It's not clear to me that contrails actually trap more heat than they reflect back. I didn't see any evidence in this blog post demonstrating that the increased heat trap offsets the increase in albedo.

Edit: I realized they cited an IPCC report, which states that contrails are "estimated to have a combined Effective Radiating Force (ERF) that is about 57% of the current net ERF of global aviation", they do go on to say that other studies estimate the forcing could be smaller.

Not sure I believe that contrails represent this big a percentage of ERF. I think far more research needs to be done before these claims by Google and researchers are made.