DataStreme ECS WEEK TWELVE: 20-24 April 2015

ITEMS OF INTEREST

• National Park Week -- The US Department of the Interior's National Park Service has designated the week commencing this week (18-26 April 2015) as National Park Week.
• Celebrate Earth Day --This Wednesday (22 April 2015) marks the 45th Earth Day, first proposed by the late Senator Gaylord Nelson of Wisconsin in 1970 as a teach-in to heighten awareness of the environment. The Nelson Institute for Environmental Studies at the University of Wisconsin-Madison has posted a website called "Gaylord Nelson and Earth Day: The Making of the Modern Environmental Movement" that highlights Senator Nelson and his idea became Earth Day. Several governmental websites provides links to various activities and resources planned for this week, including a website maintained by the US Environmental Protection Agency (EPA). NASA also provides a list of live public events and online activities between 21 and 27 April designed to celebrate Earth Day.
• Celebrating Arbor Day -- This coming Friday, 24 April 2015, many locations across the nation will celebrate Arbor Day, a day when the planting of trees is encouraged. Arbor Day was originally proposed in 1872 by J. Sterling Morton, Nebraska's first newspaper editor, and continues to be most often celebrated by individual states on the last Friday in April. However, since planting conditions vary greatly due to the state's climate it may occur from September to May. In Arkansas, Arbor Day is celebrated on the third Monday in March, but in Alaska, the date is the third Monday in May. For your state's observance (and name of the official state tree), please consult the National Arbor Day Foundation.
• 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 Climatic Data Center (NCDC). Scientists at NCDC 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.

CURRENT CLIMATE STATUS

• Review of global weather and climate for March 2015 -- Using preliminary data collected from the global network of surface weather stations, scientists at NOAA's National Climatic Data Center have determined that the combined global land and ocean surface temperature for March 2015 was the highest for any March since sufficiently detailed global climate records began in 1880. The global temperature for March 2015 was 1.53 Fahrenheit degrees above the 20th century (1901-2000) average. When considered separately, the average land temperature tied 1990 as second highest for any March since 1880, while the temperature over the oceans was the third highest for March. El Niño conditions had developed in March with above average sea surface temperatures across the equatorial Pacific. In addition, the global temperature for the first three months of 2015 were also the highest on record.
  The researchers at the National Snow and Ice Data Center noted the areal extent of the Arctic sea ice reached its annual maximum extent near the end of the third week of March. The areal extent of this sea ice for March 2015 was the smallest since satellite surveillance began in 1979. Conversely, the extent of the Antarctic sea ice was the second largest in the 37-season record. According to data from the Rutgers Global Snow Lab, the Northern Hemisphere snow cover extent for March was the seventh smallest in the 49-year period of record. [NOAA/NCDC State of the Climate] A global map of Selected Significant Climate Anomalies and Events for March 2015 is available from NCDC.
• Waiting for a classic phenological event in Alaska -- For the last 98 years the annual breakup of the ice on Alaska's Tanana River at the community of Nenana has drawn widespread attention due to the wagering in the Nenana River Ice Classic competition. A plot of the time series of the annual ice out dates since 1917 made by the National Snow and Ice Data Center shows interannual (year-to-year) variability in ice-out dates associated with changes in winter temperature and snowfall accumulation in interior Alaska are superimposed upon the nearly century long trend in earlier ice out-dates associated with long-term climate changes. [NOAA Climate.gov News] NOTE: A webcam provides a continuously updated view of the tripod on the Nenana River that is used to officially determine the winner of the Nenana Ice Classic.
• Large iceberg remains afloat off Antarctica for 15 years -- A natural-color image was made in mid January 2015 of the largest fragments of iceberg B-15 by the Operational Land Imager (OLI) onboard NASA's Landsat 8 satellite. This fragment, identified as B-15T, is floating off Antarctica's Princess Astrid Coast and has a size nearly equivalent to that of Connecticut. The original iceberg B-15 broke from Ross Ice Shelf in late March 2000. [NASA Earth Observatory]
• The 2014 hurricane season reviewed -- The 2014 hurricane seasons in both the North Atlantic and North Pacific are reviewed and compared to the more than 150 years of record keeping in the North Atlantic and the 40 years in the eastern North Pacific. [AMS DataStreme Atmosphere]

