WEEKLY CLIMATE NEWS

23-27 October 2017

• Debunking the legend of the woolly bear caterpillar and winter severity -- The long-held folklore legend that the size of the band on the midsection of the woolly bear caterpillar in early autumn can be used to forecast the severity of the upcoming winter is described and shown to be a myth. [National Weather Service Forecast Office, La Crosse WI]
• "Leaf peeping" of northern New England from satellites -- Natural color images made from data collected by the Operational Land Imager (OLI) on NASA's Landsat 8 within the last two weeks show the vibrant fall colors across northern New England. [NASA Earth Observatory]
• Accessing the national climatographies -- NOAA's National Centers for Environmental Information (NCEI) and its predecessor, the National Climatic Data Cemters have produced numerous climatographies that are quantitative descriptions of climate that include tables and charts portraying the characteristic values of selected climatic elements at a station or over an area. Some of these climatographies provide a variety of daily, monthly and annual normal climate data for agricultural, transportation and other interests. This week's Supplemental Information...In Greater Depth provides the links to selected climatographies from NCEI.

CURRENT CLIMATE STATUS

• September national drought report -- The National Centers for Environmental Information has posted its September 2017 drought report online. Using the Palmer Drought Severity Index, approximately two percent of the coterminous United States experienced severe to extreme drought conditions at the end of September, while eight percent of the area had severely to extremely wet conditions.
• Status of Arctic sea ice extent at end of September -- Scientists at the National Snow & Ice Center recently reported that the Arctic sea ice extent at the end of its melt season, determined to be 13 September, was at the eighth lowest in the daily minimum extent and seventh lowest in the monthly average since records of sea ice extent commenced in 1979. [National Snow & Ice Center News]
• September 2017 weather and climate for the globe reviewed -- Scientists at the NOAA National Centers for Environmental Information (NCEI) recently reported on their analysis of preliminary weather data collected from around the world during the month of September 2017. They found:
• The global combined land and ocean average surface temperature for September 2017 was 1.40 Fahrenheit degrees above the 20th-century average 1901-2000) for the month, which makes last month the fourth warmest September since a sufficiently dense network of global temperature records began in 1880.
  When considered separately, the land surface temperature for this recently concluded month also was the third highest September temperature in the 138-year record, with a monthly temperature that was approximately 2.11 Fahrenheit degrees above the 20th-century average. This new September record surpassed the previous record set last year by 0.20 Fahrenheit degrees.
  Over the oceans, the September globally-averaged sea surface temperature was 1.13 Fahrenheit degrees above the 20th century average, which was the fourth highest temperature on record for the month.
• According to data provided by the National Snow and Ice Data Center (NSIDC), the September Arctic sea ice extent in the Northern Hemisphere was approximately 25.5 percent below the 1981–2010 average, making it the seventh smallest September Arctic sea ice extent since satellite records began in 1979. In the Southern Hemisphere, the September 2017 Antarctic sea ice extent was the second smallest September extent in the 39-year record.
• A global map of Selected Significant Climate Anomalies and Events for September 2017 is available from NCEI.
• A summary article on the September global climate highlights is available, while more detailed analysis with tables and maps can be viewed. [NOAA/NCEI State of the Climate]
• Current year could be one of three warmest on record -- A contractor with NOAA's Climate Program Office wrote an article for ClimateWatch Magazine noting that based upon temperature data compiled NOAA's National Centers for Environmental Information through the end of September, the calendar year of 2017 could possibly be one of the three warmest since sufficiently detailed climate records from around the world began in 1880. According to NCEI, the average combined global land and ocean temperature for the first nine months of 2017 (Jan-Sept) was the second highest in the 138-year period of record, 0.23 Fahrenheit degrees behind the record Jan-Sept 2016 and 0.02 Fahrenheit degrees above the corresponding nine months in 2015 and 1998. [NOAA Climate.gov News]

CURRENT CLIMATE MONITORING

• Two federal science agencies team to begin airborne study of atmospheric chemistry over Antarctica -- Beginning one week ago, researchers from NOAA and NASA have been participating in an airborne science mission over Antarctica called AtmosphericTomography Mission (ATom) that is designed to sample the atmosphere over that continent in order to increase understanding of the distribution of human-generated pollutants and short-lived greenhouse gases. NASA's instrumented DC-8 aircraft is being used in ATom for the next six weeks, flying at altitudes that run from 500 feet to 40,000 feet. The collaboration between the two federal science agencies dates back 30 years to early measurements of the depleted stratospheric ozone layer (known as the "ozone hole") that helped lead to the 1987 Montreal Protocol. [NOAA News]

