WEEKLY CLIMATE NEWS

27 November-1 December 2017

ITEMS OF INTEREST

Beginning of meteorological winter season -- The winter meteorological season in the Northern Hemisphere starts on Friday (1 December). Recall that climatologists and meteorologists have elected to use a standard three-month grouping to identify each meteorological season. Hence, the months of December, January and February are considered the winter meteorological season. You will note that the winter solstice, marking the day where the length of daylight is least in the Northern Hemisphere is still three weeks away, falling on Thursday, 21 December 2017. Since the lowest temperatures typically fall in mid to late January, the meteorological winter tends to be centered on the coldest time of the year in the Northern Hemisphere.
In addition, Thursday (30 November) marks the end of the official 2017 hurricane seasons in the North Atlantic, which includes the Gulf of Mexico and the Caribbean, along with the eastern and central North Pacific basins.
The 2017 hurricane seasons reviewed -- With the end of the official 2017 hurricane season in both the North Atlantic and North Pacific on Thursday (30 November 2017), a quick review of this year's tropical cyclone statistics for the official 2017 hurricane season has been made for both basins. [AMS DataStreme Atmosphere]
For those who are interested in obtaining historic hurricane information, the "Historical Hurricanes Mapping & Analysis Tool" developed by NOAA allows the search and display of detailed data for more than 6000 tropical cyclones in seven of the planet's major ocean basins based upon a data set that runs from 1842 to 2016. Coastal population trends are also available for the Atlantic and Gulf Coasts of the United States.
Tropical cyclone climatologies of North Atlantic and the eastern North Pacific -- The National Hurricane Center (NHC) has an updated and revised edition of its "Tropical Cyclones of the North Atlantic Ocean, 1851-2006." While a paper copy of this book is available for a cost from NHC, a 243-pg pdf file of this edition can be downloaded for free. NHC also released the first edition of "Tropical Cyclones of the Eastern North Pacific Ocean, 1949-2006." In addition to a paper copy is available for sale, a free 164-page pdf file is available. Both of these climatologies have numerous graphics that show long-term changes in tropical cyclone frequency in the two basins.
A climatology of tropical cyclones in the central North Pacific from the 1950s to 2013 is available from the CPHC climatology website maintained by the Central Pacific Hurricane Center (CPHC) in Honolulu, HI.
High-quality maps of December temperature and precipitation normals across US available -- The PRISM Climate Group at Oregon State University's website has prepared high-resolution maps depicting the normal maximum, minimum and precipitation totals for December and other months across the 48 coterminous United States for the current 1981-2010 climate normals interval. These maps, with a 800-meter resolution, were produced using the PRISM (Parameter-elevation Regressions on Independent Slopes Model) climate mapping system.
December weather calendar for a city near you -- The Midwestern Regional Climate Center maintains an interactive website that permits the public to produce a ready to print weather calendar for any given month of the year, such as December, at any of approximately 270 weather stations around the nation. (These stations are NOAA's ThreadEx stations.) The entries for each day of the month includes: Normal maximum temperature, normal minimum temperature, normal daily heating and cooling degree days, normal daily precipitation, record maximum temperature, record minimum temperature, and record daily precipitation; the current normals for 1981-2010.
First snow of season histories are available for several thousand US weather stations -- NOAA's National Centers for Environmental Information has assembled an interactive map that allows the user to obtain the dates of the first measurable snowfall (0.1 inches or more) for several thousand weather stations across the United States (including Alaska) in the Global Historical Climatology Network that have at least 20 years of record. Clicking on a station location will provide not only the date of the first observed snowfall at that location, but the amount of this first snow and the first year of observation for that station. [NOAA Climate.gov News]
"Coldest day of the year" is on the horizon -- NOAA's National Centers for Environmental Information (NCEI) produced a set of "Coldest Day of the Year" maps for the contiguous United States, Alaska, Hawaii and Puerto Rico showing the dates of the lowest daily minimum temperatures of the year as calculated from the 1981-2010 climate normals. Many places across the West will experience their lowest daily temperatures starting during the next two to three weeks in early December. On the other hand, some areas across the West will not reach their lowest daily temperatures of the year until late January. [NOAA NCEI News]
[Notes: (1.) According to the seasonal variations in the long-term average or "normal" temperatures, many locations across the nation not along the coasts typically have their lowest normal daily high and low temperatures during the third week of January, nearly one month after the winter solstice. However, areas across the West have their lowest temperatures during the month of December, with elevation becoming an influence.
(2.) For comparison purposes, check the corresponding NCEI map for the "Warmest Day of the Year" that shows the dates of occurrence of the highest maximum temperatures. EJH]
It's Sure Dark! -- Have you noticed that the sun is setting early these days? During the first ten days of December, many locations throughout the country will experience their earliest sunset times of the year. The exact day for the earliest sunset depends upon the latitude, so you may want to check the date in your locale from the sunrise tables appearing in an on-line, interactive service available for the entire year at most cities in the United States. The reason for the earliest sunsets occurring in early December rather than on the winter solstice (during the early morning hours of Wednesday, 21 December 2016) is that the sun is not as precise a timekeeper as our watches. Because of a combination of factors involved with Earth's elliptical orbit about the sun and the tilt of Earth's spin axis with respect to the plane of the ecliptic, the sun appears to "run fast" by as much as 15 minutes as compared with clock time in November. However, with the approach of the winter solstice and perihelion (the smallest earth-sun distance during the morning of 4 January 2017), the apparent sun slows during December and finally lags the clock by 12 minutes in February. Consequently, a noticeable and welcome trend toward later sunsets can be detected by the end of December, especially by those residents in the northern part of the country. However, the latest sunrises occur at most locales in early January, meaning that early risers will continue seeing dark and dreary mornings for another month.
State, national and global instrumental records -- Temperature and precipitation data have been collected around the world since the mid-19th century. Beginning in the 1890s, a sufficiently dense climate network has been established in the United States and its territories. The records from around the nation and from around the global have been collected and archived at several central locations, such as NOAA's National Centers of Environmental Information (NCEI). Scientists at NCEI along with colleagues at NASA's Goddard Institute for Space Studies and in the United Kingdom have produced time series of area-average monthly and annual temperatures for over a century on state, national and global space scales. For more details on these records and how to access them, please read this week's Supplemental Information...In Greater Depth.
Graphical depictions of statewide annual and seasonal time series are available -- NOAA's National Centers for Environmental Information (NCEI) are making graphics available that depict the variations in the historical temperature averages each year or each season since 1895 for each of the 48 contiguous United States. These graphs are derived from the current nClimDiv version of the US Climate Division Database. [NOAA NCEI News]

