Margareta Wahlstrom, the secretary-general's special representative for disaster risk reduction, said the $380bn (Dh1.4 trillion) figure was more than 65 per cent higher than the previous record in 2005 when Hurricane Katrina struck the southern United States.
In addition to the earthquakes, Ms Wahlstrom said major floods in Thailand and other countries caused extensive damage.
"The main message is that this is an increasing - very rapidly increasing trend with increasing economic losses."
Despite the rising costs, she said, deaths from disasters are proportionally declining because countries are getting much better at instituting early warning systems and preparedness measures.
"But the economics of disasters is becoming a major threat to a number of countries.
"We say today that 50 per cent of the world's population is exposed to disaster risks because they live in the highly vulnerable areas."
Ms Wahlstrom said Japan has the highest economic exposure and the second-highest population exposure to potential disasters.
She praised Japan for its preparedness efforts but said there are lessons to be learnt from the magnitude 9.0 earthquake and tsunami that happened a year ago on Sunday.
While buildings generally withstood the massive quake, the tsunami that followed engulfed the north-east, wiped out entire towns, and inundated the Fukushima nuclear power plant, triggering the worst nuclear accident since Chernobyl.
Ms Wahlstrom said the risk of disasters is increasing globally because of climate change, the depletion of natural resources, poor land use, and worsening environmental problems.
For example, she said, by 2050 the world will need 50 per cent more food, 45 per cent more energy and 30 per cent more water for a growing population - and these resources are already under threat and are triggers of disaster.
Ms Wahlstrom said every plan to improve development in a country must include measures to deal with the effect of climate change and natural disasters.