‘The time series of total and low-level cloud cover averaged over the NE Pacific (115° to 145°W, 15° to 25°N) are displayed in Fig. 1, A and B. Both COADS and adjusted ISCCP data sets show a shift toward more total cloud cover in the late 1990s, and the shift is dominated by low- level cloud cover in the adjusted ISCCP data (bars, in Fig. 1B). The longer COADS total cloud time series indicates that a similar- magnitude shift toward reduced cloud cover occurred in the mid-1970s, and this earlier shift was also dominated by marine stratiform clouds (bars, Fig. 1A).’
‘Our observational analysis indicates that increased SST and weaker subtropical highs (Fig. 4A) will act to reduce NE Pacific cloud cover…’ http://meteora.ucsd.edu/~jnorris/reprints/PacCloudFeedback.pdf ‘Tropical and subtropical low-level marine clouds consist of optically thick stratocumulus clouds, which usually form over the regions associated with relatively cold sea surface temperatures (SST) and the atmospheric subsidence, and optically thin shallow cumuli in the tradewind regime. These low-level clouds play a pivotal role in the global climate system not only by affecting radiative budgets but also by promoting heat and moisture exchange between the sea-surface, the boundary layer, and the overlying troposphere.’ Ping, Z., Hack, J., Keilh, J and Zhu, P, Bretherton, C. 2007, Climate sensitivity of tropical and subtropical marine low cloud amount to ENSO and global warming due to doubled CO2 - JGR, VOL. 112, 2007) ‘One important development since the TAR is the apparent unexpectedly large changes in tropical mean radiation flux reported by ERBS (Wielicki et al., 2002a,b). It appears to be related in part to changes in the nature of tropical clouds (Wielicki et al., 2002a), based on the smaller changes in the clear-sky component of the radiative fluxes (Wong et al., 2000; Allan and Slingo, 2002), and appears to be statistically distinct from the spatial signals associated with ENSO (Allan and Slingo, 2002; Chen et al., 2002). A recent reanalysis of the ERBS active-cavity broadband data corrects for a 20 km change in satellite altitude between 1985 and 1999 and changes in the SW filter dome (Wong et al., 2006). Based upon the revised (Edition 3_Rev1) ERBS record (Figure 3.23), outgoing LW radiation over the tropics appears to have increased by about 0.7 W m– 2 while the reflected SW radiation decreased by roughly 2.1 W m–2 from the 1980s to 1990s (Table 3.5). 'The most accurate of the data sets in Table 3.5 is believed to be the ERBS Edition 3 Rev 1 active-cavity wide field of view data (Wielicki et al., 2005). The ERBS stability is estimated as better than 0.5 W m– 2 over the 1985 to 1999 period and the spatial and temporal sampling noise is less than 0.5 W m–2 on annual time scales (Wong et al., 2006). The outgoing LW radiation changes from ERBS are similar to the decadal changes in the HIRS Pathfinder and ISCCP FD records, but disagree with the AVHRR Pathfinder data (Wong et al., 2006). The AVHRR Pathfinder data also do not support the TOA SW radiation trends. However, calibration issues, conversion from narrow to broadband, and satellite orbit changes are thought to render the AVHRR record less reliable for decadal changes compared to ERBS (Wong et al., 2006). Estimates of the stability of the ISCCP time series for long-term TOA flux records are 3 to 5 W m–2 for SW radiative flux and 1 to 2 W m–2 for LW radiative flux (Brest et al., 1997), although the time series agreement of the ISCCP and ERBS records are much closer than these estimated calibration drift uncertainties (Zhang et al., 2004c).' ‘As noted in Section 3.4.3, the low-latitude changes in the radiation budget appear consistent with reduced cloud fraction from ISCCP. Detailed radiative transfer computations, using ISCCP cloud products along with additional global data sets, show broad agreement with the ERBS record of tropical radiative fluxes (Hatzianastassiou et al., 2004; Zhang et al., 2004c; Wong et al., 2006). However, the decrease in reflected SW radiation from the 1980s to the 1990s may be inconsistent with the increase in total and low cloud cover over oceans reported by surface observations (Norris, 2005a), which show increased low cloud occurrence. The degree of inconsistency, however, is difficult to ascertain without information on possible changes in low-level cloud albedo.’ My note here is that there is a consensus on why cloud cover is influenced by SST - and the biggest factor in variable sea surface temperature is ENSO. 'In summary, although there is independent evidence for decadal changes in TOA radiative fluxes over the last two decades, the evidence is equivocal. Changes in the planetary and tropical TOA radiative fluxes are consistent with independent global ocean heat- storage data, and are expected to be dominated by changes in cloud radiative forcing. To the extent that they are real, they may simply reflect natural low-frequency variability of the climate system.' http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-4-4-1.html Really - just picking a paragraph on some supposed inconsistency of satellite and surface observations is BS. Anything that doesn't fit the preconceived notions isn't real? Cheers Robert On Nov 8, 1:29 pm, Eric Swanson <[email protected]> wrote: > Robert, it was you who made reference to the data > > "...And if you have a look at both the ISCCP-FD and ERBE SW(up) > datasets - there is clearly a decrease in reflected SW (less cloud) > from the 1980's to the 1990's..." > > I just pointed out that there are problems with both sets, the ERBE > instrument being one which I studied. The IPCC AR4 reference to which > you pointed comments on the later ERBS data, concluding: > > "In summary, while there is some consistency between ISCCP, ERBS, > SAGE II and surface observations of a reduction in high cloud cover > during the 1990s relative to the 1980s, there are substantial > uncertainties in decadal trends in all data sets and at present there > is no clear consensus on changes in total cloudiness over decadal time > scales...." > > Yes, yet again, let me remind you that there is lots of evidence of > variation in climate. That knowledge is one of the reasons we address > "climate change" these days, not simply "global warming". However, I > do think it's important for mankind that our civilization has evolved > during the Holocene, which appears to be a warm period relative to the > norm over the past 3 million years or so. During the past 8000 years, > the variation in climate appears to have been rather minor, compared > to the climate of the Ice Ages. I do not assume that the future will > be a repeat of the warm conditions of the past 8 thousand years. If > climate were not influenced by mankind's activities, I think it's > clear that at some time in the future, Ice Age conditions would > return, continuing the long term pattern. I don't see how you can > conclude that I expect climate to be stable, as mankind is changing > the basic physics of the situation. After all, climate can be thought > of as the statistics of weather and that includes the statistics of > the longer variations as well. > > E. S. > ------------------------------------------------ > On Nov 7, 7:30 pm, Robert I Ellison <[email protected]> > wrote: > > > > > Eric, > > > I am not sure whose ERBE data reference you are talking about. The > > ERBE data is graphed and discussed in AR4 - section 3.4.3 from > > memory. The ISCCP data and a reasonably detailed dicussion of errrors > > and problems is found at -http://isccp.giss.nasa.gov/projects/browse_fc.html > > > Wild simply discusses decadal changes in surface insolation - > > brightening and dimming. The ISCCP record is discussed along with DTR > > and surface SSR records predominantly. > > > I was simply talking about climate variability - which is evident in > > any of the records and at any timescale. I can't help it of you have > > foolishly been hoisted on your own petard with a false assumption of > > climate stability. > > > Cheers > > Robert- Hide quoted text - > > - Show quoted text - -- You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. Global Change is a public, moderated venue for discussion of science, technology, economics and policy dimensions of global environmental change. 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