Twenty-eighth Report Adapting Institutions to Climate Change Cm ...

every circumstance. However, the Commission is concerned that if today’s extreme events become
more frequent, as the modelled climate projections suggest, so too will the level of disruption that
it causes if appropriate action is not taken. Not only will today’s extreme weather events become
more commonplace, but it is also likely that the events themselves will become more extreme.
GLOBAL CLIMATE CHANGE
2.8
2.9
Scientists have a range of tools that they can call upon for informing policy-makers about climate
change – both changes that have already occurred and projections for the future. These include
weather measurements from a variety of sources and climate simulations from computerised
Global Circulation Models (GCMs). GCMs are used to provide the basis from which future
climate projections are made, and the boundary conditions that enable more regional and
local-scale projections, through a process of regional climate downscaling, to be made.
Globally, data from land-based weather stations and ships as well as from satellites confirm that,
although there are regional variations in temperature, the planet is warming (see Figure 2-I and
the more recent literature cited). 1,2 Generally, the warming trend is observed in both maximum
and minimum recorded temperatures, with air masses over land warming faster than those over
oceans, and winter months warming faster than summer. The number of days with temperatures
below freezing declined during the second half of the 20th century in most land areas of the
Northern hemisphere. In the Arctic region, temperatures have increased at almost twice the
average global rate in the last century. 3
FIGURE 2-I
Global average near-surface temperatures 1850-2006 4
The deviation of annual average global mean near-surface temperature (red bars) from the average over the
1961-1990 baseline. 5 The blue line shows the data smoothed to emphasise decadal variations.
Temperature change (°C)
with respect to 1961–1990
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
1860 1880 1900 1920 1940 1960 1980 2000
Year
7
Chapter 2