From the June 1972 United Nations Conference on the Human Environment in Stockholm, Sweden, which first put climate change on the global political agenda, to the 1997 Kyoto Protocol (from which President George W Bush removed the US in 2001), to the 2007 Bali roadmap toward a 2009 agreement, followed by the failed 2009 Copenhagen and 2010 Mexico Summits, to the landmark 2015 Paris Climate Accord – the road from global awareness to an action plan was long, rocky and steep.

But the story of humanity’s knowledge of the greenhouse gas effect goes back nearly two centuries, and its awareness of its own impacts on the earth’s climate through CO2 emissions came to light at the end of the 19th century.

For many generations, humans remained largely ignorant of, and blind to, it’s invisible effects on the planet’s climate, and even today much of the US Republican Party insists that the incontrovertible evidence and largest scientific consensus in the history of science is a myth created by those who oppose capitalist economic growth (as oppose it we must, for endless growth is not only unsustainable but is the paradigm of cancer that consumes its host in order to grow).

It took the year 2015 – the warmest on record – for the world’s community of nations to finally agree, after 23 years of debate and delays, to a voluntary but enforceable agreement to reduce carbon dioxide emissions in an attempt to keep global temperatures from rising more than 1.5°C (2.7°F), which is the newly-downward-revised goal from the previous 2°C (3.6°F) consensus.

While this accord is monumental in its scope and ambition, some scientists and environmentalists believe it is too little too late, and that the earth may have already reached irreversible “tipping points” at which geophysical feedback mechanisms will make the planet far less hospitable to human habitation before the end of this century (perhaps, by mid-century), and result in the loss of half of all biodiversity on the earth.



For the edification of my readers, here is a summary timeline of the journey toward global warming awareness and action:

Black Bold – World Human Population
Red – Industrial Revolution Landmarks & Planetary Effects
Purple – UN Global Treaty Conferences
Green – IPCC Climate Assessments

1712 – British ironmonger Thomas Newcomen invented the first widely used steam engine, paving the way for the Industrial Revolution and industrial scale use of coal.

1800 – World population reaches one billion.

1800-1870 – The level of carbon dioxide gas (CO2) in the atmosphere, as later measured in ancient ice, is about 290 ppm (parts per million). The earth’s average atmospheric CO2 concentration in each of the interglacial periods of the last 2 million years was 280 ppm.

1824 – The existence of the greenhouse effect was argued for by Joseph Fourier. He writes: “The temperature [of the Earth] can be augmented by the interposition of the atmosphere, because heat in the state of light finds less resistance in penetrating the air, than in re-passing into the air when converted into non-luminous heat.”

1827,1838 – The argument and the evidence was further strengthened by Claude Pouillet.

1859 – Experimental observations that water vapor and other gases create the greenhouse effect were provided by John Tyndall, John Tyndall concludes: “This aqueous vapour is a blanket more necessary to the vegetable life of England than clothing is to man.”

1896 – Tyndall’s findings were more fully quantified by Svante Arrhenius when he published the first calculation of global warming from human emissions of CO2.

1886 – Karl Benz unveiled the Motorwagen, often regarded as the first true automobile.

1896 – Swedish chemist Svante Arrhenius concluded that industrial-age coal burning will enhance the natural greenhouse effect. His conclusions on the likely size of the “man-made greenhouse” are a few degrees Celsius for a doubling of CO2 – the same as modern-day climate models.

1900 – Another Swede, Knut Angstrom, discovers that even at the tiny concentrations found in the atmosphere, CO2 strongly absorbs parts of the infrared spectrum.

1927 – Carbon emissions from fossil fuel burning and industry reach one billion tons per year.

1930 – Human population reaches two billion.

1938 – Guy Stewart Callendaran, English steam engineer and inventor, using records from 147 weather stations around the world, argued that CO2 greenhouse global warming is underway, and that temperatures had risen over the previous century. The “Callendar effect” is widely dismissed by meteorologists.

1955 – Using a new generation of equipment including early computers, US researcher Gilbert Plass analysed in detail the infrared absorption of various gases, and concluded that doubling CO2 concentrations would increase temperatures by 3° – 4°C.

1957 – US oceanographer Roger Revelle and chemist Hans Suess showed that seawater will not absorb all the additional CO2 entering the atmosphere, as many had assumed. Revelle wrotes: “Human beings are now carrying out a large scale geophysical experiment…”

1958 – Using equipment he had developed himself, Charles David (Dave) Keeling began systematic measurements of atmospheric CO2 at Mauna Loa in Hawaii and in Antarctica. Within four years, the project – which continues today – provided the first unequivocal proof that CO2 concentrations were rising.

1960 – Human population reaches three billion.

1965 – A US President’s Advisory Committee panel warns that the greenhouse effect is a matter of “real concern”.

1967 – Taking advantage of the ability of digital computers to numerically integrate absorption curves, Manabe and Wetherald made the first detailed calculation of the greenhouse effect incorporating convection (the “Manabe-Wetherald one-dimensional radiative-convective model”), showing that, in the absence of feedback, a doubling of carbon dioxide from 300 to 600 ppm would result in approximately 2.36°C increase in temperature.

