What happened to global warming?

On 9 OCT 2009, the BBC News site published an article entitled ‘What happened to global warming?‘ which claims that for the last 11 years, since 1998, we have not observed any increase in global temperatures.

As we are bombarded on a daily basis with news telling us that man’s activities are producing carbon dioxide, carbon dioxide is responsible for global warming/climate change, and that unless we drastically reduce carbon dioxide levels then global temperatures will continue rising and we will all be doomed, the title of this article seemed very intriguing.

The article states that although carbon dioxide levels are continuing to increase, temperatures are not increasing. This seems at odds with what we should expect, according to the current consensus amongst many scientists studying climate change: i.e. more carbon dioxide should equate to higher global temperatures.

So I read the article with great interest and then took a look around at recent news from other sources to see what other people and scientists are saying on this interesting topic, and this is what I found.

While the sun sleeps

Translation approved by Henrik Svensmark

While the Sun sleeps
Henrik Svensmark, Professor, Technical University of Denmark, Copenhagen

“In fact global warming has stopped and a cooling is beginning. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable,” writes Henrik Svensmark.

The star that keeps us alive has, over the last few years, been almost free of sunspots, which are the usual signs of the Sun’s magnetic activity. Last week [4 September 2009] the scientific team behind the satellite SOHO (Solar and Heliospheric Observatory) reported, “It is likely that the current year’s number of blank days will be the longest in about 100 years.” Everything indicates that the Sun is going into some kind of hibernation, and the obvious question is what significance that has for us on Earth.

If you ask the Intergovernmental Panel on Climate Change (IPCC) which represents the current consensus on climate change, the answer is a reassuring “nothing”. But history and recent research suggest that is probably completely wrong. Why? Let’s take a closer look.

Solar activity has always varied. Around the year 1000, we had a period of very high solar activity, which coincided with the Medieval Warm Period. It was a time when frosts in May were almost unknown – a matter of great importance for a good harvest. Vikings settled in Greenland and explored the coast of North America. On the whole it was a good time. For example, China’s population doubled in this period.

But after about 1300 solar activity declined and the world began to get colder. It was the beginning of the episode we now call the Little Ice Age. In this cold time, all the Viking settlements in Greenland disappeared. Sweden surprised Denmark by marching across the ice, and in London the Thames froze repeatedly. But more serious were the long periods of crop failures, which resulted in poorly nourished populations, reduced in Europe by about 30 per cent because of disease and hunger.

It’s important to realise that the Little Ice Age was a global event. It ended in the late 19th Century and was followed by increasing solar activity. Over the past 50 years solar activity has been at its highest since the medieval warmth of 1000 years ago. But now it appears that the Sun has changed again, and is returning towards what solar scientists call a “grand minimum” such as we saw in the Little Ice Age.

The match between solar activity and climate through the ages is sometimes explained away as coincidence. Yet it turns out that, almost no matter when you look and not just in the last 1000 years, there is a link. Solar activity has repeatedly fluctuated between high and low during the past 10,000 years. In fact the Sun spent about 17 per cent of those 10,000 years in a sleeping mode, with a cooling Earth the result.

You may wonder why the international climate panel IPCC does not believe that the Sun’s changing activity affects the climate. The reason is that it considers only changes in solar radiation. That would be the simplest way for the Sun to change the climate – a bit like turning up and down the brightness of a light bulb.

Satellite measurements have shown that the variations of solar radiation are too small to explain climate change. But the panel has closed its eyes to another, much more powerful way for the Sun to affect Earth’s climate. In 1996 we discovered a surprising influence of the Sun – its impact on Earth’s cloud cover. High-energy accelerated particles coming from exploded stars, the cosmic rays, help to form clouds.

When the Sun is active, its magnetic field is better at shielding us against the cosmic rays coming from outer space, before they reach our planet. By regulating the Earth’s cloud cover, the Sun can turn the temperature up and down. High solar activity means fewer clouds and and a warmer world. Low solar activity and poorer shielding against cosmic rays result in increased cloud cover and hence a cooling. As the Sun’s magnetism doubled in strength during the 20th century, this natural mechanism may be responsible for a large part of global warming seen then.

That also explains why most climate scientists try to ignore this possibility. It does not favour their idea that the 20th century temperature rise was mainly due to human emissions of CO2. If the Sun provoked a significant part of warming in the 20th Century, then the contribution by CO2 must necessarily be smaller.

Ever since we put forward our theory in 1996, it has been subjected to very sharp criticism, which is normal in science.

First it was said that a link between clouds and solar activity could not be correct, because no physical mechanism was known. But in 2006, after many years of work, we completed experiments at DTU Space that demonstrated the existence of a physical mechanism. The cosmic rays help to form aerosols, which are the seeds for cloud formation.

Then came the criticism that the mechanism we found in the laboratory could not work in the real atmosphere, and therefore had no practical significance. We have just rejected that criticism emphatically.

