cc: tcrowley@duke.edu date: Mon Apr 7 15:03:19 2003 from: Keith Briffa to: "Jenkins, Geoff" , "Parker, Dave" , "Tett, Simon" , "Folland, Chris" , "Stott, Peter" , "Jones, Gareth" Bcc: pnl_group.all Simon and all sorry to have been somewhat silent recently . I am now back at work after my operation and eager to state that what Tom says here is right on the nail. I believe passionately that we have a long way to go to get realistic and accurate (absolute) measures of Hemispheric temperatures over the last millennium and earlier . However, we must not lose sight of the fact that the "best evidence" is certainly in support of unprecedented (truly mean Hemispheric and annual) warming in the 20th century and recent decades. The modern (instrumental) indications of Hemispheric warmth are (almost literally) incomparably superior to those based on our high-resolution proxy records (with their narrow coverage and largely summer seasonal bias) . Even pushing the few individual records to their maximum warmth limit , the most sensible interpretation of the data does provide much of a case for equivalent warmth in any "Medeival" period (or on any timescale). Those who prefer to believe in a globally warmer Medieval period largely fall back on poorly resolved , even more selective evidence that has real problems e.g. interpretable signal (temp. versus precip.) ; qualitative measurement ; non-deconvolved lagged responses, and geographical bias that is at least as poor as our high-resolution data. The science is not progressed without overcoming these problems. Our own desire to recognize and address the limitations of our own data in the search for accurate and absolute climate histories should not be confused with a clear expression that "as we stand" the evidence against unprecedented recent warming does not carry the day. At 09:57 AM 4/4/03 -0500, Tom Crowley wrote: Keith, forgot to cc you on this, Tom Date: Fri, 4 Apr 2003 09:56:40 -0500 To: Simon Tett From: Tom Crowley Subject: Re: [simon.brown@metoffice.com: PRESS: 20th century is neither the warmest century nor the centur y with the most extreme weather of the past 1000 years] Cc: "Jenkins, Geoff" , "Parker, Dave" , "Tett, Simon" , "Folland, Chris" , "Stott, Peter" , "Jones, Gareth" Bcc: pnl_group.all X-Attachments: Simon, along with others I was contacted by a New York Times reporter on the Soon and Baliunas paper - I know that Phil is chagrined by the Soon and Baliunas paper. Some of us are thinking about writing some type of rebuttal. at least three main problems in that paper are: 1) they show no data - only report what others state (sort of a pseudo-Bayesian expert assessment). 2) they report various multi-decadal warmings from different places, totally ignoring that they occur at different times - this was the point I made earlier in a paper I wrote in Ambio (others too have made the same point). 3) the reporting is suspect - in the description of my ambio paper they state that the data coverage was worldwide - it was not - all the data points were from the mid-high latitudes northern hemisphere, but the composite was compared against the northern hemisphere instrumental record. They also state that I conclude that there was no Medieval Warm Period. Yet the title of my paper was "How warm was the Medieval Warm Period?" I do state that there was such a thing as a period in the Middle Ages warmer than the Little Ice Age - just that peak composite warming was no greater than the mid-20th century warming. the reason that Soon and Baliunas have gotten a lot of attention about this is that the conservative publicity machine in the U.S. has contacts in high places - the rest of us could write the most eloquent, rigorous rebuttal and proof in the world and it would at best wind up in the trash bin of some Congressional committee. Regards, Tom Keith, Tom Baliunus and Soon are stirring things again -- does what they say make sense. Tom I think you have said that the late medieval warm period is not a coherent thing... Simon ------- Start of forwarded message ------- Content-return: allowed Date: Fri, 04 Apr 2003 10:32:18 +0100 From: "Brown, Simon" Subject: PRESS: 20th century is neither the warmest century nor the centur y with the most extreme weather of the past 1000 years To: "Jenkins, Geoff" , "Parker, Dave" , "Tett, Simon" , "Folland, Chris" , "Stott, Peter" , "Jones, Gareth" Content-type: text/plain; charset=iso-8859-1 Importance: high X-Priority: 1 Dear all, as usual with the media it's they need the answer yesterday. Comments please. Simon. > -----Original Message----- > From: Clarke, Sean > Sent: 04 April 2003 10:03 > To: Brown, Simon > Subject: FW: Past climate records > Importance: High > > > Hello Simon, > > As discussed, please find below the e-mail from Robert Matthews of the > Sunday Telegraph. Could you please get back to him ASAP. > > Many thanks > > > Sean > > > > -----Original Message----- > From: Robert Matthews [SMTP:r.matthews@physics.org] > Sent: 04 April 2003 09:49 > To: sean.clarke@metoffice.com > Subject: Past climate records > Importance: High > > Hi Sean > > Here's the press release. I'd very much appreciate any comments from Geoff > et al about what this review means for statements we often hear that "This > year is the warmest /among the warmest on record". As this is usually > taken to be since records began in 1659, during which we were in the midst > of the Little Ice Age, does this research outlined below mean that current > record-breaking years may not be as significant as once thought ? > > many thanks > Robert > =============== > > Harvard-Smithsonian Center for Astrophysics > > Release No: 03-10 > For Immediate Release: March 31, 2003 > > Cambridge, MA -- A review of more than 200 climate studies led by > researchers at the Harvard-Smithsonian Center for Astrophysics has > determined that the 20th century is neither the warmest century nor the > century with