CURRENT CLIMATE STATUS

Review of October 2017 global temperatures and sea ice cover -- Preliminary data analyzed by scientists at NOAA's National Centers for Environmental Information (NCEI) indicated that the global combined land and ocean average surface temperature for the October 2017 was 1.31 Fahrenheit degrees above the 20th century average (1901-2000) for the month. Therefore, last month's global combined temperature tied the temperature for October 2003 for being the fourth highest October temperature since global temperature records began in 1880. When considered separately, the monthly average temperature over the global oceans for October 2017 was 1.13 Fahrenheit degrees above average, the fourth highest October ocean temperature in 138 years of record. The monthly average temperature of the land surface for this recently concluded month was 1.78 Fahrenheit degrees above average, which represented the eleventh highest October land surface temperature on record.
When considering the combined land-ocean global temperature for the year to date (January-October 2017), this temperature was the third highest global temperature for the first ten months of any year since 1880. [NOAA/NCEI State of the Climate]
A global map of Selected Significant Climate Anomalies and Events for October 2017 is available from NCEI.
According to satellite data collected by National Snow and Ice Data Center, the sea ice over the Arctic Ocean during October 2017 was the fifth smallest areal extent for any October since satellite-derived ice records began in 1979. The sea ice around Antarctica also was the fifth smallest October ice extent in the last 39 years. [NOAA/NCEI Global Snow & Ice]
Extent of sea ice in Alaska waters reaches record low extent this fall -- Sea ice experts have found that the extent of sea ice covering the Bering Sea to the west of Alaska and the Chukchi Sea to the northwest of the 49th State during this past fall has been the smallest since 1978 when satellite surveillance began. The lack of sea ice into late fall has profound implications not only for Alaskan marine life, but also for the native peoples that reside in coastal communities. [NOAA Climate.gov News]
Aerial photographs of an iceberg and sea ice off Antarctica -- A scientist participating in NASA's Operation IceBridge campaign over Antarctica has taken several photographs of the ice along the coast of the continent from an aircraft during recent weeks. One of the pictures was of the iceberg named A-68A that had broken off the Larsen C Ice Shelf, a long ice shelf in the northwest section of the Weddell Sea, extending along the eastern coast of the Antarctic Peninsula. An image was also made by the Digital Mapping System (DMS), a downward-looking camera installed under the belly of the aircraft. [NASA Earth Observatory]
On another flight two days later, the scientist took a picture of the thin fingers of ice that had formed on the surface of the Weddell Sea. Another picture was made of the ice by the DMS. [NASA Earth Observatory]