1960s – Smog had become a serious local problem in many cities, and some scientists began to consider whether the cooling effect of particulate pollution could overcome global temperature rise, but began to suspect the net effect could be disruptive to climate in the matter of decades.

1968 – In his book, The Population Bomb, Paul R. Ehrlich wrote “the greenhouse effect is being enhanced now by the greatly increased level of carbon dioxide… [this] is being countered by low-level clouds generated by contrails, dust, and other contaminants… At the moment we cannot predict what the overall climatic results will be of our using the atmosphere as a garbage dump.”

1970s – Scientists started to shift from uncertainty to a prediction of future warming.

June 1972 –The United Nations Conference on the Human Environment in Stockholm, Sweden, adopted a declaration of principles for the preservation and enhancement of the human environment and an action plan that raised the issue of climate change for the first time.

1972, 1974 – In the first two “Reports for the Club of Rome”, the anthropogenic climate changes by CO2 increase as well as by waste heat were mentioned. About the latter John Holdren wrote in a study cited in the 1st report, “… that global thermal pollution is hardly our most immediate environmental threat. It could prove to be the most inexorable, however, if we are fortunate enough to evade all the rest.” More refined model calculations show noticeable contributions from waste heat to global warming after the year 2100, if its growth rates become not strongly reduced (below the averaged 2% per annum which occurred since 1973).

1975 – Human population reaches four billion.

1975 – US scientist Wallace Broecker put the term “global warming” into the public domain in the title of a scientific paper.

1975 – Newsweek magazine published a story that warned of “ominous signs that the Earth’s weather patterns have begun to change,” and reported “a drop of half a degree [Fahrenheit] in average ground temperatures in the Northern Hemisphere between 1945 and 1968.” The article continued by stating that evidence of global cooling was so strong that meteorologists were having “a hard time keeping up with it”. On October 23, 2006, Newsweek issued an update stating that it had been “spectacularly wrong about the near-term future”

1979 – The World Climate Conference of the World Meteorological Organization concluded “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 higher latitudes….It is possible that some effects on a regional and global scale may be detectable before the end of this century and become significant before the middle of the next century.”

July 1979 – The United States National Research Council published a report, concluding (in part): “When it is assumed that the CO2 content of the atmosphere is doubled and statistical thermal equilibrium is achieved, the more realistic of the modeling efforts predict a global surface warming of between 2°C and 3.5°C, with greater increases at high latitudes. … … we have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO2 to negligible proportions or reverse them altogether.”

1979 – President Jimmy Carter installed 32 solar-thermal panels on the White House amid the Arab oil embargo, calling for a campaign to conservative energy. Carter predicted that “a generation from now, this solar heater can either be a curiosity, a museum piece, an example of a road not taken, or it can be a small part of one of the greatest and most exciting adventures ever undertaken by the American people; harnessing the power of the Sun to enrich our lives as we move away from our crippling dependence on foreign oil.”

1981 – President Ronald Reagan, in one of his first moves as president, had Carter’s solar panels removed, believing that the “free market” was the best arbiter of energy policy.

1989 – UK Prime Minister Margaret Thatcher – possessor of a chemistry degree – warns in a speech to the UN that “We are seeing a vast increase in the amount of carbon dioxide reaching the atmosphere… The result is that change in future is likely to be more fundamental and more widespread than anything we have known hitherto.” She calls for a global treaty on climate change.

1989 – Carbon emissions from fossil fuel burning and industry reach six billion tons per year.

early 1980s – The slight cooling trend from 1945-1975 had stopped because aerosol pollution had decreased in many areas due to environmental legislation and changes in fuel use, and it became clear that the cooling effect from aerosols was not going to increase substantially while carbon dioxide levels were progressively increasing.

1985 – A joint UNEP/WMO/ICSU Conference on the “Assessment of the Role of Carbon Dioxide and Other Greenhouse Gases in Climate Variations and Associated Impacts” assessed the role of carbon dioxide and aerosols in the atmosphere, and concluded that greenhouse gases “are expected” to cause significant warming in the next century and that some warming is inevitable.

June 1988 – James E. Hansen of NASA made one of the first assessments that human-caused warming had already measurably affected global climate, and his testimony to Congress raised public awareness of the issue for the first time.

1988 – The WMO established the Intergovernmental Panel on Climate Change with the support of the UNEP, which issues a series of Assessment Reports and supplemental reports that describe the state of scientific understanding at the time each report is prepared. Thousands of scientists and other experts contribute (on a voluntary basis, without payment from the IPCC) to writing and reviewing reports, which are reviewed by representatives from all the governments, with summaries for policy makers being subject to line-by-line approval by all participating governments. The IPCC does not carry out its own original research, nor does it do the work of monitoring climate, but provides an internationally accepted authority on climate change, producing reports which have the agreement of all the leading climate scientists and the consensus of every one of the 120 or so participating governments.

1990 – IPCC produced its First Assessment Report. It concludes that temperatures had risen by 0.3° -0.6°C over the previous century, that humanity’s emissions were adding to the atmosphere’s natural complement of greenhouse gases, and that the addition would be expected to result in warming.

