Jan 21, 2006

Have anthropogenic aerosols delayed a greenhouse gas-induced weakening of the North Atlantic thermohaline circulation?

by
Thomas L. Delworth and Keith W. Dixon
,
Geophysical Research Letters
  • States that in many climate model simulations using realistic, time-varying climate change forcing agents for the 20th and 21st centuries, the North Atlantic thermohaline circulation (THC) weakens in the 21st century, with little change in the 20th century
  • Uses a comprehensive climate model to explore the impact of various climate change forcing agents on the THC
  • Conducts ensembles of integrations with subsets of climate change forcing agents
  • Finds that increasing greenhouse gases – in isolation – produce a significant THC weakening in the late 20th century, but this change is partially offset by increasing anthropogenic aerosols, which tend to strengthen the THC
  • Finds the competition between increasing greenhouse gases and anthropogenic aerosols thus produces no significant THC change in our 20th century simulations when all climate forcings are included
  • Finds the THC weakening becomes significant several decades into the 21st century, when the effects of increasing greenhouse gases overwhelm the aerosol effects