Lake ice is a sensitive proxy to climate variability as has been shown through observations and modeling. In this study, we used in-situ and satellite data to analyze lake ice change at the Nam Co Lake in Tibet in 2000-2013. The results from Moderate Resolution Imaging Spectrometer (MODIS) data showed that lake ice phenology changed significantly at the Nam Co Lake in the studied time period. The postponing freeze onset (FO) and advancing water clear of ice (WCI) dates were both obvious, resulting in the dramatic reduction of ice existence period (IEP) (2.8 days/year). Melt duration (MD), which stands for lake ice melting speed, was the most sensitive indicator of Nam Co Lake ice durations and MD was shortened by 3.1 days/year through the study period. Lake ice change at the Nam Co Lake was affected by regional climate variations, including air temperature and wind speed changes. In this study, daily air temperature from two automatic weather stations on the lakeshore showed highly consistent trend with lake ice phenology—both freeze onset (FO) and melt onset (MO) synchronized with air temperature variation. High wind speed in winter accelerates freezing. Lake ice tensile force rather than wind force can force the ice into pieces during the formation period. Lake ice phenology acts as a sensitive proxy of regional climate and can serve as an indicator of regional climate change. Further study on lake ice in the Tibetan Plateau is significant because of its sensitive response to climate change.

This article evaluates the precision of the temperature simulated by nine IPCC AR5 (the Fifth Assessment Report of the Intergovernmental Panel on Climate Change) GCMs (Global Climate Models) and the multi-model ensemble (MME), based on the observed temperature of 660 stations in China from 1996 to 2005. The results show that the correlation coefficients between the average daily temperature simulated by GCMs and station observations in China during 1996-2005 were very high, all above 0.86. The precision of the simulated average daily temperature in the southeast by the 10 models was higher than that in the west, judged by the lower Biases, mean relative errors (MREs), mean absolute errors (MAEs), and root mean square errors (RMSEs) in the southeast as compared to those in the west. The precision of the simulated temperature by IPSL-CM5A-LR, MRI-CGCM3, and NorESM1-M was poorer than that of the others—specially, the Biases, MREs, and RMSEs of the simulation result by IPSL-CM5A-LR , the Biases and RMSEs of the simulation result by MRI-CGCM3, and MREs and RMSEs of the simulation result by NorESM1-M, were larger. Taken into account the Biases, MREs, MAEs, and RMSEs, the simulation precision of MME was the highest.

Extreme heat events (EHEs) are a major cause of weather-related deaths. People who live in cities may be more vulnerable to EHE because the urban heat island (UHI) effect causes a slower cooling process at night, and thus provides little relief from the heat stresses of the day. Although UHI is a well-documented phenomenon, relatively little information in the literature is available about its characteristics during EHEs. Moreover, urban warming in addition to greenhouse gas-induced warming has not been taken into account explicitly in climate change simulations to date. Under the background of global climate change and rapid urbanization in China, the magnitude of future warming and the health risk of EHEs may be significantly underestimated in urban areas. With the forecast of global warming continuing into the foreseeable future, extreme heat events will become more intense, more frequent, and longer lasting with climate change. The impacts of urbanization on extreme heat events have attracted an increasing attention in recent years. The potential exposure of urban populations to climate change will be enhanced by local factors with the development of urbanization. This review systematically collates research results in three main areas: observational evidence of trends in EHEs in relation to urbanization, numerical simulation experiments of the impact of urbanization on temperature and heat stress during EHEs, and epidemiological study of excess mortality associated with urbanization during EHEs. Most observational and simulation studies show that urban heat island results in an increase in the extent and intensity of extreme heat in cities. Inhabitants of urban areas may experience increasing heat-related health risk. Heat island also significantly contributes to the long-term increasing trends in urban EHEs. The epidemiological studies reveal that heat island caused by urbanization has great impacts on excess mortality in cities during EHEs. Finally, future avenues of research are speculated, including: synergistic effect of extreme heat with other environmental factors, heat-health warning systems, mapping extreme heat health risk, and future projection of EHEs due to climate change and urban growth.

The overlay of climate change and urbanization leads cities to become the centers where greenhouse gas (GHG) reduction actions and key risks of climate change simultaneously occur. How to cope with climate change has been a huge challenge facing global cities. Conducting the study on coping with climate change based on urban spatial forms has increasingly become the frontier and hot topic of urban environment and climate change research. By analyzing and summarizing current literatures, this article reviews the core aspects and progress of study on urban spatial forms to cope with climate change, including key impacts of climate change and their assessment methods, relationships between urban forms and climate change including greenhouse gas emissions and key risks of climate change, coping strategies, and urban planning practices. Based on this, key issues for future research are put forward.