Sunday, December 18, 2011


From: Phil Jones <>
To: Kevin Trenberth <>
Subject: Re: New versions
Date: Thu Jul 28 09:37:18 2005
Cc: Susan Solomon <>

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.
The bulletted points and back references are below.
� Global-mean surface temperatures show overall warming of 0.75�C 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. []
� 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. [; 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. [; 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 0.8�C
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;]
� 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.
� 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 Ni�os 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,]
� 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. []
� 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:

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.
Kevin E. Trenberth e-mail:
Climate Analysis Section, NCAR [1]
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



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