On the evening of Sunday 6th April the baggage reclaim at Nice airport is full of people with tubes a metre or so long slung over their shoulders. They bring their tubes in from the gates alone or with a friend; soon they recognise others of their ilk and congregate collegially before the arrival of checked-in bags spurs them to break off in taxi-sized cliques and head off into the night.
The tube-bearers are coming to what is probably the largest meeting of Earth scientists ever to take place in Europe - a joint meeting of the European Union of Geosciences, the European Geophysical Society and the American Geophysical Union. The posters wrapped up in their tubes carry the results and hypotheses that they will be presenting to their peers. When the occasional poster tube turns up on the baggage carousel, there's a mild susurration of shock at the nonchalance of checking in a poster; lose your poster and you lose your presentation.
Monday morning
In the Apollon theatre, a vast auditorium at one end of Nice's Acropolis congress centre, Jan Smit of Vrije University in Amsterdam is talking about the Chicxulub crater in Mexico - the site of the asteroid impact 65m years ago that seems to have killed off the dinosaurs. Smit is part of an international team that recently drilled a borehole into the rocks of the crater, and this is one of the first presentations of their results. Unfortunately, most of the people who might want to hear him are stuck in a long queue outside the centre waiting to pick up their badges and get through security.
One person who made a point of getting here early enough to be sure of making the session is Gerta Keller of Princeton. Keller is the most prominent of the small band of scientists who believe that Chicxulub is not the impact that killed the dinosaurs. She and her colleagues think that the crater was made 300,000 years before a second impact left the global layer of fallout that marks the true boundary between the Cretaceous period and the subsequent dinosaur-free Tertiary. Today she is focusing on a layer of rock deep inside Chicxulub. Smit and his colleagues think these rocks are sediments that flowed back into the crater as soon as it was made, before the global fallout thrown up by the impact had had a chance to do its falling. But on the basis of tiny fossils within them, Keller thinks the sediments represent 300,000 years of steady sedimentation between the formation of the crater and the fallout layer, which must have come from somewhere else. The opposition just doesn't accept it, much to Keller's frustration. "I have some samples in which even you could see them," she says to Smit at one point. Given that English is not her first language it's possible that she doesn't mean this to sound as patronising as it does.
During a coffee break I talk to one of the majority group. He tells me how important it is that a hypothesis should have insistent critics like Keller. It keeps everyone on their toes. He then tells me just how irritating it is that she won't shut up.
Monday afternoon
I am beginning to realise how vast this meeting is. There are about 11,000 delegates, maybe more - no one is sure. The talks are divided into 22 "programme areas" corresponding to sub-disciplines or interest groups: tectonism and sedimentary processes, natural hazards, volcanology, geochemistry and petrology, and so on. There are four or five sets of talks going on in any one of these areas at any time. They are accommodated in about two dozen theatres or large rooms on the conference centre's three floors. For the next week, each space will have a new presentation every 15 or 30 minutes.
And that's before the fruit of the tubes. In a huge marquee on a nearby parking lot - reached by a walkway that is doubtless much more sturdy than it feels - there is room for the display of over 1,900 posters, which change every day.
If I'm diligent, I guess I could do some justice to 30 presentations a day, more than half in the form of posters, though I won't get all the subtleties. That represents about 1 per cent of what's on offer.
Unlike people with posters to display, I don't have a single outstanding reason for being here. I write about the Earth and planetary sciences; I've written a book about Mars and am planning a couple about the Earth, and part of the point of coming is to build up ideas and contacts for those projects. Shorter term, there are some subjects here I should be digging into for articles I am working on. But mainly I really enjoy a good scientific conference, and this one sounded so promising I wanted to sample it. It's a kind of high-intensity face to face browsing.
One field I can browse with great pleasure is paleo-climatology, the study of the various and often peculiar climates that the Earth has managed to produce for itself over time. Among the most intriguing is the very warm climate of the Eocene period, about 50m years ago; fossils from the Eocene show that the world as a whole was warmer then than it is today, and that at high latitudes it was much, much warmer. The Thames valley was choked by mangrove swamps; forests reached pretty much to the poles themselves.
There's good evidence that during the Eocene (and similar earlier periods) carbon dioxide levels were higher than they are today, and that they warmed the world. But if you bump up the carbon dioxide levels in computer models that reproduce today's climate, you don't produce what the fossils seem to show happened in the Eocene. You get a warmer world - but not a world so startlingly warm at high latitudes. You can't get the poles hot enough.
Daniel Kirk-Davidoff, of the University of Maryland, offers a possible mechanism for warming those recalcitrant poles. In a warmer world, he argues, the flow of heat out of the tropics towards the poles - the meridional flow - will be reduced. As a result, the altitude of the tropopause - the boundary between the lower atmosphere and the stratosphere - will be lower, at the equator, than it is today. More water vapour will leak into the stratosphere, making it a lot damper. This moisture will flow north and south, and eventually form stratospheric clouds over the poles, trapping the heat so that the poles will warm up. (The details of which clouds warm the earth and which cool it are a week of talks on their own; but polar stratospheric clouds are definitely warmers.)
This mechanism provides a way for a world that is warmer overall to get a lot warmer at the poles, which is what is needed to make sense of some of those past greenhouse climates. Though Kirk-Davidoff doesn't expound on this, it's possible that when the amount of carbon dioxide reaches Eocene levels we will see such an effect starting to amplify global warming.
Back in the press room - an oddly shaped space below the banked seating of the Athena lecture theatre on the first floor - I try to explain the virtues of Kirk-Davidoff's argument to my friend Gabrielle Walker, a former editor at New Scientist and the author of Snowball Earth, a wonderful book about a very different type of extreme climate from the past. Gabrielle isn't impressed, partly because I can't reproduce some of the subtleties of the argument well enough. The fact that I can't pronounce the word "meridional" consistently doesn't help. Moreover, Gabrielle has seen polar stratospheric clouds in Finland and found them incredibly beautiful, like a sky "full of peacock feathers." She is unwilling to see a downside to such beauty.
Tuesday morning
The day is packed with talks on methane - there's even a press conference on it. Press conferences, like the well-hidden press room, are the result of the American Geophysical Union's presence. The AGU, like most US scientific organisations, takes press communications more seriously than its European counterparts.
The methane press conference, chaired by the unflappable AGU press officer, Harvey Leifert, covers several lines of research into the vast deposits of clathrate - a sort of methane-rich ice - that have been found under the sediments of various seas and oceans. The methane is produced by bacteria in the deepest sediments. Some people - notably James Kennett of the University of California, Santa Barbara - think that sudden releases of methane from these clathrate stores have huge effects on the climate (methane is a much more powerful greenhouse gas than carbon dioxide). Kennett thinks that methane in the air bubbles trapped in ice laid down at the ends of various ice ages is evidence of a "methane trigger," and that a sudden spike of methane-induced warming set off a longer term, carbon dioxide-based warming. Others think the methane spikes at the ends of ice ages are a response to the initial warming, not its cause. After an hour of press conference and another hour of milling around with the speakers, it's not clear if any side in the debate has the upper hand. Carbon 14 dating of the methane in the ice would do the trick - but it is difficult to measure, and the people trying it may not have definitive results for some time.
Later, at one of the hundreds of posters on the topic, I come across a German clathrate cynic. German researchers have set the pace on methane research, but he tells me the field only has the prominence that it has because of interest from Germany's press, and that claims about the amount of clathrate beneath today's oceans are greatly overblown. He thinks it is an interesting issue, but secondary. He works on it anyway; it's where the funding is.
Tuesday evening
Peter Westbroek is honoured with the Vernadsky medal for contributions to geobiology, the discipline which uses biology to understand the workings and history of the Earth. Peter, a retired professor from the University of Leiden, gives an idiosyncratic and endearing lecture about the way that, over the history of the Earth, the production of carbonate rocks has gone from being a purely chemical process to one driven almost entirely by biology.