June 1992 – The United Nations Framework Convention on Climate Change (UNFCCC), an international environmental treaty, was negotiated at the Earth Summit in Rio de Janeiro, and entered into force on March 21, 1994. The UNFCCC objective is to “stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system”. The framework, however, set no binding limits on greenhouse gas emissions for individual countries and contained no enforcement mechanisms.

1995 – IPCC Second Assessment Report concludes that the balance of evidence suggests “a discernible human influence” on the Earth’s climate. This has been called the first definitive statement that humans are responsible for climate change.

1997 – Kyoto Protocol was agreed, in which developed nations pledged to reduce emissions by an average of 5% by the period 2008-12, with wide variations on targets for individual countries. The US Senate immediately declares it will not ratify the treaty.

1998 – Strong El Nino conditions combine with global warming to produce the warmest year on record, with average global temperature reaching 0.52°C above the mean for the period 1961-90 (a commonly used baseline).

1998 – Publication of the controversial “hockey stick” graph indicating that modern-day temperature rise in the northern hemisphere is unusual compared with the last 1,000 years. The work would later be the subject of two enquiries instigated by the US Congress.

1999 – Human population reaches six billion.

2001 – President George W Bush removed the US from the Kyoto process.

2001 – IPCC Third Assessment Report found “new and stronger evidence” that humanity’s emissions of greenhouse gases are the main cause of the warming seen in the second half of the 20th Century.

2005 – The Kyoto Protocol became international law for those countries still inside it (the US Senate rejected it).

2005 – UK Prime Minister Tony Blair selected climate change as a priority for his terms as chair of the G8 and president of the EU.

2006 – The Stern Review concluded that climate change could damage global GDP by up to 20% if left unchecked, but that curbing it would cost about 1% of global GDP.

2006 – Carbon emissions from fossil fuel burning and industry reach eight billion tons per year.

2007 – The IPCC’s Fourth Assessment Report concluded it is more than 90% likely that humanity’s emissions of greenhouse gases are responsible for modern-day climate change.

2007 – The IPCC and former US vice-president Al Gore received the Nobel Peace Prize “for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change”.

2007 – At UN negotiations in Bali, governments agree the two-year “Bali roadmap” aimed at hammering out a new global treaty by the end of 2009.

2008 – The American Meteorological Society published “The Myth of the 1970s Global Cooling Consensus”.

2008 – Half a century after beginning observations at Mauna Loa, the Keeling project showed that CO2 concentrations have risen from 315 parts per million (ppm) in 1958 to 380ppm in 2008.

2008 – Two months before taking office, incoming US president Barack Obama pledged to “engage vigorously” with the rest of the world on climate change.

2009 – China overtakes the US as the world’s biggest greenhouse gas emitter – although the US remains well ahead on a per-capita basis.

2009 – Computer hackers download a huge tranche of emails from a server at the University of East Anglia’s Climatic Research Unit and release some on the internet, leading to the “ClimateGate” affair.

2009 – 192 governments convene for the UN climate summit in Copenhagen with expectations of a new global agreement high, but they leave with only a controversial political declaration, the Copenhagen Accord.

2010 – Developed countries begin contributing to a $30bn, three-year deal on “Fast Start Finance” to help them “green” their economies and adapt to climate impacts.

2010 – A series of reviews into “ClimateGate” and the IPCC ask for more openness, but clear scientists of malpractice.

2010 – The UN summit in Mexico does not collapse, as had been feared, but ends with agreements on a number of issues.

2011 – A new analysis of the Earth’s temperature record by scientists concerned over the “ClimateGate” allegations proves the planet’s land surface really has warmed over the last century.

2011 – Human population reaches seven billion.

2011 – Data shows concentrations of greenhouse gases are rising faster than in previous years.

2012 – Arctic sea ice reaches a minimum extent of 1.32 million square miles, a record for the lowest summer cover since satellite measurements began in 1979.

2013 – The Mauna Loa Observatory on Hawaii reported that the daily mean concentration of CO2 in the atmosphere has surpassed 400 parts per million (ppm) for the first time since measurements began in 1958. In the past 2 million years of earth’s temperature cycling, the atmospheric CO2 has never exceeded 300 ppm.

2013 – The first part of the IPCC’s fifth assessment report says scientists are 95% certain that humans are the “dominant cause” of global warming since the 1950s.

2015 – The year is the warmest on record and droughts plague many areas of the planet.

Dec 2015 – The Paris Climate Accord is signed by 196 nations, calling for voluntary but monitorable and enforceable reductions in carbon dioxide of between 40% and 70% by 2050 compared to 2010, an agreement to recommit to higher levels of reductions every five years with an aim to keep temperature rise to 1.5°C, a commitment to sustainable development and a commitment to increase the previously-agreed $100 billion 2020 annual investment in poor countries in 2025.


For the deep history of the earth’s climate and humanity’s influence on it, see A New Green History of the World

For a fanciful but scientifically accurate exploration of the heat balance of our planet and life’s role in its maintenance, see The Thermodynamics of an Intelligent Living Universe


copyleft by Robert Riversong: may be reproduced only with attribution for non-commercial purposes and a link to this page

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