by Ian Arthur

Our understanding of the science that underlies changes in the world’s climate dates from early in the nineteenth century. In 1824 the French mathematician and physicist Joseph Fourier calculated the quantity of heat transmitted to the surface of the earth by high frequency visible radiation from the sun and the quantity of heat emitted in turn by infrared radiation from the earth. He found that the temperature of the earth was higher than would be expected as a result of these exchanges of heat and that this was because a part of the reflected infrared radiation from the earth was absorbed in the atmosphere, which acted like a blanket making the earth warmer. He named this the Greenhouse Effect.

An American, Eunice Newton Foote, conducted experiments, the results of which were reported in a paper published in 1856, showing that that the absorption of infrared radiation from the atmosphere was strongly affected by its carbon dioxide (CO2) content.

John Tyndall, an Irish physicist, in 1859 showed that besides CO2, other gases in the atmosphere, water vapour and methane (CH4), strongly absorbed infrared radiation.

By late in the 18th century, scientists had been finding increasing evidence that very significant changes in the earth’s temperature had occurred in the past. The first evidence discovered was giant boulders in alpine valleys that must have been moved there by glaciers that no longer existed. In 1837 Louis Agassiz, a Swiss geologist, developed a theory that he named Ice Age, that proposed that the earth had experienced one or more periods of low temperature.

Over time evidence accumulated that there the earth had experienced several ice ages or ‘glacial periods’ in which large parts of the earth’s surface  were covered by ice sheets, and in which there had been major changes in vegetation, animal and human life. Direct measurements of temperature do not exist since temperatures of the earth and atmosphere were not systematically recorded until the middle of the 19th century.

But there have been proxy indicators of temperature change that have gradually accumulated. They include tree rings, lake and bog sediments, coral growth rings, ice cores, ocean sediment cores, glacial moraines, coastal landforms, and for the most recent millennia, documentary evidence.

These climate changes have been brought about by various means. There have been changes in the earth’s orbit and its orientation, green house gases, variations in solar output, volcanoes, cosmic collisions and aerosols. We can expect all or any of these changes to occur in the future, and some in our own lifetime. We have been able to measure some of them, such as volcanoes, aerosols and greenhouse gases. Until the nineteenth century there had been no world wide climate changes that have been caused by human activity. We now know that human activities in the present age are producing world wide climate changes with very serious consequences.

Climate change developments in the twentieth century

In 1896 Swedish scientist Svant Arhenius calculated that cutting the amount of CO2 in the atmosphere by a half would suffice to produce an ice age. He saw that the modest increase in CO2 from industrial sources that was occurring (at that time mainly as result of coal burning) would eventually lead to warming, but he believed the temperature increase would be modest and of benefit to mankind.

In fact the rate of burning of coal increased steadily during the 20th century, and other sources of CO2 such as cement making and the burning of natural gas and petroleum also became important. By the end of the 20th century the earth’s global mean surface temperature had increased relative to an 1850-1905 base was nearly 1°C, and was continuing to increase, a matter for serious concern.

In 1968 a study by the Stanford Research Institute noted that with temperature increases a number of events might be expected to occur, including the melting of the Antarctic ice cap, a rise in sea levels, warming of the oceans and an increase in extreme weather changes. All living things would be significantly affected.

The World Meteorological Organization (WMO) held a World Climate Conference in 1979 reaching a cautious conclusion that ‘it appears plausible that an increased amount of carbon dioxide in the atmosphere can contribute to a gradual warming of the lower atmosphere, especially at high latitudes’.

In 1998 a conference of hundreds of scientists and others at Toronto in Canada concluded that the changes in the atmosphere due to human pollution ‘represent a major threat to international security and are already having harmful consequences over many parts of the globe.’ and declared that by 2005 the world governments should act to push emissions of greenhouse gases to some 20% below the 1988 level.

In 1988 the WMO established the Intergovernmental Panel on Climate Change (IPCC) which has continued to publish a series of influential reports right up to the present day. It published its first report in 1990.