Afterwards a number of us head out to eat seafood in one of the colonnades that ring nearby Place Garibaldi. This is a hardcore seafood restaurant: no salads, no vegetables, no vertebrates. The service is a touch on the brusque side, and the temperature drops alarmingly when one of the gas heaters sputters and dies. The sediments of the Mediterranean may be packed with methane, but not this restaurant. Still, the conversation, wine and food make up for everything. Peter gets stuck in to a large plate of oysters, doubtless attracted by their carbonate shells. Next to me, Graham Budd, a palaeontologist with great expertise in arthropod anatomy, tries out his dissecting skills on a crab, with mixed results. He might have done better on a trilobite.
Wednesday morning
I bump into a geophysicist I've known for several years. For all that time he has been working on ways to transport seismometers to the surface of Mars, most recently as part of a French-led project called Netlander. Unfortunately, the spacecraft that was meant to take the four little Netlanders to Mars has recently been cancelled, sending the project into a spin. For a while it looked possible that Nasa might help out by providing room on a mission it has planned for 2009, but while one part of Nasa was studying that possibility, the part that was funding the American instruments on the landers pulled out. So my friend's careful study of Marsquakes looks likely to be deferred for another decade. It's hard not to think that the past few months have probably not been the most propitious time for French space scientists to look to Washington for help. Collateral damage?
Wednesday afternoon
Graham Budd, neophyte eater of crabs, gives a terrific account of the "Cambrian explosion" - the sudden burst of diversity seen in fossils 540m years ago. The arguments are clear and convincing, the delivery droll, the attacks on the various theories with which Budd disagrees sharp to near brutal. (Asked what he thinks of a theory that links the explosion to the genetic programmes by which arthropods develop, Budd replies "It's utter nonsense." When asked to expand on this his head rocks back in bewilderment. Is utter nonsense a difficult concept to grasp?)
Later on, Andy Ridgwell - a one-time eco-warrior with partially dreadlocked hair and just short of wild eyes - gives a talk on the role of the oceans around Antarctica in governing the amount of carbon dioxide in the atmosphere at the end of the most recent ice age. Like Budd's, the talk takes the audience through a field overburdened with competing theories; again, there is clarity, wit and insight, although the delivery is a little less barbed. It strikes me that maybe Cambridge, where they were both undergraduates, imbues its students with a rhetoric particularly well suited to the complex histories of the living Earth. That said, it is entirely possible that, while studying at Cambridge at roughly the same time, my idea of what a good talk on the biogeosciences should sound like became fixed on what I was exposed to. Budd's style, in particular, reminds me of Simon Conway Morris, one of the palaeontologist heroes of Stephen Jay Gould's Wonderful Life, and by far the most entertaining lecturer on the year-long introductory geology course I took at Cambridge. Both explanations probably work: they're really good at it and I still carry prejudices fixed as an undergraduate.
There is a set of sessions tomorrow on why the Himalayas are so tall and on what their shooting up may have meant for the climate; the fact that a lot of the work is by the Cambridge professor whose lectures I remember least fondly is the shameful reasons I won't be going.
Knackered, I head off to a little pizzeria by the old port, thinking to dine with just the Herald Tribune. The patron thinks differently, and I share a table and a conversation with a Swiss petrologist. As time goes by I realise that, even by the standards of the Swiss, he speaks truly excellent English. Not many non-native speakers will use the word "hullabaloo" in just the right way; still fewer will do so without a certain relish of accomplishment. It turns out, though, that English is not his second language but his fifth, from a total of nine or ten (two of them, admittedly - classical Greek and Latin - are written, not spoken). I learn this only by digging; he is entirely unboastful about it, although aware it's unusual. As someone who finds even rudimentary language-learning hard, I am normally somewhat envious of polyglots. But achievement this prodigious is heartening; if humans can do something as wonderful as that, I'm all for them.
