I like nature- I am a dirty, crunchy, organic-eating, bike-riding hippie.

[Ernie Elkins]

I'm stumped by your question about the distribution of ozone, pj. Does anyone else know anything about it? As for why the ozone hole appeared over Antarctica, my understanding is that it comes about as a result of somewhat unique high-altitude weather conditions. Here's yet another address for further reading — it's part three of the ozone depletion FAQ that I referenced above:

http://www.faqs.org/faqs/ozone-depletion/antarctic/

[paul johnson]

Sorry, for the 'poser' Ernie. My Profs always hated my questions in class – particularly when they couldn't answer them. They could always tell that one was coming when they smelled the wood in me noggin' smoldering. They thought i should do less thinkin' and more "parroting" back what they were teaching. Maybe that's why i never did real good in school?

Hopefully, those links you provided will have an answer to my question. Guess i'll have to read them sooner rather than later (was just hoping that you would give me the "Reader's Digest Condensed Version", so to speak).

Anyways, thanks again for the add'l URL.

[Ernie Elkins]

As far as volcanoes and global warming go, here's a really interesting article on what massive, sustained eruptions might do to the global climate:

http://www.washingtonpost.com/wp-dyn/articles/A24732-2005Jan20.html

And here's an article that I stumbled upon that makes some interesting points, including one that echoes what pj said above about the potential for volcanoes to bring about a cooling event:

http://www.popularmechanics.com/science/research/1282246.html

Finally, here's a brief discussion about the warming trend that you mention occuring around 1000 AD, pj:

http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html

I'm pretty sure that the current consensus is that this warming was localized phenomenon that primarily affected the North Atlantic region and was related to changes in ocean current circulation.

[Ernie Elkins]

Going back to your comments on population, bd, that really is the crux of the matter, and China's global impact in the coming decades extends far beyond air quality, global warming, etc. I recently read a truly fascinating book by James Martin entitled The Meaning of the 21st Century: Transformation and Survival, in which the author suggests that climate change and China's growing population could work in tandem to cause a big jump in the price of grain, putting it even further out of reach of the world's poorest nations. I highly recommend the book, which has a truly vast scope — climate change, terrorism, nuclear proliferation, nanotechnology, genetic engineering, and the list goes on…

And while I'm on the subject of recommended reading, anyone interested in a very accessible treatment of global warming should take a look at Tim Flannery's The Weather Makers. Flannery is a biologist and former global warming skeptic.

[Miguel Arboleda]

Very interesting discussion here. It's funny why the discussions in the forums often tend be more involved than during the summer… I guess there is just more "sitting around the fire" at this time of year.

People have made good points on both sides of the environmental crisis question, and the tone of the discussion, with people showing one another respect for their opinions, is something that politicians and others who supposedly are taking up the reins for protecting our global home, could learn a lot from. My one concern is that we are all spending so much time discussing the problems, and in so many cases getting overly concerned about the differences in opinions, that nothing is being done about a potentially civilization-threatening situation. Whether or not there really is global warming or the end of our species, it just makes good sense to look at the way we are doing things and try to make our lifestyles more efficient and sustainable…"economical" in other words. Just looking at a well-run household will give you an idea of what smart practices will do to ensure a touble-free existence. You don't wait for your household to fall apart before adopting sensible measures.

While China certainly has a lot of environmental problems, to say that China does not think about environmental problems reveals quite a lack of knowledge about China. China has been battling environmental problems for hundreds, if not thousands, of years. The logistics of making any of it work are enormous; just trying to deal with the gigantic erosion problem of the Yang Tze River alone has always stymied Chinese governments, They are attempting to do things about their problems, though. And there is probably no country on earth more committed to curbing the population problem than China… so much so that they have taken what westerners consider Draconian measures to control the population: since the 1970's every family (with a few exceptions in the countryside where bigger families are needed for the farm work) has been limited to one child (six months ago when a new Chinese student entered my class and I asked her and the other Japanese students to talk about their brothers and sisters, I was at first taken aback when my Chinese student told me she and no one else she knew had any brothers and sisters… it then occurred to me that the entire country was made up of single child families…I still haven't been able to get my head around this. But it did strengthen my amazement at the Chinese ability to make big sweeping changes a lot more easily than in the west.). Westerners might consider this a violation of human rights, but from the Chinese perspective it is a realistic solution to a very real and dangerous problem. The Chinese have to be concerned with environmental problems because they see the worst of it around them every day. I don't think most Americans are truly aware of this reality yet. Intellectually, yes, but viscerally, no. Global warming is still seen in America as an intellectual exercise (though I doubt northern Alaskans would agree. And Katrina has made a first, lasting impression… but not enough yet). Therefore these rhetorical discussions.

I'm curious, too, about why the ozone holes concentrate at the poles. I wonder if it has to do with the atmosphere being thinner at the poles and with such things as the lack of the Coriolis Force and the axes of the global electromagnetc field there. It might also have to do with the concentration and angle of the sun at these latitudes and with the albedo effect of the ice and snow caps, and with the year long temperatures there.

