With its freezing, dark winters and summer days that in the north of the country that literally never end, Sweden wouldn't appear to share much in common with the equatorial heat of Malaysia.

Gray says the ocean's thermal heat capacity is high and sea-surface temperatures are increasing; what's more, a La Nina effect, bringing cold water to the eastern equatorial Pacific, has taken hold.

He attributed part of the rise in temperatures this year to El nino, in which warming waters in the equatorial Pacific Ocean pump a lot of heat into the atmosphere.