Thursday morning
I'm not meant to be concentrating too much on Mars at this conference but sometimes it is hard to resist. Jim Head, a planetary geologist from Brown University, is giving a number of presentations on the iciness of Mars. On Earth, most of the ice we see has its origins in liquid water - cloud droplets freeze to form snowflakes that fall to form ice caps and glaciers - and ends up as water again when it melts. Earthlings have thus come to think that because the surface of Mars shows relatively few signs of liquid water, there can't be much ice moving across it, even though there is clearly ice at the poles. New images, though, are convincing Head and others that there is ice all over the place: ice that falls as snow, sits as glaciers and turns back into water vapour, hardly ever messing up the dust below by melting into a liquid.
Head has a poster showing some superb evidence for this. Pictures of the flanks of a crater in Mars's southern highlands show a set of what seem to be smoothly flowing lobes of rock which are more or less impossible to see as anything but the remains of dirt-covered glaciers. Head, recently returned from a field trip to the dry valleys of Antarctica that taught him a lot about what earthly glaciers can look like in arid situations, is clearly very pleased with them. A Norwegian glaciologist ambles by, looks at the pictures, looks away, looks again. "Are these really on Mars?" he asks with a tone of what I take to be subdued Scandinavian wonder. "They are," replies Head. And the two of them grin at each other, delighted by the universe in general and planets in particular.
Thursday lunchtime
Every day brings more talks about links between sun and climate. The amount of energy given off by the sun varies over a number of timescales - most famously the 11-year solar cycle - but not by very much, and so most specialists tend to see solar variability as only a minor factor in the variability of the climate. However, a growing body of data and hypotheses argue that the sun may have a greater role to play.
One possibility is that ultraviolet radiation is important. Although the overall brightness of the sun varies only a little, the amount of UV it generates changes a lot more, and could affect the stratosphere, which could in turn affect the lower atmosphere. Another possibility hinges on the solar wind - the constant stream of charged particles that pours off the sun. The magnetic fields carried by this wind help to shelter the Earth from cosmic radiation; at times of low wind more radiation gets through, creating more electrically charged ions in the lower atmosphere. These ions may then catalyse the formation of water droplets and clouds. The sort of clouds formed, according to this theory, are those which reflect sunlight back to space, cooling the surface below.
These are provocative possibilities, and from chatting to people looking at posters on the subject I get the impression that people interested in the history of the climate are taking them more seriously than they did a few years ago. But the suggested mechanisms for linking changes in the climate to the sun are not yet widely accepted, for a number of reasons. One is that the evidence is still basically circumstantial. Another is that most of the people championing such a link do so from outside the mainstream of climate science; they come at it from a physics background. Outsiders who think they know better are rarely welcomed in any discipline.
Another issue is that on more than one occasion these sun-Earth connections have been championed by people, institutions and corporations with a history of trying to downplay the importance of the vast build-up in atmospheric carbon dioxide now underway. A bigger role for the sun is a way to argue that this carbon dioxide doesn't matter much. From there it's a short, often easily taken step to saying that the climate science establishment is just feathering their own nests with grant money. This is not fair, and doesn't help the debate.
Listening to the sun-Earth evidence, though, I can't help feeling that even if it is true that the sun is a bigger player in climate change than previously thought, it's hardly the reassuring message the carbon lobby seems to think it is. It's just another thing to worry about. The idea that sun-induced climate change over the course of this century will offset any greenhouse-induced climate change seems absurdly optimistic. Although their net effects on global average temperature might be of the same sort of magnitude, the patterns of climate change they would be expected to produce will not be equal and opposite. If UV is dominant, solar cooling will be felt more at low latitudes; if clouds play a role, cloudy places will cool more; greenhouse warming, on the other hand, tends to affect the high latitudes. It also works at night as well as by day, while solar effects would probably be daytime only. Rather than expecting such different patterns of change to cancel each other out, you might more plausibly expect that, by pushing the climate system in opposite directions, the two different influences will set it ringing like a bell, or bouncing like a jack-in-the-box.
Thursday afternoon
The threat of global climate change has not only brought about a proliferation of new hypotheses, it has also led to a salutary interest in monitoring the Earth and finding out how its atmosphere and oceans really work. A lot of this interest is expressed through the building of satellites - there must be dozens of different satellite missions already producing data, about to launch, or still at the planning stage. On Thursday afternoon I went to a presentation about one of these missions, a joint Japanese-European satellite designed to find out how clouds work. I am ashamed to say that I fell asleep during some of the details (many of us noticed that the seats in the vast Apollon hall were by far the comfiest in the conference centre) but the gist seemed excellent.
