Category Archives: GCMs

Hysteresis of the Atlantic MOC in an AOGCM

Atlantic, GCMs, hysteresis, MOC

UPDATE (16/06/11) – the paper describing this work has now been published and highlighted.

The potential for a rapid collapse in the strength of the Atlantic overturning circulation (AMOC) has long been recognised. The pioneering work of Stommel first suggested that the density driven circulation in the Atlantic Ocean has two equilibrium states, either ‘on’ or ‘off’. If the climate is altered, a transition may occur between these states which is not reversible by returning the climate to its previous regime (this irreversibility is termed ‘hysteresis‘). Continue reading Hysteresis of the Atlantic MOC in an AOGCM →

Consensus in precipitation projections

GCMs, precipitation, projections, variability

In the AR4, the IPCC presented this figure showing the consensus in precipitation projections for the 21st century, designed to be of use to planning for adaptation and mitigation. The coloured regions show where changes are likely to occur. My interest is in the white areas where models cannot agree on the sign of the change. This could mean that half the models predict a large drying and half predict a large increase in rainfall. But, it could also just mean that the changes are small, but that the sign is uncertain. Continue reading Consensus in precipitation projections →