the most extreme weather of the past 1000 years. The review > also confirmed that the Medieval Warm Period of 800 to 1300 A.D. and the > Little Ice Age of 1300 to 1900 A.D. were worldwide phenomena not limited > to the European and North American continents. While 20th century > temperatures are much higher than in the L ittle 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 Idso and Sherwood Idso (Center for the Study 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 over the past four decades. > Their repor t, covering a multitude of geophysical and biological climate > indicators, provides a detailed look at climate changes that occurred in > different regions around the world over the last 1000 years. > > "Many true research advances in reconstructing ancient climates have > occurred over the past two decades," Soon says, "so we felt it was time to > pull together a large sample of recent studies from the last 5-10 years > and look for patterns of variability and change. In fact, clear patterns > did em erge 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 medieval warmth." > > Soon and his colleagues concluded that the 20th century is neither the > warmest century over the last 1000 years, nor is it the most extreme. > Their findings about the pattern of historical climate variations will > help make computer climate models simulate both natural and man-made chan > ges more accurately, and lead to better climate forecasts especially on > local and regional levels. This is especially true in simulations on > timescales ranging from several decades to a century. > > Historical Cold, Warm Periods Verified > > Studying climate change is challenging for a number of reasons, not the > least of which is the bewildering variety of climate indicators - all > sensitive to different climatic variables, and each operating on slightly > overlapping yet distinct scales of space and time. For example, tree ring > studies can yield yearly records of temperature and precipitation trends, > while glacier ice cores record those variables over longer time scales of > several decades to a century. > > Soon, Baliunas and colleagues analyzed numerous climate indicators > including: borehole data; cultural data; glacier advances or retreats; > geomorphology; isotopic analysis from lake sediments or ice cores, tree or > peat celluloses (carbohydrates), corals, stalagmite or biologi cal > fossils; 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 fossils; pollen; seafloor sediments; luminescent analysis; > tree ring growth, including either ring width or maximum late-wood > density; and shifting tree line positions plus tree stumps in lakes, > marshes and streams. > > "Like forensic detectives, we assembled these series of clues in order to > answer a specific question about local and regional climate change: Is > there evidence for notable climatic anomalies during particular time > periods over the past 1000 years?" Soon says. "The cumulative evidence > showed that such anomalies did exist." > > The worldwide range of climate records confirmed two significant climate > periods in the last thousand years, the Little Ice Age and the Medieval > Warm Period. The climatic notion of a Little Ice Age interval from 1300 to > 1900 A.D. and a Medieval Warm Period from 800 to 1300 A.D. appears to be > rather well-confirmed and wide-spread, despite some differences from one > region to another as measured by other climatic variables like > precipitation, drought cycles, or glacier advances and retreats. > > "For a long time, researchers have possessed anecdotal evidence supporting > the existence of these climate extremes," Baliunas says. "For example, the > Vikings established colonies in Greenland at the beginning of the second > millennium that died out several hundred years later when the climate > turned colder. And in England, vineyards had flourished during the > medieval warmth. Now, we have an accumulation of objective data to back up > these cultural indicators." > > The different indicators provided clear evidence for a warm period in the > Middle Ages. Tree ring summer temperatures showed a warm interval from 950 > A.D. to 1100 A.D. in the northern high latitude zones, which corresponds > to the "Medieval Warm Period." Another database of tree growth from 14 > different locations over 30-70 degrees north latitude showed a similar > early warm period. Many parts of the world show the medieval warmth to be > greater than that of the 20th century. > > The study -- funded by NASA, the Air Force Office of Scientific Research, > the National Oceanic and Atmospheric Administration, and the American > Petroleum Institute -- will be published in the Energy and Environment > journal. A shorter paper by Soon and Bal iunas appeared in the January 31, > 2003 issue of the Climate Research journal. ------- End of forwarded message ------- -- Dr Simon Tett Managing Scientist, Data development and applications. Met Office Hadley Centre Climate Prediction and Research London Road Bracknell Berkshire RG12 2SY United Kingdom Tel: +44 (0)1344 856886 Fax: +44 (0)1344 854898 E-mail: simon.tett@metoffice.com [1]http://www.metoffice.com -- Thomas J. Crowley Nicholas Professor of Earth Systems Science Dept. of Earth and Ocean Sciences Nicholas School of the Environment and Earth Sciences Box 90227 103 Old Chem Building Duke University Durham, NC 27708 tcrowley@duke.edu 919-681-8228 919-684-5833 fax -- Thomas J. Crowley Nicholas Professor of Earth Systems Science Dept. of Earth and Ocean Sciences Nicholas School of the Environment and Earth Sciences Box 90227 103 Old Chem Building Duke University Durham, NC 27708 tcrowley@duke.edu 919-681-8228 919-684-5833 fax -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [2]http://www.cru.uea.ac.uk/cru/people/briffa/ -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [3]http://www.cru.uea.ac.uk/cru/people/briffa[4]/