The presenters had a well thought through plan to use a number of different instruments, including radar and lasers, to measure the particles that make up specific clouds and find out whether they were ice or water, see how they were influenced by dust, smoke and other aerosols and work out how much energy they reflect back into space. They had dramatic graphics - the illustrator, the speaker said, seemed to have developed his idea of what a laser looked like by watching James Bond films. And they had a good acronym: EarthCARE, standing for Earth, Clouds, Aerosol and Radiation Explorer. Sounds like a winner; in ten years it could be the talk of the conference. Or at least the cloud sessions.
Friday morning
By now I'm acutely aware of how much I've missed. I have not heard a single volcanologist. I failed to get to the meeting on the digital divide in the earth sciences. (The lack of third world participation here reminds me of a meeting of scientists studying Gondwanaland, the ancient supercontinent made up of India, Africa and nearly all of the rest of the land south of the equator, which took place in South Africa in the late 1990s. Nelson Mandela addressed the conference, and while welcoming the almost exclusively northern delegates expressed the hope that a few more scientists native to Gondwana might soon swell their ranks. Not much evidence of it here.)
I have spurned the geodynamics and hydrological sciences talks almost completely, not to mention the geodesy panels, the geophysical instrumentation sessions, the natural hazards and the tectonism and sedimentary processes. Hundreds of pages of the vast programme book I've been carrying around are unsullied. At the same time, I feel entirely full of new information. Random example: John Priscu of Montana State University, if I have understood him correctly, thinks there is as much biomass inside the Antarctic ice cap as in the world's freshwater lakes.
There is one man I have been meaning to track down all week: a Dutch palaeontologist and climate specialist called Henk, whose work may be relevant to a Chicxulub-related story I'm working on. I decide not to seek him out actively, but to trust to fate. If I meet him, I tell myself, it will be an omen of completeness. I will have done my duty.
Leaving the press room I spot Dick Kerr, the veteran geosciences correspondent for Science magazine, and a man who may know more about the breadth of what is going on here than anyone else. He is looking at a website that appears to be about rain, and my guilt for ignoring hydrology wells up. But he only wants to know whether the pitch on which he will be playing soccer back in DC tomorrow will be waterlogged.
Friday afternoon
There's a session on the climatic history of Antarctica. One of the outstanding presentations is by Rob DeConto. His topic is the sudden growth of the first major Antarctic ice sheets, about 30m years ago. A lot of previous work has been devoted to the idea that the key to the ice sheets was the drift away from Antarctica of all the other continents. As a complete hoop of ocean opened up around Antarctica, encircling ocean currents isolated it from the rest of the climate, allowing it to cool and ice sheets to become established. This idea was developed by James Kennett, the man now championing methane triggers for the ends of ice ages. Both these ideas represent exactly what the planetary sciences need - the tying together of a number of different phenomena into a story that can then be tested. The result of the tests matters much less than the fact there was something testable in the first place.
DeConto and his colleague Dave Pollard have now tested the ocean-current isolation idea and aren't convinced. Their models suggest that the opening up of the southern oceans may have helped but it was carbon dioxide that drove the show. A long gradual drop in atmospheric carbon dioxide levels could have caused the sudden glaciation through a threshold effect; once it was cold enough for the ice sheets to start growing, they grew at a terrific lick. A smooth change in carbon dioxide with dramatically spiky, world-changing results - that's something to think about.
When I go over to ask DeConto a few questions afterwards he is deep in conversation with a broad-shouldered Dutchman wearing a T-shirt from Mauna Kea that is identical to one that my brother once gave me. A surreptitious glance at the name badge on his denim jacket - surreptitious glances at name badges are a key part of the journalist's trade at this sort of thing - brings a surge of fulfilment. I have found Henk.