It turns out that the Sun itself performs what might be called natural experiments. Giant solar eruptions can cause the cosmic ray intensity on earth to dive suddenly over a few days. In the days following an eruption, cloud cover can fall by about 4 per cent. And the amount of liquid water in cloud droplets is reduced by almost 7 per cent. Here is a very large effect – indeed so great that in popular terms the Earth’s clouds originate in space.

So we have watched the Sun’s magnetic activity with increasing concern, since it began to wane in the mid-1990s.

That the Sun might now fall asleep in a deep minimum was suggested by solar scientists at a meeting in Kiruna in Sweden two years ago. So when Nigel Calder and I updated our book The Chilling Stars, we wrote a little provocatively that “we are advising our friends to enjoy global warming while it lasts.”

In fact global warming has stopped and a cooling is beginning. Mojib Latif from the University of Kiel argued at the recent UN World Climate Conference in Geneva that the cooling may continue through the next 10 to 20 years. His explanation was a natural change in the North Atlantic circulation, not in solar activity. But no matter how you interpret them, natural variations in climate are making a comeback.

The outcome may be that the Sun itself will demonstrate its importance for climate and so challenge the theories of global warming. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable. A forecast saying it may be either warmer or colder for 50 years is not very useful, and science is not yet able to predict solar activity.

So in many ways we stand at a crossroads. The near future will be extremely interesting. I think it is important to accept that Nature pays no heed to what we humans think about it. Will the greenhouse theory survive a significant cooling of the Earth? Not in its current dominant form. Unfortunately, tomorrow’s climate challenges will be quite different from the greenhouse theory’s predictions. Perhaps it will become fashionable again to investigate the Sun’s impact on our climate.

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Professor Henrik Svensmark is director of the Center for Sun-Climate Research at DTU Space. His book The Chilling Stars has also been published in Danish as Klima og Kosmos Gads Forlag, DK ISBN 9788712043508)

Hosted by wattsupwiththat.com, winner of the 2008 Weblog Awards for the best science blog.

Despite the claims of some politicians and scientists, the science of climate change is far from settled. While the mainstream seems to have accepted that global warming is real and that it is caused mainly by man-made carbon dioxide (CO2) emissions, there are many scientists who dispute what is still a speculative theory that depends heavily on mathematical models rather than solid theoretical understanding and empirical evidence. However, the political climate is such that discussion of these issues is difficult, and those who dispute the official position (as exemplified by the IPCC Summary Reports) are likely to be attacked as ‘climate change deniers’.

For those who accept that global warming is taking place, there are a number of alternative theories as to the causes. One of the leading alternative theories is that proposed by Danish physicists Henrik Svensmark and Eigil Friis-Christensen, which suggests that it is variations in cloud cover that have a large effect on climate, and that clouds are seeded by cosmic rays, which are in turn influenced by the Sun’s magnetic field.

In ‘The Chilling Stars’, science writer Nigel Calder and Henrik Svensmark present the first popular exposition of the theory. In doing so they present not just the bare bones of the theory, but also show how it can explain both past climate events and the present situation. In particular the authors make sure that a whole range of supporting evidence is used to establish historical climate trends (including events such as the Medieval Warm Period and the Little Ice Age) and to tie this in with records of solar activity.

See the following Amazon customer reviews which describe the book’s message, and the implications for global governmental CO2 policy if the theory proves to be valid:
Amazon UK customer reviews
Amazon US customer reviews

April 1, 2009: The sunspot cycle is behaving a little like the stock market. Just when you think it has hit bottom, it goes even lower.

2008 was a bear. There were no sunspots observed on 266 of the year’s 366 days (73%). To find a year with more blank suns, you have to go all the way back to 1913, which had 311 spotless days: plot. Prompted by these numbers, some observers suggested that the solar cycle had hit bottom in 2008.

Maybe not. Sunspot counts for 2009 have dropped even lower. As of March 31st, there were no sunspots on 78 of the year’s 90 days (87%).

It adds up to one inescapable conclusion: “We’re experiencing a very deep solar minimum,” says solar physicist Dean Pesnell of the Goddard Space Flight Center.

“This is the quietest sun we’ve seen in almost a century,” agrees sunspot expert David Hathaway of the Marshall Space Flight Center.

Quiet suns come along every 11 years or so. It’s a natural part of the sunspot cycle, discovered by German astronomer Heinrich Schwabe in the mid-1800s. Sunspots are planet-sized islands of magnetism on the surface of the sun; they are sources of solar flares, coronal mass ejections and intense UV radiation. Plotting sunspot counts, Schwabe saw that peaks of solar activity were always followed by valleys of relative calm—a clockwork pattern that has held true for more than 200 years: plot.

The current solar minimum is part of that pattern. In fact, it’s right on time. “We’re due for a bit of quiet—and here it is,” says Pesnell.

