From: Phil Jones <p.jones@uea.ac.uk>
To: Kevin Trenberth <trenbert@ucar.edu>
Subject: Re: New versions
Date: Thu Jul 28 09:37:18 2005
Cc: Susan Solomon <ssolomon@al.noaa.gov>

    Kevin/Susan,
        I'll look over 3.9. A quick look at the back references to sections which contain
    the detail summarized here, suggests that you've got the right level of section. I guess
    we could add a sentence to say that this/these are the principal section(s), but the whole
    of the x.x section is likely also relevant.
        I've added Susan in to show what we're doing. It might be appropriate for other
    chapters. Part of my reason was traceability, but also we are referring to subsequent
    sections in Chapters 4 and 5.
        The figures seem to be coming along well. Pdfs are also. I'll send another
    reminder about these out later today, when I've had one last look for a few of them.
    I'll attach section numbers as there are so few now.
    Cheers
    Phil
    The bulletted points and back references are below.
     ·         Global-mean surface temperatures show overall warming of 0.75ºC over the
   19012004 period although rates of temperature rise are much greater after 1979.   Both land
   surface air temperatures and SST show warming although land regions have warmed at a faster
   rate than the oceans for both hemispheres in the past few decades, consistent with the much
   greater mass and thermal inertia of the oceans.  Some areas have not warmed in recent
   decades, and a few have cooled although not significantly. [3.2.2]
   ·         The warming of the climate is consistent with a widespread reduction in the
   number of frost days in mid-latitude regions. The latter is due to an earlier last day of
   frost in spring rather than a later start to the frost season in autumn. The increase in
   the number of daily warm extremes and reduction in cold extremes across over 70% of land
   regions studied have been most marked at night over the 1951-2003 period.  The greater
   increase in nighttime as opposed to daytime temperatures has continued. [3.8.2.1]
   ·         Widespread (but not ubiquitous) decreases in continental DTR since the 1950s
   occur with increases in cloud amounts, as expected from the impact of cloud cover on solar
   heating of the surface. [3.2.2; 3.4.3]
   ·         The temperature increases are consistent with the observed nearly worldwide
   reduction in mountain glacier mass and extent. A few regions of the world where mountain
   glacier termini are determined by winter precipitation totals, as opposed to summer
   temperatures, do show some advances, but these are consistent with changes in circulation
   and associated increases in winter precipitation (e.g., southwestern Norway, parts of
   coastal Alaska, southern Chile and Fjordland of the South Island of New Zealand). Tropical
   ice caps in South America, Africa and Tibet have all shown remarkable declines in recent
   decades. If continued, some may disappear within the next 30 years. Reduction in mass of
   such glaciers depends on local heat budgets, which is not necessarily reflected in local
   temperature changes. The temperature records all show a slight warming, but nowhere near
   the magnitude required to explain the rapid demise of the many of the ice caps. [4.5]
   ·         Snow cover has decreased in many NH regions, particularly in the spring season,
   consistent with greater increases in spring as opposed to autumn temperatures in
   mid-latitude regions. The decrease is accompanied by increased active layer thickness above
   permafrost and decreased seasonally frozen ground depths. [3.3.2.3; 4.2.4, 4.8]
   ·         Sea-ice extents have decreased in the Arctic, particularly in the spring and
   summer seasons, and patterns of the changes are consistent with regions showing a
   temperature increase, although changes in winds are also a major factor. Decreases are
   found in the length of the freeze season of river and lake ice. [3.2.2.3; 4.3, 4.4, 5.3.3]
   ·         Surface temperature variability and trends since 1979 are consistent with those
   estimated by most analyses of satellite retrievals of lower-tropospheric temperatures,
   provided the latter are adequately adjusted for all issues of satellite drift, orbit decay,
   different satellites and stratospheric influence on the T2 records, and also with ERA-40
   estimates of lower-tropospheric temperatures. The range from different datasets of global
   surface warming since 1979 is 0.15 to 0.18 compared to 0.12 to 0.19 K decade^-1 for MSU
   estimates of lower tropospheric temperatures. [3.4.1]
   ·         Stratospheric temperature estimates from radiosondes, satellites (T4) and
   reanalyses are in qualitative agreement recording a cooling of between 0.3 and 0.8ºC
   decade^-1 since 1979. Increasing evidence suggests increasing warming with altitude from
   1979 to 2004 from the surface through much of the troposphere in the tropics, cooling in
   the stratosphere, and a higher tropopause, consistent with expectations from observed
   increased greenhouse gases and changes in stratospheric ozone. Over extratropical land, the
   larger warming at night is associated with larger surface temperature changes. [3.4.1]
   ·         Radiation changes at the top-of the atmosphere from the 1980s to 1990s, possibly
   ENSO related in part, appear to be associated with reductions in tropical cloud cover, and
   are linked to changes in the energy budget at the surface and in observed ocean heat
   content in a consistent way. [3.4.3; 3.4.4]
   ·         Surface specific humidity has also generally increased after 1976 in close
