Temperature and Salinity Change
Too much change in ocean temperature and salinity could disrupt the North American thermohaline circulation enough to slow or possibly halt the conveyor belt — causing climate changes in time span as short as a decade.~ Robert Gagosian (1944 age:73) National Geographic 2004-09.
Ocean currents are propelled by temperature differences and by salinity differences. If you screw things up, the massive global conveyor belt ocean currents such as a the Gulf Stream stop flowing. Scotland is at the same latitude as Alaska. It is habitable only because of the moderating influence of the Gulf Stream. European agriculture could not possibly adjust if everything changed over a period of only ten years. (Note in this climate change case, the problem for Europe is cooling, not warming, though it is a side effect of overall global warming.)