But is it supposed to be this quiet? In 2008, the sun set the following records:

A 50-year low in solar wind pressure: Measurements by the Ulysses spacecraft reveal a 20% drop in solar wind pressure since the mid-1990s—the lowest point since such measurements began in the 1960s. The solar wind helps keep galactic cosmic rays out of the inner solar system. With the solar wind flagging, more cosmic rays are permitted to enter, resulting in increased health hazards for astronauts. Weaker solar wind also means fewer geomagnetic storms and auroras on Earth.

A 12-year low in solar “irradiance”: Careful measurements by several NASA spacecraft show that the sun’s brightness has dropped by 0.02% at visible wavelengths and 6% at extreme UV wavelengths since the solar minimum of 1996. The changes so far are not enough to reverse the course of global warming, but there are some other significant side-effects: Earth’s upper atmosphere is heated less by the sun and it is therefore less “puffed up.” Satellites in low Earth orbit experience less atmospheric drag, extending their operational lifetimes. Unfortunately, space junk also remains longer in Earth orbit, increasing hazards to spacecraft and satellites.

September 3, 2009: The sun is in the pits of the deepest solar minimum in nearly a century. Weeks and sometimes whole months go by without even a single tiny sunspot. The quiet has dragged out for more than two years, prompting some observers to wonder, are sunspots disappearing?

“Personally, I’m betting that sunspots are coming back,” says researcher Matt Penn of the National Solar Observatory (NSO) in Tucson, Arizona. But, he allows, “there is some evidence that they won’t.”

Penn’s colleague Bill Livingston of the NSO has been measuring the magnetic fields of sunspots for the past 17 years, and he has found a remarkable trend. Sunspot magnetism is on the decline.

If sunspots do go away, it wouldn’t be the first time. In the 17th century, the sun plunged into a 70-year period of spotlessness known as the Maunder Minimum that still baffles scientists. The sunspot drought began in 1645 and lasted until 1715; during that time, some of the best astronomers in history (e.g., Cassini) monitored the sun and failed to count more than a few dozen sunspots per year, compared to the usual thousands.

“Whether [the current downturn] is an omen of long-term sunspot decline, analogous to the Maunder Minimum, remains to be seen,” Livingston and Penn caution in a recent issue of EOS. “Other indications of solar activity suggest that sunspots must return in earnest within the next year.”

Whatever happens, notes Hathaway, “the sun is behaving in an interesting way and I believe we’re about to learn something new.”

September 29, 2009: Planning a trip to Mars? Take plenty of shielding. According to sensors on NASA’s ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high.

“In 2009, cosmic ray intensities have increased 19% beyond anything we’ve seen in the past 50 years,” says Richard Mewaldt of Caltech. “The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions.”

The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Researchers have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls “a perfect storm of cosmic rays.”

“We’re experiencing the deepest solar minimum in nearly a century,” says Dean Pesnell of the Goddard Space Flight Center, “so it is no surprise that cosmic rays are at record levels for the Space Age.”
Galactic cosmic rays come from outside the solar system. They are subatomic particles–mainly protons but also some heavy nuclei–accelerated to almost light speed by distant supernova explosions. Cosmic rays cause “air showers” of secondary particles when they hit Earth’s atmosphere; they pose a health hazard to astronauts; and a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit.

The world’s source for global temperature record admits it’s lost or destroyed all the original data that would allow a third party to construct a global temperature record. The destruction (or loss) of the data comes at a convenient time for the Climatic Research Unit (CRU) in East Anglia – permitting it to snub FoIA requests to see the data.

The CRU has refused to release the raw weather station data and its processing methods for inspection – except to hand-picked academics – for several years. Instead, it releases a processed version, in gridded form. NASA maintains its own (GISSTEMP), but the CRU Global Climate Dataset, is the most cited surface temperature record by the UN IPCC. So any errors in CRU cascade around the world, and become part of “the science”.

Canadian statistician and blogger Steve McIntyre, who has been asking for the data set for years, says he isn’t impressed by the excuses. McIntyre obtained raw data when it was accidentally left on an FTP server last month. Since then, CRU has battened down the hatches, and purged its FTP directories lest any more raw data escapes and falls into the wrong hands.

His site was the winner of the 2007 Weblog Awards for the best science blog, and finalist for the 2008 Weblog Awards.

It’s happening, people. In Austria. In Montana. In Iowa. In Chicago. In Idaho. In Nebraska. In southern California. In Texas. In Denver, where baseball games are getting snowed out.

Last month Climate Rush members dumped a pile of manure on the driveway of the star’s house in Oxfordshire. Speaking about the incident, Clarkson, 49, said: “Teenage girls get into a strop about all sorts of things.”

When asked what he thought about climate change, he said he found reading about it “all rather boring”.

He added: “I read the reports that come in from various scientific bodies and as far as I can work out nobody actually knows whether man is contributing to global warming or not.”