Global Warming Could Cause Disastrous Climate Shutdown
The thermohaline circulation transports warm water to the North Atlantic and vice versa, helping to keep global climate in balance. If this circulation is disrupted or shut down, warm water could stop flowing northward, leading to cooling of the northern hemisphere.
Natural thermohaline shutdowns have occurred in the distant past, usually corresponding with dramatically cooler temperatures and ice ages worldwide. Global warming could disrupt the thermohaline by melting glaciers, introducing more fresh water into the oceans and throwing off the salinity balance of ocean waters.
What exactly affects the thermohaline circulation is not clear, and scientists do not know if global warming would necessarily be a factor. But if the thermohaline were to change, the impact on the world's climate would be catastrophic.