CURRENT CLIMATE MONITORING

• One day of rain causes flooding in "world's driest climate" -- A low pressure system moving onto the coast of central and northern Chile produced in late March produced one to two inches of rain in a 24-hour span on 25 March 2015 at several locations on the Atacama Desert, arguably the "world's driest climate." This high-altitude South American desert typically receives less than 0.2 inches of rain per year, while some locations claim no measurable rainfall in recorded human history. The recent rain caused flooding of Chile's Copiapó River that had been essentially dry for the last 17 years. Several cities sustained flood damage that claimed at least 24 lives. The combination of strong subtropical high pressure located over the eastern South Pacific Ocean and the cold Humboldt Current near the coast typically create a sufficiently stable atmosphere that limits precipitation across the region. This pattern was disrupted most likely by the current El Niño event, which resulted in the historic rains. [NOAA Climate.gov News]
• A dozen years of satellite data help assess changes in climate -- The Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite has amassed 12 years of global temperature, greenhouse gas and cloud data that scientists have been using to assess how the atmosphere responds to changes from the short term such as El Niño Southern Oscillation (ENSO) events to long term climate trends. [NASA Global Climate Change News]

CLIMATE FORCING

• Wildfires in California emit more greenhouse gases than expected in state climate targets -- In a study conducted by the University of California, Berkley and the National Park Service, wildfires in California's forests and wildlands are contributing more than expected to the Golden State's targeted greenhouse gas emissions. In the Global Warming Solutions Act passed in 2006, the state had mandated goals for no net emissions from wildland ecosystems by 2020. The current study has produced a more detailed assessment quantifying the amount of carbon sequestered in the state's forests and wildlands than previously done. [University of California, Berkley News Center]
• Darkening of Greenland is expected to continue -- A scientist from The City College of New York predicts that based upon a computer model output, a darkening of the Greenland Ice Sheet should continue a consequence of projected increases in temperature. His model only accounts for the effects of warming upon snow grain size and melting. He also noted that a darkening of the Greenland Ice Sheet associated with increasing temperatures and enhanced melting had occurred between 1996 and 2012. [The City College of New York News]
• Wind bursts can affect severity of El Niño events -- Scientists from the University of Maryland and their colleagues from Columbia University and China report that large-scale bursts in the westerly winds across the Tropical Pacific Ocean have a strong influence on El Niño events, which help produce three distinct varieties or "flavors" of El Niño. These westerly wind bursts that form over the western Pacific tend to be "intra seasonal," or at scales between weather and climate. Analyzing 50 years of tropical Pacific sea surface temperature and westerly wind burst data, differences in El Niño events. The researchers hope that new knowledge about detecting and measuring these wind bursts may help in the forecasting of El Niño events. [University of Maryland News]

CLIMATE FORECASTS

• New Seasonal Climate Outlooks released -- During the last week, forecasters at NOAA's Climate Prediction Center (CPC) released their Three-Month (Seasonal) Climate Outlooks for the three-months running from May through July 2015, which contains the last month of meteorological spring and the first two months of two months of meteorological summer. Specific details of their outlooks include:
• Temperature and precipitation outlooks -- According to their temperature outlook, the western third of the nation that consist of the 48 contiguous United States should experience a high chance of above average temperatures for these three upcoming months, with the greatest probability of such an occurrence along the Pacific Coast running southern California north to Washington. Above average temperatures appear to be likely across the Southeast, primarily over the Florida Peninsula. On the other hand, sections of the southern Plains, especially in Texas, appear to have a good chance for below average temperatures. The rest of the "lower 48" were expected to have near equal chances of warmer or cooler than normal conditions.
  Their precipitation outlook calls for better than even chances of dry conditions for May through July 2015 across sections of the Great Lakes States centered on Michigan's Upper Peninsula and northern Wisconsin appearing to have the highest chance of drier than average weather conditions. Conversely, the Southeast and a large section of the southern Plains, the Rockies and the Four Corners area (Arizona, Utah, Colorado and New Mexico) were expected to have a better than even chance of having above average precipitation. The rest of the contiguous United States should have equal chances of below and above average precipitation for late spring and early summer. [NOAA Climate Prediction Center] Outlooks for May are also available. A summary of the prognostic discussion of the outlook for non-technical users is available from CPC. These forecasts were based in part upon the occurrence of El Niño conditions across the equatorial Pacific that should be maintained through at least autumn 2015 in the Northern Hemisphere.
  
• Seasonal Drought Outlook released -- The forecasters at NOAA's Climate Prediction Center also released their US Seasonal Drought Outlook that would run from mid April through July 2015 in which drought conditions were expected to persist across many of the Western States, especially along the West Coast, across the Southwest and the southern Plains. Drought conditions should either develop or continue across the northern Plains and sections of the Midwest around the western Great Lakes. Improvement in drought conditions was expected across the central Plains and sections of the Great Basin, with some areas being removed from drought consideration. Note: a Seasonal Drought Outlook Discussion is included describing the forecasters' confidence.

