Environmental Engineering Reference
In-Depth Information
Figure 4.1 shows patterns of warming normalized “per degree C of
global annual average warming”. Ranges across models or across scenarios
are shown in Figures 4.4 and 4.5. We show maps of global geographical
patterns and North American patterns for annual average warming and
December-January-February and June-July-August average warming.
We highlight here the main features characterizing warming patterns:
The annual and DJF mean patterns present a typical gradient of warming
that decreases from north to south, with the higher latitude of the Northern
Hemisphere seeing the largest increases, and the land masses warming more
than the oceans. The JJA patterns' main characteristics are an enhanced
warming of the interior of the continents and the Mediterranean Basin, with
a gradient that is generally equator to poles rather than north-south. The
largest source of variation resides in the inter-model spread rather than the
inter-scenario spread, and it is mainly localized over and at the edge of the
ice sheets of the Arctic and Antarctica.
We also present in Figure 4.2 a number of scatter plots depicting the
relation between the magnitude of global average warming (by 2080-2099
compared to 1980-1999) and the magnitude of regional warming across
models (each model one dot) and scenarios (color-coded) for several of the
“Giorgi regions” (Giorgi and Francisco, 2000). We chose four regions that
subdivide the North American continent (western, central, and eastern North
America—WNA, CNA, and ENA respectively—and Alaska, ALA) plus two
regions in other climates for comparison, the Mediterranean Basin (MED)
and Southern Australia (SAU). The linearity of the relationship and the fairly
tight spread around it is clear. As already noted, the source of variation
between different models is larger than from the scenarios: averaging each
model across the three scenarios would not reduce the scatter as much as
averaging all the models within one scenario, as shown by the larger star-
shaped marks.
Finally, in Figure 4.3 we show December-January-February and June-
July-August warming patterns as calculated in models including both an-
thropogenic and natural forcing
for the 20th century
, together with 20th
century observations. Figure 4.3 shows that the warming patterns in the
models and observations display many common large-scale features, and a
comparison with Figure 4.1 demonstrates how 20th century patterns con-
tain already many of the large-scale features that characterize 21st century
patterns. Among these, the relatively larger magnitude of the warming in
December-January-February than in June-July-August in both observed and
modeled patterns; the amplification of the warming in the high latitudes
of the Northern Hemisphere characteristic of December-January-February
