Chapter 1. Historical Background

1. Chapter 1. Historical Background ESC 305.01 GLOBAL CLIMATE CHANGE

2. Historical Background to the Study of Climate Change • In the 19th century, scientists realized that gases in the atmosphere caused a "greenhouse effect" which affected the planet's temperature. These scientists were interested chiefly in the possibility that a lower level of carbon dioxide gas might explain the ice ages of the distant past. At the turn of the century, Svante Arrhenius calculated that emissions from human industry might someday bring a global warming. Other scientists dismissed his idea as faulty.

3. The History of Atmospheric Science • 1750s: Joseph Black identifies CO2 in the air. • A Scottish scientist known for his work on latent heat, specific heat and CO2.

4. The History of Atmospheric Science • 1781: Henry Cavendish measures the percentage composition of Nitrogen and Oxygen in the air.

5. The History of Atmospheric Science • Henry Cavendish was a British scientist noted for his discovery of Hydrogen.

6. Historical Background • 1820s: Joseph Fourier postulated that some of the gases in the atmosphere must trap heat.

7. Historical Background • John Tyndall was a prominent Irish physicist in the 19th century. • Beginning in the late 1850s, Tyndall studied the action of radiant energy on the constituents of air.

8. Historical Background • John Tyndall found out that gases like water vapour (H2O), carbon dioxide CO2 and CH4 could trap heat rays in the Earth’s atmosphere.

9. Historical Background • Svante August Arrhenius was a Swedish scientist from Stockholm, who won a Nobel Prize in chemistry in 1903.

10. Historical Background • 1890s: Svante Arrhenius completed a numerical experiment, which suggested that cutting the amount of carbon dioxide-CO2 in the Earth’s atmosphere by half could lower the temperature in Europe by some 4-5 oC. • This lowering is sufficient for an ice age.

11. Historical Background • Arvid Gustaf Högbom was also a Swedish scientist. • Arrhenius discussed his findings with Högbom, who was working on carbon cycles through natural geochemical processes.

12. Historical Background 1890s: • Arvid Högbom calculated the amounts of CO2 emitted by factories and other industrial sources. • He found out that the added gas through human activities was not much compared with the amount of CO2 already present in the Earth’s atmosphere.

13. 1890s: Svante Arrhenius made another calculation for doubling the CO2 in the atmosphere, and estimated that this increase would raise the Earth’s temperature some 5-6 oC. Svante Arrhenius further estimated that if industry continued to burn fuel at the 1890s rate (1896 to be exact), it would take perhaps about 3000 years for the CO2 level to double. Historical Background

14. Historical Background • Högbom doubted it would ever rise that much. • Another highly respected scientist, Walter Nernst, even fantasized about setting fire to useless coal seams in order to release enough CO2 to deliberately warm the Earth's climate. • Walther Hermann Nernst was a German physical chemist and physicist, who won the 1920 Nobel Prize in chemistry.

15. Historical Background • Actually, scientists were pursuing the ice ages and other ancient climatic changes (age of the dinosaurs). • Nobody was interested in the hypothetical future warming caused by human industry.

16. Historical Background • Knut Johan Ångström was a Swedish physicist and he was the son of physicist Andres Jonas Angström. • He devoted himself to investigations of the radiation of heat from the sun and its absorption by the Earth's atmosphere.

17. Historical Background • Another blow came from Knut Angström, who did experiments to show that CO2 absorbed radiation only in specific bands of the spectrum so that more gas would make little difference.

18. Historical Background • Water vapour, which is more abundant in the atmosphere than CO2, intercepts infrared radiation. • That is absorption bands of CO2 and H2O overlapped one another, so that more CO2 could not affect more radiation absorption. • However, these measurements and arguments, which were carried out by the assistant of Angström, had fatal flaws.

19. Historical Background • After Ångström published his conclusions in 1900, the few scientists who had taken an interest in the matter concluded that Arrhenius's hypothesis had been proven wrong. • Theoretical work on the question stagnated for decades, and so did measurement of the level of CO2 in the atmosphere.

