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The article discusses the role of Arctic sea ice and sea surface temperatures (SSTs) in the cold event in North America in February 2015. Topics include the impact of natural atmospheric variability, anthropogenic activity to the increase in the probability of the cold spells in the region, and generalized Pareto distribution (GPD).

The article presents a study which applies the extreme value theory to quantify the intensity and duration of the eastern cold in the U.S. in February 2015. The study involves analysis of the daily surface temperature data from the Global Historical Climatology Network-Daily Database. Results show the impact of climate change to the distribution of cold winter temperatures.

This fifth edition of explaining extreme events of the previous year (2015) from a climate perspective continues to provide evidence that climate change is altering some extreme event risk. Without exception, all the heat-related events studied in this year's report were found to have been made more intense or likely due to human-induced climate change, and this was discernible even for those events strongly influenced by the 2015 El Niño. Furthermore, many papers in this year's report demonstrate that attribution science is capable of separating the effects of natural drivers including the strong 2015 El Niño from the influences of long-term human-induced climate change. Other event types investigated include cold winters, tropical cyclone activity, extreme sunshine in the United Kingdom, tidal flooding, precipitation, drought, reduced snowpack in the U.S. mountain west, arctic sea ice extent, and wildfires in Alaska. Two studies investigated extreme cold waves and monthly-mean cold conditions over eastern North America during 2015, and find these not to have been symptomatic of human-induced climate change. Instead, they find the cold conditions were caused primarily by internally generated natural variability. One of these studies shows winters are becoming warmer, less variable, with no increase in daily temperature extremes over the eastern United States. Tropical cyclone activity was extreme in 2015 in the western North Pacific (WNP) as measured by accumulated cyclone energy (ACE). In this report, a study finds that human-caused climate change largely increased the odds of this extreme cyclone activity season. The 2015 Alaska fire season burned the second largest number of acres since records began in 1940. Investigators find that human-induced climate change has increased the likelihood of a fire season of this severity. Confidence in results and ability to quickly do an attribution analysis depend on the "three pillars" of event attribution: the quality of the observational record, the ability of models to simulate the event, and our understanding of the physical processes that drive the event and how they are being impacted by climate change. A result that does not find a role for climate change may be because one or more of these three elements is insufficient to draw a clear conclusion. As these pillars are strengthened for different event types, confidence in the presence and absence of a climate change influence will increase. This year researchers also link how changes in extreme event risk impact human health and discomfort during heat waves, specifically by looking at the role of climate change on the wet bulb globe temperature during a deadly heat wave in Egypt. This report reflects a growing interest within the attribution community to connect attribution science to societal impacts to inform risk management through "impact attribution." Many will watch with great interest as this area of research evolves in the coming years. INSET: EDITORIAL AND PRODUCTION TEAM. [ABSTRACT FROM AUTHOR]

Weather and climate extremes have been varying and changing on many different time scales. In recent decades, heat waves have generally become more frequent across the United States, while cold waves have been decreasing. While this is in keeping with expectations in a warming climate, it turns out that decadal variations in the number of U.S. heat and cold waves do not correlate well with the observed U.S. warming during the last century. Annual peak flow data reveal that river flooding trends on the century scale do not show uniform changes across the country. While flood magnitudes in the Southwest have been decreasing, flood magnitudes in the Northeast and north-central United States have been increasing. Confounding the analysis of trends in river flooding is multiyear and even multidecadal variability likely caused by both large-scale atmospheric circulation changes and basin-scale "memory" in the form of soil moisture. Droughts also have long-term trends as well as multiyear and decadal variability. Instrumental data indicate that the Dust Bowl of the 1930s and the drought in the 1950s were the most significant twentieth-century droughts in the United States, while tree ring data indicate that the megadroughts over the twelfth century exceeded anything in the twentieth century in both spatial extent and duration. The state of knowledge of the factors that cause heat waves, cold waves, floods, and drought to change is fairly good with heat waves being the best understood. [ABSTRACT FROM AUTHOR]

The article summarizes the temperature and precipitation conditions across East Asia in 2013. Topics discussed include the annual mean temperatures across the region, the annual average surface temperature over Japan, South Korea and Mongolia, and the mean annual total precipitation for the year. Notable events include the cold wave conditions in South Korea, the heavy rains in Japan, and the dust and sandstorm in Mongolia.

The article discusses the possibility that global warming contributed to insufficient ice thickness in the Netherlands in February 2012 despite the cold spell that much of Western Europe experienced at the time. It mentions the requirement of 15 centimeters of ice thickness for holding the 11-City Tour of Fyrsia ice-skating marathon, which was last held in January 1997. Snowfall on thin ice that had just formed is shown to have limited ice growth more strongly than the effect of global warming.

The article discusses the cold wave that happened in Germany in early June 2016 which is termed Schafskälte or "sheep's cold". It states that the event is caused by advection of cool and moist air from the North Sea following a rapid warming of land surfaces with high sun angles while the sea surface temperatures lag behind.

The article presents a climatological assessment of the unusually intense and long cold spells that occurred in Eurasia from January 2011-February 2012. The cold spells occurred along with a high pressure system over western Siberia, several intense low pressure systems over the Mediterranean Sea, a high pressure area over Europe and frontal systems from the Atlantic Ocean. A record of heavy snowfall around the Mediterranean was observed during this period.

The article presents an analysis on the effect of external climate forcings and sea surface temperatures (SSTs) on the temperatures in the U.S. It discusses the data of two sets of climate models, the Coupled Model Intercomparison Project (CMIP) and the atmospheric general circulation models with the monthly evolution of observed SSTs or the Atmospheric Model Intercomparison Project (AMIP). It discusses the changes in the U.S. temperatures from 1895 to 2008 and the factors that causes it.