Present changes, causes
and observed impacts
Observed changes in climate
and their effects
Warming of the climate system is beyond argument, Temperature rise
as shown by observations of increases in global av- Of the last 12 years (1995–2006), 11 are among the 12
erage air and ocean temperatures, the widespread warmest since records began in 1850. The warming
melting of snow and ice, and rising global average sea trend over the previous century was reported as 0.6ºC
levels. In the following paragraphs, some of the most in the IPCC’s Third Assessment Report (TAR) pub-
striking changes that are already taking place are de- lished six years earlier in 2001: it is now 0.74ºC. The
scribed and illustrated. temperature increase is widespread across the world
but is most marked in the northern Polar Regions.
Trends in global average surface temperature
Warming of the climate system has been detected on
the Earth’s surface and up in the atmosphere, as well
Differences in temperature Estimated actual
as in the upper few hundred metres of the oceans.
from 1961-1990 global mean
The land has warmed faster than the seas.
Mean value, °C temperature, °C
0.6 14.6 Average Northern Hemisphere temperatures after
1950 have been higher than during any other 50-year
0.4 14.4
Temperature change 1970 - 2004
0.2 14.2
0.0 14.0
- 0.2 13.8
- 0,4 13.6
- 0,6 13.4
1880 1900 1920 1940 1960 1980 2000
-1.0 -0.2 0.2 1.0 2.0 3.5°C
Source: US National Oceanic and Atmospheric Administration (NOAA), 2008.
Source: IPCC, 2007.
8 Planet in Peril
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