In 1992 IIPC reported that ‘it could calculate with confidence that atmospheric concentrations of the long-lived gases (carbon dioxide, nitrous oxide and the chlorofluorocarbons) adjust only slowly to changes in emissions. Continued emissions of these gases at present rates would commit us to increased concentrations for centuries ahead. The longer emissions continue to increase at present day rates, the greater reductions would have to be for concentrations to stabilize at a given level. The long-lived gases would require immediate reductions in emissions from human activities of over 60% to stabilize their concentrations at today’s levels; methane would require a 15-20% reduction.’

An outcome of these serious concerns was the international treaty the United Nations Framework Convention on Climate Change (UNFCC) adopted in 1992 with 154 signatory nations and entering into force in March 1994. Its objective was to stabilise concentrations in the atmosphere at a level that would prevent human interference with the climate system. The Framework sets non-binding limits on greenhouse gas emissions for individual countries and contains no enforcement mechanisms.

Article 3 of the Convention states that Parties should act to protect the climate system on the basis of ‘common but differentiated responsibilities’, and that developed country Parties should “take the lead” in addressing climate change. One of the first tasks set by UNFCC was for signatory nations to establish national greenhouse gas inventories. The UNFCC specified that the aim of developed Parties should be the stabilising their greenhouse gas emissions at 1990 levels.


UNFCC holds Annual conferences of the parties to assess progress in dealing with climate change. At its first conference it decided that the aim of developed country Parties stabilizing their emissions at 1990 levels by the year 2000 was ‘not adequate’.  Further discussions led to the Koyoto Protocol which sets emissions targets for developed countries which are binding under international law.

The Protocol, with 192 signatories, came into force in February 2005 with a first commitment beginning in 2008 and expiring in December 2012. In 2011 Canada, Japan and Russia stated they would not take on further Kyoto targets. Canada was committed to cutting its greenhouse emissions to 65% below 1990 levels, but in 2009 its emissions were 175% higher than 1990 levels. The USA was not a party to the Protocol.

Climate changes in the present century

A second commitment to the Protocol, known as the Doha Amendment, was agreed on in 2012 in which 37 countries (including Australia) had binding commitments that will end in 2020. Parties noted ‘with grave concern’ that current efforts to hold global warming to below 2 or 1.5 °C relative to the pre-industrial level appear inadequate.

In 2015, all 196 parties to the Convention came together for the UN Climate Change Conference in Paris and adopted by consensus the Paris Agreement, aimed at limiting global warming to less than two degrees Celsius, and pursue efforts to limit the rise to 1.5 degrees Celsius. Its long term goal was to limit the increase to 1.5 degrees Celsius since this would substantially reduce the risks and the effects of climate change. Under the agreement each country must determine, plan and regularly report on the Nationally Determined Contributions (NDCs) that it makes to mitigate global warning. There would be no mechanism to force a country to set a target in their NDC by a specific date and no enforcement if a set target in an NDC is not met. The contributions would take effect from 2020 on the expiry of the Doha commitments. Unlike the Kyoto Protocol the Paris Agreement makes no distinction between developed and developing nations; all parties will be required to submit emissions reduction plans.

In 2017 US President Donald Trump announced that he would withdraw from the Agreement when it took effect in 2070. Other nations announced their plans, with France planning to ban all petrol and diesel vehicles in France by 2040 and to no longer use coal to produce electricity after 2022. Australia set an ambitious target to reduce emissions by 26-28 per cent below 2005 levels by 2030, which builds on its 2020 target of reducing emissions by five per cent below 2000 levels.

In November 2018 the IPCC published a Special Report on the impacts of global warming above pre-industrial levels. It concluded that to limit temperature rise to 1.5 °C as proposed in the Paris Agreement would require a steady rate of reduction in CO2 emissions beginning in 2020 and reaching zero by 2055 or earlier.  Model projections estimate that with a temperature rise of 1.5 °C would result in a rise in sea levels of the order of 0.5 metres by 2100.

The IPCC undertook studies in connection with the report that showed that with a with a temperature rise limited to 1.5 °C above pre-industrial levels there would be climate related risks to health, livelihoods, food security, water supply, human security and economic growth. The results of the studies clearly indicated that it would be highly desirable to aim at achieving a limit above preindustrial levels of less than 1.5 °C.

