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Friday, December 14, 2012

Global Warming's Greenhouse Effect First Posited By Swedish Physicist In 1896

The father of climate change

Ian Sample looks at how the study of the climate has moved from being a relatively minor branch of science to one that now dominates most others, thanks largely to the work of one man
Behind the treelined embankment that borders the campus of Stockholm University lies building 92E, a red brick villa as big as a fire station, its back turned to Roslagsvägen, the main artery linking the capital city with Norrtälje 70km away.
What few markings there are on the building suggest nothing of its history. A sign above the entrance identifies it as Cafe Bojan, a student canteen, and a few shirtless students on a bench in the morning sun recall it as nothing more.
At the end of the 19th century, building 92E was the home and laboratory of Svante Arrhenius, a chemist who became Sweden's first Nobel prizewinner. He was destined to have a bigger impact than he could have imagined, far beyond his mainstream work. Unwittingly, he uncovered secrets of the Earth's atmosphere and in doing so triggered research into what many see as the biggest threat to modern humans. He is arguably the father of climate change science. http://en.wikipedia.org/wiki/Svante_Arrhenius
That title would be a surprise, even to him. The son of a land surveyor, Arrhenius thrived at school, showing a particular aptitude for arithmetic, but his diversity of thought and penchant for maverick theories dealt him a hefty blow at university. His PhD research, which he began at Uppsala University to the north of Stockholm, focused on the conductivity of electrolytes, but the ideas he put forward in his thesis baffled his professors and he was awarded the lowest possible pass grade. At once, any hopes of staying on at Uppsala were destroyed, and Arrhenius embarked on a tour of European laboratories before landing a job in Stockholm several years later.
Arrhenius became interested in a debate occupying the scientific community, namely the cause of the ice ages. Could it be, he wondered, that vast swings in the levels of atmospheric CO2, lasting tens of millions of years, were the trigger?
The link between CO2 and the Earth's temperature had been made years beforehand. It was the French scientist Joseph Fourier who first realised that certain atmospheric gases shrouded the planet like a bell jar, transparent to sunlight, but absorbing to infrared rays. It means the atmosphere is heated from above and below: first, by sunlight as it shines through and second by the infrared the Earth emits as it cools overnight.
Arrhenius set himself the task of working out just how much water and CO2 in the atmosphere warmed the planet. From others' work, he knew that CO2 was only part of the process. While CO2 and other gases trapped infrared radiation and so heated the atmosphere, warmer air holds more water vapour, itself the most potent contributor to the greenhouse effect. So, if atmospheric CO2 levels increased, water vapour would ensure the warming effect was seriously magnified.
What followed was a year doing what Arrhenius described as "tedious calculations". His starting point was a set of readings taken by US astronomer Samuel Langley, who had tried to work out how much heat the Earth received from the full moon. Arrhenius used the data with figures of global temperatures to work out how much of the incoming radiation was absorbed by CO2 and water vapour, and so heated the atmosphere.
Between 10,000 and 100,000 calculations later, Arrhenius had some rough, but useful, results that he published in 1896. If CO2 levels halved, he concluded, the the Earth's surface temperature would fall by 4-5C. There was a flipside to his calculations: doubling CO2 levels would trigger a rise of about 5-6C.
Beyond the argument over ice ages it wasn't lost on Arrhenius that human activity, in the form of widespread burning of coal, was pumping atmospheric CO2 above the natural levels that help make the Earth habitable. Almost as a passing comment, he estimated that coal burning would drive a steady rise in CO2 levels of about 50% in 3,000 years, a prospect he found entirely rosey. At a lecture that same year, he declared: "We would then have some right to indulge in the pleasant belief that our descendants, albeit after many generations, might live under a milder sky and in less barren surroundings than is our lot at present."
As the first to put hard figures on the greenhouse effect, it's unsurprising Arrhenius's estimates weren't spot on. He thought it would take millenia to see a 50% rise in CO2 - but modern measurements show a 30% rise during the 20th century alone. He thought a doubling of CO2 would raise temperatures by 5-6C. Scientists now say 2-3C is more likely.
Over the next decades, his work was criticised, backed up and criticised again. Many disregarded his conclusions, pointing to his simplification of the climate and how he failed to account for changes in cloud cover and humidity. The oceans would absorb any extra CO2 pumped into the atmosphere, and any remainder would be absorbed by plant life, leading to a more lush landscape, sceptics argued.
In 1938, nine years after Arrhenius had died a Nobel prizewinner for his work on ionic solutions, English engineer Guy Callendar gave the greenhouse theory a boost. An expert on steam technology, he took up meteorology as a sideline and became interested in suggestions of a warming trend. Callendar pieced together temperature measurements from the 19th century onwards and saw an appreciable rise. He went on to check CO2 over the same period and discovered levels had increased about 10% in 100 years. The warming was probably due to the higher levels of CO2
The existence of an increasing greenhouse effect was hotly debated until the postwar funding of the 1950s kicked in and researchers began to get firm data. In 1956, physicist Gilbert Plass confirmed adding CO2 to the atmosphere would increase infrared radiation absorbed, adding that industrialisation would raise the Earth's temperature by just over 1C per century. By the end of the 1950s, Plass and other scientists in the US started warning government officials that greenhouse warming might become a serious issue in the future.
