Story submitted by Jens Raunsø Jensen The IPCC dismisses in its
AR4 report of 2007 natural climate variability as a major reason
for the global temperature increase in the second half of the
20th century. The basic arguments are “greenhouse physics”,
increasing and accelerating temperatures in the second half of
the 20th century, and the inability of climate models to
reproduce the temperature changes if only natural processes are
considered. However, many local, regional and global temperature
curves for 1960-2010 may be summarised as consisting of step
changes, coinciding with one or more major ENSO-related events
(El Niño) and separated by periods of near constant temperature.
Thus, the temperature increase (proxy for global warming) in the
second half of the 20th century could have taken place in steps
driven by major ENSO events. This challenges IPCC’s notion of
increasing and accelerating temperatures and IPCC’s modelling
argument for accepting the anthropogenic global warming (AGW)
hypothesis as the ma