Only a skeptic who doubts the science behind global warming or a curmudgeonly purveyor of fossil fuels could fail to be amused by this computer-animated sequel. Which is not to suggest Ice Age: The Meltdown attempts to transmit a green message. Global warming is used only as a plot device and the real theme is blended families. 

The story and animation weren't the strong suits of the first go-round in 2002, which became a hit despite lukewarm reviews. It was a character-driven cartoon and two out of the three most enjoyable characters have been enhanced. The persistent, acorn-chasing squirrel-rat Scrat and Sid the Sloth, voiced by John Leguizamo, are even more entertaining. A pair of cheeky possums, vultures with a flair for musical comedy, and a legion of Sid-worshiping sloths more than compensate for the absence of those wacky Dodo birds.

The gag and action-filled confection opens with Scrat clawing his way up a massive glacier wall in pursuit of the elusive acorn. You're left wanting more after this quick segment, a sterling example of the universal appeal of cartoons. Thankfully, the Harold Lloyd-cum-Wily E. Coyote figure is incorporated into the story more than last time; he shall return.   

Though its cause is unknown, melting ice has created a water park for a multitude of prehistoric critters. In an effort to prove his usefulness, Sid is acting as a camp counselor to a group of disrespectful tykes. All are frolicking oblivious to the impending danger behind the amusements Mother Nature has provided -- except for a snake-oil salesman called Fast Tony (Jay Leno). He ignorantly warns of an impending flood so he can peddle his wares.

His stab in the dark is bolstered by a hungry vulture, who tells all the animals to flee to the other end of the valley where a boat awaits. Another migration begins, with Manny the woolly mammoth (Romano), Diego the saber-toothed tiger (Dennis Leary), and Sid bringing up the rear. Unbeknownst to the bickering threesome, two vicious marine creatures have been unthawed and give chase. 

Soon the stragglers encounter two feisty possums called Crash and Eddie (voiced by Seann William Scott and Josh Peck) and Ellie a female mammoth (Queen Latifah) who thinks she's a possum. Diego and Sid push Manny into a courtship to keep his species alive and help him get over being separated from his herd. Ellie plays hard to get as any anthropomorphized animal would.

During the ensuing heroics and humor, the central beasts take big steps toward becoming full-blown characters. Diego overcomes his feline fear of water, pessimistic Manny gets with the program, and Sid cracks wise at every opportunity in his quest for a sense of self-worth. Some borderline language is tossed in, and a few audience members might be a wee bit frightened by the menacing piscatorial pursuers. 

Though not on the level of Pixar, the animation is more than adequate, with the receding ice allowing more greens and earth tones to color a less glacial landscape. Three sequences rise far above the rest and reward a trek to the Cineplex. First is Sid's apparent dream featuring a tribe of worshipful mini-sloths; the second is the vultures belting out a rousing rendition of "Food Glorious Food." And, finally, Scrat's arrival at the Pearly Gates (with an acorn motif of course) is masterful.

Ice Age: The Meltdown encourages everyone to challenge the herd mentality and find family and sense of belonging wherever it feels right. This movie feels right more often than the first Ice Age, which means a third installment is inevitable and eagerly anticipated.

(Released by 20th Century Fox and rated "PG" for some mild language and innuendo.)