CURRENT CLIMATE MONITORING

New instrument to measure total solar irradiance from International Space Station -- NASA is preparing to send an instrument to the orbiting International Space Station in December called the "Total and Spectral solar Irradiance Sensor" (TSIS-1) will measure the total amount of solar radiation distributed over all wavelength bands reaching the top of Earth's atmosphere. TSIS-1 will be able to measure the ultraviolet light portions of the solar spectrum, including UV-B and UV-C, as it will be orbiting above the ozone layer in the stratosphere. [NASA Goddard Space Flight Center Feature]

CLIMATE FORECASTS

Making a snow forecast for North America during a La Nina winter -- With a weak La Niña event being anticipated for this upcoming winter, a meteorologist for NOAA's Climate Prediction Center posted a guest article in which he compares snowfall patterns across North America during La Niña winters between 1950 and 2009 with average snowfall totals for that same period. He provides maps of the snowfall departures for all La Niña winters during this span, as well as for winters that are associated with both weak and strong La Niña events. These maps show that a La Niña tends to favor increased snowfall across sections of the West Coast of North America from Oregon northward to southwestern Alaska, across the Cascades and the northern Rockies, the Upper Midwest, areas downwind of the Great Lakes and across eastern Canada. On the other hand, reduced snowfall is seen across scattered areas that tend to experience snow in the Southwest, the central-southern Plains, and the Middle Atlantic States. [NOAA Climate.gov News]
Australian tropical cyclone season outlook issued -- Forecasters at the Australian Government's Bureau of Meteorology recently released an outlook for the upcoming 2017-18 Australian tropical cyclone season that typically begins in November and runs through April. These forecasters foresee close to average tropical cyclone activity in the five regions that surround that continent, with the best chances for above-average numbers of tropical cyclones being in the Australian region in the south central section of the country (with a 56- percent chance) and the Northwestern sub-region (56-percent chance). Their outlook for an average season is based upon anticipated ENSO-neutral to weak La Niña conditions across the tropical Pacific Ocean, together with warmer than average ocean waters located to the north and east of Australia. [Australian Bureau of Meteorology]
Summer storm clusters across North America could produce significantly more rainfall in future -- Scientists at the National Center for Atmospheric Research (NCAR) report that clusters of summertime thunderstorms called mesoscale convective systems (MCSs) developing across the North American continent by the end of the 21st century could become larger and more intense, generating as much as 80 percent more rainfall as currently produced. The increase in size and intensity, as well as increased frequency, could increase the risk of widespread flooding. The researchers based their predictions upon computer simulations of MCSs and thunderstorms across North America, considering situations where emissions of greenhouse gases continue unabated. [NCAR/UCAR AtmosNews]
La Niña droughts could be predicted two years in advance -- Researchers at the University of Texas at Austin and at the National Center for Atmospheric Research (NCAR) claim that prediction of the strength and duration of droughts caused by a La Niña event across the southern United States is possible, especially if this event were to stretch into a second year, because they found the effects of La Niña tend to be stronger in second year. [University of Texas at Austin News]

CLIMATE AND SOCIETY

Climate changes in Europe during 19th century triggered immigration to North America -- Researchers at Germany's University of Freiburg claim that a changing climate in western Europe during the mid-19th century associated with the latter stages of the Little Ice Age appears to have been a major factor in driving the migration of many people from southwestern Germany to North America. During the early to mid-19th century, mountain glaciers re-advanced in the Alps due to cool summers and harsh winters. Other extreme weather events such as droughts and floods also helped cause low crop yields and rising cereal prices that ultimately lead to emigration. The researchers identified several waves of emigration, beginning with the "Year without a Summer" (1816) that followed the previous year's eruption of the Tambora volcano in Indonesia, and then in 1846, when an extremely hot and dry summer led to bad harvests and high food prices. However, climate may have been less of a significant factor in driving the largest emigration wave that extended from 1850 to 1855. [European Geosciences Union News]
Earthweek -- Diary of the Planet [earthweek.com]

Concept of the Week: Climate Sensitivity

Climate sensitivity is a relatively new and powerful concept in climate science. It is a measure of how responsive the temperature of Earth's climate system is to a change in radiative forcing due to increases in atmospheric carbon dioxide, an important greenhouse gas, combined with the contributions of feedbacks within the system. Specifically, the term is defined as how much the global mean surface temperature will increase if there is a doubling of atmospheric greenhouse gases (in terms of equivalent CO₂), once the planet has had a chance to settle into a new equilibrium after the increase occurs. In other words, it's an assessment of how Earth's climate will respond to that doubling.

