Why not put it into more graspable terms? 28,397 tons of CO2 is what you get when you burn about 76 barrels of oil. (Each barrel is the standard 42-gallon size.)
Now compare these 76 barrels to the 19.96 million barrels of oil consumed each day in the US.
Notice that the contribution of spam is so small!
For example, the average American burns (or has burned on their behalf) the equivalent of about 2.8 gallons of oil per day. At that rate, a group of just 1140 people will emit 28,397 tons of CO2 in a day.
(I hope I got all these figures right. Don't be angry if they're off a little bit.)
Making your headline dependent on innumeracy isn't a nice thing to do. Framing things with an obvious spin is fine. But cherry-picking your units to make your numbers seem big isn't honest.
We did try to cherry pick stats that were relatable to the average person. There's a problem in talking about this in that the numbers can so big they're basically meaningless, which is why we introduced things like the equivalent number of plastic bags.
That said, I'm not sure your stats are correct.
Assuming the sources are correct, I found that the combined liquid fuels from an average barrel of crude oil will produce a minimum of 317kg of CO2 when consumed [1]. If we then extrapolate from that base amount then 28,397 tonnes of CO2 is what you get when you burn about 90,000 barrels of oil.
Which is quite a bit different to 76 barrels.
If we're starting from a similar base amount then I think maybe you misread tonnes in my post as kg, as 76 barrels is closer to 24,000kg (24 tonnes).
I've seen figures for 1gb of data transfer ranging from 200-600g of CO2 or thereabouts.
If you look at email and think that you might have a tab open at home on a computer that it pops up in, that it might also push to your tablet and your phone and that if it is Gmail it might be mirrored on multiple servers, then add in a several kilobytes (or more) of images... I can definitely see it starting to add up to 3-4 grams.
Now factor in that excel sheet or word doc, some photos or a pdf that you're sending to a few (or hundreds) of coworkers...
Now compare these 76 barrels to the 19.96 million barrels of oil consumed each day in the US.
Notice that the contribution of spam is so small!
For example, the average American burns (or has burned on their behalf) the equivalent of about 2.8 gallons of oil per day. At that rate, a group of just 1140 people will emit 28,397 tons of CO2 in a day.
(I hope I got all these figures right. Don't be angry if they're off a little bit.)
Making your headline dependent on innumeracy isn't a nice thing to do. Framing things with an obvious spin is fine. But cherry-picking your units to make your numbers seem big isn't honest.