   association with higher temperatures over both land and ocean.  Consistent with a warmer
   climate, total column water vapour has increased over the global oceans by 1.2 ± 0.3% from
   1988 to 2004, consistent in patterns and amount with changes in SST and a fairly constant
   relative humidity.  Upper tropospheric water vapour has also increased in ways such that
   relative humidity remains about constant, providing a major positive feedback to radiative
   forcing. [3.4.2]
   ·         Over land a strong negative correlation is observed between precipitation and
   surface temperature in summer and in low latitudes throughout the year, and areas that have
   become wetter, such as the eastern United States, have not warmed as much as other land
   areas.  Increased precipitation is associated with increases in cloud and surface wetness,
   and thus increased evaporation. Although records are sparse, continental-scale estimates of
   pan evaporation show decreases, due to decreases in surface radiation associated with
   increases in clouds, changes in cloud properties, and increases in air pollution in
   different regions from 1970 to 1990. There is tentative evidence to suggest that this has
   reversed in recent years.  The inferred enhanced evaporation and reduced temperature
   increase is physically consistent with enhanced latent versus sensible heat fluxes from the
   surface in wetter conditions. [3.3.5; 3.4.4.2]
   ·         Surface observations of cloud cover changes over land exhibit coherent variations
   on interannual to decadal time scales which are positively correlated with gauge-based
   precipitation measurements. [3.4.3]
   ·         Consistent with rising amounts of water vapour in the atmosphere, increases in
   the numbers of heavy precipitation events (e.g., 90/95^th percentile) have been reported
   from many land regions, even those where there has been a reduction in total precipitation.
   Increases have also been reported for rarer precipitation events (1 in 50 year return
   period), but only a few regions have sufficient data to assess such trends reliably.
   [3.4.2; 3.8.2.2]
   ·         Patterns of precipitation change are much more spatially- and seasonally-variable
   than temperature change, but where significant changes do occur they are consistent with
   measured changes in streamflow. [3.3.4]
   ·         Droughts have increased in various parts of the world.  The regions where they
   have occurred seem to be determined largely by changes in SSTs, especially in the tropics,
   through changes in the atmospheric circulation and precipitation. Inferred enhanced
   evaporation and drying associated with warming and decreased precipitation are important
   factors in increases in drought. In the western United States, diminishing snow pack and
   subsequent summer soil moisture reductions have also been a factor. In Australia and
   Europe, direct links to warming have been inferred through the extreme nature of high
   temperatures and heat waves accompanying drought. [3.3.4, QACCS 3.3, 3.8.3, 4.x.x]
   ·         Changes in the freshwater balance of the Atlantic Ocean over the past four
   decades have been pronounced as freshening has occurred in the North Atlantic and also
   south of 25°S, while salinity has increased in the tropics and subtropics, especially in
   the upper 500 m. The implication is that there have been increases in moisture transport by
   the atmosphere from the subtropics to higher latitudes, in association with changes in
   atmospheric circulation, including the NAO, thereby increasing precipitation over the
   northern ocean and in adjacent land areas (as observed). [3.3.2, 3.3.3, 5.3.2, 5.5.3]
   ·         Changes in the large-scale atmospheric circulation are apparent. Increasing
   westerlies have been present in both hemispheres as enhanced annular modes. In the NH, the
   NAM and NAO change the flow from oceans to continents and are a major part of the
   wintertime observed change in storm tracks, precipitation and temperature patterns,
   especially over Europe and North Africa. In the SH, SAM changes, in association with the
   ozone hole, have been identified with recent contrasting trends of large warming in the
   Antarctic Peninsula, and cooling over interior Antarctica. [3.5, 3.6, 3.8.3]
   ·         The 19761977 climate shift toward more El Niños has affected Pacific rim
   countries and monsoons throughout the tropics. Over North America, ENSO and PNA-related
   changes appear to have led to contrasting changes across the continent, as the west has
   warmed more than the east, while the latter has become cloudier and wetter. [3.6, 3.7]
   ·         Variations in extratropical storminess are strongly associated mostly with
   changes in mean atmospheric circulation, such as changes and variations in ENSO, NAO, PDO,
   and SAM. Wind and significant wave height analysis support the reanalysis-based evidence
   for an increase in extratropical storm activity in the NH in recent decades. After the late
   1990s, however, some of these variations seemed to change sign. [3.5, 3.6, 3.8.3.2]
   ·         Changes are observed to occur in the number, distribution and tracks of tropical
   storms that are clearly related to ENSO phases and to a slightly lesser extent to the AMO
   and QBO modulations.  Increases in intensity and lifetimes of tropical storms since the
   1970s are consistent with increases in SSTs and atmospheric water vapour. [3.8.3.1]
   ·         Sea level likely rose about 18±3 cm during the 20^th century, but increased
   3.0±0.4 mm/year after 1992, when confidence increases from global altimetry measurements.