Or it could just be that finally the years of accumulated National Geographics in people's homes have reached their critical mass and their combined weight has compressed the shape of the earth's crust enough to lift the North and South Poles high enough out of the atmosphere to poke holes into the sky? So many high school science class movies showed the candy cane striped poles that it's a wonder to me that scientists never noticed them before.

[paul johnson]

Again, Ernie, many thanks for the reply and URLs (more to read – haven't done so yet, but will).

Wonder how much will be left alive to die of the warming after the, potentially, many years, of "volcanic winters" which will affect the food chain.

The 1000AD warming apparently had an effect in Europe also based up some reading i had done a few months ago, so this could agree with the point on the No. Atlantic region.

[Ernie Elkins]

I think I remember something about grapes in England during the medieval warming period that we're talking about, pj, as you may have read as well. That lines up in an interesting way with a recent news story that I saw — apparently, changing weather conditions in the UK are once again making grape-growing a worthwhile endeavor.

Also, thanks Miguel for your historical insights on China. Your point on losing sight of solutions because we're so wrapped up in arguing about the problems is very well put. That's really where things get interesting — from an optimist's perspective, global warming offers some great opportunities for the world as a whole. It's a problem that has the potential to unite nations and spur fascinating technologocal advances. For example, there are scientists out there right now pioneering technologies that actually pull greenhouse gases out of the atmosphere. That's pretty cool, if you ask me, and it shows that dedicated people are already working hard to fix a problem that many people (including our dear president) dismiss as hocus-pocus. And if scientists are wrong, and global warming is just a naturally occuring event? Or if global warming doesn't progress as expected? What have we lost by making the changes that scientists recommend? Well, the coal industry will have lost some money, as will the petroleum industry (although BP has already positioned itself as a major provider of solar energy). And I'm sure there are other costs that will need to be addressed. What have we gained? Cleaner, more efficient technologies, a cleaner environment, and the knowledge that we don't have to pollute the planet to prosper. That, to me, is well worth the effort. If scientists are correct, we'll have gained all of those things PLUS done our best to address a problem that could have dire implications for millions if not billions of our fellow citizens.

Addendum: I should also add that modern, market-driven economies put remarkable power in the hands of individual consumers. To quote Tim Flannery, the author of The Weather Makers that I mentioned above, "if enough of us buy green power, solar panels, solar hot water systems, and hybrid vehicles, the cost of these items will plummet" (306). Not to mention energy-efficient appliances, recycled building materials, better home insulation, etc. As costs plummet, sales will grow, not just in California, Maine, or Quebec, but also in China, India, and other developing nations where affordable, sustainable energy is a pressing need. So global warming isn't just about doomsday pronouncements (thanks again, Miguel, for bringing that into focus) — it's about an opportunity for us to make important changes in our own personal lives whose ramifications are potentially global in scope.

[s k]

The late winter ozone degradation that occurs over Antarctica seems to result from a unique set of meteorological conditions. A basic but understandable
explanation (for me) can be found at:

http://ozonewatch.gsfc.nasa.gov/index.html

The Meteorology tab reveals a menu subset of contributing factors.

As for general climate information, I’ve found the following site helpful in separating hype from fact from probability:

http://www.giss.nasa.gov/

(Yes, it’s a strong reliance on NASA, but NASA does have a record of accomplishment. I regard a successful thirty-five year old lunar landing conspiracy as more of an achievement than the actual return of men from the moon).

[Ernie Elkins]

Thanks for the links, skots. The NASA site really has a lot to offer — I've just brushed the surface at this point. I did find a point, though, in the article on the current warming trend that offers a good object lesson in how climate change can affect the places that hikers and backpackers know and love:

"Global warming is already beginning to have noticeable effects in nature. Plants and animals can survive only within certain climatic zones, so with the warming of recent decades many of them are beginning to migrate poleward."

Here in the southeast, we've already witnessed serious damage to spruce and fir forests in our higher elevations (over 4500 ft) due to acid rain, ozone pollution, and invasive insect species that were imported (accidentally, of course) from Europe. Although air quality legislation has improved the odds of survival for the spruce population, which is hardest hit by air pollution, it's unlikely that the firs are going to make a comeback anytime soon.

As if these issues weren't enough, now we have to add the additional threat of climate change — warmer, drier conditions could have a major impact on the spruce and fir populations. This, of course, is growing threat on a global scale. Mountaintop ecosystems throughout the world harbor incredibly diverse populations of plant and animal species, and, as temperatures rise and weather patterns change, those species simply have nowhere to go. Here in NC, some of the species in question are holdovers from the last ice age, persisting in small, delicately balanced micro-climates. If these micro-climates disappear, so will the species who inhabit them.

