A B R U P T c l i m a t e c h a n g e Syd Partridge Shannon Buckley EESC W December 2006

‘transition of the climate system into a different state (of temperature, rainfall, and other aspects) on a time scale that is faster than the responsible forcing (mechanistic); change of the climate system that is faster than the adaptation time of social and/or ecosystems (impacts)’ definition: source:

o c e a n c o n v e y o r b e l t triggers o r b i t a l f o r c i n g s source: Hansen, et al., Science 305 (13), 2004

source: Rahmstorf 2002 the last glaciation * d a n s g a a r d – o e s c h g e r (d/o) e v e n t s (n u m b e r s) * h e i n r i c h e v e n t s (r e d s q u a r e s) * y o u n g e r d r y a s

possible effects * r e g i o n a l c o o l i n g i n n o r t h a t l a n t i c l a s t i n g h u n d r e d s o f y e a r s * l i k e l y s t r a i n o n f o o d s e c u r I t y * r e g i o n a l d r o u g h t s a n d f l o o d s * g l o b a l e f f e c t s ?

the future U N C E R T A I N T Y * m o d e l f l a w s * n o n – l i n e a r i t y * l a c k o f p r e d i c t a b i l i t y n e a r t h r e s h o l d s * l o w p r o b a b i l i t y for n e x t y e a r s * e v i d e n c e o f c i r c u l a t i o n d e c l i n e ?

Summary Paleoclimate evidence suggests abrupt climate changes have occurred throughout Earth’s past. Consequences of future abrupt climate change are possibly severe, but uncertainties in models and triggers are still very high. Future studies are ongoing to resolve these issues. It is thought that increased greenhouse forcing from human activity is increasing the likelihood of abrupt climate change in the future.