Oh! Awesome experiment! Yes, they’re shorter because of perspective (foreshortening). With a mirror surface it’s better to think of a duplicate of the object flipped across the mirror plane, then you can apply the same tricks to draw in perspective, which may make it look shorter.
In your example here, since we’re viewing from the side the perspective is not going to factor in as much, so we land at “roughly the same size”
Just one small correction, which is in the article but somehow is wrong in the title.
Rainfall increases the ocean’s uptake of carbon by 6%, and the ocean accounts for one quarter of global uptake. So the amount we’re talking about here is 1.5% and doesn’t include the amount rainfall contributes to uptake of carbon on land unless we just chalk all rainfall up to oceanic uptake.