regions with emissions of coarse particles. The simulated sensitivity of radiative forcing to aerosol optical depth is consistent with estimates from measurements. The simulated direct forcing is within the uncertainty of estimates from measurements in the North Atlantic.
The indirect effect of anthropogenic aerosols, whereby aerosol particles change cloud optical properties, is the most uncertain component of climate forcing over the past 100 years. Here we use a mechanistic treatment of droplet nucleation and a prognostic treatment of the number of cloud droplets to study the indirect aerosol effect from changes in carbonaceous and sulfate aerosols. Cloud droplet nucleation is parameterized as a function of total aerosol number concentration, updraft velocity, and an activation parameter, which takes into account the mechanism of sulfate aerosol formation. Where previous studies focussed either on sulfate aerosols or carbonaceous aerosols only, here we estimate the combined effect. The combined indirect aerosol effect amounts to -1.1 W m-2 for an internally mixed aerosol and -1.5 W m-2 for an externally mixed aerosol compared to -1.4 W m-2, which we obtained by empirically relating sulfate mass to cloud droplet number. In the case of an internally mixed aerosol, the contribution from increasing carbonaceous and sulfate aerosols is close to being additive as the individual simulations yield an indirect effect of -0.4 W m-2 due to anthropogenic sulfate aerosols and -0.9 W m-2 due to anthropogenic carbonaceous aerosols. The contribution of anthropogenic sulfate to the indirect effect is close to zero if an externally mixed aerosol is assumed, while the contribution of carbonaceous aerosols increases to -1.3 W m-2. The effect of sulfate in the external mixture approach is much smaller than that of carbonaceous aerosols because its burden only increases by a third of that of carbonaceous aerosols and because the mode radius of sulfate is much larger than that of black and organic carbon.
ABSTRACT The Climate System Model, a coupled global climate model without ‘‘flux adjustments’’ recently developed at the National Center for Atmospheric Research, was used to simulate the twentieth-century climate using historical greenhouse,gas and sulfate aerosol forcing. This simulation was,extended,through the twenty-first century under two newly developed scenarios, a business-as-usual case (ACACIA-BAU, CO2 710 ppmv in 2100) and a CO2 stabilization case (STA550, CO 2 540 ppmv in 2100). Here we compare the simulated and observed twentieth-century climate, and then describe the simulated climates for the twenty-first century. The model,simulates the spatial and temporal,variations of the twentieth-century climate reasonably well. These include the rapid rise in global and zonal mean surface temperatures since the late 1970s, the precipitation increases over northern mid- and high-latitude land areas, ENSO-induced precipitation anomalies, and Pole‐ midlatitude oscillations (such as the North Atlantic oscillation) in sea level pressure fields. The model,has a cold bias (28‐68C) in surface air temperature over land, overestimates of cloudiness (by 10%‐30%) over land, and underestimates,of marine stratus clouds to the west of North and South America and Africa. The projected global surface warming,from the 1990s to the 2090s is ;1.98C under the BAU scenario and ;1.58C under the STA550 scenario. In both cases, the midstratosphere cools due to the increase in CO 2, whereas the lower stratosphere warms in response to recovery of the ozone layer. As in other coupled models, the surface warming,is largest at winter high latitudes ($5.08C from the 1990s to the 2090s) and smallest (;1.08C) over the southern oceans, and is larger over land areas than ocean areas. Globally averaged precipitation increases by ;3.5% (3.0%) from the 1990s to the 2090s in the BAU (STA550) case. In the BAU case, large precipitation increases (up to 50%) occur over northern mid- and high latitudes and over India and the Arabian Peninsula. Marked differences occur between,the BAU and STA550 regional precipitation changes resulting from inter- decadal variability. Surface evaporation increases at all latitudes except for 60 8‐908S. Water vapor from increased tropical evaporation is transported into mid- and high latitudes and returned to the surface through increased precipitation there. Changes in soil moisture content are small (within 63%). Total cloud cover changes little, although there is an upward,shift of midlevel clouds. Surface diurnal temperature range decreases by about 0.28‐ 0.58C over most land areas. The 2‐8-day synoptic storm activity decreases (by up to 10%) at low latitudes and over midlatitude oceans, but increases over Eurasia and Canada. The cores of subtropical jets move slightly up- and equatorward. Associated with reduced latitudinal temperature gradients over mid- and high latitudes, the wintertime Ferrel cell weakens (by 10%‐15%). The Hadley circulation also weakens (by ;10%), partly due to
The time-dependent climate response to changing concentrations of greenhouse gases and sulfate aerosols is studied using a coupled general circulation model of the atmosphere and the ocean (ECHAM4/OPYC3). The concentrations of the well-mixed greenhouse gases like CO2, CH4, N2O, and CFCs are prescribed for the past (1860-1990) and projected into the future according to International Panel on Climate Change (IPCC) scenario IS92a. In addition, the space-time distribution of tropospheric ozone is prescribed, and the tropospheric sulfur cycle is calculated within the coupled model using sulfur emissions of the past and projected into the future (IS92a). The radiative impact of the aerosols is considered via both the direct and the indirect (i.e., through cloud albedo) effect. It is shown that the simulated trend in sulfate deposition since the end of the last century is broadly consistent with ice core measurements, and the calculated radiative forcings from preindustrial to present time are within the uncertainty range estimated by IPCC. Three climate perturbation experiments are performed, applying different forcing mechanisms, and the results are compared with those obtained from a 300-yr unforced control experiment. As in previous experiments, the climate response is similar, but weaker, if aerosol effects are included in addition to greenhouse gases. One notable difference to previous experiments is that the strength of the Indian summer monsoon is not fundamentally affected by the inclusion of aerosol effects. Although the monsoon is damped compared to a greenhouse gas only experiment, it is still more vigorous than in the control experiment. This different behavior, compared to previous studies, is the result of the different land-sea distribution of aerosol forcing. Somewhat unexpected, the intensity of the global hydrological cycle becomes weaker in a warmer climate if both direct and indirect aerosol effects are included in addition to the greenhouse gases. This can be related to anomalous net radiative cooling of the earth's surface through aerosols, which is balanced by reduced turbulent transfer of both sensible and latent heat from the surface to the atmosphere.
