Climate change projections of the North American Regional Climate Change Assessment Program (NARCCAP)

We investigate major results of the NARCCAP multiple regional climate model (RCM) experiments driven by multiple global climate models (GCMs) regarding climate change for seasonal temperature and precipitation over North America. We focus on two major questions: How do the RCM simulated climate changes differ from those of the parent GCMs and thus affect our perception of climate change over North America, and how important are the relative contributions of RCMs and GCMs to the uncertainty (variance explained) for different seasons and variables? The RCMs tend to produce stronger climate changes for precipitation: larger increases in the northern part of the domain in winter and greater decreases across a swath of the central part in summer, compared to the four GCMs driving the regional models as well as to the full set of CMIP3 GCM results. We pose some possible process-level mechanisms for the difference in intensity of change, particularly for summer. Detailed process-level studies will be necessary to establish mechanisms and credibility of these results. The GCMs explain more variance for winter temperature and the RCMs for summer temperature. The same is true for precipitation patterns. Thus, we recommend that future RCM-GCM experiments over this region include a balanced number of GCMs and RCMs.     

Atmospheric and Terrestrial Water Balances of Labrador's Churchill River Basin,as Simulated by the North American Regional Climate Change Assessment Program

In an effort to understand the sources of uncertainty and the physical consistency of climate models from the North American Regional Climate Change Assessment Program (NARCCAP), an ensemble of general circulation models (GCMs) and regional climate models (RCMs) was used to explore climatological water balances for the Churchill River basin in Labrador, Canada. This study quantifies mean atmospheric and terrestrial water balance residuals, as well as their annual cycles. Mean annual atmospheric water balances had consistently higher residuals than the terrestrial water balances due, in part, to the influences of sampling of instantaneous variables and the interpolation of atmospheric data to published pressure levels. Atmospheric and terrestrial water balance residuals for each ensemble member were found to be consistent between base and future periods, implying that they are systemic and not climate dependent. With regard to the annual cycle, no pattern was found across time periods or ensemble members to indicate whether the monthly terrestrial or atmospheric root mean square residual was highest. Because of the interdependence of hydrological cycle components, the complexity of climate models and the variety of methods and processes used by different ensemble members, it was impossible to isolate all causes of the water balance residuals. That being said, the residuals created by interpolating a model's native vertical resolution onto NARCCAP's published pressure levels and the subsequent vertical interpolation were quantified and several other sources were explored. In general, residuals were found to be predominantly functions of the RCM choice (as opposed to the GCM choice) and their respective modelling processes, parameterization schemes, and post-processing.     

Current and perturbed climate as simulated by the second-generation Canadian Regional Climate Model (CRCM-II) over northwestern North America

An updated version of the Canadian Regional Climate Model (CRCM-II) has been used to perform time-slice simulations over northwestern North America, nested in the coupled Canadian General Circulation Model (CGCM2). Both driving and driven models are integrated in a scenario of transient greenhouse gases (GHG) and aerosols. The time slices span three decades that were chosen to correspond roughly to single, double and triple current GHG concentration levels. Several enhancements have been implemented in CRCM-II since the CRCM-I climate-change simulations reported upon earlier. The larger computational domain, extending further to the west, north and south, allows for a better spin-up of weather systems as they enter the regional domain. The increased length of the simulations, from 5 to 10 years, strengthens the statistical robustness of the results. The improvements to the physical parameterisation, notably the moist convection scheme and the diagnostic cloud formulation, cure the excessive cloud cover problem present in CRCM-I, reduce the warm surface bias and prevent the occurrence of grid-point precipitation storms that occurred with CRCM-I in summer. The dynamical ocean and sea-ice components of CGCM2 that is used to provide atmospheric lateral and surface boundary conditions to CRCM-II, as well as the use of transient rather than equilibrium conditions of GHG and the inclusion of direct aerosols forcing, in both CGCM2 and CRCM-II, increase the realism of the CRCM-II climate-change simulation.     

气候变化国家评估报告(Ⅰ):中国气候变化的历史和未来趋势

The climate change in China shows a considerable similarity to the global change, though there still exist some significant differences between them. In the context of the global warming, the annual mean surface air temperature in the country as a whole has significantly increased for the past 50 years and 100 years, with the range of temperature increase slightly greater than that in the globe. The change in precipitation trends for the last 50 and 100 years was not significant, but since 1956 it has assumed a weak increasing trend. The frequency and intensity of main extreme weather and climate events have also undergone a significant change. The researches show that the atmospheric CO2 concentration in China has continuously increased and the sum of positive radiative forcings produced by greenhouse gases is probably responsible for the country-wide climate warming for the past 100 years, especially for the past 50 years. The projections of climate change for the 21st century using global and regional climate models indicate that, in the future 20-100 years, the surface air temperature will continue to increase and the annual precipitation also has an increasing trend for most parts of the country.     

