Dave Degan predicts that, “the tide of climate meltdown will wait for no one” (Back climate protesters, Letters. July 19).

READ MORE: Letter: Back climate protesters

But ice ages support another point of view. Since carbon dioxide levels rise AFTER the earth starts to warm and fall AFTER the earth starts to cool, CO2 cannot be the sole ‘cause’ of global warming. Ice ages grow gradually colder for tens of thousands of years, then suddenly warm up again in the space of a few thousand years when the world enters a warmer interlude - such as the one we have been enjoying for 10,000 years. What can have induced the sudden warming?

In 2016 a fascinating paper based on the growth rate of plants and satellite data was published. It reported a roughly 14 per cent increase in green vegetation over 30 years and attributed 70% of the increase to the extra carbon dioxide in the atmosphere! The lead author on the study, Zaichun Zhu, says this is equivalent to adding a new continent of green vegetation twice the size of the mainland United States. Global greening has affected all ecosystems – from arctic tundra to tropical rain forests – but shows up most strongly in arid places like the Sahel region of Africa where desertification has largely now reversed. This is because plants lose less water in the process of absorbing carbon dioxide when the concentration of the trace gas is higher. This greening means more food for all life-forms, from insects to elephants. The effect has added about $3 trillion to farm incomes over the last 30 years. So less land is needed to feed the human population and more can be spared for wildlife instead. Global greening is happening faster than climate change. The brilliant Swedish physical chemist, Nobel laureate Svante Arrhenius (1859-1927), who first measured the greenhouse effect, suggested that the human emission of CO2 would prevent the world from entering a new ice age.

Average global temperature has dropped by almost half a degree Celsius since the Super El-Niño three years ago. Although global temperatures have been rising slowly for the last thirty years, since the start of this century the warming trend has been slowing rather than accelerating. And this is in complete contrast to the predictions of almost all climate models. Meanwhile, the IPCC Special Report on Global Warming has concluded that neither the number nor the intensity of drought, floods, forest fires or hurricanes has increased in the past 30 years.

‘Doom scenarios’ empower governments, create corporate cronies chasing tax-funded subsidies and distort the market-place. When state-funded scientists say, we want you to change society, we need to employ scientific scepticism - even if they have abandoned it. Aiming to decarbonise everything to net zero by 2050 would cost tens of billions a year without the hoped for effect. And anyway, countries like China and India have declared that they will not be cutting their fossil-fuel powered advance any time soon; they will not destroy their economies to save the planet. So far, no one has been prepared to put a figure on the level of climate sensitivity.

Meanwhile, outgoing PM Theresa May together with outgoing German Chancellor Angela Merkel, beleaguered French President Macron (whose working and middle classes have been rioting about his hike in fuel taxes since last November), mystic environmentalist Prince Charles, keen royalist David Attenborough and lots of obscurely funded supra-national organisations are certain that the apocalypse is nigh - if independent nation-states do not immediately agree to a permanent one-world-government and abolish annoying democratic accountability.

Prof. Christine Wheeler McNulty

Oxhey