Google announced they have increased the default font size for AdSesnse ad units.
Should you have not customized your font sizes (Google announced last week the launch of font size controls), or if your ad units are set to 'AdSesese default font size', you'll notice that the text in your ad units is now the equivalent of 'medium' instead of 'small'.
Google said that it decided to make this change based on publisher feedback and its own internal testing, which showed that this increased font size improved performance. I personally don't have any doubts that it increases CTR (click-through rate) and ultimately earnings, which of course benefits Google the most. Let's see how well the default fonts perform and monetize, because at least to me it's actually quite aggressive visually.
The default, increase font size can be seen in the image below: