In late 2006, I wrote a post about the energy consumption of modern computing plants, in which I made a prediction:

As soon as activists, and the public in general, begin to understand how much electricity is wasted by computing and communication systems – and the consequences of that waste for the environment and in particular global warming – they’ll begin demanding that the makers and users of information technology improve efficiency dramatically. Greenpeace and its rainbow warriors will soon storm the data center – your data center.

Soon is now. Today, Greenpeace issued a report on “cloud computing and its contribution to climate change,” in which it specifically targets big cloud operators like Google, Amazon, Apple, Facebook, Salesforce.com, and Microsoft. The report is timed to coincide with the launch of Apple’s iPad, an event that underscores just how dramatically personal computing has changed, and expanded, over the last few years. Many of us now own a slew of computers in various forms – desktops, laptops, smartphones, iPods, tablets, e-readers, gaming consoles – that don’t just suck up electricity themselves but are connected to the vast cloud grid that also consumes enormous amounts of energy. Drawing mainly on a 2008 analysis by the Climate Group and the Global e-Sustainability Initiative, Greenpeace predicts that the electricity consumed by the cloud – defined as both Internet data centers and the communications network that connects all of us to those centers – will rise from 623 billion kWh in 2007 to 1,964 billion kWh in 2020.

The rise of cloud computing is a two-edged sword when it comes to energy consumption and related carbon emissions. On the one hand, since electricity is a critical component of the cost of running a cloud operation, major cloud computing providers like Google and Microsoft have a big economic incentive to become more energy efficient, and they have been admirably aggressive in pioneering technologies that reduce energy use. The energy-conserving equipment, designs, and processes that the cloud giants invent should in time spread throughout the information technology industry, making computing in general much more energy efficient. At the same time, however, the free data and services supplied through the cloud are rapidly expanding the scope of computing and its attractiveness – people use computers, particularly internet-connected computers, much more than in the past – and so even as computing is becoming more efficient, when measured by units of output, the dramatic expansion in its use means that it is, in absolute terms, sucking up much more electricity than it has in the past, a trend that promises to accelerate pretty much indefinitely.

What that means is that, as the Greenpeace report makes clear, both the economic and the political stakes involved in mitigating the environmental impact of the cloud will increase. Greenpeace argues that what’s important is not only the efficiency of data centers but the sources of the power they use. The heavenly cloud, it turns out, runs largely on earthbound coal. In this regard, it singles out Facebook for criticism:

Facebook’s decision to build its own highly-efficient data centre in Oregon that will be substantially powered by coal-fired electricity clearly underscores the relative priority for many cloud companies. Increasing the energy efficiency of its servers and reducing the energy footprint of the infrastructure of data centres are clearly to be commended, but efficiency by itself is not green if you are simply working to maximise output from the cheapest and dirtiest energy source available.

Greenpeace also links Apple’s decision to locate a huge cloud data center in North Carolina to that state’s cheap electricity supplies, which come mainly from coal-fired plants. Other companies, including Google, also run big data center operations in the Carolinas. Noting that the IT industry “holds many of the keys to reaching our climate goals,” Greenpeace says that it is pursuing a “Cool IT Campaign” that is intended to pressure the industry to “put forward solutions to achieve economy-wide greenhouse gas emissions reductions and to be strong advocates for policies that combat climate change and increase the use of renewable energy.”

The Greenpeace action promises to intensify the public’s focus on the cloud’s environmental shadow. But while Greenpeace’s main target appears to be the big cloud providers, its report also suggests, if only in passing, that the devices that all of us use to connect to the cloud actually consume more energy than the cloud itself. Those of us who spend a large proportion of our waking hours peering into multiple computer screens can’t offload responsibility for the environmental consequences of our habits to companies like Google and Facebook. The cloud, after all, exists for us.