CLIMATE FORECASTS

• New winter and seasonal Climate Outlooks issued -- Late last week, forecasters at the NOAA Climate Prediction Center (CPC) issued their initial US Winter Climate Outlooks for the nation covering meteorological winter (in the Northern Hemisphere) that includes the three months of November, December and February. They foresee a good chance for warm and dry weather across the southern and eastern sections of the 48 contiguous United States, running from the deserts of the Southwest eastward to Florida and northward along the Atlantic Seaboard. On the other hand, a cooler than average winter is anticipated across northern sections of the country, running from the Pacific Northwest eastward to the Upper Midwest, with wetter than average conditions foreseen across the northern Rockies and adjacent northern Plains, along with the area around the Great Lakes in the Midwest. Elsewhere, the forecasters could not find a distinct signal that would suggest either above or below average conditions, resulting in "Equal Chances." These outlooks were based upon CPC anticipating a 55- to 65-percent chance of the development of a La Niña event by the beginning of meteorological winter that would favor these conditions. An updated winter season climate output will be posted during the third week of November. [NOAA News] A 2.5-minute mp4 video of a CPC forecaster delivering the outlook is posted.
  
  At the same time, CPC also released its new national Three-Month (Seasonal) Climate Outlooks for November 2017 through January 2018, corresponding to the last month of the meteorological autumn season (in the Northern Hemisphere) and the first two months of meteorological winter. Specific details of the outlooks include:
  • Temperature and precipitation outlooks -- According to their temperature outlook, more than three-quarters of the contiguous United States should experience a high chance of above average temperatures for the three upcoming months. The greatest probability of such an occurrence should be found across the Southwest, especially in Arizona, New Mexico and Texas. The outlook indicates that only a small strip running across the northern tier of states from the Pacific Northwest eastward to the Upper Midwest would have nearly equal chances of warmer or cooler than normal conditions for late autumn and early winter.
    The CPC precipitation outlook calls for a better than even chance for below average precipitation during the next three months across the southern tier of states running from southern New Mexico eastward to Florida and the Carolinas. On the other hand, the northern Rockies and adjacent high Plains in Montana and Wyoming would have the best chances of above average precipitation through next January. The remainder of the contiguous states were given essentially equal chances of below and above average precipitation through the first half of winter 2017-18.
    A summary of the prognostic discussion of the 3-month outlook for non-technical users is available from CPC. These forecasts were based in part upon the anticipated transition of the current ENSO conditions (neither an El Niño or La Niña event) to La Niña conditions during the upcoming winter.
    A description is also provided as how to read these 3-class, 3-month Outlook maps.
  • Seasonal Drought Outlook -- The forecasters at NOAA's Climate Prediction Center also released their US Seasonal Drought Outlook last week that would run from late-October 2017 through January 2018. Their outlook would call for the persistence of extensive drought conditions across the northern Plains of Montana and the Dakotas. In addition, sections of the Southwest (southern California, Arizona and Texas), the Mid-South and the southern Appalachians should either experience the continuation of existing drought conditions, or see development of drought. On the other hand, sections of the Northwest (Washington, northern Idaho and western Montana) could see sufficient improvement in drought conditions that would result in the possible removal from drought status. Similarly scattered sections across the nation's midsection and coastal New England) could also see elimination of drought conditions by the end of January 2018. Note: a Seasonal Drought Outlook Discussion is included describing the forecasters' confidence.
• Future temperature and soil moisture conditions associated with a changing climate may alter location of agricultural regions -- An international team of scientists recently completed an US Geological Survey (USGS) study in which they reported that anticipated high temperature extremes and soil moisture conditions associated with a changing climate may cause some regions to become more suitable for rainfed, or non-irrigated, agriculture, while causing other areas to lose suitable farmland. Increases in acreages of rainfed agriculture are projected in North America, western Asia, eastern Asia and South America. In contrast, suitable areas are projected to decline in European dryland areas. [USGS News]

CLIMATE AND THE BIOSPHERE

• Satellite imagery shows contrast between blue waters and green waters over South Pacific -- A map of chlorophyll concentration in the near-surface ocean waters across the South Pacific Ocean was recently assembled from data collected during September by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NASA/NOAA Suomi NPP satellite. The map shows green and yellow colors, which indicate the highest chlorophyll concentrations due to phytoplankton, across the eastern and central equatorial Pacific, as well as across the extratropical waters farther south, while the blue colors over the subtropical regions of the South Pacific have the lowest chlorophyll concentrations. This pattern reflects the counterclockwise circulation of ocean water in the South Pacific Gyre located well away from land masses. [NASA Earth Observatory]

PALEOCLIMATE RECONSTRUCTIONS

• Fossil coral reefs off Texas coast reveals sea level bursts during last major warming event -- A team of scientists from Rice University and Texas A&M University-Corpus Christi's Harte Research Institute for Gulf of Mexico Studies recently discovered Earth's sea level did not rise steadily following the end of the last Ice Age when widespread global warming was occurring, but rather rose in sharp, punctuated bursts. The researchers found this evidence from fossils in drowned reefs offshore of the Texas coast, with several of the bursts ranging in length from a few decades to roughly one century. Consequently, future sea-level rises may also occur sporadically. [Rice University News]

