Strategic Panorama 2009 - 2010 - IEEE

Yolanda Castro Díez
overall average net effect of human activities since 1750 very likely (6)
has led to a warming, with a radiative forcing of +1.6 Wm-2 [between 0.6
Wm-2 and 2.4 Wm-2] (7).
To assess the changes in the Earth’s climate system it is necessary to
consider not only the atmosphere but also the ocean and the cryosphere
(8), as well as phenomena linked to changes in atmospheric and oceanic
circulation in order to glean greater knowledge of the trends, variability
and processes of climate change on a world and regional scale. Analyses
based on observational data include fundamental variables such as
atmospheric temperature, sea surface temperature, precipitation, winds
and atmospheric circulation. The term «extreme climate» is a key expression
of climatic variability and its assessment includes current information
providing an enhanced view of changes in many types of extreme phenomena
such as warming, droughts, heavy precipitation events and tropical
cyclones (including hurricanes and typhoons).
Warming of the climate system is unequivocal, as evidenced by observed
increases in global average air and ocean temperatures, widespread
melting of snow and ice and rising global average sea level. The warmest
years in the instrumental record of global surface temperature (since
1850) are 2005 and 1998. Of the past 12 years (1995 to 2006), 11 of them,
except 1996, rank among the 12 warmest recorded since 1850. The IPCC-
4AR puts the linear trend of the past 100 years at 0.74°C [between 0.56°C
and 0.92°C]. This temperature rise is distributed across the planet and is
more accentuated in the upper northern latitudes. Land areas have warmed
more quickly than the oceans.
The rise in sea level is consonant with this warming. On average, the
level of the world’s oceans has been rising by 1.8 mm/year (between 1.3
and 2.3 mm/year) since 1961 and by 3.1 mm/year (between 2.4 and 3.8
mm/year) since 1993 owing partly to the effect of the thermal dilatation of
water and the melting of glaciers, icecaps and polar ice sheets. It is not
possible to ascertain to what extent this higher rate witnessed in recent
year reflects a decadal variation or an increase in the long-term trend.
(6) The IPCC-4AR uses the following scale of probability: virtually certain (>99%); extremely
likely (>95%); very likely (>90%); likely (>66%); more likely than not (>50%); about as likely
as unlikely (33% to 66%); unlikely (