CLIMATE AND SOCIETY

• Broadcast meteorologists are increasingly convinced of human-caused climate change -- In a recent poll conducted of 464 broadcast meteorologists by George Mason University, more than 90 percent of the respondents agree that climate change is currently happening and 74 percent believe that human activity is at least half responsible. These results were up by roughly ten percent over what a survey showed just four years ago. [Washington Post - Capital Weather Gang ]
• Earthweek -- Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

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).

Concept of the Week: Questions

1. All other factors being equal, the addition of CO₂ to the atmosphere [(increases) (decreases)(has no effect upon)] the flux of infrared radiation from Earth's surface to space.
2. Charney's initial estimate of the amount of global warming that would accompany a doubling of atmospheric CO₂ [(did)(did not)] account for the temperature change(s) likely to accompany feedbacks in Earth's climate system.

Historical Events:

• 20 April 1880...Sacramento, CA had its heaviest 24-hour rainfall when 7.24 inches fell. (Intellicast)
• 20 April 1901...A spring storm produced unusually heavy snow in northeast Ohio. Warren received 35.5 inches in thirty-six hours, and 28 inches fell at Green Hill. Akron established April records of 15.6 inches in 24 hours, and 26.6 inches for the month. Pittsburgh, PA established April records of 12.7 inches in 24 hours, and 13.5 inches for the month. (David Ludlum) (The Weather Channel)
• 20 April 1984...A temperature of 106 degrees in Del Rio, TX set a new record high for April. (Intellicast)
• 20 April 1987...Fifty-two cities in the central and eastern U.S. reported new record high temperatures for the date. The high of 92 degrees at Memphis, TN was a record for April, and the high of 94 degrees at Little Rock, AR equaled their April record. (The National Weather Summary)
• 20 April 1989...Hot weather spread from the southwestern U.S. into the Great Plains Region. Twenty-three cities reported new record high temperatures for the date. The afternoon high of 104 degrees at Tucson, AZ was an April record, and highs of 87 degrees at Provo, UT, 90 at Pueblo, CO, and 85 at Salt Lake City, UT, equaled April records. (The National Weather Summary)
• 21 April 1989...The temperature at Las Animas, CO soared to 100 degrees to establish a state record for April. Twenty-two cities in the central and southwestern U.S. reported record high temperatures for the date. Eight cities equaled or exceeded previous April records. Tucson, AZ experienced its fourth consecutive day of record heat with an afternoon high of 104 degrees, bringing the total number of days during the month of April 1989 to 11 when record high values had either been matched or broken. (The Weather Channel) (The National Weather Summary) (Intellicast)
• 21 April 1992...Two inches of snow fell at International Falls, MN, bringing the winter season snowfall to 106.7 inches and setting a new all-time record for the city. The old record was 104.7 inches set back in the 1988-89 winter season. (Intellicast) Editor's Note: The seasonal snowfall accumulation for the 2008-09 winter reached a record 125.6 inches. EJH
• 22 April 2003...Tropical Storm Ana formed in the southwestern North Atlantic Ocean, becoming the first Atlantic tropical storm (since records began in 1871) to form during the month April. Maximum sustained winds reached 50 mph. (The Weather Doctor)
• 23 April 1910...The temperature at the Civic Center in Los Angeles, CA hit 100 degrees to establish an April record for the city. (The Weather Channel)
• 23 April 1989...Salina, KS was the hot spot in the nation with a high of 105 degrees. The high of 105 degrees established an April record for the state of Kansas. A total of eighteen cities in the central U.S. reported record high temperatures for the date. (The National Weather Summary) (Storm Data) (The Weather Channel)
• 23 April 1996...One inch of snow on this day at Cleveland, OH brought its seasonal snowfall to 101.1 inches -- the city snowiest winter ever. The old record was 100.5 inches set in 1981-82. (Intellicast)
• 24 April 2003...The temperature at Juneau, AK soared to a maximum of 70 degrees, the earliest occurrence of a 70-degree reading for the period of record in Alaska's capital city. (The Weather Doctor)
• 25 April 1875...New York City received three inches of snow, the latest measurable snow of record for that location. (David Ludlum)
• 25 April 1898...The temperature at Volcano Springs, CA hit 118 degrees to establish an U.S. record for the month of April. (The Weather Channel)

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Prepared by Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2015, The American Meteorological Society.