20. Historical Background • It was also further argued that the Earth automatically regulated itself in a “balance of nature”. • The oceans would absorb any excess gases that came into the atmosphere. • If the oceans failed to stabilize the system, organic matter would stabilize it through. • Just as sea water would absorb more gas if the concentration increased, so would plants grow more lushly in air that was "fertilized" with extra carbon dioxide.

21. Historical Background • Rough calculations seemed to confirm the comfortable belief that biological systems would stabilize the atmosphere by absorbing any surplus. • One way or another, then, whatever gases humanity added to the atmosphere would be absorbed — if not at once, then within a century or so — and the equilibrium would automatically restore itself.

22. Historical Background • As one respected expert put it baldly in 1948, "The self-regulating mechanisms of the carbon cycle can cope with the present influx of carbon of fossil origin.“ • Yet the theory that atmospheric CO2 variations could change the climate was never altogether forgotten.

23. Historical Background • In 1920, Milutin Milankovitch published his theory of ice ages based on variations in the Earth’s orbit.

24. Historical Background • In 1938, an English engineer, Guy Stewart Callendar, who was an expert in steam technology, tried to revive the old idea.

25. Historical Background • Guy Stewart Callendar compiled temperature measurements from the 19th century on and found out that there was a warming trend. • He evaluated the old CO2 measurements and concluded that the concentration of the gas had increased. He asserted that this rise could account for the observed warming. • As for the future, Callendar estimatedthat a doubling of CO2 could gradually bring a 2°C rise in future centuries. But future warming was a side issue for Callendar. Like all his predecessors, he was mainly interested in solving the mystery of the ice ages.

26. Historical Background • Guy Stewart Callendar calculated that 150 billion tons of CO2 was added to the atmosphere during the past half century, increasing the Earth’s temperature by 0.005°C per year during that period.

27. Historical Background • Callendar's publications attracted some attention, and climatology textbooks of the 1940s and 1950s routinely included a brief reference to his studies. But most meteorologists gave Callendar's idea scant credence. • In the first place, they doubted that CO2 had increased at all in the atmosphere. The old data were untrustworthy, for measurements could vary with every change of wind that brought emissions from some factory or forest.

28. Historical Background • According to a well-known estimate published in 1924, even without ocean absorption it would take 500 years for fuel combustion to double the amount of CO2 in the atmosphere. • There was also the old objection, which most scientists continued to find decisive, that the overlapping absorption bands of CO2 and water vapor already blocked all the radiation that those molecules were capable of blocking.

29. Historical Background • In the 1950s, Callendar's claims provoked a few scientists to look into the question with improved techniques and calculations. What made that possible was a sharp increase of government funding, especially from military agencies with Cold War concerns about the weather and the seas. • The new studies showed that, contrary to earlier crude estimates, carbon dioxide could indeed build up in the atmosphere and should bring warming. Painstaking measurements drove home the point in 1960 by showing that the level of the gas was in fact rising, year by year.

30. Historical Background • In the 1950s, it was found out that absorption bands of gases exhibited vast differences at lower pressures (such as high altitudes). • At lower pressures each absorption band resolved into sharply defined peaks, with gaps where radiation could get through.

31. Historical Background • Precise laboratory measurements showed that CO2 absorption lines did not lie on top of H2O vapour lines. They were two sets of narrow lines with spaces in between. • Another revolution in analytical chemistry was the discovery of the radioactive isotope carbon-14. This isotope of carbon exists at low concentrations in the atmosphere and has a half life of 5500 years.

32. Historical Background • From measurements of how much of the isotope was found in air and how much in sea water, it was possible to calculate the movements of CO2. • More recent studies showed that the chemicals that existed in sea water created a buffering mechanism that stabilized the acidity. This would prevent the water from retaining all the extra CO2 it took up.

33. Historical Background • The insight was that although seawater did absorb CO2 most rapidly, most of the added gas would promptly evaporate back into the air before the slow oceanic circulation sent it down into deeper waters (solubility pump). • More and more scientists were joining the greenhouse effect club in the late 1950s.

