The Atlantic Ocean’s surface temperature swings between warm and cold phases every few decades. Like its higher-frequency Pacific relative El Nino, this so-called “Atlantic Multidecadal Oscillation” can alter weather patterns throughout the world. The warmer spell we’ve seen since the late 1990s has generally meant warmer conditions in Ireland and Britain, more North Atlantic hurricanes, and worse droughts in the US Midwest.
However a colder phase in the Atlantic could bring drought and consequent famine to the developing countries of Africa’s Sahel region. In the UK it would offer a brief respite from the rise of global temperatures, while less rainfall would mean more frequent summer barbeques. A cold Atlantic also means fewer hurricanes hitting the southern US.