At the time of writing, The Guardian's Treadlightly site boasts that "3,712 readers have pledged to save a total of 5.33 tonnes of CO2". The Treadlightly home page also carries an ad for "South Africa: unforgettable scenery at Table Bay".
A return flight to Cape Town (12,021 Miles) for one person accounts for 2.82 tonnes (according to one popular carbon calculator). So if just two people among the 3,172 who have so far pledged to "tread lightly" with The Guardian reward themselves with a holiday (a success rate for the advertisers of just over 0.063%), all the emissions saved by the other 3,170 and then some, will be cancelled out.
The front page of this morning's Guardian print edition prominently displayed news of a BEMA award to the newspaper for, among other things, "inspir[ing] readers to alter their lifestyles".