The worldwide public cloud market is projected to grow 18.5% this year to $131 billion, up from $111 billion last year, according to Gartner.

That number includes a 47.3% jump in Infrastructure-as-a-Service to $9 billion. IaaS was up 42.4% to $6.1 billion last year.

Gartner expects $677 billion to be spent on cloud services between 2013 and 2016 and estimates that $310 billion of that will go for cloud-based advertising. Cloud advertising was 48% of the total market last year.

Gartner found that business process services was the second-largest segment last year, accounting for 28% of the cloud market, followed by Software-as-a-Service at 14.7%, cloud system infrastructure at 5.5%, cloud management and security services at 2.8% and Platform-as-a-Service at 1%.

Gartner warns that the cloud adoption varies from country-to-country. Cloud adoption is highest in North America, projected to account for 59% of all new spending on cloud services from 2013-2016. Western Europe is expected to account for 24%.

"IT services providers, particularly those focused on delivering cloud services offerings or related services, must consider these disproportionately large mature markets if they want to play a leading role in cloud services growth worldwide," Gartner said. "Similarly, markets in Emerging Asia/Pacific, Greater China and Latin America should also be important considerations for IT services providers that want to capitalize on the high growth of these regions, particularly Latin America and Greater China."