cc: gschmidt@giss.nasa.gov, jhansen@giss.nasa.gov, christy@nsstc.uah.edu, mears@remss.com, frank.wentz@remss.com, p.jones@uea.ac.uk, shs@stanford.edu, wallace@atmos.washington.edu, cdcamp@amath.washington.edu, lean@demeter.nrl.navy.mil, david.parker@metoffice.com, santer1@llnl.gov, peter.thorne@metoffice.gov.uk, manabe@splash.princeton.edu, j.m.gregory@reading.ac.uk, meehl@ucar.edu
date: Thu, 28 Feb 2008 00:37:37 -0700
from: Kevin Trenberth <trenbert@ucar.edu>
subject: Re: cold winter in context... a story
to: Andrew Revkin <anrevk@nytimes.com>

   Andy
   I am in Germany and not up to speed on this.  However, past experience suggests that the
   weather signal is dominant at any instant and ENSO related variability far overwhelms any
   greenhouse signal in any year.  It is well established that there is a moderate to strong
   La Nina underway. That should be the null hypothesis.  La Nina not only cools the tropical
   Pacific as cold anomalies built up over time and buried beneath the surface emerge, but
   also radically changes the atmospheric circulation across the world, especially in the
   winter hemisphere.  This changes the jet stream, storm tracks, cloud, precipitation and
   temperatures.   These are general statements, not ones specific to this event, and no doubt
   detailed analysis of this event is available from CPC NOAA.
   In short, this says nothing about long-term global warming.  In fact such things should be
   expected.  Weather and climate variability continues.
   Kevin
   Andrew Revkin wrote:

   As you all are aware, a very vocal and plugged-in crew has been making much of the recent
   downturn in temps.

   Because the 'Average Joe' out there is only hearing radio soundbites about the sun turning
   off, or cable-news coverage or some stray TV image of snow in baghdad (and particularly
   with a big 'skeptics conference' coming next week), I think it's important to do a story
   putting a cold stretch in context against the evidence for the long-term warming trajectory
   from greenhouse forcing. Would need input from you by end of Thursday ideally.

   I've already queried a heap of Arctic hands on sea-ice fluctuations with intrsting
   responses (as I wrote 10/2/07, it's still mainly first-year thin ice, and -- by volume of
   sea ice -- there ain't much).

   Also need to explore questions related to solar trends.

   First request (for those of you from the four groups tracking temps) is for you to to look
   at the data below. Anthony Watts has (potentially usefully, if the data are accurate)
   compiled the four main ongoing efforts to track things. Can you tell me if the datasets
   he's used are correct for your groups??

   here's text file

   [1]http://wattsupwiththat.files.wordpress.com/2008/02/4metrics_temp_anomalies.txt

   here's his graph

   [2]http://wattsupwiththat.files.wordpress.com/2008/02/giss-had-uah-rss_global_anomaly_1979-
   2008.png

   We'd like to explore this graphically as well, perhaps looking at winter temps in
   isolation, or just doing something akin to what's been done above.

   And then there are the substance questions. I'd love it if you'd weigh in on any or all,
   either in an email or call.

   1) How unusual is the current downturn? In particular, in relation to ENSO and other cycles
   that might cut the other way etc?  Any 'easy' explanations, or is it good old-fashioned
   variability?

   2) Anything pop out when you look at the hemispheres as opposed to global?

   3) Do  you see ANY evidence of solar activity playing a role, either background or
   foreground?

   4) Presumably global HEATING is continuing apace, even as global TEMP fluctuates. Is that
   right, and/or are there ocean data showing ongoing heating of seas etc?

   5) The folks using the cold snap to attack greenhouse theory include some of the same
   people who blamed 'hot heads' for using hot years to support their view of what's coming.
   Does that seem the case to you ?

   6) Takehome message?

   As always, your thoughts are much appreciated. Feel free to respond to me alone or to the
   group to inspire some multi-logue.

--

   Andrew C. Revkin
   The New York Times / Science
   620 Eighth Ave., NY, NY 10018
   Tel: 212-556-7326 Mob: 914-441-5556
   Fax:  509-357-0965

   [3]www.nytimes.com/revkin

--
****************
Kevin E. Trenberth                              e-mail: [4]trenbert@ucar.edu
Climate Analysis Section, NCAR                  [5]www.cgd.ucar.edu/cas/
P. O. Box 3000,                                 (303) 497 1318
Boulder, CO 80307                               (303) 497 1333 (fax)

Street address: 1850 Table Mesa Drive, Boulder, CO  80305

