During the 1970s, the Meteorological Office's numerical models of the global atmospheric circulation began to simulate the main features of the world's climate and its variations and show that the climatic consequence of increasing the carbon dioxide content of the atmosphere was global warming. The Office's previous predictions by simpler models of a general warming much accentuated in polar regions were confirmed, but further study with improved models and a more powerful computer would be required to assess these climatic effects and their likely economic and social impact with real confidence.

The causes and the economic and social consequences of climatic change were debated in the House of Lords on 30 November 1978. The opening speaker, Lord Tanlaw, asked the government whether there was cause for concern in the current increase in atmospheric carbon dioxide and apparent change in global weather patterns. He referred to an article by the Office's Director-General that had been published in Nature (1978, Vol. 276, pp. 327–328). In this, Dr Mason had suggested that a doubling of carbon dioxide would lead to an increase in global temperature of two or three degrees Celsius. Though this was a modest increase, Lord Tanlaw said, it “might well lead to increased food production by prolonging the growing season and, furthermore, produce considerable savings in energy consumption”. There might, though, be “unforeseen disadvantages”, such as adverse effects on agriculture in some parts of the world as a result of changes in rainfall patterns. The melting of glaciers might also cause sea level to rise and thus threaten coastal communities.