Yes, but how much bigger is not well known. ADEME's calculation rules for email add about 1 gCO2e per megabyte, assuming the email is kept for 10 years in 6 copies. ADEME's storage reference point (0.24 g for 1 GB kept for 1 year) gives about 70 times less for the same duration and number of copies. The number of recipients matters too: without an attachment, an email sent to 10 people comes to 2.8 g instead of 1.6 g, with the manufacture of the phone included. The per-megabyte figure, the ratio of 70 and the 2.8 g come from our calculation with these rules.
Read the source article: Carbon footprint of an email: about 2.5 gCO2e for 1 MB