Ray of hope: Can the sun save us from global warming?

Could the Sun's inactivity save us from global warming? David Whitehouse explains why solar disempower may be the key to combating climate change

Something is happening to our Sun. It has to do with sunspots, or rather the activity cycle their coming and going signifies. After a period of exceptionally high activity in the 20th century, our Sun has suddenly gone exceptionally quiet. Months have passed with no spots visible on its disc. We are at the end of one cycle of activity and astronomers are waiting for the sunspots to return and mark the start of the next, the so-called cycle 24. They have been waiting for a while now with no sign it's on its way any time soon.

Sunspots dark magnetic blotches on the Sun's surface come and go in a roughly 11-year cycle of activity first noticed in 1843. It's related to the motion of super-hot, electrically charged gas inside the Sun a kind of internal conveyor belt where vast sub-surface rivers of gas take 40 years to circulate from the equator to the poles and back. Somehow, in a way not very well understood, this circulation produces the sunspot cycle in which every 11 years there is a sunspot maximum followed by a minimum. But recently the Sun's internal circulation has been failing. In May 2006 this conveyor belt had slowed to a crawl a record low. Nasa scientist David Hathaway said: "It's off the bottom of the charts... this has important repercussions for future solar activity." What's more, it's not the only indicator that the Sun is up to something.

Sunspots can be long or short, weak or strong and sometimes they can go away altogether. Following the discovery of the cycle, astronomers looked back through previous observations and were able to see it clearly until they reached the 17th century, when it seemed to disappear. It turned out to be a real absence, not one caused by a lack of observations. Astronomers called it the "Maunder Minimum." It was an astonishing discovery: our Sun can change. Between 1645 and 1715 sunspots were rare. About 50 were observed; there should have been 50,000.

Ever since the sunspot cycle was discovered, researchers have looked for its rhythm superimposed on the Earth's climate. In some cases it's there but usually at low levels. But there was something strange about the time when the sunspots disappeared that left scientists to ponder if the sun's unusual behaviour could have something to do with the fact that the 17th century was also a time when the Earth's northern hemisphere chilled with devastating consequences.

Scientists call that event the "Little Ice Age" and it affected Europe at just the wrong time. In response to the more benign climate of the earlier Medieval Warm Period, Europe's population may have doubled. But in the mid-17th century demographic growth stopped and in some areas fell, in part due to the reduced crop yields caused by climate change. Bread prices doubled and then quintupled and hunger weakened the population. The Italian historian Majolino Bisaccioni suggested that the wave of bad weather and revolutions might be due to the influence of the stars. But the Jesuit astronomer Giovanni Battista Riccioli speculated that fluctuations in the number of sunspots might be to blame, for he had noticed they were absent.

Looking back through sunspot records reveals many periods when the Sun's activity was high and low and in general they are related to warm and cool climatic periods. As well as the Little Ice Age, there was the weak Sun and the cold Iron Age, the active sun and the warm Bronze Age. Scientists cannot readily explain how the Sun's activity affects the Earth but it is an observational correlation that the Sun's moods have a climatic effect on the Earth.

Today's climate change consensus is that man-made greenhouse gases are warming the world and that we must act to curb them to reduce the projected temperature increase estimated at probably between 1.8C and 4.0C by the century's end. But throughout the 20th century, solar cycles had been increasing in strength. Almost everyone agrees that throughout most of the last century the solar influence was significant. Studies show that by the end of the 20th century the Sun's activity may have been at its highest for more than 8,000 years. Other solar parameters have been changing as well, such as the magnetic field the Sun sheds, which has almost doubled in the past century. But then things turned. In only the past decade or so the Sun has started a decline in activity, and the lateness of cycle 24 is an indicator.