So, having said all of that, my point is that global warming does threaten to change the places that I, as a backpacker, know and love. The NC spruce and fir forests had already suffered from local environmental issues when I first encountered them 17 years ago, and now I have to worry that they will completely vanish if global warming accelerates. That's something that I'd really hate to see come top pass.

[David Olsen]

CO2 levels are up. It is easily measured, anywhere. I have
yet to hear an argument stating otherwise.

Even if the earth's temperature isn't effected by this, plants will be. Those that thrive with increased co2 will take over.

Look for more cheat grass taking over the native's grasses on the prairies.

If you look at the industries that could be negatively effected by global warming, you see where they are putting
their support. The ski areas around here are WAY into green
energy etc. They are otherwise pretty traditionally conservative businesses.

Oh, just on the news
http://news.yahoo.com/s/ap/20070103/ap_on_bi_ge/exxonmobil_global_warming

[Scott Robertson]

It is very hard for an environmentalist such as myself to sit and not note the changes that I see around me. I have lived in the same spot my entire life and have observed with a keen eye the world around me- natural and artificial. A few notes from my own observation:

-The invasion of the Air Potato plant (an invasive species) has taken over most of the natural wilderness where I live. This plant does not die easily in the winter and grows very quickly (up to a foot a day). It chokes out the native landscape and fells treelines. The winters in Florida are getting progressively warmer and therefore more air potato survives each year.

-Fertilizers from lawns that run off into the creeks and rivers have caused a huge shift in the balance of plant species. Algae and water cabbage thrive off of the nitrates and phosphates in the fertilizer and choke out other species of plant and animal. The fish population in my area has bottomed out.

-Warmer winters have affected the patterns of bird migrations. Robins come in record numbers each year. They stay longer and drive out other native non-migratory species. Sandhill Cranes stay for shorter periods of time each year and have almost stopped coming altogether.

-A few years ago I witnessed firsthand the effect of the pine bark beetle. Beautiful landscapes with sweeping native pines were stripped bare, leaving stumps behind. Deer, raccoons, and other native species were stripped of their habitats and ended up as roadkill on the side of the road.

It is is very difficult for me to hear that people deny the existence of an unnatural rate of global warming when the signs can be found all around. As a side note, I read today that 2007 will be the hottest year in recorded history.

[John S.]

how long is recorded history…a hundred years?

[Erin McKittrick]

History from a weather station in Florida? Maybe only 100 years.

Paleo-climate records from ice cores in Antarctica: Over 200,000 years.

From these ice cores, climate scientists have data going back through multiple ice ages and interglacial warm periods, with temperature and CO2 levels. see info from NOAA, and info from AGU
So when they say that the human-caused CO2 rise/warming trend is unprecedented in "recent" history, they have a very different idea of "recent" than the rest of us (hundreds of thousands of years – a lot longer than humans have been around). If I remember correctly, the last time CO2 levels were higher than today, there were alligators in the arctic.

As far as species changing their ranges with the warming, studies have been done showing the northward migration of most of the generalist butterflies in England (there's good data back to the Victorian era on those ranges).

For good information about climate science: http://www.realclimate.org/

-Erin
http://www.groundtruthtrekking.org/WildCoast.html

[Ernie Elkins]

England is an interesting case in point when discussing how climate change may affect specific locales. The northward migration of butterflies that Erin mentions and the growing success of viticulture that I referred to in a previous post both suggest that the English countryside might look very different in the not-too-distant future.

[Lorraine Pace]

This really amused me, especially in light of Heidi Cullen of Weather Channel wanting to strip professional credentials away from people who disagree with the global warming cult.

Will the sun cool us?

LAWRENCE SOLOMON
Financial Post

Friday, January 12, 2007

The science is "settled" on climate change, say most scientists in the field. They believe that man-made emissions of greenhouse gases are heating the globe to dangerous levels and that, in the coming decades, steadily increasing temperatures will melt the polar ice caps and flood the world's low-lying coastal areas.

Don't tell that to Nigel Weiss, Professor Emeritus at the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, past President of the Royal Astronomical Society, and a scientist as honoured as they come. The science is anything but settled, he observes, except for one virtual certainty: The world is about to enter a cooling period.

Dr. Weiss believes that man-made greenhouse gases have recently had a role in warming the earth, although the extent of that role, he says, cannot yet be known. What is known, however, is that throughout earth's history climate change has been driven by factors other than man: "Variable behaviour of the sun is an obvious explanation," says Dr. Weiss, "and there is increasing evidence that Earth's climate responds to changing patterns of solar magnetic activity."

The sun's most obvious magnetic features are sunspots, formed as magnetic fields rip through the sun's surface. A magnetically active sun boosts the number of sunspots, indicating that vast amounts of energy are being released from deep within.

Typically, sunspots flare up and settle down in cycles of about 11 years. In the last 50 years, we haven't been living in typical times: "If you look back into the sun's past, you find that we live in a period of abnormally high solar activity," Dr. Weiss states.