Unwittingly, the US especially had already started monitoring what many believed were the direct effects of a warming world. Submarines operating in the Arctic Circle took accurate readings of the thickness of the ice sheets above them. When the Pentagon released the data nearly 40 years later, it revealed a startling melting of the ice, on average a 40% thinning of 1.3m since 1953.
In the 1960s, researchers at Scripps Institution of Oceanography in San Diego took on the testing challenge of taking a vast number of measurements of atmospheric CO2. The aim was to establish a baseline level with which future readings in a decade or so could be compared.
Charles Keeling spent two years taking measurements in Antarctica and above the Mauna Loa volcano in Hawaii but reported that even in this short period, CO2 levels had risen. He concluded that the oceans weren't absorbing greenhouse gases being pumped out by industry. Instead, emissions were driving levels of CO2 higher. "It was a seminal discovery. For the first time, scientists knew that the oceans weren't going to absorb all this carbon dioxide," says Mike Hulme at the Tyndall Centre for climate change research at the University of East Anglia.
Still, few saw the greenhouse effect and the warming it would bring as being a problem. At the time, computer models were suggesting modest increases, perhaps 2C in hundreds of years.
By the 1980s, climate change had become a megascience, attracting scientists from diverse fields, each attacking the problem from a different angle. One technique was especially useful. Deep cores of ice cut from Greenland and elsewhere held pockets of air dating back hundreds of thousands of years. By analysing the trapped air, scientists worked out CO2 levels in the atmosphere during past ice ages. In 1987, a core cut from central Antarctica showed that in the previous 400,000 years, CO2 had dropped to 180 parts per million (ppm) during the most extreme glacial periods and climbed as high as 280ppm in warmer times, but not once had been higher. In the outside air, CO2 was measured at 350ppm, unprecedented for nearly half a million years.
To mainstream scientists, evidence that warming was down to human activity was becoming too big to ignore. While scientists uncovered evidence for the greenhouse effect and warming it was producing, others pointed to different processes impacting on global climate. Volcanos, for example, blast millions of tonnes of sulphur dioxide into the atmosphere that form aerosol particles which reflect sunlight back into space. The 1991 eruption of Mount Pinatubo in the Phillipines sent about 20m tonnes of the gas into the atmosphere, leading to a global cooling of around 0.5C a year later. Scientists now believe that the warming experienced in the early 20th century can largely be explained by the lack of volcanic activity.
Variations in the sun's intensity have also been fingered as a driver of climate change. According to Joanna Haigh at Imperial College London, about a third of the warming since 1850 can be explained by solar activity. The identification of disparate contributors to warming has been seized upon by a minority who claim global warming is driven far more by nature than human activity, and the ensuing controversy is still not settled.
By 1988, the United Nations had established the Intergovernmental Panel on Climate Change to review relevant research. The panel's latest estimate points to a warming of 1.4-5.8C by 2100, depending on what strategies, if any, are adopted to curb emissions. The 20th century saw a rise in temperature of 0.6C, about half of which occured since 1970.
Arguably the most concerted effort to cut global emissions has been triggered by the Kyoto Protocol. Since ratification began in 1997, more than 100 countries have adopted the protocol, which for the first time committed them to cutting emissions of six greenhouse gases.
Now, barely a week goes by without a major study on climate change. A flurry of papers started the year with warnings that the Gulf Stream would grind to a halt, ski resorts would move to higher altitudes and Antarctic glaciers were melting fast. More than 100 years after Arrhenius set out to discover why the world fell into periodic ice ages, the scientist has become a pillar of the megascience that is global warming research.
Back in Stockholm' meteorology department, Erland Kallen is musing about progress since Arrhenius first set about his calculations. "Even when I came to this field 20 years ago, I was very sceptical about global warming. There were too many uncertainties I just couldn't see how anyone could say anything sensible about it. Now, I struggle to see what other explanation there could be."
Timeline
1898
Swedish scientist, Svante Arrherius, puts forward the theory of the greenhouse effect and calculates that doubling of carbon dioxide in the atmosphere will increase temperatures by 5°C to 6°C
1956
US weapons researcher Gilbert Plass pursues climate research in his free time and analyzes how carbon dioxide traps heat. He announces that climate change could be a severe problem to future generations.
1979
The First World Climate Conference, sponsored by the World Meteorological Organization, is held in Geneva, Switzerland. Extremeweather events earlier during the decade had focussed public attention on climate.
1982
Ice cores from the Greenland ice sheet show dramatic temperature oscillations in a single century from the past, an extremely short period for climate change. Scientists also call 1981 the warmest year on record.
1997
The Kyoto Protocol is negotiated to reduce greenhouse gas emissions 5.2% below 1990 levels by 2012 in the developed countries including the former communist bloc.
2005 Kyoto Protocol enters into legal force on Feb 16. The treaty was ratified by more than 140 countries. Concentration of carbon dioxide now stands at 372 parts per million, higher than at any time in at least the past 420,000 years.

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