Astronomers are watching the Sun, hoping to see the first stirrings of cycle 24. It should have arrived last December. The United States' National Oceanic and Atmospheric Administration predicted it would start in March 2007. Now they estimate March 2008, but they will soon have to make that even later. The first indications that the Sun is emerging from its current sunspot minimum will be the appearance of small spots at high latitude. They usually occur some 12-20 months before the start of a new cycle. These spots haven't appeared yet so cycle 24 will probably not begin to take place until 2009 at the earliest. The longer we have to wait for cycle 24, the weaker it is likely to be. Such behaviour is usually followed by cooler temperatures on Earth.

The past decade has been warmer than previous ones. It is the result of a rapid increase in global temperature between 1978 and 1998. Since then average temperatures have held at a high, though steady, level. Many computer climate projections suggest that the global temperatures will start to rise again in a few years. But those projections do not take into account the change in the Sun's behaviour. The tardiness of cycle 24 indicates that we might be entering a period of low solar activity that may counteract man-made greenhouse temperature increases. Some members of the Russian Academy of Sciences say we may be at the start of a period like that seen between 1790 and 1820, a minor decline in solar activity called the Dalton Minimum. They estimate that the Sun's reduced activity may cause a global temperature drop of 1.5C by 2020. This is larger than most sensible predictions of man-made global warming over this period.

It's something we must take seriously because what happened in the 17th century is bound to happen again some time. Recent work studying the periods when our Sun loses its sunspots, along with data on other Sun-like stars that may be behaving in the same way, suggests that our Sun may spend between 10 and 25 per cent of the time in this state. Perhaps the lateness of cycle 24 might even be the start of another Little Ice Age. If so, then our Sun might come to our rescue over climate change, mitigating mankind's influence and allowing us more time to act. It might even be the case that the Earth's response to low solar activity will overturn many of our assumptions about man's influence on climate change. We don't know. We must keep watching the sun.



Dr David Whitehouse is an astronomer and the author of 'The Sun: A Biography' (John Wiley, 2004)

Seasons of the Sun

Modern Solar Minimum (2000-?)

Modern Climatic Optimum (18902000) the world is getting warmer. Concentrations of greenhouse gas increase. Solar activity increases.

Dalton Solar Minimum (17901820) global temperatures are lower than average.

Maunder Solar Minimum (16451715) coincident with the 'Little Ice Age'.

Sprer Solar Minimum (1420-1530) discovered by the analysis of radioactive carbon in tree rings that correlate with solar activity colder weather. Greenland settlements abandoned.

Wolf Solar Minimum (12801340) climate deterioration begins. Life gets harder in Greenland.

Medieval Solar Maximum (10751240) coincides with Medieval Warm Period. Vikings from Norway and Iceland found settlements in Greenland and North America.

Oort Solar Minimum (1010-1050) temperature on Earth is colder than average.

There seem to have been 18 sunspot minima periods in the last 8,000 years; studies indicate that the Sun currently spends up to a quarter of its time in these minima.



http://www.solarcycle24. com/

The Great Frost of 1683: http://www.londononline.co.uk/history/thames/4/

Sport
formula oneLive lap-by-lap coverage of championship decider
News
Boxing promoter Kellie Maloney, formerly known as Frank Maloney, entered the 2014 Celebrity Big Brother house
people
Arts and Entertainment
tvStrictly presenter returns to screens after Halloween accident
News
video
PROMOTED VIDEO
News
peopleFormer civil rights activist who was jailed for smoking crack cocaine has died aged 78
Arts and Entertainment
Jerry Hall (Hand out press photograph provided by jackstanley@theambassadors.com)
theatre
Arts and Entertainment
tv
Arts and Entertainment
Carrie Hope Fletcher
booksFirst video bloggers conquered YouTube. Now they want us to buy their books
Arts and Entertainment
Damien Hirst
artCoalition's anti-culture policy and cuts in local authority spending to blame, says academic
Sport
premier leagueMatch report: Arsenal 1 Man United 2
Arts and Entertainment
Kirk Cameron is begging his Facebook fans to give him positive reviews
film
News
ebooksNow available in paperback
News
i100
Life and Style
Small winemakers say the restriction makes it hard to sell overseas
food + drink
Arts and Entertainment
Jason goes on a special mission for the queen
tvReview: Everyone loves a CGI Cyclops and the BBC's Saturday night charmer is getting epic
Sport
Jonny May scores for England
rugby unionEngland 28 Samoa 9: Wing scores twice to help England record their first win in six
Life and Style
fashionThe Christmas jumper is in fashion, but should you wear your religion on your sleeve?
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Reach Volunteering: Financial Trustee and Company Secretary

Voluntary Only - Expenses Reimbursed: Reach Volunteering: A trustee (company d...