Friday evening
The last talk of the conference takes me back to the Apollon theatre, in all its luxurious vastness. Uriel Frisch, a mathematician based here in Nice, has been honoured with the EGS's Lewis Fry Richardson medal for work on nonlinear processes in geophysics. To mark the award, he is giving a lecture titled "Back to the Primordial Universe by a Monge-Amp?-Kantotovich Mass Transportation Method." Maybe it is this striking but not necessarily alluring title, maybe it's the fact that the lecture is taking place at eight in the evening on Friday after a gruelling week, maybe it's the confusion about which room it should be in - whatever the reason, the most notable feature of the talk is that the theatre is basically empty.
Over the week I've made various attempts to estimate the size of the Apollon, and I've settled on 2,000 seats in the stalls and first balcony, another 1,000 higher up. Twenty of these seats are occupied. Having thought all week I was seeing about 1 per cent of the conference, I can now see what 1 per cent really looks like. It looks like nothing at all.
Stomping around the sound desk before the start, Frisch appears a little pissed off, and who can blame him? Giving a man a high honour and then setting him up for humiliation through lack of audience is a mean trick. But Frisch - author, I'm told by one of the other 19 audience members, of a "really good" book about turbulence - is clearly a trooper. Once on stage he gives an excellent and erudite talk, the daunting differential equations leavened with entertaining disquisitions on how they came to be misnamed and misunderstood. The heart of the talk is an equation developed by the French mathematician and engineer Gaspard Monge in the 18th century to find the most efficient way of moving earth taken out of holes on to ramparts. Frisch has seen a way to apply a form of this equation to new maps of the distribution of galaxies in the known universe, and thus to work out where they all came from.
At the end of this tour de force he asks the intergalactic void stretching out in front of him for questions. To the great relief of the other 19 of us someone manages to think of one. Frisch answers it, and honour is satisfied. Our conference is over. We wander out into the night past vast piles of discarded posters not deemed worth taking back to the universities they came from.
Saturday
I take a train up into the mountains to hike and clear my head. I end up walking about six miles along the side of a valley overlooking the little town of Annot. The last two miles or so are something of a trudge owing to the snow on the paths. From the valley floor the snow looked sparse, but that, I realise, was because I was seeing it through the canopy of pines. Earlier in the week, I remember, I talked to a climate modeller about just this issue - the way that pine forests make the planet darker and thus warmer, even when there is snow on the ground beneath their needles. Obviously, I need to work on integrating my theoretical knowledge with my everyday life.
The walk is hard work; the view back over the maritime Alps is magnificent. As I take it in, I realise that every passing detail has been thought hard about by someone I brushed past over the past week. How the cliffs of sandstone in the opposite wall of the valley were formed on the bottom of a long lost sea; how cycles in the ancient climate left their rhythms in those sediments, interleaving thin laminations and great monolithic bands; how deep the sandstones must have been buried, and then how high they were lifted when the collision of two tectonic plates drove them up into the skies; how ice-age erosion carved the valley through them; how floods - the most recent just a few years ago - continue to whittle away at them; how their sediments whiten the streams in spate below on their way to the Mediterranean; how the roots of the pines and oaks and chestnuts eat into the rock for their nutrients, producing new soil; how the timing of the first spring flowers, just coming into bloom at the snowline, tells us of the changes in the climate; how the forest canopies mist the sky with volatile chemicals, creating a blue haze in the valleys beyond; how the clouds that form over the peaks affect the world below.
Thousands of people who live to try to understand these wonders are now fanning out from Nice and around the world. Even thousands are not that many; you could lose ten thousand people in this one valley. Walking back down from the pass, I imagine seeing those conference posters again, unpacked from their tubes, one for every metre of the path, and in front of them a conga line of academics in a vast chain of conversation about this landscape and other landscapes; about the processes that join them and the histories that distinguish them; about the understanding that flows from them.
For all that we try, humankind still does not really grasp the Earth. We damage it out of ignorance. We do not yet understand all its wonders, even less the ways that they fit together. But we try to understand, and that adds a crucial last wonder to the list.