Two simulations, one for the control run and another for the
perturbation run, with a global coupled
ocean—atmosphere—land system model (IAP/ LASG GOALS version
4) have been carried out to study the global warming, with much detailed
emphasis on East Asia. Results indicate that there is no climate drift
in the control run and at the time of CO2 doubling the global
temperature increases about 1.65°C. The GOALS model is able to
simulate the observed spatial distribution and annual cycles of
temperature and precipitation for East Asia quite well. But, in general,
the model underestimates temperature and overestimates rainfall amount
for regional annual average. For the climate change in East Asia, the
temperature and precipitation in East Asia increase 2.1°C and 5%
respectively, and the maximum warming occurs at middle—latitude
continent and the maximum precipitation increase occurs around 25°N
with reduced precipitation in the tropical western Pacific.
Observations of the Earth's near-surface temperature show a global-mean temperature increase of approximately 0.6 K since 1900 (ref. 1), occurring from 1910 to 1940 and from 1970 to the present. The temperature change over the past 30–50 years is unlikely to be entirely due to internal climate variability2, 3, ⁴ and has been attributed to changes in the concentrations of greenhouse gases and sulphate aerosols⁵ due to human activity. Attribution of the warming early in the century has proved more elusive. Here we present a quantification of the possible contributions throughout the century from the four components most likely to be responsible for the large-scale temperature changes, of which two vary naturally (solar irradiance and stratospheric volcanic aerosols) and two have changed decisively due to anthropogenic influence (greenhouse gases and sulphate aerosols). The patterns of time/space changes in near-surface temperature due to the separate forcing components are simulated with a coupled atmosphere–ocean general circulation model, and a linear combination of these is fitted to observations. Thus our analysis is insensitive to errors in the simulated amplitude of these responses. We find that solar forcing may have contributed to the temperature changes early in the century, but anthropogenic causes combined with natural variability would also present a possible explanation. For the warming from 1946 to 1996 regardless of any possible amplification of solar or volcanic influence, we exclude purely natural forcing, and attribute it largely to the anthropogenic components.
Keywordsglobal-mean temperature-greenhouse gases-sources of natural climate variability
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.
The atmospheric general circulation model ECHAM-4 is coupled to a chemistry model to calculate sulfate mass distribution
and the radiative forcing due to sulfate aerosol particles. The model simulates the main components of the hydrological cycle
and, hence, it allows an explicit treatment of cloud transformation processes and precipitation scavenging. Two experiments
are performed, one with pre-industrial and one with present-day sulfur emissions. In the pre-industrial emission scenario
SO2 is oxidized faster to sulfate and the in-cloud oxidation via the reaction with ozone is more important than in the present-day
scenario. The atmospheric sulfate mass due to anthropogenic emissions is estimated as 0.38 Tg sulfur. The radiative forcing
due to anthropogenic sulfate aerosols is calculated diagnostically. The backscattering of shortwave radiation (direct effect)
as well as the impact of sulfate aerosols on the cloud albedo (indirect effect) is estimated. The model predicts a direct
forcing of −0.35 W m-2 and an indirect forcing of −0.76 W m-2. Over the continents of the Northern Hemisphere the direct forcing amounts to −0.64 W m-2. The geographical distribution of the direct and indirect effect is very different. Whereas the direct forcing is strongest
over highly polluted continental regions, the indirect forcing over sea exceeds that over land. It is shown that forcing estimates
based on monthly averages rather than on instantaneous sulfate pattern overestimate the indirect effect but have little effect
on the direct forcing.
The distribution of unmyelinated nerve fiber in the ovary of amphioxus was found with transmission electron microscopic technique
for the first time. The fiber is located under the ovary coat, and in close contact with it. There are two types of synaptic
vesicles in the terminals of nerve fiber: one is durse-cored vesicle, the other is clear vesicle. In addition, the nerve terminals
contact with follicle cells of ovary can be seen. Using immunohistochemical method. it is further demonstrated that the unmyelited
nerve fiber nlay be a noradrenergic nerve fiber which is located on the ovary coat and follicle cell.
