Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Table 3-5: Computed trend values and differences of trend values in cirrus/high cloud
amounts (% of Earth surface cover per decade) from surface and ISCCP satellite data sets
taken between 1971 and 1991 for regions categorized as having a mean value of contrail
coverage less than and greater than 0.5% as computed by Sausen et al. (1998) for 1992
aircraft operations (Minnis et al., 1998b). Differences in trends between contrail cover
regions are shown as "trend difference" values.
The last two rows (Global ISCCP, Global Surface) indicate global (ocean + land) trends in
respective data sets. The time periods of the data sets are also indicated. Statistical
significance refers to level of confidence in difference between trends for the two regions.
An asterisk indicates insufficient resolution for analysis. Dashes indicate a confidence level
less than 95%.
Ocean
from ISCCP
Land from
ISCCP
Ocean
from
surface
Land from
surface
Ocean
from
surface
Land from
surface
Global
ISCCP
Period
Trend (% per in Regions
decade) Contrail
with Computed Cover
< 0.5%
> 0.5%
Trend Difference
(% per decade)
Significance
of
Difference (%)
1984-90 4.3 5.9 1.6 -
1984-90 1.2 4.7 3.5 95
1971-81 * * *
1971-81 -0.21 2.1 2.3 99
1971-92 0.75 0.24 -0.51 -
1971-92 -1.5 0.10 1.6 99
1984-90 3.2 5.2 1.9 99
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decade).