“气候变化与气候变异、生态-环境演变及可持续发展科学研讨会“在乌鲁木齐召开

中国科协2005年学术年会第2分会场“气候变化与气候变异、生态-环境演变及可持续发展科学研讨会”于2005年8月22-23日在新疆乌鲁木齐隆重召开。这次研讨会是由中国气象学会、国家气候中心以及新疆维吾尔自治区气象局共同主办的一次大型学术会议。中国气象局局长秦大河院士担任这     

气候变化国家评估报告（Ⅲ）：中国应对气候变化对策的综合评价

 回顾了国际社会应对气候变化的进程，对国内外的碳排放状况、中国减缓碳排放的技术潜力、中国减缓碳排放的宏观影响、全球减缓气候变化的公平性与国际合作行动等问题进行了分析与评估。提出了中国减缓气候变化的思路与对策，指出在全球应对气候变化的形势下，中国要积极适应国际政治、经济及贸易格局变动的趋势，将减缓气候变化对策纳入国家经济与社会发展战略与规划之中，促进国家经济和社会的全面、协调和可持续发展。     

华北地区夏季水资源特征分析及其对气候变化的响应（Ⅰ）:近40年华北地区夏季水资源特征分析

近年来 ,淡水资源匮乏问题已经成为全人类普遍关注的严重问题。华北地区是我国的政治、经济和文化中心 ,该区水资源严重不足 ,缺水问题一直困扰着该区经济的发展和人民生活水平的提高。本文利用NCEP/NCAR的 40a(195 8— 1997年 )再分析资料分析发现 ,近 40a来 ,华北地区年平均水资源略有盈余 ,但水资源年内分布很不均匀 ,一年内仅 6 9月份水资源有盈余 ,其它各月均有不同程度亏损。对华北地区水资源最充足的夏季水资源各分量进行EOF分析 ,结果表明 ,华北地区夏季水资源各分量空间分布的最主要特征都表现为全区一致型 ;最主要的时间变化趋势都表现为自 6 0年代至 80年代中期持续下降 ,80年代中期以后略有回升 ,但回升幅度较小 ,降水仍然低于 40a来的平均水平。对各物理量进行M -K突变检验的结果表明 ,各量在 6 0年代中期前后都发生了一次突变过程 ,但发生时间略有差别     

A sensitivity study of the Regional Climate Model (RegCM3) to the convective scheme with emphasis in central eastern and southeastern Europe

Regional climate simulations have been performed over the greater European area for 3 years using three convective parameterizations: (a) the Grell scheme with Arakawa-Schubert (AS) closure assumption, (b) the Grell scheme with Fritsch-Chappell (FC) closure assumption and (c) the MIT scheme. The comparison of the model results of near-surface temperature with near-surface temperature observations indicates a cold bias with both Grell scheme configurations. This bias is significantly reduced when the MIT convective scheme is introduced, even during months of low convective activity. The temperature differences between the Grell (with either AS or FC closure schemes) and the MIT scheme are largest in the lower troposphere, extending up to 700 hPa. In terms of total precipitation, no systematical differences between Grell and MIT schemes are observed throughout the year for the European domain but the convective portion of total precipitation is greater in the MIT scheme simulations. For the central Eastern Europe region, MIT scheme simulations generally produce more precipitation during the warm season than Grell simulations, while for the southern Eastern Europe region, the MIT precipitation enhancement is small and not systematically positive. It is evident that the cause of the differences between the convective schemes is the more intense convection in the MIT scheme configuration, which in turn imposes a more effective drying of the atmosphere, less low-level clouds, more short-wave solar radiation absorbed from the ground and hence warmer low level temperatures.     

Assessment and Measurement Issues Related to Soil Carbon Sequestration in Land-Use, Land-Use Change, and Forestry (LULUCF) Projects under the Kyoto Protocol

Mitigating the potential large negative impacts of a change in the earth's climate will require strong and definite actions in the different economic sectors, particularly within agriculture and forestry. Specifically, soils deserve a close examination due to their large carbon mitigation potential. The Kyoto protocol establishes the possibility for crediting greenhouse gas emission reductions from forestry and agriculture activities. In most circumstances, particularly those regarding developing countries, greenhouse gas mitigation activities will be carried out through projects. These projects will have to meet a series of criteria, for the carbon benefits to be measurable, transparent, verifiable and certified. These criteria include: establishing credible baselines (without-project or reference scenario), additionality, permanence, quantifying and reducing potential leakage of greenhouse gases across project borders, coping with natural or human induced risks, accurately measuring changes in carbon stocks using carbon accounting techniques, and – in the case of the Clean DevelopmentMechanism – resulting in sustainable development benefits. In this paper we describe the methods and approaches that have been developed to cope with the different criteria and discuss their implications for carbon sequestration in soils. Soil carbon represents the largest carbon pool of terrestrial ecosystems, and has been estimated to have one of the largest potentials to sequester carbon worldwide. However, getting credits from soil carbon sequestration through project activities presents several challenges: the need to monitor small incremental changes in soil carbon content relative to large carbon pools, long-time periods to accrue the full carbon benefits, high local variability of soil carbon content, and relatively costly soil carbon measurement procedures. Also, the responses of soil C stocks to forestry and agriculture activities are complex and need careful attention. Specifically, the time dynamics of soil C responses to land use changes, the diversity of soil types, soil-plant interactions, and the availability of accurate soil C inventories, should be considered to successfully implement LULUCF projects.     