These hyperactive periods do not last long, "perhaps 50 to 100 years, then you get a crash," says Dr. Weiss. 'It's a boom-bust system, and I would expect a crash soon."

In addition to the 11-year cycle, sunspots almost entirely "crash," or die out, every 200 years or so as solar activity diminishes. When the crash occurs, the Earth can cool dramatically. Dr. Weiss knows because these phenomenon, known as "Grand minima," have recurred over the past 10,000 years, if not longer.

"The deeper the crash, the longer it will last," Dr. Weiss explains. In the 17th century, sunspots almost completely disappeared for 70 years. That was the coldest interval of the Little Ice Age, when New York Harbour froze, allowing walkers to journey from Manhattan to Staten Island, and when Viking colonies abandoned Greenland, a once verdant land that became tundra. Also in the Little Ice Age, Finland lost one-third of its population, Iceland half.

The previous cooling period lasted 150 years while a minor crash at the beginning of the 19th century was accompanied by a cooling period that lasted only 30 years.

In contrast, when the sun is very active, such as the period we're now in, the Earth can warm dramatically. This was the case during the Medieval Warm Period, when the Vikings first colonized Greenland and when Britain was wine-growing country.

No one knows precisely when a crash will occur but some expect it soon, because the sun's polar field is now at its weakest since measurements began in the early 1950s. Some predict the crash within five years, and many speculate about its effect on global warming. A mild crash could be beneficial, in giving us Earthlings the decades needed to reverse our greenhouse gas producing ways. Others speculate that the recent global warming may be a blessing in disguise, big-time, by moderating the negative consequences of what might otherwise be a deep chill following a deep crash. During the Little Ice Age, scientists estimate, global temperatures on average may have dropped by less than 1 degree Celsius, showing the potential consequences of even an apparently small decline.

Dr. Weiss prefers not to speculate. He sees the coming crash as an opportunity to obtain the knowledge necessary to make informed decisions on climate change, and the extent to which man-made emissions have been a factor.

"Having a crash would certainly allow us to pin down the sun's true level of influence on the Earth's climate," concludes Dr. Weiss. Then we will be able to act on fact, rather than from fear.

Lawrence Solomon is executive director of Urban Renaissance Institute and Consumer Policy Institute, divisions of Energy Probe Research Foundation.

CV:

Nigel Weiss, professor emeritus of mathematical astrophysics in the University of Cambridge, discovered the process of "flux expulsion" by which a conducting fluid undergoing rotating motion acts to expel the magnetic flux from the region of motion, a process now known to occur in the photosphere of the sun and other stars. He is also distinguished for his work on the theory of convection, and for precise numerical experiments on the behaviour of complicated non-linear differential equations. Nigel Weiss is a recipient of a Royal Society Citation, he is a past President of the Royal Astronomical Society, and a past Chairman of Cambridge's School of Physical Sciences. He was educated at Clare College, University of Cambridge.

http://www.canada.com/nationalpost/story.html?id=5c8d30c6-9d77-4ccc-99d9-c3a095750cdc&p=1

[paul johnson]

Thanks. Have previously read similar writings attributing much climatic change to sunspots and to a lesser or more limited degree to volcanic activity (volcanic winters).

[Richard Nelridge]

I do not think that there is enough information to confirm the likelihood of going into a cooling period. Having gone to school for graduate work in Geology and Zoology we were introduced to the suggestion of the effects of sunspot activity and their cycles upon the possibility of global cooling. The little ice age that took place was also referenced. Additionally we were aware of the affects of the possibilities of sufficient ejection of material from numerous large volcanic erruptions. Potentially this material could in fact blanket the earth and result in a global cooling. Additionally, we were taught that based upon the geologic record through the last glacial periods that we were in an interglacial period and were overdue for the planets next glacial period.

On the other hand, there is no question that man has been dumping large amounts of green house gasses and particulates into the earth's atmosphere. The green house gases are thought to bring about global warming. Global warming is thought at least for some period of time to cause or result in large unsettled changes in weather as the earth's tempurtature would rise. The particulate materials that we as people and our manufacturing release into the atmosphere tend to increase the reflection in the earth's atmosphere which would tend to cause a cooling effect.

Without question, the earth's atmospheric temperatures, weather, and climate are a bit fragile. Only slight amounts of temperature differences either way of 1/2 to several degrees could potentially result in: 1) our moving toward a cooling or even glacial period or 2) going the other direction into a potentially large increase in temperature with the concerns of runaway heating. We just do not have enough information regarding the variables in this very complex system. But, we should most definitely be concerned about the affects and contributions of man as a species and the potential global effects that may be irreversible.

Rich

[Ernie Elkins]

Here's a more in-depth discussion of this topic from the New Scientist magazine. I found it reprinted in a blog at arstechnica.com. I think two of the more salient points are as follows:

• The scientists in question all appear to agree that global warming is a real phenomenon and that human-produced greenhouse gases are its primary cause.
• A crash in solar activity will not get rid of greenhouse gases. At best, it will grant us a temporary reprieve from rising global temperatures.

