Geoscience Reference
In-Depth Information
Land and Ocean Temperature Changes
1.0
Land
5-Yr Mean
Ocean
5-Yr Mean
.8
.6
.4
.2
.0
-.2
-.4
-.6
1880
1900
1920
1940
1960
1980
2000
Figure 13.8
Long-term instrumental records of annual average surface air temperature, expressed as
anomalies with respect to the base period 1951-1980 for the global land and ocean areas. The solid lines
depict the time series smoothed with five-year means.
Source: NASA, Goddard Institute for Space Sciences (http://data.giss.nasa.gov/gistemp/).
4
Mid-1970s-2008, during which there was a
marked overall warming of about 0.5
Global mean surface temperatures during the
past decade reached their highest levels on record
and probably for the last millennium. In the
NASA GISS analysis used to compile
Figure 13.7
,
the warmest year on record was 2005, with 2007
and 1998 tied for second warmest. Rankings based
on other global temperature analyses (e.g., from
the Climatic Research Unit of the UK) differ
somewhat, but tell the same basic story of very
warm conditions for the past decade. The key
spatial feature of change over the past decade
(
Figure 13.9
) is very strong warming over
northern high latitudes. This is especially apparent
C, but
with strong regional variability (see
Plate 13.1
).
°
Based on balloon soundings and assessments
from satellite sounders, lower tropospheric tem-
peratures over the period 1958 to the present
have increased at slightly higher rates than at
the surface. This interpretation, however, must
acknowledge discontinuities and biases in the time
series introduced by changing satellites, orbit
decay, drift and other factors. There is evidence
that balloon soundings may have a cooling bias.