中国气候与环境演变评估(Ⅱ)：气候与环境变化的影响与适应、减缓对策

 气候与环境变化对我国的影响表现在自然、社会、经济和政治等各个方面。通过对我国气候与环境影响的评估，从生态系统、农业、水资源、重大工程等方面进行了论述。在此基础上，从冰冻圈、生态系统、土地退化、工业、交通、服务业、城市与生活等几个方面进行了气候影响的利弊分析。进而评估了气候变化对我国区域可持续发展的影响，提出了气候变化的适应与减缓对策。     

Complex use of satellite radiometric,surface radar,and cloud numerical modeling data for controlling the modification works aiming to prevent precipitation in Peterhof

Results are presented of complex study of the clouds during the modification works aiming to prevent precipitation. To estimate the modification effect, a new technique is presented based upon comparison of the IR-radiometer measurements data, from the Meteosat satellite, on radiation temperature of the clouds after modification and those in natural development cycle. It is shown that for the case under study, radiation temperature increase is observed in the pixel corresponding to the city in which precipitation should be prevented.     

Spatial Response to Major Volcanic Events in or about AD 536, 934 and 1258: Frost Rings and Other Dendrochronological Evidence from Mongolia and Northern Siberia: Comment on R. B. Stothers, ‘Volcanic Dry Fogs, Climate Cooling, and Plague Pandemics in Europe and the Middle East’ (Climatic Change, 42, 1999)

Hypothesized large-scale climatic extremes require verification from distantregions in order toconfirm the magnitude and timing of such events. Three of the most massivehypothesized volcanic events of the past two millennia, occurring in or aboutAD 536, 934 and1258, had profound climatic and demographic repercussions over much of Europe,the MiddleEast, and other areas, according to historical accounts recently described inStothers (1998, 1999,2000) as well as other research. Here we report on frost ring and otherdendrochronologicalevidence derived from a 1738-year tree-ring chronology from Mongolia andmillennial-scaletree-ring data from northern Siberia which demonstrate that these three eventsmay have alsoimpacted conditions in these distant regions.     

Modelling Sea Surface Temperature (SST) in the Hudson Bay Complex Using Bulk Heat Flux Parameterization: Sensitivity to Atmospheric Forcing,and Model Resolution

ABSTRACT

Sea surface temperature (SST) from four Nucleus for European Modelling of the Ocean (NEMO) model simulations is analyzed to study the bulk flux parameterization to compute SST over the Hudson Bay Complex (HBC) for the summer months (August and September) from 2002 to 2009. The NEMO simulation was forced with two atmospheric forcing sets with different resolutions: the Coordinated Ocean-ice Reference Experiment, version 2 (COREv2), as the lower resolution and the Canadian Meteorological Centre’s Global Deterministic Prediction System Reforecasts (CGRF) as the higher resolution. The CGRF forcing is also implemented in the third and fourth runs using different runoff data and different NEMO resolutions (1/12° versus 1/4°). Results show that all four modelled SSTs followed observed SST patterns, with regional differences in SST bias between simulations with different atmospheric forcing. The SST differences are small between simulations forced with the same atmospheric forcing but with different model resolution or runoff. This implies that the model resolution and runoff have a small effect on the simulated SST in the HBC. Moreover, to better capture the effect of near-surface temperature (T_air) on simulated SST, we conducted three analyses using the Haney flux linearization formula. Results from these assessments did not indicate any direct influence on the model-simulated SSTs by T_air. Looking at the heat flux as a signature for SST showed that both averaged spatial distribution and time series of net heat flux produced by the three CGRF forcing simulations were higher than the net heat flux generated by the CORE 2 simulation. This was generally true for all four components of the total heat flux (sensible, latent, shortwave, and longwave) individually as well. Total heat flux in summer is governed by the shortwave heat flux, with values up to 120?W?m^?2 in August, and the longwave heat flux is the main contributor to the total heat flux differences. These heat flux differences lead to corresponding colder model SSTs for the CGRF runs and warmer SSTs for the CORE 2 simulations.