Large progress has been made in the past few years towards quantifying and
understanding climate variability during past centuries. At the same time, present-day
climate has been studied using state-of-the-art data sets and tools with respect to the
physical and chemical mechanisms governing climate variability. Both the
understanding of the past and the knowledge of the processes are important for
assessing and attributing the anthropogenic effect on present and future climate.
The most important time period in this context is the past approximately 100 years,
which comprises large natural variations and extremes (such as long droughts) as
well as anthropogenic influences, most pronounced in the past few decades.
Recent and ongoing research efforts steadily improve the observational record
of the 20th century, while atmospheric circulation models are used to underpin the
mechanisms behind large climatic variations. Atmospheric chemistry and composition
are important for understanding climate variability and change, and considerable
progress has been made in the past few years in this field. The evolving integration
of these research areas in a more comprehensive analysis of recent climate variability
was reflected in the organisation of a workshop “Climate variability and extremes
in the past 100 years” in Gwatt near Thun (Switzerland), 24–26 July 2006. The aim
of this workshop was to bring together scientists working on data issues together
with statistical climatologists, modellers, and atmospheric chemists to discuss gaps
in our understanding of climate variability during the past approximately 100 years.
The peer-reviewed chapter contributions together provide an overview of this entire
period, and incorporate both physical and chemical aspects of climate science,
employing observational data and models. In summary, the book aims at providing
an overview of the current state of research on 20th-century climate variability.