The Atmosphere and Climate Modeling - Introduction to Carbon Capture and Sequestration - page 62

1.0

Instrumental data (AD 1902 to 1999)
Reconstruction (AD 1000 to 1980)
Reconstruction (40 year smoothed)

1998 instrumental value

0.5

0.0

− 0.5

− 1.0

1000 1200 1400 1600 1800 2000

Year

Figure 2.4.3 Average temperature on the Northern Hemisphere
Millennial Northern Hemisphere (NH) temperature reconstruction (blue — tree rings, cor-
als, ice cores, and historical records) and instrumental data (red) from AD 1000 to 1999.
A smoother version of the NH series (black) and two standard error limits (shaded in
gray) are shown. Figure from IPCC, reproduced with permission [2.4].

Oceans

If the earth is heating, because of the thermal expansion and the melting
of ice, the level of the oceans should rise. Hence, if we measure the sea
level as a function of time we should be able to observe this trend. Figure
2.4.4 shows two sets of data [2.2]. The older data are from measure-
ments of the height of the tide relative to the land. More recently, it has
become possible to use satellites to measure the height of the sea level.
These tide data need to be corrected for change in ocean water volume
and land motion, which increases the uncertainties in the earlier data.
The conclusion of these studies is that convincing experimental evidence
supports the claim that the global mean sea level gradually rose in the
20 th century and is currently rising at an increased rate, after a period of
little change between 0 and 1900. These observations are consistent with
our expectations on the basis of the global temperatures.