Nonetheless, if this crash in solar activity does occur, it would certainly give us some much needed time to deal with greenhouse gases before their effects get out of hand. As the writer of this article points out, though, it could just as easily lead to complacency.

New Scientist magazine, 16 September 2006

It is known as the Little Ice Age. Bitter winters blighted much of the northern hemisphere for decades in the second half of the 17th century. The French army used frozen rivers as thoroughfares to invade the Netherlands. New Yorkers walked from Manhattan to Staten Island across the
frozen harbour.

Sea ice surrounded Iceland for miles and the island's population halved. It wasn't the first time temperatures had plunged: a couple of hundred years earlier, between 1420 and 1570, a climatic downturn claimed the Viking colonies on Greenland, turning them from fertile farmlands into arctic wastelands.

Could the sun have been to blame? We now know that, curiously, both these mini ice ages coincided with prolonged lulls in the sun's activity – the sunspots and dramatic flares that are driven by its powerful magnetic field.

Now some astronomers are predicting that the sun is about to enter another quiet period. With climate scientists warning that global warming is approaching a tipping point, beyond which rapid and possibly irreversible damage to our environment will be unavoidable, a calm sun and a resultant cold snap might be exactly what we need to give us breathing space to agree and enact pollution controls. "It would certainly buy us some time," says Joanna Haigh, an atmospheric physicist at Imperial College London.

Global average temperatures have risen by about 0.6 °C in the past century, and until recently almost all of this has been put down to human activity. But that may not be the only factor at work. A growing number of scientists believe that there are clear links between the sun's activity and the temperature on Earth. While solar magnetic activity cannot explain away global warming completely, it does seem to have a significant impact. "A couple of years ago, I would not have said that there was any evidence for solar activity driving temperatures on Earth," says Paula Reimer, a palaeoclimate expert at Queen's University, Belfast, in the UK. "Now I think there is fairly convincing evidence."

What has won round Reimer and others is evidence linking climate to sunspots. These blemishes on the sun's surface appear and fade over days, weeks or months, depending on their size. More than a mere curiosity, they are windows on the sun's mood. They are created by contortions in the sun's magnetic field and their appearance foretells massive solar eruptions that fling billions of tonnes of gas into space. Fewer sunspots pop up when the sun is calm, and historically these periods have coincided with mini ice ages.

The number of sunspots and solar magnetic activity in general normally wax and wane in cycles lasting around 11 years, but every 200 years or so, the sunspots all but disappear as solar activity slumps (see "Field feedback"). For the past 50 years, on the other hand, the sun has been particularly restless. "If you look back into the sun's past, you find that we live in a period of abnormally high solar activity," says Nigel Weiss, a solar physicist at the University of Cambridge.

Fortunately, an indirect record of the sun's moods stretching back thousands of years has been preserved on Earth in the concentrations of rare isotopes locked into tree rings and ice cores. The story begins way out beyond the orbit of Pluto, at the boundary of the sun's magnetic field. While the sun is magnetically calm, its field extends around 12 billion kilometres into space, but the field puffs up to 15 billion kilometres when the sun is active. Cosmic rays – the high-energy particles from deep space that are constantly hurtling towards us – are deflected by the field, so at active times far fewer of them reach the Earth.

Cosmic correlation

The rays that do reach our planet leave traces in the form of carbon-14 and beryllium-10, isotopes that are only created when cosmic rays slam into the Earth's atmosphere. Plants and trees then absorb carbon-14, while beryllium-10 settles onto the polar ice sheets and becomes incorporated into that year's ice layer. So by measuring the levels of the isotopes in tree rings and polar ice cores, we can work out how many cosmic rays were reaching Earth when the rings or ice layers were formed, and so estimate how active the sun was at those times.

Sami Solanki and his team at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, have looked at the concentrations of carbon-14 in wood and beryllium-10 in ice as far back as back 11,000 years ago. The similarity of the fluctuations in both isotopes convinced them that they were seeing effects due to the sun. The peaks and slumps showed a recognisable pattern: "Periods of high solar activity do not last long, perhaps 50 to 100 years, then you get a crash," says Weiss. "It's a boom-bust system, and I would expect a crash soon."

Although another crash is likely, predicting the sun's activity with any certainty is difficult because of the chaotic way in which the solar magnetic field is generated. If anyone can do it, though, it's solar physicist turned computer programmer Leif Svalgaard, from Stanford University in California, who has been forecasting solar activity for nearly three decades. In the 1970s, he pioneered the best forecasting method yet devised, which uses the strength of the magnetic field at the sun's poles to predict future levels of solar activity.

He too expects a crash. The sun's polar field is now at its weakest since measurements began in the early 1950s, and to Svalgaard, the latest figures indicate that the sun's activity will be weaker during the next decade than it has been for more than 100 years. "Sunspot numbers are well on the way down in the next decade," he predicts. He expects fewer than six new sunspots per month, less than half the average number seen over the past decade.

