Not only average temperatures but also other aspects
of the climate are changing because of distinguishable
Human activity
human influences. Human activities have contributed to
By comparing a number of natural factors and human
sea level rise during the second half of the 20th centu-
activities, and their effect on climate, scientists have
ry; they have probably helped to change wind patterns
proved that human activity is responsible for part of
and increased temperatures on extreme hot nights,
the temperature rise. So computer models which in-
cold nights and cold days. In addition, our actions may
clude the human influence on the climate show a clear
have contributed to increasing the risk of heat waves,
increase in temperature. This accurately reflects the
the area affected by drought since the 1970s, and the
actual pattern of warming we have been experienc-
frequency of episodes of heavy precipitation. Human-
ing. In contrast, temperatures predicted by models
caused warming over the last three decades has had a
that take into account natural factors alone stay well
discernible global influence on the changes observed
below the actual temperatures measured.
in many physical and biological systems.
Observed and modelled temperature change between 1906 and 2005
Temperature anomaly
1.5
relative to 1901-1950 average
EUROPE
Celsius degrees
1.0
1.5
0.5
NORTH AMERICA
1.5
1.0 0.0
ASIA
1.0
0.5
-0.5
1906 2000
0.0
0.5
0.0
-0.5
1906 2000
1.5 -0.5
AFRICA 1906 2000
1.0
1.5
SOUTH AMERICA
0.5
1.5
AUSTRALIA
1.0
0.0 1.0
0.5
-0.5
0.5
0.0
1906 2000
0.0
-0.5
-0.5
1906 2000
1906 2000
Models using only natural factors influencing the climate (volcanoes and solar activity)
Models using natural and anthropogenic factors
Source: IPCC, 2007.
Observed continental average temperature (decadal average)
16 Planet in Peril
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