RCEC Email 6.2.03


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Reconstructing Climatic and Environmental Changes
Email 6.2.03

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RCEC Email 6.2.03

  1. 1. V "Card, Robert" <Robert.Card §hq.dae.gav> A 06/0212003 07:49:18 AM Record Type: RecordMhoy To: Phil Cooney/CEQ/EOP~EOP, "James Mhey(E-mail)" <James.R.Mahoney~noaa.gov> cc: Subject: FW: 20th Century Climate Not So Hot I assume you all saw this but just in case. …---OriginalMessage --- From: Richard Seibert [mnailto:rseibert~annctr.org Sent: Friday, May 30, 2003 10:59 AM Subject: 20th Century Climate Not So Hot Harvard ShieldSmithsonian Sunburst Harvard-Smithsonian Center for Astrophysics Press Release [red bar] <http:I/cfa-www.harvardl.edul> [CfA Hor e] <http://cfa-www.harvard.edu/flewtop/search.html> [CfA Search] <http://cfa-www.harvard.edu/lev~top/cfahelp.htmI- [CfA Help] Release No.: 03-10 For Release: March 31, 2003 20th Century Climate Not So Hot Cambridge, MA - A review of more than 200 clime te studies led by researchers at the Harvard-Smithsonian Center for Astrophysi s has determined that the 20th century is neither the warmest century nor th E)century with the most extreme weather of the past 1000 years. The revipw also confirmed that the Medieval Warm Period of 800 to 1300 A.D. and tl e Little Ice Age of 1300 to 1900 A.D. were worldwide phenomena not limnite to the European and North American continents. While 20th century tempera res are much higher than in the Little Ice Age period, many parts of the world show the medieval warmth to be greater than that of the 20th century. Smithsonian astronomers Willie Soon and Sallie Baliunas, with co-authors Craig ldso and Sherwood ldso (Center for the StLudy of Carbon Dioxide and Global Change) and David Legates (Center for Climatic Research, University of Delaware), compiled and examined results from more than 240 research papers published by thousands of researchers o er the past four decades. Their report, covering a multitude of geophysical ~nd biological climate indicators, provides a detailed look at climate chahges that occurred in different regions around the world over the last idoij years. "Many true research advances in reconstructing ncient climates have
  2. 2. time to occurred over the past two decades," Soon says, "s we felt it was pull together a large sample of recent studies from :he last 5-1 0 years and look for patterns of variability and change. In fact, clear patterns did emerge showing that regions worldwide experienced the highs of the Medieval Warm Period and lows of the Little Ice Age, and that 20th century temperatures are generally cooler than during the rjiedieval warmth." the Soon and his colleagues concluded that the 2Oth c ntury is neither Their warmest century over the last 1000 years, nor is it 5he most extreme. make findings about the pattern of historical climate vani ~tions will help computer climate models simulate both natural andI man-made changes more and accurately, and lead to better climate forecasts esoiecially on local regional levels. This is especially true in simulationh on timescales ranging from several decades to a century. Historical Cold, Warm Periods Verified not the Studying climate change is challenging for a number of reasons, least of which is the bewildering variety of climate idicators - all sensitive to different climatic variables, and each cperating on slightly tree ring overlapping yet distinct scales of space and time. l~r example, trends, studies can yield yearly records of temperature an precipitation while glacier ice cores record those variables over longer time scales of several decades to a century.I Soon, Baliunas and colleagues analyzed numerou climate indicators including: borehole data; cultural data; glacier advhnces or retreats; tree or geomorphology; isotopic analysis from lake sediments or ice cores, fossils; peat celluloses (carbohydrates), corals, stalagmit4 or biological net ice accumulation rate, including dust or chemical counts; lake fossils and sediments; river sediments; melt layers in ice cores; phenological (recurring natural phenomena in relation to climate) and paleontological growth, fossils; pollen; seafloor sediments; luminescent analysis; tree ring including either ring width or maximum late-wood density; and shifting tree line positions plus tree stumps in lakes, marshes and streams. order to "Like forensic detectives, we assembled these se 1es of clues in Is there answer a specific question about local and region I climate change: over evidence for notable climatic anomalies during pqrticular time periods that such the past 1000 years?" Soon says. "The cumulative evidence showed anomalies did exist.''" climate The worldwide range of climate records confirmeli two significant periods in the last thousand years, the Little Ice a~g the Medieval Warm and tol1900 Period. The climatic notion of a Little Ice Age intehal from 1300 A.D. and a Medieval Warm Period from 800 to 13aoo A.D. appears to be rather one region to well-confirmed and wide-spread, despite some differences from drought another as measured by other climatic variables ike precipitation, cycles, or glacier advances and retreats. supporting "For a long time, researchers have possessed a ecdotal evidence the existence of these climate extremes," Baliun s says. "For example, the second Vikings established colonies in Greenland at the beginning of the millennium that died out several hundred years I tar when the climate turned warmth. colder. And in England, vineyards had flourished during the medieval Now, we have an accumulation of objective data to back up these cultural indicators." in the The different indicators provided clear evidence 'or a warm period Middle Ages. Tree ring summer temperatures sl owed a warm interval from 950 to A.D. to I1100 A.D. in the northern high latitude zc nes, which corresponds from 14 the "Medieval Warm Period." Another database ) tree growth similar early different locations over 30-70 degrees north latituide showed a to be greater warm period. Many parts of the world show the A medievai warmth
  3. 3. eerh h - than that of the 20th century. aSinii cetfc eerh h The study funded by NASA, the Air Force Officeor hnd the American Petroleum - National Oceanic and Atmospheric Administration, journal. A seo Institute will be published in the Energy and Envirjnment 31, 2003 isseo shorter paper by Soon and Baliunas appeared in tile January the Climate Research journal.I indicators are available online at NOTE TO EDITORS: Photos of key climate Il http://cfa-www~harvard.edu/press/prSl 3 Oimage.ht <http://cfa-www.harvard.edu/press/prO I oimnage.hjml> the IHarvard-Smithsonian Center Headquartered in Cambridge, Massachusetts, between the Smithsonian for Astrophysics (CTA) is a joint collaborationColleg E Observatory. CfA Astrophysical Observatory and the Harvard study the origin, scientists organized into six research divisions evolution, and ultimate fate of the universe. For more information, contact: David Aguilar, DirectorCenter for Affairs of Public Astrophysics Harvard-Smithsonian Fax: 617-495-7468 Phone: 617-495-7462 <mailto:daguilar~cfa. arvard.edu> daguilar~cfa.harvard.edu Christine Lafon Public Affairs Specialist Harvard-Smithsonian Center for Astrophysics Phone: 617-495-7463, Fax: 617-495-7016 clafon~cfa.harvard.edu <mailto:clafon@Cfa.harvard.edu> EST Last modified on Monday, 31-Mar-2003 15:18:29 a.harvard.edui Comments or Questions? Contact pubaffairs~cf <mailto:pubaffairs@Cfa.harvard ,edu> I i-mageOO.if ID -imageOO3.gif D I m gi-. I maeD-gi I mage16.g-