The debate on the 'science of climate change' focuses mainly on 1) whether the climate is changing and 2) if mankind's activities play a role in climate change. This report was written after the symposium on "Man-made versus natural climate change; Changes in climate during the past 100 years from a Holocene perspective" at the Royal Swedish Academy of Sciences, March 1999, where these issues were also dealt with. The report provides same additional background, review of same recent work on climate and includes some more philosophical reflections as well. The following topics are addressed, in same detail:

• introduction to the climate change debatewhat is known of climate (change)
• what is known of climate ( change) in the near past and in geological time scales
• how climate variability and climate change are interrelated
• what factors force climate ( change and/or variability)
• same observations relevant to the climate change debate
• same recent climate modeling relevant to the climate change debate