This is hardly the sunspot crash that observations from 1645 to 1715 suggest. Back then, the appearance of even a single sunspot was major astronomical news, sparking hurriedly penned communications from one observatory to another. Nevertheless, it's a sign of things to come. "Sunspot numbers will be extremely small, and when the sun crashes, it crashes hard," says Svaalgard. "The upcoming sunspot crash could cause the Earth to cool"

Hot link

So what does the sun's magnetic activity have to do with the climate on Earth? To pin down the connection, Solanki and his colleagues compared records of solar activity derived from tree rings with meteorological records from 1856 to the present day. They found that the temperature of the Earth's atmosphere changed in step with sunspot numbers until 1970. This is the evidence that has done more than anything else to convince climatologists to take the link seriously. What's more, the most recent calculations by Solanki's team suggest that the sunspot crash could lead to a cooling of the Earth's atmosphere by 0.2 °C. It might not sound much, but this temperature reversal would be as big as the most optimistic estimate of the results of restricting greenhouse-gas emissions until 2050 in line with the Kyoto protocol.

There is still a big puzzle, though. Astronomers and climate scientists have always struggled to understand exactly how solar activity could influence the temperature on Earth. Whatever the variations in the sun's magnetic activity, the total energy it emits changes by only 0.1 per cent – too small a change to have any direct effect. As a result, the sun's role in climate change is highly controversial. "People have been arguing over this for years," says Reimer.

What other factor is at work? Important clues have emerged recently from solar observatories, including the SOHO spacecraft operated by NASA and the European Space Agency for the past 10 years. Although the change in overall solar energy is small, measurements made by SOHO and other solar observatories have revealed much greater variation in the levels of ultraviolet radiation, which can peak at up to 100 times its minimum level. "This means that there is scope for ultraviolet to have a much larger effect on our atmosphere," says Haigh, who for the past decade has been studying the impact of the sun's variability on climate.

According to computer models she has developed, ultraviolet radiation heats the upper reaches of the Earth's atmosphere by energising atoms and molecules there. This drives chemical reactions involving ozone and other molecules, which can release still more heat. This heating changes the temperature structure of the atmosphere at all altitudes, although the details are unclear because of the sheer complexity of Haigh's model. "By varying the amount of ultraviolet radiation, solar activity changes the circulation of the whole atmosphere," she says. Change the circulation, and you change the weather.

Haigh's work may help to explain one of the most puzzling aspects of the Little Ice Age: "Europe was badly hit, but other parts of the world may not really have noticed it," says Solanki. This might have been due to the different distribution of land masses in the northern and southern hemispheres. While Antarctica is surrounded by a wide belt of ocean, the distribution of land and oceans in the northern hemisphere is much less regular. This means that the interaction between the circulating atmosphere and the ground is more complex in the northern hemisphere. It gives rise to the North Atlantic Oscillation, an interplay of low and high pressure that dictates the movement of storms across the continents bordering the north Atlantic.

Haigh has found that at times of low solar activity the air pressure over the North Pole is higher than normal and forces storms south, funnelling colder weather to lower latitudes. What happens in the southern hemisphere is less well known, but Haigh says she wouldn't be surprised if the reaction here to changes in solar activity is different.

Solar activity might also influence climate through its effect on cosmic rays. In another study, Solanki has found an intriguing correlation between the temperature of the Earth's atmosphere and the number of cosmic rays striking it, with lower temperatures in periods of high numbers of cosmic rays.

How could cosmic rays lead to cooler temperatures? Enter a theory proposed by Henrik Svensmark and Eigil Friis-Christensen of the Danish Meteorology Institute in Copenhagen almost a decade ago. They suggested that cosmic rays create an electric charge in particles in our atmosphere that then act as seeds for the formation of clouds at low altitudes. A spell of low solar activity would mean more cosmic rays and therefore more clouds and lower temperatures.

Svensmark and Friis-Christensen's idea is controversial, however (New Scientist, 11 July 1998, p 45). Most climatologists accept that more low clouds would reflect more radiation back into space, thus lowering temperatures.

But many dismiss Svensmark and Friis-Christensen's evidence of a link between cosmic rays and cloud cover as coincidence (see "Cloud cover"). Others want the theory investigated, if only to rule it out. To this end, an international group of more than 50 scientists have proposed an experiment at the CERN particle physics laboratory near Geneva, Switzerland, to begin in 2008.

No room for complacency

The coming years could settle the sun's role on temperatures once and for all. If the expected sunspot crash does takes place, Solanki's work could receive dramatic confirmation. "Having a crash would certainly allow us to pin down the sun's true level of influence on the Earth's climate," says Weiss.

