You can yes… the original css for it is found in the style.css around line 381
h1.site-title a {
margin-bottom: 0;
font: normal 2.313em alexbrush;
line-height: 0.813em;
color: #FFF;
}
Hopefully you will use a child theme to make this change, or a CSS edit plugin, or a font plugin. Basically you would do this:
h1.site-title a {font-size: 2em;}
….or whatever size you want.