Azer Bestavros
Department of Computer Science
College of Arts & Sciences
Boston University

Office: 111 Cummington Street, MCS-276, Boston, MA 02215
Tel: 617.353.9726 / Fax: 617.353.6457 / Email: best

How Does CS Help Mitigate Global Warming?

In lecture and in the discussion sections, we are starting to appreciate one of the major aspects of CS -- the importance of coming up with algorithms (programs) that are efficient in terms of the amount of time (e.g., number of steps) it takes them to complete.

For example, a binary search of a trillion entries (e.g., a Google index of web pages) would be much more preferable to a linear search -- the former taking around 3*log(1 trillion) = 120 setps whereas the latter taking 2 trillion steps.

Coming up with efficient ways to solve a problem is important not only because the results would be obtained faster (milliseconds as opposed to decades), but also because it means that we would impact the environment much less!

As some of you may know, computers are now one of the largest consumers of energy (and thus contributing to carbon emissions and global warming). So, by making programs/algorithms (whether for a Google search or an XBox game) even slightly more efficient (say by 20% or 50%) could make a huge difference on the environment.

Indeed, to elucidate this point, some scientists went through the trouble of figuring out the carbon footprint of a Google search -- how much energy it takes for Google to respond to a search query?

According to Google, an individual search needs 1 kilojoule (0.0003 kilowatt hours) of energy, which is equivalent to about 0.2 grams (0.007 ounces) of carbon. Google says in a blog post (check it here) that this amount of energy is consumed by the human body in about 10 seconds. Another way to look at this is that doing 1,000 searches on Google has the same carbon footprint as driving a car for one kilometer (0.6 miles). Just think about the energy savings resulting from using Google to do research at home versus having to drive to a local library (not to mention all the energy needed to keep the library lit, air-conditioned, etc.)

By coming up with efficient algorithms to solve problems (like searching and sorting and others we will see as examples in this course), CS can make significant contributions to saving the planet.