The climates simulated by 15 coupled atmosphere/ocean climate models participating in the first phase of the Coupled Model
Intercomparison Project (CMIP1) are intercompared and evaluated. Results for global means, zonal averages, and geographical
distributions of basic climate variables are assembled and compared with observations. The current generation of climate models
reproduce the major features of the observed distribution of the basic climate parameters, but there is, nevertheless, a considerable
scatter among model results and between simulated and observed values. This is particularly true for oceanic variables. Flux
adjusted models generally produce simulated climates which are in better accord with observations than do non-flux adjusted
models; however, some non-flux adjusted model results are closer to observations than some flux adjusted model results. Other
model differences, such as resolution, do not appear to provide a clear distinction among model results in this generation
of models. Many of the systematic differences (those differences common to most models), evident in previous intercomparison
studies are exhibited also by the CMIP1 group of models although often with reduced magnitudes. As is characteristic of intercomparison
results, different climate variables are simulated with different levels of success by different models and no one model is
“best” for all variables. There is some evidence that the “mean model” result, obtained by averaging over the ensemble of
models, provides an overall best comparison to observations for climatological mean fields. The model deficiencies identified
here do not suggest immediate remedies and the overall success of the models in simulating the behaviour of the complex non-linear
climate system apparently depends on the slow improvement in the balance of approximations that characterize a coupled climate
model. Of course, the results of this and similar studies provide only an indication, at a particular time, of the current
state and the moderate but steady evolution and improvement of coupled climate models.
Human activity has perturbed the Earth's energy balance by altering the properties of the atmosphere and the surface. This perturbation is of a size that would be expected to lead to significant changes in climate. In recent years, an increasing number of possible human-related climate change mechanisms have begun to be quantified. This paper reviews developments in radiative forcing that have occurred since the second assessment report of the Intergovernmental Panel on Climate Change (IPCC), and proposes modifications to the values of global-mean radiative forcings since pre-industrial times given by IPCC. The forcing mechanisms which are considered here include those due to changes in concentrations of well-mixed greenhouse gases, tropospheric and stratospheric ozone, aerosols composed of sulphate, soot, organics and mineral dust (including their direct and indirect effects), and surface albedo. For many of these mechanisms, the size, spatial pattern and, for some, even the sign of their effect remain uncertain. Studies which have attributed observed climate change to human activity have considered only a subset of these mechanisms; their conclusions may not prove to be robust when a broader set is included.
Recent work suggests a discernible human influence on climate. This finding is supported, with less restrictive assumptions
than those used in earlier studies, by a 1961 through 1995 data set of radiosonde observations and by ensembles of coupled
atmosphere-ocean simulations forced with changes in greenhouse gases, tropospheric sulfate aerosols, and stratospheric ozone.
On balance, agreement between the simulations and observations is best for a combination of greenhouse gas, aerosol, and ozone
forcing. The uncertainties remaining are due to imperfect knowledge of radiative forcing, natural climate variability, and
errors in observations and model response.
Calculations of the effects of both natural and anthropogenic tropospheric sulfate aerosols indicate that the aerosol climate forcing is sufficiently large in a number of regions of the Northern Hemisphere to reduce significantly the positive forcing from increased greenhouse gases. Summer sulfate aerosol forcing in the Northern Hemisphere completely offsets the greenhouse forcing over the eastern United States and central Europe. Anthropogenic sulfate aerosols contribute a globally averaged annual forcing of -0.3 watt per square meter as compared with +2.1 watts per square meter for greenhouse gases. Sources of the difference in magnitude with the previous estimate of Charlson et al. are discussed.
The simulation of climatic effects induced by external forcing factors
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The simulation of climatic effects induced by external forcing factors. Ph. D dissertation, Institute of Atmospheric Physics
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Ma Xiaoyan, 2002: The simulation of climatic effects induced by external forcing factors. Ph. D dissertation,
Institute of Atmospheric Physics, Chinese Academy
of Sciences, 17-76. (in Chinese)
LASG global ocean-atmosphere-land system model (GOALS/LASG) and its performance
- Wu Guoxiong
- Zhang Xuehong
- Liu Hui
- Yu Yongqiang
- Jin Xiangze
- Guo Yufu
- Sun Shufen
- Li Weiping
Wu Guoxiong, Zhang Xuehong, Liu Hui, Yu Yongqiang,
Jin Xiangze, Guo Yufu, Sun Shufen, and Li Weiping,
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of Applied Meteorology, 8(Suppl), 15-28. (in Chinese)
IAP Global Ocean Atmosphere Land System Model
- Zhang Xuehong
- Shi Guangyu
- Liu Hui
- Yu Yongqiang
The numerical calculation of radiative forcing of sulfate and black carbon. Ph. D dissertation of the Institute of Atmospheric Physics
- Zhang Lisheng
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(in Chinese)