   During this period, glacier melt has increased ocean mass by order 1.0 mm/year, increases
   in ocean heat content and associated ocean expansion are estimated to contribute 1.6
   mm/year, while changes in land water storage are uncertain but may have taken water out of
   the ocean.  Isostatic rebound contributes about 0.3 mm/year. This near balance gives
   increased confidence that the observed sea level rise is a strong indicator of warming, and
   an integrator of the cumulative energy imbalance at the top of atmosphere.[4.5, 4.7, 4.9.8,
   5.2, 5.5]
   At 23:47 27/07/2005, Kevin Trenberth wrote:

     Phil
     I placed new versions of the figure and text files on my ftp site.  I implemented your
     suggestion of adding section numbers to the 3.9.  I used the ones from the ZOD wrt other
     chapters.  So they may change.  I also added a small piece on freezing seasons on lakes
     and rivers that was mentioned in the last para but not in any bullets.  You may like to
     comment on this as some are x.x, some are y.y.y and some are z.z.z.z.
     In the first case the whole section is really applicable and so mentioning each
     subsection does not seem worthwhile.  Should we go to the z.z.z.z level, as that is not
     in the TOC?
     In doing this I found that two sections in 3.8 had very similar titles and so I changed
     that of 3.8.3 to explicitly say tropical and extratrtopical storms and extreme events,
     which are the 3 subsections. The Table of contents (TOC) is all up to date, and now
     corrected for one subsection that was mislabeled as level 2 instead of 3.
     Several figures have been revised.
     I am out tomorrow all day but Lisa tells me she is up to w in the references.  So should
     have a complete new version on Friday.  Hopefully several of the figures will be by
     upgraded then too.  I have a new Fig 3.3.1 but can't work with it: something wrong with
     it, so I've asked Dave E for a different one. Main outstanding stuff is all waiting on
     Dave Easterling.  I have requests in to Tom Karl on the 2 CCSP figures.
     Following my earlier email I have responses on Figs 3.2.3: now good, 3.4.6 I did, 3.5.2,
     and one from Groisman.  So only 7 figures not in final form.
     I believe we have 74 figures in the sense that they are separate files.
     That includes counts of 1 for several multipanel files (like some T ones or the
     hurricane one), but 4 for some 4 panel ones like the ENSO one, where the files were all
     generated anew and independently.  So the good part is that 67 of them are in great
     shape.  We actually have 48 figures counting the 2 TAR ones that will be in 3.9, and 3
     in the 3 QACCS.
     Cheers
     Kevin
     --
     ****************
     Kevin E. Trenberth                              e-mail: trenbert@ucar.edu
     Climate Analysis Section, NCAR                  [1]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  80303

   Prof. Phil Jones
   Climatic Research Unit        Telephone +44 (0) 1603 592090
   School of Environmental Sciences    Fax +44 (0) 1603 507784
   University of East Anglia
   Norwich                          Email    p.jones@uea.ac.uk
   NR4 7TJ
   UK
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References

   1. http://www.cgd.ucar.edu/cas/