34. Historical Background • A group of scientists were arguing that it was important to measure and monitor the CO2 in the atmosphere more accurately.

35. Historical Background • Charles David Keeling installed CO2 measuring instruments into the Mauna Loa volcano in Hawaii and started to monitor its concentration starting in 1958. As the CO2 record extended, it became increasingly impressive and each year noticably higher.

36. Historical Background

37. Historical Background • Soon Keeling’s curve was widely cited by scientific circles and it become the primary icon for the greenhouse effect. • Although CO2 increase in the atmosphere was evident, many scientists were not convinced with the rate of temperature increase it was associated with. • To make matters more complicated the warming trend until the 1940s had switched to a cooling trend.

38. Historical Background

39. Historical Background • During the 1970s and 1980s, calculations showed that the other gases emitted by human activities also have a strong green house effect. Methane was one of these gases. • Carbon cycle studies were made. Amount of CO2 emitted to the atmosphere through fossil fuel combustion was easy to calculate. However there was a carbon deficit. Half of the CO2 output was missing.

40. Historical Background • In the 1980s, convincing data came from ice core studies. During the last ice age the level of CO2 in the atmosphere had been as much as 50 % lower than in our warmer times. • A two kilometer deep ice core showed a 150,000 years record, a complete ice age cycle of warmth, cold and warmth. It was found that CO2 levels had gone up and down in close step with temperature.

41. Historical Background • After 1987, more ice core data going back to 400,000 years (four complete glacial cycles) were obtained. • The CO2 levels got as low as 180 ppm in the cold periods and reached 280 ppm during the warm periods, but never higher. • Now it was at 380 ppm, never seen in the geological era.

42. Historical Background • During the 1990s, careful analysis of ice core measurements exhibited that during past glacial periods temperature changes had preceded CO2 changes by a few centuries. • A key point was in the network of feedbacks that made up the climate system, CO2 was a main driving force.

43. Historical Background • Analyses of ancient climates using entirely geological data independent of computer models showed that there was a “climate sensitivity”- the response of temperature to a rise in the CO2 level- in the same range as computer models predicted for future greenhouse warming.

44. Historical Background • One unexpected discovery was that the level of certain other gases was rising, which would add seriously to global warming. Some of these gases also degraded the atmosphere's protective ozone layer, and the news inflamed public worries about the fragility of the atmosphere. • Moreover, by the late 1970s global temperatures had begun to rise again. Many climate scientists had become convinced that the rise was likely to continue as greenhouse gases accumulated.

45. Historical Background • 1970-1974/ Destruction of stratospheric ozone by man-made chemicals (CFCs) is described by several scientists. • 1985/ The British Atlantic Survey reported a 40 % drop in springtime stratospheric ozone between 1956-1985. • 1986/ Montreal Protocol

46. Historical Background • By around 2000, some predicted, an unprecedented global warming would become apparent. Their worries first caught wide public attention in the summer of 1988. • An international meeting of scientists warned that the world should take active steps to cut greenhouse gas emissions.

47. Historical Background • The world's governments had created a panel to give them the most reliable possible advice, as negotiated among thousands of climate experts and officials. • By 2001, this Intergovernmental Panel on Climate Change (IPCC) managed to establish a consensus:

48. Historical Background • Scientists knew the most important things about how the climate could change during the 21st century. • How the climate would actually change now depended chiefly on what policies humanity would choose for its greenhouse gas emissions. • Since 2001, greatly improved computer models and an abundance of data of many kinds strengthened the conclusion that human emissions are very likely to cause serious climate change.

49. Historical Background • In 2007 the IPCC reported that scientists were more confident than ever that humans were changing the climate. Although only a small fraction of the predicted warming had happened so far, effects were already becoming visible in some regions — more deadly heat waves, stronger floods and droughts, heat-related changes in the ranges and behavior of sensitive species. • Depending on what steps people took to restrict emissions, by the end of the century we could expect the planet’s average temperature to rise anywhere between about 1.4 and 6°C (2.5 - 11°F).