date: Wed, 05 Apr 2000 10:48:51 -0400
subject: Re: SPM informal review
to: "Griggs, Dave" <djgriggsatXYZxyzo.gov.uk>, aldiroffatXYZxyznoaa.gov
Dan, this is an outstanding format --- substantially cleaner than the last
draft which was excellent as a first draft. This will be a very useful
document. I have listed below additions and changes to areas where Chapter
2 has a major input, and then listed more specific comments, where I would
urge others to respond.
Figure 1 needs to be reworked --- I am sending you the correct version of
the 1000 year time series, plus some other time series that may help with
temperatures prior to 1000 years, e.g., Vostok and Greenland Ice Cores,
plus other shorter paleo records.
Figures 2 & 3 are very good
Figure 4 --- I hope this figure will be in color, because right now it is
too complicated to send an easy to understand message, there are too many
options and it appears a bit overwhelming to disentagle. If the details of
are not important it may be better to just show the bands of response
without regard to specific models and emission scenarios.
Page 3 line 21 --- replace with ---- "oceans have increased by between 0.4
and 0.8C since 1861, which is when direct"
Page 3 line 25 --- replace with --- " We now know that the global warming
of the 20th Century was likely to have been the largest "
Page 3 line 41 --- replace with --- "estimated uncertainties, there remains
an unexplained difference of about 0.05 to 0.10 deg C per decade"
Page 3 line 49 --- replace with --- "which has now been shown to closely
relate to observed increase in water vapor and"
Page 4 line 14 --- insert --- "New data from submarines indicate that that
there has been about a 40% decline in Arctic sea ice thickness in summer or
early autumn between the mid 1990s and the period 1958-76. Restricted
sampling however, leaves open the possiblity that these changes may not
reflect broad areas of the arctic.
Page 4 line 20 --- Why have we lowered the range of sea level rise from
10-25cm to 10-20cm?
Page 4 line 30 --- I am concerned about using the phrase "but the causes
are not clear" becuase for some changes like the second bullet in this
section lines 39-41, the causes seem quite clear --- all models in a warmer
world project increases in extreme and heavy precipitation events compared
whereas moderate and light events change little or decrease in intensity
Page 4 line 34 --- See Trenberth's suggested change I am strongly in favor
of adding something along the lines he has proposed. It would be a serious
omission to leave it out.
Page 7 line 12 --- replace with "trends in some extreme events, such as
hurricanes, remains problematic"
Page 9 line 16 --- replace with "Globally average water vapor,
precipitation, and very heavy and extreme precipitation events are
projected to increase, especially in areas with increased precipitation.
Most tropical areas are projectedc to have increased precipitation, with
decreases in most of the subtropics, and relatively smaller increases of
precipitation amounts in mid and high latitudes (but larger relative
increases in terms of percentages based on the current climate).
Page 10 line 12 ---- replace with " Knowledge is insufficient to project
changes in the intensity and frequency of mid-latitude storms, but there is
evidence to suggest that hurricane winds are likely to modestly increase
(5-10%) by the end of the Century as related rainfall signficantly
NOTE this is consistent with the work of Knutson, and the fact that all of
the GCM model simulations that have been analyzed (at least to my
knowledge) also show that the higher rainfall rates have the large
increases in precipitation. Admittedly that don't have real hurricanes,
but given the results of Knutson, I don't see any strong quantitative
arguements to argue otherwise.