None of this means that we can stop worrying about global warming caused by emissions into the atmosphere. "The temperature of the Earth in the past few decades does not correlate with solar activity at all," Solanki says. He estimates that solar activity is responsible for only 30 per cent, at most, of the warming since 1970. The rest must be the result of man-made greenhouse gases, and a crash in solar activity won't do anything to get rid of them.

What might happen is that the sun gives the planet a welcome respite from the ravages of man-made climate change – though for how long, nobody knows. During the Little Ice Age, the fall in average global temperature is estimated to have been less than 1 °C and lasted 70 years. The one before that persisted for 150 years, but a minor crash at the beginning of the 19th century lasted barely 30. For now, we will have to keep watching for falling sunspot numbers. "The deeper the crash, the longer it will last," Weiss says.

There is a dangerous flip side to this coin. If global warming does slow down or partially reverse with a sunspot crash, industrial polluters and reluctant nations could use it as a justification for turning their backs on pollution controls altogether, makingmatters worse in the long run. There is no room for complacency, Svalgaard warns: "If the Earth does cool during the next sunspot crash and we do nothing, when the sun's magnetic activity returns, global warming will return with a vengeance."

Field feedback

Sunspots and solar activity are driven by the strength of the sun's complex magnetic field. Although solar scientists are still debating the detail, most believe that the magnetic field is generated in a shell of hot gas 35,000 kilometres thick and buried some 200,000 kilometres deep inside the sun. Known as the tachocline, this layer is made of plasma – a gas so hot that the atoms break up into charged electrons and ions.

Material at different latitudes and depths of the tachocline rotates at different rates. This variability moves electric charges and generates the sun's magnetic field. Once created, the magnetic field is strong enough to influence the movement of the electrically charged gas that creates it, a feedback mechanism that can either strongly amplify or diminish the overall strength of the field. For the past 50 years the field has been building, and the sun has been experiencing a period of unusually high magnetic activity.

Predicting future solar activity is tricky because of this complexity. The best method in use today was formulated in the 1970s by Leif Svalgaard, then at Stanford University. He showed that the magnetic field at the sun's poles is the best predictor. "The polar field is the magnetic seed for solar activity," Svalgaard says.

The polar fields are the accumulation of dead sunspots, transient dark patches on the sun's surface that have immense magnetic fields. When a spot fades from view, its residual magnetic field is gradually swept polewards by a surface current of solar gas known as the meridional flow. At the poles, this flow turns down into the sun, where astronomers believe it sinks to the tachocline and begins a return journey towards the sun's equator. En route, the magnetic field is rejuvenated by the tachocline to produce new sunspots.

Cloud cover

In 1997, meteorologists Henrik Svensmark and Eigil Friis-Christensen of the Danish Meteorology Institute in Copenhagen analysed weather satellite records from 1979 to 1992. This was long enough for the sun's activity to complete one of its regular 11-year cycles.

The researchers found that the Earth was 3 per cent cloudier when the sun's activity was at a minimum than when it was at its peak. They also noted the influx of cosmic rays at five experiments across the globe and found that it was as much as 25 per cent higher at the solar minimum. They called their discovery a "missing link in solar-climate relationships" and argued that cosmic rays were responsible for increasing cloud formation by electrically charging the lower atmosphere.

Intriguing as this link is, it is far from proof that solar activity and cloud cover are connected. "You have to demonstrate such an effect with an experiment, otherwise it is not physics," says Robert Bingham, a physicist at the UK's Rutherford Appleton Laboratory in Didcot, Oxfordshire.

Bingham is part of an international collaboration building an experiment called CLOUD to test the idea that cosmic rays seed clouds. CLOUD will start up in 2008 using a particle accelerator at the CERN laboratory near Geneva as a source of simulated cosmic rays. The researchers will fire charged particles through a chamber holding a mixture of gases similar to the Earth's atmosphere to determine how often the particles trigger cloud formation. "CLOUD will go a long way towards understanding the microphysics of droplet formation," says Bingham.

Copyright 2006, New Scientist

[paul johnson]

>>"Intriguing as this link is, it is far from proof that solar activity and cloud cover are connected. "You have to demonstrate such an effect with an experiment, otherwise it is not physics," says Robert Bingham, a physicist at the UK's Rutherford Appleton Laboratory in Didcot, Oxfordshire." [emphasis mine]

I like this quote (just don't tell it to the Cosmologists and String Theorists; it also applies to other fields of science as well, but they wouldn't want to hear it either).

w/o SOUND experimentation, we move from fact to faith, science to religion, knowledge to opinion (my father told me when i was a wee laddie that opinions are like armpits; everyone has 'em and they usually stink).

So, what experiment was done on a global scale that proves global warming? — what's good for the goose is good for the gander! — too may variables to accurately reproduce a global environment in a laboratory experiment; experimental conditions may not precisely match the earth's condition at any point in time. Get a handle on accurately reproducing the "system" known as Earth (with all it's myriads of chaotic variables, some little understood and highly unpredictable) in a laboratory experiment and then it will be conclusive. Until then, the experiment is only accurate as far as the experimental conditions go and only "might" be accurate as far as the Earth as whole is concerned.

