By Adrian Searle, Issue 13.

This is me, this is you. This is how I was, this is how I am. Does this look like me, does this look like you? Is it a good likeness? Time has passed, but your image still stares back at me, and I look at how you were. It’s a kind of you. How will we look, in years to come? Will we still be here? What’s the weather like, where you are?

In the mid 1990s, Roni Horn photographed Magrét Haraldsdóttir Blöndal 100 times, over a period of six weeks. Her face looks back at the camera from Iceland’s thermal pools.  Her head inclined this way and that way, but always looking back and never, quite, smiling. What’s on her mind? And what’s the difference between looking at the camera and looking at the photographer, and looking at whoever happens to be looking back at her frozen image? Whenever I am surrounded by You Are the Weather I think the woman in the photograph is looking at me, just as I look at her, and am the sole focus of her attention. Some of her multiples selves must be staring at one or other of my ears, my nose in profile, the back of my head. But it’s more complicated even than that. I also imagine I am standing in the place of the photographer, dissolving into Roni as she takes all those photographs, but I know that’s not true. Witnessing the mutual regard of photographer and subject you ask yourself not only who is the subject of these images, but what does it all amount to?  Fifteen years on, Horn has photographed Magrét again, the same poses, that same quizzical scrutiny. The woman in the water looking at Roni, her camera and at her future witnesses – us, in other words. In this case, me. Always that same unknowable exchange. But so much has changed over the years. You imagine what the woman in the photographs is thinking, but that’s just a projection, your own weather report of the situation.

Roni Horn and I were in the car outside the town of Stykkishólmur in the west of Iceland. The weather was getting worse by the minute. Should we go on? It was snowing hard. The air ahead was a greyish-green colour, thick and impenetrable. We just sat there on the narrow road. At one point I took a photograph. The photograph shows what we are both looking at, which isn’t much: a few fence-posts marching into nothing, the snow piling up, the view veiled by the glassy windblown ripple of melted ice on the windscreen. “It’s such typical Iceland”, she says. The prospect is bleak.

Whenever I look at this photograph it reminds me not just of that ill-advised ride, but of looking into one of those great glass blocks that Roni makes. When you stare into them you begin to see mysterious inner flaws and fault-lines. You imagine worlds in there. They have what looks like personalities. Some boil with glacial refractions. Some are black and grave, others have a crystalline indifference to being looked at. Some are like clear round pools, others sumps of oil or tar. Some you might almost think of paddling around in, others look dangerous. You get sucked in. Snow roars in the wind, rocking the car on its axles, with us in it.

Stuck here on the road looking into the weather feels like being trapped inside a bubble in one of those glass blocks. Roni complains about the weather, almost apologising for it. Who is responsible for the weather? You Are the Weather, says the title.  Weather Reports You, says another, this time a compendium of stories about the weather (which say as much about the tellers of the stories as of the weather itself). Our ears pop. You can feel the isobars moving through. We sat in silence and looked at the worsening situation.  A raven flew by, backwards, like a lost umbrella. Did I really see that? I’ve been to other northern isles but none so raw as Iceland. She’d been coming here for decades, and I’d gone to visit just as she was finishing her Library of Water in Stykkishólmur.

Somehow she turned the car around and we went back. I lay on the bed in my cold and weirdly empty hotel, and waited for things to improve. A few days later I was in London, flying in on warm, wet March winds, mild Atlantic weather that bypassed Iceland completely. I met Roni again a few times in London when she was coming through.  She had her Tate Modern show, and then we met again in New York. It was autumn, two years after that trip to Iceland. The weather was beautiful. I was feeling unhinged, my life unravelling but I didn’t yet know how.  Then it was Halloween and the streets were filled with ghouls and vampires and a guy dressed as a giant octopus flailed on the sidewalk. It began to rain and I had to walk for blocks through the crowds to get to the restaurant where Roni waited with a friend. Later, parting at Union Square, Roni said she’d seen me battling through the Halloween revellers like a ship lost at sea.

Two months later, I went to New York again, seeing in the New Year in one of those dismal airport hotels at Newark. I stayed up most of the night drinking whisky in my room, then woke to a room filled with white light, and a view of a vast parking lot filled with cars buried in snow, the airport Marriotts and Hiltons rising like mesas over the endless snowbound lot. The air steamed. Roni’s Tate show was now at the Whitney. I stood again in the middle of You Are The Weather and realised that though the work was the same as I’d seen it in London, I had changed. The configuration was a bit different but more importantly something in me had shifted. You never see things the same way twice.  The art hadn’t changed but I had.  The first time the photographs had almost looked accusatory, and I felt small in the space amongst them. Now they appeared complicit and almost conspiratorial. Here you are again, they said. What’s up?

There were also lots of pictures of Roni in the Whitney exhibition: younger, older, a child, a teen, smiling, sassy, serious, boyish, butch, Roni long-haired and Roni with a don’t-mess-with-me look; an itinerary of the same person, shown in pairs. Older and younger portraits with the same smile. Innocent Roni and the knowing adult. Roni duplicated and doubled. Startling contrasts: good girl and bad boy, knowing brat, the artist with attitude, a register of self-possessions.

Like the weather in Iceland, these echoing presences are fleeting glimpses. Iceland, someone once said, doesn’t have weather, it has examples of weather.  These are examples of Roni. But also like the weather, she’s always there. I look back at earlier pictures of myself with a kind of affection and embarrassment. If only you knew, you say to yourself, and What on earth were you thinking?  You want to go back and tell these earlier selves how wrong they were, give them a shake or a slap, or just get them out of there. This urge is signal to a continuing immaturity.

Horn’s work is mostly about her and the world, being a spectator, being a subject, being in the world, its mutability. What else is there? I have seen her squally, temperate, calm, balmy, changeable – words she wrote on the floor of her Library of Water. Words for the weather and words for the self. I bring some of my own weather with me, wherever I am.

It is summer in upstate New York. Snakes in the undergrowth, the hum of insects.  I heard about this but I wasn’t there. Another subject in the water: the photographer Juergen Teller up to his neck in the pond at the back of Roni’s place, small inquisitive fish nibbling his skin, a catfish sidling by. Roni has photographed him here before. Just the head, up to his neck, mismatched by his own reflection, and inverted. Which way is up? The images are a play of real presence and virtual reflection. Or virtual presence and real reflection. At any event, the reflection doesn’t seem to match the head. Juergen is part Neptune, part satyr. His head swims and Roni’s camera wallows in the surface. They wait for the wind to drop, for the reflections to settle down to something recognisable. Roni photographs Juergen and, later Juergen photographs Roni, at night, naked in the water. Shooting her with a flash, the light penetrates the tea-stained water, illuminating swarms of daphnia seething in the warm upper layers. Bubbles float by. She’s luminous in the rich black night, eyes closed, floating. It seems such an unguarded moment you wonder if you really should be looking, not least because the artist looks unobserved, absorbed in the moment.

This is you, this is me, looking. Isn’t writing another kind of weather report? It also has its own calms and tempests, squalls and doldrums. You can’t always predict where it will go. She got stranded by early snow in London last year, on her way to the Cabo de Creus in Catalonia, where the chain of the Pyrenees falls into the sea. Airports were closed and she never left town, and stayed in her hotel for a week. Horn likes places on the edge. Even a hotel room. It’s like a car in a snow drift, but with room service.