Question: I'm exclusively breastfeeding my baby, and occasionally give him pumped bottles. I generally try to warm them up before giving them to him, at least to room temperature. (I was once told as a tip to get babies used to room-temperature bottles right away, just in case sometime you don't have a way to heat it up...) Sometimes, though, he is frantically crying as I'm trying to warm up the bottle... Is it ok to give him a cold bottle? He doesn't seem to mind, and drinks the whole thing. Are there any problems with feeding a 2-3 month old a cold bottle?

Answer: 
I did find research on the effect of milk temperature￼ on preterm infants at <http://milkbank.com/pdf/Stanford_Study_milk_feeding_temperature.pdf>

A summary of the results included the following statement: The infants in this study had a similar tolerance (as measured by gastric residuals) to both cool temperature milk (10°C) and room temperature milk (24°C). Based on these data, there appears to be no advantage to warming frozen or refrigerated milk to room temperature. 

The study did reveal better tolerance for warmed milk for these fragile infants.
I can't provide any supporting evidence, but I can tell you that at my very first pediatrician appointment with my first son, I had this exact conversation with my pediatrician. 

I live in Southern California (a warm climate anyway) and my son was born in the summer, so the weather was quite warm. My son started fussing a bit, and I was having typical new mom anxiety because I didn't have anyway to warm his bottle (I wasn't good enough at breastfeeding to do that in public yet). I asked my pediatrician if they had some way I could warm the bottle, and his response "Would you want to drink something warm when it is this hot outside? I bet your son would also prefer his drinks cold." 

That was the last time I heated any bottle for either of my kids.