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 subject: Re: cold winter in context... a story to: Andrew Revkin 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