According to NASA climate scientist James Hansen, the concept of climate sensitivity has its origins in a request made by President Jimmy Carter in 1979 for the National Academy of Sciences (NAS) to report on the potential impact on climate of the increasing atmospheric concentration of carbon dioxide. Jule G. Charney (1917-1981) of the Massachusetts Institute of Technology (MIT) led the Academy investigation team. He designed a now classic experiment where computer models of Earth's climate system had the atmospheric concentration of CO₂ doubled while all other variables (except temperature) were held constant.

The addition of CO₂ makes the atmosphere more opaque for outgoing infrared radiation (heat), warming the lower atmosphere and cooling the upper atmosphere. Applying basic radiation laws, Charney found that doubling the atmospheric CO₂ concentration would reduce the net radiative flux (from Earth to space) at the tropopause by a global average of about 4 watts per square meter (W/m²). How much warmer would Earth's surface become as a consequence of this enhanced greenhouse effect? According to the Stefan-Boltzmann law, the radiation emitted by an object is directly proportional to the fourth power of the object's absolute temperature. To reestablish radiative equilibrium following a doubling of atmospheric CO₂, Earth must radiate to space an additional 4 W/m², brought about by a global warming of 1.2 Celsius degrees (or 0.3 Celsius degrees per W/m²).

Charney's initial experiment accounted for the effect of a forcing agent (i.e., atmospheric CO₂) on global climate but not the influence of feedbacks. As noted in the Concept of the Week for Week 2, forcing agents and mechanisms drive climate change, while feedbacks determine the magnitude of climate change. Hence, Charney's "no-feedback" experiment significantly underestimates the amount of global warming likely to accompany a doubling of atmospheric CO₂. With inclusion of feedbacks, the 1979 Academy study indicated that global warming could range from 2 to 3.5 Celsius degrees. The most recent IPCC report (AR4) estimates the magnitude of warming with feedbacks incorporated as 3 Celsius degrees with a range of uncertainty of 2 to 4.5 Celsius degrees. This greater sensitivity depends primarily on all the different feedbacks, both positive and negative, that either amplify or diminish the greenhouse effect. The three primary feedbacks involve clouds, sea ice, and water vapor.

In summary, climate sensitivity is usually expressed in terms of the equilibrium change in global mean annual surface temperature caused by an increment in downward infrared radiative flux that would result from sustained doubling of atmospheric CO₂ concentration compared to its pre-industrial level (taken to be 280 ppmv).

Historical Events:

27 November 1701...Anders Celsius, the astronomer who invented the Celsius thermometer scale, was born in Uppsala, Sweden. (National Weather Service files)
27 November 1912...Snow fell across northern Florida, marking one of the few times it has ever snowed there in November. (National Weather Service files)
29 November 1975...Red River was buried under 34 inches of snow in 24 hours, establishing a record for the state of New Mexico. (The Weather Channel)
29 November 1985...The temperature at Bismarck, ND plunged to 30 degrees below zero to establish their record low for the month of November. The high that day was 4 degrees below zero. (The Weather Channel)
29 November 1989...Sault Ste Marie, MI finished the month of November with a record 46.8 inches of snow. (The National Weather Summary) (Storm Data)
30 November 1976...MacLeod Harbor, AK reported a precipitation total for November of 70.99 inches, which established a state record for any month of the year. (The National Weather Summary)
30 November 1991...Minneapolis, MN ended the month with 46.9 inches of snow, the most ever for November and for any month. Although the official start of winter was still 3 weeks away, the city had already surpassed the normal seasonal snowfall record with 55.1 inches since 1 October (normal for the entire winter is 49.2 inches). (Intellicast)
30 November 2001...For the first time in 122 years of weather records, Buffalo, NY finished the entire month of November without any snowfall. (National Weather Service files)
1 December 1831...The coldest December of record in the northeastern U.S. commenced. Temperatures in New York City averaged 22 degrees, with just four days above freezing, and at Burlington, VT the temperature never did get above freezing. The Erie Canal was closed the first day of December, and remained closed the entire month. (David Ludlum)
1 December 1913...A six-day Front Range snowstorm began, ultimately producing 45.7 inches of snow at Denver, CO, the biggest single snowstorm on record for that city. It produced a record total of 46 inches at Denver, CO. (David Ludlum) (Intellicast)
3-10 December 1926...Record rain fell on Yuma, AZ over a one-week period. On the 4^th 1.10 inches of rain fell, and by the 10^th a total of 4.43 inches had fallen, to set an all-time December monthly record. The mean annual precipitation for Yuma is only 3.38 inches. (Accord Weather Guide Calendar)
3 December 1982...Big Fork, AR received 14.06 inches of rain, setting a 24-hour maximum precipitation record for the state. (NCDC)

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