Partial Results - Climate Change: Identification and Projections - page 86

that the warming between 1970 and 2000 is entirely due to solar activity and
natural climatic variation does not seem incompatible with the observations.
Once again, this needs to be confirmed by statistical analysis.

Constraint on sensitivity to volcanic activity

A detailed illustration of this point would not be of any great value. If the
sensitivity to volcanic activity is constrained to zero, the degradation of the
output error is insignificant.

7.4. Statistical analysis

Output errors

Let us now reconsider the output errors in Figure 7.6 (with and without
the constraint on sensitivity to TSI). Despite the temporal variability of
paleoclimatic data (proxies, the instrumental measurements), they do provide
a certain regularity, which justifies the examination of correlation and inter-
correlation functions. The difference between the two types of errors can be
clearly seen on the graphs in Figure 7.10.
a) b)

0.03 0.03

0.02 0.02

0.01 0.01

0 0

-0.01 -0.01

0 100 200 300 400 500 0 100 200 300 400 500

0.4 0.4

0.2 0.2

0 0

-0.2 -0.2

0 100 200 300 400 500 0 100 200 300 400 500

0.4 0.4

0.2 0.2

0 0

-0.2 -0.2

0 100 200 300 400 500 0 100 200 300 400 500

0.4 0.4

0.2 0.2

0 0

-0.2 -0.2

0 100 200 300 400 500 0 100 200 300 400 500

Figure 7.10. Functions of auto and cross-correlation of the error:
free identification a) and identification forced by S 2 <1.62 b)