Cloud service providers have previously drawn ire from environmentalists for not being transparent when it comes to the energy efficiency of their data centres.
However, a new report (PDF) from the University of Melbourne says that the real sustainability threat comes not from the growing demand for data centres to house cloud-ready infrastructure, but from the rising use of cellular and Wi-Fi networks to access cloud services.
A 2012 report produced by Greenpeace titled How Clean is Your Cloud? argued that three of the biggest businesses delivering cloud-based offerings — Amazon, Apple and Microsoft — were "rapidly expanding without adequate regard to source of electricity, and rely heavily on dirty energy to power their clouds."
It sounded a warning over the growing demand for data centre space (and consequently energy consumption) driven by cloud adoption. The report cited an estimate that nearly US$450 billion was being spent annually on new data centre space that that data centre demand was consuming 31 gigawatts of electricity, with an increase of 19 per cent in 2012.
However, by 2015, the energy used to run data centres will be a "drop in the ocean", compared to the wireless networks used to access cloud services, said Dr Kerry Hinton, deputy director of the Centre for Energy-Efficient Communications, the University of Melbourne-based research centre that produced the report.
"There is a significant emerging convergence between cloud computing and wireless communication, providing consumers with access to a vast array of cloud applications and services with the convenience of anywhere, anytime, any network functionality from the device of their choice," states the report, The Power of Wireless Cloud.
This 'emerging convergence' has big implications for the energy consumption associated with cloud services, including SaaS, PaaS and IaaS. The report predicts that by 2015 energy consumption associated with 'wireless cloud' will reach 43 terawatt-hours, compared to 9.2 terawatt-hours in 2012.
"This is an increase in carbon footprint from 6 megatonnes of CO2 in 2012, up to 30 megatonnes of CO2 in 2015," which is the equivalent of an additional 4.9 million cars on the road, the report states.
Data centres will comprise only 9 per cent on this increased energy consumption, compared to up to 90 per cent for wireless access.
"The trend towards wireless is the real problem, and the networks are to blame," Hinton said.
"Industry needs to focus on the real issues with wireless network technologies if it wants to solve this problem... We often think of bandwidth as the barrier to the way online services evolve and improve. The very real message here is that the real bottleneck, looming sooner than we think, may be energy."
"To ensure the energy sustainability of future wireless cloud services, there needs to be a strong focus on the part of the ecosystem that consumes the most energy: wireless access networks," the report concludes.