COMPARATIVE PLANETOLOGY

• The ancient Moon could have had an atmosphere serving as a source for lunar water -- Researchers at the NASA Marshall Space Flight Center and at the Lunar and Planetary Institute in Houston, TX recently discovered that the Moon could have had a sufficiently dense atmosphere approximately 3.5 billion years ago. They claim that this atmosphere, which may have been denser than the current atmosphere on Mars, may have been a source for some, if not all, of the water that has been detected on the Moon by such spacecraft as NASA's Clementine as early as 1994. [NASA Marshall Space Flight Center News]

CLIMATE AND SOCIETY

• Earthweek -- Diary of the Planet [earthweek.com]

Concept of the Week: Feedback in Earth's Climate System

Consider examples of positive and negative feedback. A warming trend in climate is likely to accelerate the rate of melting of snow and ice, producing more bare ground that absorbs more solar radiation, further raising the air temperature. A cooling trend prolongs snow and ice cover in spring and summer so that less solar radiation is absorbed, more reflected to space, bringing about additional cooling. In both cases, feedback is positive because the initial change in temperature is amplified.

Consider an example of negative feedback. While feedbacks among temperature, cloud cover, and radiation are not well understood and depend upon circumstances (e.g., type and height of clouds), they could be either positive or negative. It is thought that a warming trend in climate should increase the rate of evaporation of water from Earth's surface and thereby increase low cloud cover. A thicker and more extensive low-cloud cover reflects more solar radiation to space thereby inhibiting a further rise in surface temperature. Hence, this negative feedback would dampen the initial temperature change.

Understanding feedback in the climate system is essential for modeling and predicting climate change. If some agent or mechanism alters the climate, then feedback may either amplify (positive feedback) or dampen (negative feedback) the change in climate. As demonstrated later in this course, many agents and mechanisms can bring about climate change (e.g., variations in solar energy output, regular fluctuations in Earth-Sun geometry). While these climate forcing agents and mechanisms drive climatic change, processes within the planetary climate system involving feedbacks significantly impact the magnitude of climate change.

Overall, which type of feedback prevails in Earth's climate system, positive or negative? A system in which positive feedback prevails is unstable. For Earth, this would move the climate regime toward an extreme characterized by excessive cold that would encase the planet in snow and ice ("snowball" or "ice ball" Earth) or toward the other extreme resulting in much higher temperatures--the product of a runaway greenhouse effect. Although Earth's climate has varied considerably over the billions of years that constitute geologic time, it appears likely that Earth's climate system has been nearly stable with negative feedbacks generally compensating for positive feedbacks.

Historical Events:

• 24 October 1951...Sacramento, CA reported a barometric pressure of 29.42 inches, to establish a record low for October. (The Weather Channel)
• 25 October 1977...Dutch Harbor in Alaska reported a barometric pressure reading of 27.31 inches (925 millibars) in a non-tropical storm to establish an all-time record for the state. (The Weather Channel)
• 26 October 1859...New York City had their earliest substantial snow of record as four inches blanketed the city. (David Ludlum)
• 26 October 1919...The temperature at Bismarck, ND plunged to ten degrees below zero, the earliest subzero reading of record for the city, and a record for the month of October. (The Weather Channel)
• 26 October 1926...Barrow, AK received a record fifteen inches of snow, and also established a 24-hour precipitation record of 1.00 inch, which lasted until the 21st of July in 1987. (The Weather Channel)
• 26 October 1993...The temperature at Eureka, CA soared to 87 degrees to set an all-time high temperature record for the city. (Intellicast)
• 26 October 2010...The lowest barometric pressure ever recorded in the U.S. between the Rockies and the Appalachians with a non-tropical system was set at Big Fork, MN, with a pressure of 955.2 millibars (28.21 inches of mercury). (National Weather Service files)
• 27 October 1929...A snowstorm dumped 27 inches upon Ishpeming, MI in 24 hours to establish a state record. (David Ludlum)
• 28 October 1936...The temperature at Layton, NJ dipped to 9 degrees above zero to establish a state record for the month of October. (The Weather Channel)
• 28 October 1991...Yakima, WA recorded 2.4 inches of snow, equaling the record for October. (Intellicast)
• 29 October 1917...The temperature at Soda Butte, WY the mercury plunged to 33 degrees below zero, an U.S. record for the month of October. (David Ludlum)
• 29 October 1991...Bismarck, ND received 15.9 inches of snow on the 28^th and 29^th. This brought the October snowfall total to 23.5 inches, a new record. (Intellicast)

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Prepared by Edward J. Hopkins, Ph.D., email hopkins@aos.wisc.edu
© Copyright, 2016, The American Meteorological Society.