My two shekels.

On the other hand, some areas of modern science were born out of ancient man's many generations of OBSERVATION. Anecdotal? Yes. Proven? No (at least not then). Fact? In some cases (proven later on by science).

[Ernie Elkins]

Here's a good example of how accurate computer modeling can be:

Simulated Annual Global Mean Temperatures

In this case, the researchers were hindcasting — they started the model in the past, provided it with confirmed observational data, and then let it go. The results are strikingly accurate.

On another note, here's a link to a brief article by Nigel Weiss (among others) about the difficulties of predicting solar activity:

Long-term prediction of solar activity – a discussion…

Although it's a bit dense, it would seem to confirm the observation in the Financial Post article that "Dr. Weiss prefers not to speculate."

[paul johnson]

Just like the "Psychic Friends", who can tell us the past, but are just plain miserable at predicting the future, so too is the result of some modeling activities.

First thing i thought of was…

If it's so good, "Why isn't the whole world using this model to predict the weather?" Hmmm,…makes one think. Perhaps, it's a little like the "Psychic Friends".

Here's how it works. I come up with a complicated sixth order polynomial equation that i think accurately models historic data. I tweak it to optimize the correlation coefficient for that historic data. Then i present my results. See, we have a 0.98 r value! Quite excellent, if i do say so myself. However,…

using that same "final" equation on future little understood (or non-fully understood) chaotic phenonmenon generally produces poorer results. Oops…time to tweak my equation [again]. See,…now, it works better. This is the iterative nature of the process.

Look, don't misunderstand me (particularly since i'm not being very clear). I've worked in a Corporate ThinkTank's Advanced AI lab doing some cutting edge system modeling using the principles of Qualitative Physics/Reasoning as well as some other statistical work to predict materials characteristics for fatigue methodological purposes. I'm a big fan of modeling (some of my software employs somewhat advanced statistical methods – NOT that i'm any kind of super statistician or anything – didn't invent any new statistical methods, just used existing methods), but i think i also have a handle (hope i don't lose my grip) on some of its limitations.

I'm also not sure that records have been kept (globally speaking) accurately enough, long enough to permit having any significant degree of confidence in statistical modeling. This is just one point i would need addressed in order to be convinced that, at this point in time, it is a real useful tool.

[Ernie Elkins]

pj:

Your mention of psychic friends, sixth order polynomial equations, and statistical models made my head spin. So, I'm going to focus on the one thing that I do feel up to addressing, and that's your question about why climate models can't predict the weather. It's all too easy to confuse the two. Climate is an averaging out of weather patterns over a given period of time (usually 30 years), so it smooths out the localized bumps that complicate weather forecasting. Not surprisingly, then, climate models are no good for predicting short-term, localized weather patterns. Here's a brief quotation from an article at RealClimate.org:

"It's important to note what these models are not good for. They aren't any good for your local weather, or the temperature of the water at the nearest beach or for the wind in downtown Manhattan, because these are small scale features, affected by very local conditions. However, if you go up to the regional scale and beyond (i.e. Western Europe as a whole, the continental US) you start to expect better correlations."

In fact, this article is a good place to start for an overview of what climate modeling is all about. Also, here's a link to an article about climate modeling from Physics Today. It, too, addresses the weather vs. climate issue:

The physics of climate modeling

He also provides a good summation of where climate modeling stands at this point in history: "the models are far from perfect, but they have successfully captured fundamental aspects of air, ocean, and sea-ice circulations and their variability. They are therefore useful tools for estimating the consequences of humankind's ongoing and audacious planetary experiment."

[paul johnson]

Excellent reply. Thank you.

[s k]

pj,Ernie,
Since these exchanges are so often mired in conclusion, it's a pleasure to catch a glimpse of your thoughts and rational. I tip my hat to both of you.
pj,
On a lighter note,if I may, this guy doesn't seem swayed by verbosity.

[Steven Hanlon]

i have often wondered how those who care deeply about the environment reconcile owning the equipment they carry while backpacking. i love the environment – i work for my state's Dept. of Natural Resources. everytime i read about some new fabric treatment or high tech gizmo, i can't help think about what is required to make the item and it's effect on the environment.

beyond the fuel costs of getting the item to market, the process of collecting the raw materials, processing those materials, and then the manufacture of the item are sometimes tremendous.

our high tech fabrics are in no way environmentally friendly – nylon was first made using coal – a product that is in no way environmentally friendly to "gather." aluminum requires vasts amounts of electricity to create, and the process to create titanium requires some nasty chemicals.

please don't mistake my post as slagging of "hippies," i am curious how others reconcile this issue. i love the products i use, but sometimes i wonder what my high tech backpacking lifestyle is doing to our Mother Earth. are my Ti tent stakes are more than just a guilty pleasure?

-Steve

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