Recruitment Genius: Senior Project Manager

£45000 - £65000 per annum: Recruitment Genius: This is a fantastic opportunity...

Recruitment Genius: Shopfitter

Negotiable: Recruitment Genius: This is an opportunity to join a successful an...

Recruitment Genius: Digital Sales Account Manager

£25000 - £30000 per annum: Recruitment Genius: A Digital Sales Account Manager...

Day In a Page

Mau Mau uprising: Kenyans still waiting for justice join class action over Britain's role in the emergency

Kenyans still waiting for justice over Mau Mau uprising

Thousands join class action over Britain's role in the emergency
Isis in Iraq: The trauma of the last six months has overwhelmed the remaining Christians in the country

The last Christians in Iraq

After 2,000 years, a community will try anything – including pretending to convert to Islam – to avoid losing everything, says Patrick Cockburn
Black Friday: Helpful discounts for Christmas shoppers, or cynical marketing by desperate retailers?

Helpful discounts for Christmas shoppers, or cynical marketing by desperate retailers?

Britain braced for Black Friday
Bill Cosby's persona goes from America's dad to date-rape drugs

From America's dad to date-rape drugs

Stories of Bill Cosby's alleged sexual assaults may have circulated widely in Hollywood, but they came as a shock to fans, says Rupert Cornwell
Clare Balding: 'Women's sport is kicking off at last'

Clare Balding: 'Women's sport is kicking off at last'

As fans flock to see England women's Wembley debut against Germany, the TV presenter on an exciting 'sea change'
Oh come, all ye multi-faithful: The Christmas jumper is in fashion, but should you wear your religion on your sleeve?

Oh come, all ye multi-faithful

The Christmas jumper is in fashion, but should you wear your religion on your sleeve?
Dr Charles Heatley: The GP off to do battle in the war against Ebola

The GP off to do battle in the war against Ebola

Dr Charles Heatley on joining the NHS volunteers' team bound for Sierra Leone
Flogging vlogging: First video bloggers conquered YouTube. Now they want us to buy their books

Flogging vlogging

First video bloggers conquered YouTube. Now they want us to buy their books
Saturday Night Live vs The Daily Show: US channels wage comedy star wars

Saturday Night Live vs The Daily Show

US channels wage comedy star wars
When is a wine made in Piedmont not a Piemonte wine? When EU rules make Italian vineyards invisible

When is a wine made in Piedmont not a Piemonte wine?

When EU rules make Italian vineyards invisible
Look what's mushrooming now! Meat-free recipes and food scandals help one growing sector

Look what's mushrooming now!

Meat-free recipes and food scandals help one growing sector
Neil Findlay is more a pink shrimp than a red firebrand

More a pink shrimp than a red firebrand

The vilification of the potential Scottish Labour leader Neil Findlay shows how one-note politics is today, says DJ Taylor
Bill Granger recipes: Tenderstem broccoli omelette; Fried eggs with Mexican-style tomato and chilli sauce; Pan-fried cavolo nero with soft-boiled egg

Oeuf quake

Bill Granger's cracking egg recipes
Terry Venables: Wayne Rooney is roaring again and the world knows that England are back

Terry Venables column

Wayne Rooney is roaring again and the world knows that England are back
Michael Calvin: Abject leadership is allowing football’s age-old sores to fester

Abject leadership is allowing football’s age-old sores to fester

Those at the top are allowing the same issues to go unchallenged, says Michael Calvin