3.2.6 1990 to the present: a growing consensus

Back to 3.2.5

Unit 3 Contents



Over the past two decades, there has come to be a very wide consensus among scientists about climate change – both that it is happening and that it is, in large part, a result of human activities.  This consensus is represented especially in the worldwide scientific body called ‘The Intergovernmental Panel on Climate Change’ (www.ipcc.ch).  However there continue to be a small number of scientists who dissent from the consensus and who make a number of arguments in critique of it.  These include that recent increases in temperatures on earth are probably a result of changes in activity in the sun, for which, of course, humans are not responsible.

One leading climate scientist is Sir John Houghton, a Christian (a member of the Church of England), who has written extensively on the evidence about global warming.  If you wish, you can read a very good outline written by Houghton of both the science and the evidence.  This is on the website of ‘Operation Noah’, an ecumenical Christian body that campaigns on climate change.  Its slogan is: ‘Science-informed. Faith-motivated. Hope-driven.’


Optional reading (10pp)

Sir John Houghton, ‘What is Global Warming?


It has been a series of reports by the Intergovernmental Panel on Climate Change (IPCC) between 1990 and today which, probably more than anything else, has contributed to establishing the current consensus about the evidence – and also, therefore, on the need for urgent action to address the problem.

You may know that a few years ago, in 2009, a row erupted about the reliability of certain aspects of the IPCC’s reports, after emails involving staff of the University of East Anglia made clear that they had sought to play down or suppress some evidence that didn’t fit the overall picture which the IPCC was presenting.  That row contributed to a new growth of scepticism about the whole climate change issue, even though with a few years hindsight it appears that it was not much more than a storm in a teacup.

At the time of writing, the most recent IPCC report on the physical evidence of climate change was issued in 2013. Along with a vast quantity of scientific data, this included the following among its conclusions:1

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. (p. 4)

The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions… The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification. (p. 11)

Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes… This evidence for human influence has grown since [2007]. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. (p. 17, italics original)

Some years previously, the United States Conference of Catholic Bishops (USCCB) published a report called Global Climate Change which included a short assessment of the scientific evidence as it then stood.  You may wish to look at this.


Optional reading (4pp)

1. Section headed, ‘The Science of Global Climate Change’, in

United States Conference of Catholic Bishops, Global Climate Change: A Plea for Dialogue, Prudence, and the Common Good (2001)

For that section, scroll through most of the document until, after the word ‘Sidebar’, you will see the heading.

2. A website which includes a great deal of reliable and fascinating material about how the debate about global warming and climate change has developed over recent decades is

The Discovery of Climate Change‘.

For one interesting article, see ‘The Public and Climate Change’.




Having looked at some main environmental problems, what is your sense of the strength of the evidence?

What is your reaction to the following statement about climate change?

The IPCC represents a very wide consensus of scientists from all round the world.  So if they think that there is a very high probability that human activities are changing the atmosphere in ways that will heat the planet and change the climate, I had better accept it.  I can’t claim to know enough to challenge their authority.

To what extent do you agree with it?

While this statement is not a quotation (it was formulated for this reflection), it represents the view which the United States Catholic Bishops take in the document just set as optional reading: “As Catholic bishops, we make no independent judgment on the plausibility of ‘global warming.’ Rather, we accept the consensus findings of so many scientists and the conclusions of the Intergovernmental Panel on Climate Change…” (From section headed, ‘Scientific Knowledge and the Virtue of Prudence’)



End of 3.2.6

Go to 3.2.7 Ecological destruction and human poverty


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  1. These quotations come from ‘Summary for Policymakers’, in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge: Cambridge University Press, 2013, accessible (14 Mar. 2014) at http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf