Solar is a sly, sardonic novel about a dislikable English physicist and philanderer named Michael Beard. He's a recognisable Ian McEwan type, a one-dimensional, self-deceiving man of science. We have met others like him before in McEwan's novels  such as Joe Rose, the science writer who narrates Enduring Love, or Henry Perowne, the brian surgeon protagonist of Saturday  but none is quite as repulsive as Beard. Perhaps McEwan should have written against expectation by choosing as his protagonist a scientist who has a profound artistic sensibility in the model of his friend Richard Dawkins, or an artist who is articulate in the language of science, as McEwan is himself. As it is, he remains a determined binarist; what continues to interest him are stark dichotomies, the clash and interplay of stable oppositions. Repeatedly in his fiction he sets reason against unreason, science against art, the mind against the body, technology against nature.

Beard, who we are encouraged to believe won a Nobel prize in physics as a young man for something called the Beard-Einstein Conflation, is a short, fat, balding, much-married man of immense bodily appetites and scant self-discipline. He rapaciously consumes food, women and drink, with little regard for the consequences. He's a resolute short-termist, fearful of commitment and of becoming a father, living for the here and now. His behaviour is a local example of the more general problem of human over-consumption: just as Beard devours everything around him, so we are devouring our world, with its finite resources and fragile ecosystems.

The trick of the novel, its central comic turn, is to make Beard, the greedy, selfish uber-consumer, an accidental expert on anthropogenic climate change. Through his expertise as a physicist, and then his opportunism in stealing the research ideas of a graduate student who works with him at an institute in Berkshire known only as the Centre, Beard is engaged in a programme to create cheap renewable energy through a process of artificial photosynthesis (you'll need to read the book to be filled in on the science).

McEwan's great gamble is to narrate Solar, which is in three parts and spans nine years, from 2000 to 2009, entirely from Beard's point of view. Some of this is satisfying, especially the pithy scientific elaborations: McEwan, who has a precise, technician's vocabulary, has swotted up to PhD level on physics, just as he did on neurosurgery for Saturday, musicology for Amsterdam and molecular biology for Enduring Love. None of this extracurricular learning feels perfunctory, especially when compared with, say, a novel such as Martin Amis's The Information. In that novel, disquisitions on infinity, black holes, dwarf planets and astronomy felt imposed on the narrative rather than being intrinsic to it. In Solar, the physics never feels forced or unearned but rather is embedded in the deep structures of Beard's consciousness. We see the world just as he does, in all its cold reductiveness.

In McEwan's early fiction, in his strange, experimental short stories and novellas, with their isolated, sexually deviant male protagonists, he wrote from the outside in, as it were. His was always the controlling intelligence, aggressively masculine, and he followed his young male protagonists less in thought than in action, detailing their psychosis and alienation with the cold detachment of a coroner examining a corpse. So devoid of emotion were these early fictions that reading them felt almost like an act of voyeurism. McEwan appeared to have no feelings for his characters; instead, he dissected them as if they were rats in a laboratory experiment. Here was, as John Updike said of Amis in a different context, "an atrocity-minded author"  but one with perhaps the most controlled, exact and fastidious prose style of all contemporary British novelists.

McEwan's cruellest book, the one in which the violence seems most gratuitous and nasty, is The Comfort of Strangers (1981), his novella about a young British couple adrift in an autumnal Venice of shadows and fear that marked a point of transition for him: after this, and a long period of silence, he returned as a different writer. The instinct for cruelty remained but it was mitigated by a much deeper, more sophisticated, even feminine, moral and aesthetic sensibility. From The Child in Time (1987) onwards, he was less a postmodernist than a realist, with a 19th-century interest in character, agency and storytelling, in the what, how and why of the human dilemma. In addition, he was developing a modernist's concern with consciousness, and began to experiment with different ways of representing the essence of what Virginia Woolf called the "quick of the mind".

McEwan was now writing from inside out: thought determined action, and there was a new descriptive density to his writing. Where once he had shrunk and compressed, he now expanded and inflated. He was no longer a miniaturist, and yet he was still a writer of great, self-contained set-pieces, such as his description of a ballooning accident that provides the celebrated opening to Enduring Love; or the disappearance of an infant from a supermarket at the beginning of The Child in Time, a scene of such intense and urgent panic that it would torment any parent who read it; or the extended scene in On Chesil Beach, where the virginal newlyweds try and fail to consummate their marriage, with devastating consequences for the rest of their lives.

Yet what unifies all McEwan's fiction is his preoccupation with the randomness of human endeavour in a post-religious, Darwinian world: his novels invariably turn on one sudden, unaccountable, life-changing happening or fatal equivocation. In Solar, the moment of crisis occurs when Beard returns from a trip to the Arctic to discover one of his graduate students at play in his house. It's quickly apparent that he is having an affair with Beard's unhappy and desperate wife (the marriage is over; Beard is a serial adulterer), and, in the ensuing confusion, the student falls and hits his head: "No breathing, no pulse." Instead of helping the student or calling for an ambulance, Beard stumblingly intervenes to make it appear as if he has been murdered  as you would  so as to frame one of his wife's previous lovers, a thuggish builder whom Beard has confronted earlier in the novel.

The circumstances of the death are used by Beard to extricate himself from his marriage, to punish the loathed builder and to reanimate his moribund career by appropriating the student's research into climate change and claiming it as his own. In one bound, it seems, he's free.

That's a lot of change to believe in, however, and from this point everything feels excessively neat, ruthlessly schematic. Solar is very similar in style to the Booker prize-winning Amsterdam, especially in its narrative tidiness, jauntiness of tone and desire to punish foolish men. But Amsterdam was a novella, whereas Solar feels as if it has been stretched far beyond its natural length. Much of the first part, which is set in 2000 and culminates in the death of the student, reads like an exercise in extended scene-setting, to no obvious purpose or effect. The protracted episode in which Beard travels with a group of scientists, artists and green activists to the Arctic, played mostly for laughs  he pisses outside and his penis freezes; he is menaced by a polar bear  is laboriously over-described. There is, sentence by sentence, an uncharacteristic verbosity.

The chief revelation of the Arctic mission is to show how the bootroom, where the well-intentioned group keeps its foul-weather clothing, becomes, after only a few days, a site of anarchy and chaos. This then is another parable of human rapacity: we take what we can, when we can.

The best and most complex scene occurs towards the end of the second part. Beard and his latest lover, a kind, generous, full-figured woman, are together at her house. She has prepared a meal, and just before they sit down to eat it she tells Beard that she's pregnant and determined to keep the baby. In sentences of extraordinary poise and precision, McEwan contrasts Beard's selfish sense of revulsion at the news with that of his lover's hopeful joy. So minutely does he track Beard's ever-shifting, contradictory positions you have a returning sense, so familiar in McEwan's fiction, of events somehow sliding inexorably towards disaster. But then the lens blurs, there's an unexpected softening of focus and, after having sex, exhausted, the couple fall asleep.

We next encounter Beard, four years later, in 2009, at the beginning of part three. He's in New Mexico preparing for a conference, and it is there, under the ferocious sun, that a lifetime of carelessness eventually catches up with him in a denouement that wouldn't be out of place in a West End farce.

It was always going to be high risk, wagering so much on having as your central character a comic grotesque so loathsome and self-pitying, with thoughts mostly so banal, and then leaving the reader trapped, unrelieved, in his company for nearly 300 pages.

In Atonement, the character Bryony writes fiction in which she seeks "to show separate minds, as alive as her own, struggling with the idea that other minds were equally alive".

What is absent from Solar, ultimately, are other minds, the sense that people other than Beard are present, equally alive, with something to contribute. Without them, after a while, it feels as if you are locked inside an echo chamber, listening only to the reverberations of the one same sound  the groan of a fat, selfish man in late middle age eating himself.

Jason Cowley is editor of the New Statesman

Climate change is chiefly an engineering problem to Michael Beard, the central character in Ian McEwan's new novel. In a different sense, it is to McEwan too. A practised manipulator of his readers' expectations and responses, he has plainly thought hard about the difficulties of dealing in a work of fiction with something that comes trailing strong emotions and unhelpful narrative models.

In contrast to the politics of global warming, for example, the science can't easily be debated dramatically without giving undue weight to the denialist camp, which he's unwilling to do. On the other hand, apocalyptic urgency, which shadows so much of the rhetoric around the issue, is equally unattractive to McEwan, a long-term fan of Norman Cohn's The Pursuit of the Millennium. Finally, and maybe most intractably, there's the problem of response-fatigue. Pressing invitations to think about global warming aren't thin on the ground. McEwan's solution is both elegant and surprising: instead of applying doom and gloom, he reaches for a lighter, more comic mode than usual.

Beard, a short, fat, philandering physicist, serves as the novel's scientifically informed focal consciousness and as a quasi-allegorical figure. In this, he resembles Henry Perowne, the neurosurgeon at the heart of Saturday (2005). But here too comedy gets McEwan round a problem. The earlier novel's unironic stance towards its central figure, along with its vanilla-flavoured politics, grated badly on many readers, who saw it  whatever its technical merits  as a novel about a smug, rich man who's almost proud of his inability to decide if invading Iraq is a good idea. Beard shares Perowne's distaste for zeal: though never in doubt about the basic science of global warming, he begins the novel suspicious of the "Old Testament ring" to environmentalists' forewarnings. This time, however, it's made clear from the start that we won't be asked to admire this mildly preposterous character, a generator of ironies as much as an observer of them.

The first of the book's three sections begins in 2000. Beard is 53, his best days long behind him. A Nobel laureate for his early theoretical work ("the Beard-Einstein Conflation") on the photoelectric effect, he sits on committees, lends his name and prestige to institutional letterheads, and fills the role of "Chief" at a research centre outside Reading that has been set up to allow the Blair government to be seen as doing something to combat climate change. For Beard, this phenomenon is merely "one in a list of issues, of looming sorrows, that comprised the background to the news, and he read about it, vaguely deplored it and expected governments to meet and take action . . . But he himself had other things to think about." The most insistent of these things is his fifth wife Patrice's affair with the builder who did up their house in Belsize Park, an affair she's embarked on in a mood of buoyant vengefulness after coming across evidence of Beard's numerous infidelities.

In order to escape Patrice's icy good cheer, and the attentions of a young physicist at the centre, Tom Aldous, who keeps trying to interest him in artificial photosynthesis, Beard signs up for a trip to the Arctic. This entirely selfish decision is greeted as a great step forward by the centre's idealists and its time-serving co-boss. Beard heads north in the company of various arts-world luminaries. "Everyone but Beard was worried about global warming and was merry"; only the semi-sceptical physicist is appropriately sombre. There's an echo of Perowne's somewhat priggish disapproval of the anti-war protesters' levity in Saturday, but Beard's moroseness springs less from intellectual consistency than the fact that he has nearly frozen off his penis by emptying his bladder in subzero temperatures. This uncomfortable episode, and the journey it takes place on, is the first of McEwan's customary set-pieces in the book, and it's as though he's decided to give full rein to the comic overtones held back in 2007's On Chesil Beach.

Returning to London, Beard is quickly embroiled in more of McEwan's traditional tropes  a life-altering accident and a suspenseful sequence, again given a comic spin. Then a new section starts, set in 2005. Divorced and even fatter, Beard has reinvented himself as a clean-energy entrepreneur. He has, it turns out, been sacked from the centre after making some off-the-cuff remarks on the low numbers of women in high-level physics jobs. McEwan draws fruitfully on his own experiences with the press here and has some satiric fun at the expense of arts academics, though Beard's troubles, modelled on Larry Summers's at Harvard, aren't quite believable in an English setting. The physicist has also acquired a new girlfriend and an addiction to salt and vinegar crisps; weirdly, McEwan uses these last items to have him experience a well known anecdote  another set-piece  and then has an irritating know-all pop up to explain what a well known anecdote it is.

Beard's main business, however, is to lecture a group of institutional investors on alternative energy. The novel carefully undercuts both his virtue and his dignity: he spends his time at the podium trying not to vomit, having eaten a dodgy smoked salmon sandwich, and parts of his pitch are either plagiarised or hypocritical fabrications. All the same, his actual arguments are compelling, and it's hard not to root for him as, in the final section, he prepares to throw the switch on a prototype array of next-generation solar panels in New Mexico. It's now 2009, and Beard, fatter still and trying to ignore a worrying melanoma, has further romantic entanglements and professional complications on his plate. As various chickens from the first two sections start coming home to roost, still in comic mode, McEwan builds up considerable suspense about the fate of Beard's enterprise, a revolutionary technology that, you end up half-believing, might save the world.

In the course of his trip to the Arctic circle, Beard hears some unfamiliar guitar music, "reflective, with a touch of lightness and precision, like something of Mozart's". Solar seems to aim for something similar and, as you'd expect, precision isn't a problem in its brisk tour d'horizon of the ironies arising from climate change. McEwan swiftly persuades the reader that he can write authoritatively not only about science but the culture of scientific institutions, too. He also revels in clever, sometimes over-neat reversals. At one point, Beard's business partner starts to worry that the climate might not be changing after all. "It's a catastrophe," Beard assures him. "Relax!"

Lightness, however, comes less easily to McEwan, whose style depends on deliberateness and a certain ponderousness. The ominous lining up of causes and effects and the patient tweaking of narrative tension don't always mesh well with the aimed-for quickness and brio. Some of the humour is quite broad: there's a rather clunking motif concerning polar bears, and Beard gets involved with a stereotypical Southern waitress who's called, in the way of trailer-trash types, Darlene. He emerges as a figure of some comic dynamism, but the pages on his childhood and youth, though brilliantly done, articulate poorly with the knockabout parts of the plot. Once it became clear that the book's world is comic, I also found myself wondering if it wouldn't have benefited from being more loosely assembled, with shorter, discontinuous episodes and Beard functioning along the lines of Updike's Bech, Nabokov's Pnin or the consciousness in Calvino's Cosmicomics.

At the same time, the overarching plot pulls off a clinching novelistic coup, using comedy to sneak grimmer matters past the reader's defences. Beard's argument about the correct response to climate change, an argument that McEwan has also made, is that we have no choice but to hope that technological ingenuity, enlightened self-interest and the market's allocation of resources can get us off the hook; personal virtue counts for little. For a while it seems as though the slobbish, self-centred Beard might actually bring about such an outcome, and the reader starts to hope he'll manage it. But Beard  self-deluding, a serial breaker of resolutions, hopelessly addicted to overconsumption  also stands for humanity in general. When he gets his comeuppance, it's a powerful reminder that reality isn't a comic novel, and in its deepest implications, this book isn't one either.