He belonged to that class of men — vaguely unprepossessing, often bald, short, fat, clever — who were unaccountably attractive to certain beautiful women.” This first sentence of Ian McEwan’s new novel describes Michael Beard, age 53, a British Nobel-winning physicist and television celebrity. Unfortunately for Beard, the fifth of those women to marry him is openly sleeping with the couple’s building contractor, Rodney Tarpin. Although Beard has cheated on Patrice, he now wants her back and decides to make her jealous by pretending that he has a female visitor while Patrice is in her bedroom. He finds a woman’s voice on the radio, turns it up, and intercuts it with his voice. After a few minutes, “He went into the bathroom, ran a tap, flushed the lavatory and laughed out loud. Then he gave out a muted whoop. Patrice should know he was having fun.” With this not so “clever” scheme and more to follow, Beard joins a distinguished line of bumbling cuckolds — Joyce’s Bloom, Nabokov’s Humbert, Bellow’s Herzog — in McEwan’s first go at a comic novel.

Professor Beard did his original work, “the Beard-Einstein Conflation,” when young. Since then he has become the kind of globe-trotting guest lecturer familiar from David Lodge novels. Beard is an insatiable eater, constant drinker, and non-stop womanizer, favoring younger ones who can cook. He’s also a slob, introducing entropy into any room he occupies. He’s “aggressively unpolitical,” and, despite heading the National Centre for Renewable Energy, suspects climate scientists are apocalypse mongers. McEwan amuses early on by slapping around his largely unlikable protagonist — literally when Beard tries to kick Tarpin in the shin, figuratively when Beard’s penis freezes to his zipper on an Arctic junket.

Returning home early from the Arctic boondoggle, Beard surprises Patrice’s lover lounging in Beard’s robe — but this time it’s not Tarpin, but a young physicist named Aldous who works for Beard’s Centre. As Aldous rushes toward Beard to beg for mercy, the young man slips on a rug, hits his head on a table, and dies. Beard then uses some tools left behind by Tarpin to frame the contractor for the “murder.” As Part One, dated 2000, ends, Beard is no longer a bumbler, is even more unlikable, and the light of Solar seems to darken.

But as in Enduring Love and Saturday, an accident, like a small initial change in the Chaos Theory Beard dismisses, can have large, improbable consequences. In Part Two, dated 2005, Beard has used Aldous’s ideas to patent processes for solar energy and is on a mission to save the world from global warming if people will just let him. After making some innocuous remarks about science and gender, he is hounded by newspapers and politically correct academics, both ably satirized by McEwan, who has had several run-ins with journalists in recent years. Beard’s bad luck continues when his new lover, Melissa, secretly goes off the pill, becomes pregnant, and refuses to have an abortion.

Readers (well, male readers) can share Beard’s sympathies with himself as “victim.” Consider the poor guy on a train. Beard is eating from a bag of “crisps” (potato chips) on the table between seats. A young man across from him takes a crisp from the bag, and the quantum-influenced Beard ponders multiple realities:

The act was naked theft, however trivial the goods…. Or a tease, in the old-fashioned Situationist mode, of a stuffy bourgeois. Or worse, the fellow believed that Beard was gay, and this was a come-on, a kind of modern opening known only to certain sub-groups for whom his purple silk tie, as a hypothesis, was an accidental signal, an open invitation to seduction…. The physicist knew much about light, but about forms of public expression in contemporary culture he was in the dark. Finally, returning to his initial surmise, Beard continued to wonder if his fellow passenger was a psychiatric case on an unlicensed drug holiday from the lithium, in which case it was a bad idea to continue to stare into his eyes. At this, Beard looked away and did the only thing that came to mind. He took another crisp.

The scene — in McEwan’s signature style, it mixes perception and paranoia, sex and science, narration and commentary — goes on for another two pages until Beard realizes that his own bag of crisps is in his pocket and that he has been eating the other passenger’s crisps. Once again, Beard is the fool, but now he could be a holy fool, with occult formulas for artificial photosynthesis.

Beard scatters disorder wherever he goes, but in Part III, dated 2009, McEwan conventionally, if somewhat improbably, gathers together the splinters of Beard’s life at his solar installation in the New Mexico desert: his new, not-so-young American lover, Darlene, pressing him to marry; his still occasional lover Melissa and their daughter; the paroled Tarpin; and a lawyer accusing Beard of intellectual property theft. Beard also faces a new problem — a highly symbolic but real melanoma. Can our lying, cheating, self-deluding, self-aggrandizing, self-defeating “hero” clever his way out?  Does the sun usually rise in the east?

McEwan feels strongly enough about climate change to have written an essay on the subject, but perhaps anxious about seeming too earnest or topical, he said before Solar was published that global warming provided only the novel’s “background hum.” After Beard’s transformation from warming sceptic to solar savior, he becomes McEwan’s beard, articulating the author’s arguments against warming deniers such as Michael Crichton in his novel State of Fear. These passages, like the neurology in Saturday, are well-researched and thankfully more than a “hum.”

But, McEwan also said, the novelist needs a metaphor to incarnate his information. His begins with a “boot room” on the boat where Beard stays in the Arctic. In that entryway, the visiting intellectuals don’t store their protective clothing in an orderly fashion and end up “borrowing” others’ gloves and boots. The metaphor grows with the “crisp” scene. More serious manifestations are Tarpin’s stealing Beard’s wife, Beard’s robbing Tarpin of his freedom, Beard’s plagiarizing Aldous’s formulas, Melissa’s appropriating the Nobel genius’s sperm, and, though never mentioned, Prometheus’ theft of fire. Growing fatter and sicker with every year, Beard is described as a “monster” of consumption, thieving energy from the biosphere while trying to get a free lunch from solar radiation. Ultimately, McEwan implies, the unlikable but ingenious Beard is the metaphor for us humans.

Sometimes accused of being too solicitous of his readers, McEwan may alienate them with his metaphor. But from a novelist of McEwan’s stature writing on a subject of this magnitude, I expect more. Not necessarily more information about rising sea levels and dead polar bears but more artistic risk than the comedy takes, more inventiveness than witty third-person indirect discourse allows, more range than this one-man show provides. In the Arctic, Beard mocks artists who would “inspire the public to take thought, take action.” Solar has little such ambition, and McEwan’s Beard-man metaphor is paltry when compared with the encompassing metaphors of great environmental fictions: the arc of the rocket and industrial civilization in Pynchon’s Gravity’s Rainbow, the loop of patriarchal poison in Smiley’s A Thousand Acres, the war against insects in Vollmann’s You Bright and Risen Angels. Or, more positively, the elegant formal helices of Richard Powers’s novel about genetics and nature, The Gold-Bug Variations.

Reviewing his achievements in the novel’s final pages, Beard quotes Newton, who said that he stood “on the shoulders of giants,” an appropriate phrase for Solar because Newton “borrowed” the words from many earlier writers. In this entertaining and, yes, clever, novel, McEwan doesn’t aim quite so high, but is content to crouch near the solar plexus of giants. That lower region generates visceral comedy but not, in Solar, planetary inspiration.