The 2018 annual United Nations Conference of Parties (COP} held in the framework of the UNFCC was held in Katowice, Poland  in  December 2018. David Attenborough told delegates that ‘Right now we are facing a man-made disaster of global scale, our greatest threat in thousands of years: If we don’t take action, the collapse of our civilisations and the extinction of much of the natural world is on the horizon.’

For the last fourteen years the Climate Change Performance Index (CCPI) has tracked countries’ efforts to combat climate change. Its recently published report titled Results 2019 gives mixed signals on the decarbonisation of the global energy system. In 2017 coal production and consumption increased despite increasing coal prices, and indications are for further increases in 2018. On the other hand almost all countries included in the index maintained double digit growth in renewable energy in 2017. By 2020, all major renewable power generation technologies will be competitive or even undercutting fossil fuels in their generation costs. The CCPI tracks the performance of 56 countries and the EU, and these account together for more than 90 % of global greenhouse gas emissions. In all 184 parties have ratified the Paris Agreement and have promised to combat dangerous climate change.

The results  of tracking promises and performance have shown that so far even if all countries were as committed as the current frontrunners’ efforts will not be sufficient to prevent dangerous climate change.

Summary of the present situation

So far attention has been largely focussed on reducing CO2 emissions to the atmosphere by means such as:

  • Replacing coal as a source of heat for industry, and particularly for electricity generation, by fuels that burn with lower production of CO2 such as natural gas and petroleum products;
  • Generating electricity using renewable sources of energy such as wind, solar radiation and hydro, replacing fossil fuels altogether;
  • Using electrical energy to replace burning of hydrocarbons in vehicles;
  • Improving the efficiency of energy use such as by improved building design and insulation;
  • Afforestation, that results in increased capture of CO2 from the atmosphere for the growth of trees, along with efforts to reduce deforestation;
  • Capturing CO2 produced in processes such as generation of electricity, cement manufacture and ammonia manufacture.

Another possibility that has been demonstrated on a pilot scale is the direct removal of CO2 from the atmosphere by capturing it and converting it by treatment to a product such as calcium carbonate that can be readily handled and stored indefinitely. The main disadvantage of this process is the cost, mainly for energy, of implementing it compared with other available means of achieving climate change.

There is also a range of possibilities for achieving climate change that can be grouped under the heading of solar radiation management. They act by intercepting incoming high frequency radiation from the sun and reflecting it back into space. It has been demonstrated that this can be readily accomplished by seeding the atmosphere or clouds with sulphate aerosols. The process is not expensive in relation to the extent of cooling achieved. The aerosol has a short life so the seeding would need to be ongoing. These processes are discussed in the paper Fighting global warming by climate engineering referenced in the list of suggestions for further reading.

Sources and further reading


Wikipedia is a convenient starting point for reading. It includes a number of articles related to climate change. They are up to date, unlike some of the useful books on the subject, and have extensive biographies and links to sources.

Henson, Robert, The rough guide to climate change Rough guides, London, 2008.

This book provides a concise and readable introduction to the subject of climate change, but is not up to date.

Pittock, A. Barrie, Climate change : the science, impacts and solutions, Earthscan, London, 2009.

A comprehensive coverage of the subject by a retired leader of the Climate Impact Group in CSIRO.

Hamilton, Clive, Requiem for a Species, Allen and Unwin, Sydney, 2010.

A good coverage of climate change and its effects, with a pessimistic conclusion. The writer is Charles Sturt Professor of Public Ethics at the University of New South Wales. 

CSIRO, National Hydrogen Roadmap, CSIRO, Australia, 2018

An account of current work leading to the use of hydrogen on a large scale as a fuel that does not lead to adverse climate change.

Series of articles on climate change under the title Conquering CO2, The Economist, London, Dec. 1–7, 2018.

Describes current work on projects to manage climate change.

Germanwatch, Climate Change Performance Index (CCPI) Results 2019:

A summary of the results of Climate Change Performance Index by individual countries to 2019.

Intergovernmental Panel on Climate Change (IPCC); Special Report on the impacts of global warming of 1.5°C.;

Special report published in 2018 for policymakers on the impacts of global warming of 1.5°C above pre-industrial levels.

Tingzhen Ming et al, Fighting global warming by climate engineering; Elsevier, Renewable and Sustainable Energy Reviews 31(2014)792–834

A comprehensive  review of solar radiation management options for fighting climate change.