First, his numbers for Deepwater seem to be quite low. The best estimates from Woods Hole Oceanographic say that Deepwater is "42 million to 84 million gallons" so far, which works out to 1.35-2.7 million barrels or 198,000-394,000 tonnes, 3-6x the amount listed. Except it's worse than that. He's comparing spills which have ended to an ongoing oil spill. Deepwater is spilling an average of 4-8000 barrels per day, and if this continues until August that will put the spill at 408,000-812,000 tonnes. So I've depicted four numbers: the current minimum, current maximum, anticipated total minimum when this is all over, and anticipated total maximum.
Second and more importantly, he's measuring length but depicting volume, which has the effect of exaggerating differences at the top end. His high res image is scaled to 10869 tonnes per linear pixel. The droplets grow in X and Y, changing their surface area. He should have either made the drops bars that scale in only one direction, or drawn each drop's surface area in proportion to the spill size. His 259x259 Gulf War droplet represents 22 tonnes per pixel area. I've scaled the remaining droplets so that their areas are in the same relative proportion.
