THE HISTORICAL RECORD

INTRODUCTION

This text gives a brief outline of how the study of climate change evolved. It is intended to give relative newcomers to the subject an insight into how key features of the science were developed, how the urgent need for international scientific cooperation became apparent and how further research may develop in the immediate future.

PRIMARY REFERENCES

The Center for History of Physics at the American Institute of Physics (AIP), Maryland maintains a website describing the scientific discoveries which led to the recognition of global warming. It also contains a number of essays relating to the subject. The home page is at: http://www.aip.org/history/climate/index.html

The summary chronology below draws from material on this website and from other sources, particularly Wikipedia. See the comprehensive timeline included on the AIP website for information on other pertinent events.

CHRONOLOGY UP TO 1988

In 1824 Joseph Fourier, best known for the development of Fourier series, discovered that the presence of certain gasses in the atmosphere might influence the Earth’s surface temperature, leading to the concept of planetary heat balance. Link at: http://en.wikipedia.org/wiki/Joseph_Fourier

In the 1870s John Tyndall conducted measurements of the transparency or absorptive capacities of nitrogen, oxygen, water vapour and other atmospheric gasses in relation to radiant heat. He recognised that even small quantities of hydrocarbon gasses, particularly methane, would have a significant effect on the atmosphere. His work is generally recognised as the foundation of the ‘greenhouse gas’ concept. Link at: http://en.wikipedia.org/wiki/John_Tyndall

In 1896 Svante Arrhenius published an analysis of the way that changes in atmospheric CO2 levels would affect surface temperatures, and speculated that CO2 variations might have been a cause of successive Ice Ages. He painstakingly calculated the effects of doubling CO2, obtaining a value of 5–6 degrees C (quite close to recent estimates by IPCC), but felt that industry, at its current levels, would take about 3000 years to create this effect. However, it is now estimated that this doubling will take place well before the end of this century. Link at :

http://en.wikipedia.org/wiki/Svante_Arrhenius

In the 1930s Milutin Milankovich proposed the cyclic behaviour of Earth’s orbital parameters as the primary cause of successive Ice Ages. This theory is now generally accepted in principle, but with the proviso that CO2 positive feedback is an essential amplifying mechanism.

In 1938 Guy Callendar, an amateur climatologist, compared the contemporary British temperatures and CO2 levels with 19th Century records. He concluded that conjectured warming trends in our climate were real and that a 10% rise in atmospheric CO2 was largely responsible. He also argued that CO2 would not be completely absorbed by the oceans, as commonly assumed, since the surface water layers would soon saturate with the gas. Other scientists dissented and many claimed that in any case biological systems (vegetation etc.) were fully capable of absorbing any surplus CO2. See link at:

http://en.wikipedia.org/wiki/Carbon_dioxide_sink

In 1958, at Revelle’s instigation, Charles Keeling began a series of high-precision measurements of CO2 levels, initially in Antarctica and later at Mauna Loa, Hawaii. Quite quickly (from 1960) he was reporting that CO2 levels were unquestionably rising, and at a rate suggesting that oceanic absorption would not be sufficient to stabilise the situation. Thereafter, the remorseless annual increase of the Keeling Curve soon achieved iconic status. Link at:

http://en.wikipedia.org/wiki/Keeling_Curve

In 1961, James Lovelock, best known today for his Gaia Hypothesis (treating the biosphere as a self-regulating system), became involved in NASA work on the analysis of planetary atmospheres. During the 1960s he discovered the widespread presence of CFCs as trace gasses in the Earth’s atmosphere. Subsequent scientific work found that they had long lives and could be highly damaging to the ozone layer. Lovelock observed that the possible climatic effects of such gasses should also be investigated. Since then, Lovelock’s warnings on the growing dangers of global warming and man’s interference with natural processes within the biosphere have made him a public figure, particularly in UK. Link at:

http://en.wikipedia.org/wiki/James_Lovelock

Also during the 1960s Edward Lorenz and others pointed to the essentially chaotic nature of the climatic system. They stressed the possibility of sudden shifts or ‘tipping points’ which would drastically alter the behaviour of the global climate. Link at: http://en.wikipedia.org/wiki/Edward_Norton_Lorenz

By 1976 experiments by V. Ramanathan and others had shown that some CFCs have a global warming potential (GWP) up to 10,000 times that of CO2, although they would only be present in minute amounts. Methane (GWP measured at 25 over 100 years) and nitrous oxide (GWP of 296 over 100 years) were also identified as powerful enough to be significant in larger concentrations, perhaps equal to that of CO2 itself. Link at: http://en.wikipedia.org/wiki/Global_warming_potential

At this stage scientific opinion began to converge on global warming, rather than a potential new Ice Age, as the chief climatic risk in the 21st Century and beyond. An international scientific workshop on climate issues was held, leading to a World Climate Conference in Geneva (1979). As a direct result, the World Meteorological Organisation launched the World Climate Programme to improve our knowledge of the climate system. Link: http://www.wmo.ch/pages/prog/wcp/index_en.html

INTERNATIONAL COOPERATION SINCE 1988

In 1987 the Montreal Protocol had set demanding standards for limiting CFC emissions. These proved a resounding success in reducing ozone layer damage and demonstrated the feasibility of international action on such matters, but had little effect on greenhouse gas emissions. However, in 1988 the growing scientific concern about rising CO2 emissions led to the Toronto Conference (formally entitled the World Conference on the Changing Atmosphere: Implications for Global Security). Its report concluded that atmospheric pollution presented a major threat to international security and called for specific targets to limit greenhouse gas emissions.

During the 1980s work on the various disciplines contributing to greater understanding of climate change had continued in a fairly low key, largely due to limited funding. However, in 1988 the Intergovernmental Panel on Climate Change was formed, and in this body scientific experts attended as representatives of their national governments, an important change. The Panel has become the primary international forum for information exchange on climate science. Links at:

http://www.ipcc.ch/

http://en.wikipedia.org/wiki/IPCC

From 1988 onwards global warming became an international issue, with growing public attention exerting significant pressure on the search for effective policies. The First IPCC Report, issued in 1990, stated that global warming was indeed occurring, but conceded that this might be partly due to natural processes. It concluded that it would be some time before we could be sure that greenhouse gas increases were the dominant cause. Immediately thereafter the Second World Climate Conference issued a strong call for policy action, leading to the UN’s top-level Conference on Environment and Development in Rio in 1992.

The Rio Agreement failed to produce the mandatory limits for greenhouse gas emissions which many governments had hoped for, but it did establish a cyclic process whereby the IPCC would periodically assemble and discuss recent research, and then publish a consensus statement about the prospects for climate change. This in turn was intended to lay the foundation for international negotiations, which would then guide participating governments in determining national policies.

The Second IPCC Report in 1995 was noteworthy for its positive assessment of more sophisticated climatic modelling; this now incorporated the effects of smoke and dust pollution, increasing the level of agreement with ‘real world’ climatic records. Global warming, the Report concluded, was definitely happening and human activity was at least partly responsible. Although political lobbying had succeeded in weakening the wording used, the message remained unmistakably clear.

The UN Conference on Climate Change was held in Kyoto, Japan in 1997. After extended and difficult negotiations a compromise Kyoto Protocol was agreed; this excused the poorest countries from action for the time being, but nominally bound more wealthy countries to cut their emissions significantly by 2010. However, the result was greatly weakened by the US refusal to take any action, and it has since become clear that Kyoto has achieved relatively little.

The Third IPCC Report (2001) reinforced the conclusions of its predecessors and stated with greater conviction that human action was the primary cause of climate change. It established a number of prediction scenarios and reviewed the already considerable research effort on methods of mitigating climate change. The Fourth IPCC Report (2007) stated that the evidence of anthropogenic warming during the 20th Century was now unequivocal and warned that emission rates were likely to increase appreciably over the period 2000-2030. It pointed out that to continue emissions at such rates until 2100 would induce much greater changes in the global climate system than any seen thus far. Many technologies were potentially deployable to stabilise emission levels, but new mitigation policies to encourage action were urgently needed.

In the past many governments and large-scale business interests have adopted attitudes of scepticism or indifference towards the significance of climate change. However, these attitudes are now being undermined by the relentless pressure of public opinion, stimulated by worldwide evidence of firmly established trends towards warmer and less stable climatic conditions. The Bali Conference in late 2007 established an international consensus that a more effective international agreement was needed to supersede the Kyoto Protocol. Most governments now recognise the need to limit emissions, but progress towards more effective policies has so far been inadequate to meet the urgency of the situation.

This unsatisfactory position is illustrated by the outcome of the the UN Conference on Climate Change held in Copenhagen in December 2009. In the latter stages of the conference, lacking any sign of a formal consensus, the Copenhagen Accord was drafted under the leadership of the US delegation, together with the BASIC group - China, India, Brazil and South Africa. The Accord was 'recognised', but not formally approved, by all attending delegations before the closure of the conference. Its text accepted the scientific view that UN countries should cooperate to prevent global temperatures rising more than 2C above pre-industrial levels, but did not declare this figure as a formal target. The text also did not specify a year by which carbon emissions should peak, although it asked all leading countries to make pledges for controlling their carbon emissions beyond 2020, and stated that progress to meet these pledges by developed countries (whose economies are generally significant emitters) would come under regular scrutiny. The implementation of this Accord is to be reviewed at the next UN Climate Conference in 2015, but the document does not have the status of a formal international agreement, as originally intended to replace the Kyoto Protocol in 2012. The Accord included some useful outline provisions for financial aid to developing nations, but there was a general feeling after the conference that developing a coordinated UN programme will require considerable work and intergovernmental negotiation.

FUTURE WORK

Deeper scientific investigations and further refinements in climatic modelling continue to bear fruit, but major areas of uncertainty remain to be explored. Further work is likely to be directed towards:

1. Refinement of climate sensitivity measurements, and identification of positive feedback mechanisms which might accelerate existing trends.

2. More accurate predictions of extreme weather events, and means of protection for human populations and key resources.

3. The degree to which global warming will affect regional climates, and hence possible impacts on human living standards and economic activities.

4. Research leading to mitigation technologies suitable for rapid development and exploitation within industry and commerce, transportation, buildings, construction techniques, etc.

5. Identification of potential tipping points which might generate sudden and irreversible climatic change.

6. Exploring proposals for the application of large-scale geoengineering techniques.