by William Kininmonth, News Weekly.

The emergence of the Extinction Rebellion phenomenon over recent months has seen community disruption in many Western cities, heralded by a generally fawning and uncritical media.

The tolerance of Western democracies has made it possible for a few determined protestors to close thoroughfares and, with their extraordinary claims of a global climate and ecological emergency, get broad media coverage.

In their doomsday predictions, the activists confuse real environmental issues with issues that are largely imagined, or an exaggerated extrapolation from recent trends. For example, air pollution is a major contributor to ill health and death, but it will not be eliminated by closing down industry and reducing carbon-dioxide emissions into the atmosphere.

Extinction Rebellion draws on the pronouncements of climate alarmists, such as Professor James Hansen, formerly of NASA, and Professor Han Joachim Schellnhuber of Potsdam Institute, to give weight to their link between carbon-dioxide emissions and a perceived climate emergency.

It is claimed, based on computer model projections of global temperature, that there will be a range of dire impacts. To name a few: melting polar ice sheets and rising sea levels; more droughts and expanded deserts; and ocean acidification leading to a loss of marine life as atmospheric carbon-dioxide concentration rises. The extent and consequence of the possible impacts claimed by Extinction Rebellion seems only limited by the human imagination!

There is no climate emergency and, since the demise of the dinosaurs 65 million years ago, life has evolved, though waxing and waning, with the changing climate.

It is true that the global temperature is today as warm as it has been at any time in the last three million years, but that is no bad thing. Our current bountiful warmth should be viewed in the context of the prevailing cold of earlier times.

For most of the past million years, Earth has been gripped by glacial conditions, interrupted only by a few relatively brief interglacial events such as we are currently experiencing.

As recently as 20,000 years ago, Earth was in a glacial period. Great ice sheets up to two kilometres thick extended over much of North America and northern Europe.

Earth’s ever-changing temperature is recorded in the oxygen isotopes of marine skeletal material laid down in the accumulating sediments of the ocean floor [From Lisiecki and Raymo (2005)].

Sea level was about 130 metres lower. Atmospheric carbon dioxide, fundamental for photosynthesis and life on Earth, had been absorbed by the colder oceans and fallen to a near critically low level of 180 parts per million (ppm). Continuation of life on Earth was really threatened.

By 10,000 years ago, Earth had recovered from the glacial period and global temperatures were very much like the present.

Our historical records inform us that Western civilisation flourished during three energising periods. These were the Greek-Roman period from about 400 BC to about 400 AD, the Medieval Period from about 900 AD to 1400 AD, and the current expansion beginning about 1700 AD. These were all periods of higher temperature with expanded food production.

The domination of the Romans came to an end in AD 420 when Vandals crossed the frozen Rhine River and sacked what is now Cologne. With the onset of a cold interval, agriculture across Europe declined and much land returned to forests.

Declines in agriculture and in rural populations were in evidence across Europe during the 14th century as another period of cold set in; its onset marked the end of the Medieval Warm Period. The demise of Norse settlements in Greenland followed, and frozen rivers across Western Europe again become common throughout much of the 17th century.

The hysteria of the Extinction Rebellion movement arises from an extreme interpretation of the human-caused global-warming hypothesis. Adherence to this hypothesis has gathered since the 1970s as a coterie of scientists harnessed new computing capabilities and attempted to model the complex climate system.

The United Nations, through its Intergovernmental Panel on Climate Change (IPCC), has since 1988 promoted community fear through regular assessments of the change in global temperature since the mid-19th century, together with computer model-based projections.

The dangerous human-caused global-warming hypothesis and the derived computer models are based on a naïve view of the climate system.

The starting point of the hypothesis is that Earth is in radiation equilibrium such that the absorption of radiation from the sun is offset by emission of radiation to space.

Supposedly, as carbon-dioxide concentration in the atmosphere increases (because of human activities, such as burning fossil fuels), more of Earth’s radiation is absorbed, thus warming the atmosphere and reducing the emission of energy to space. The computer models are claimed to simulate these processes and project an expected global warming.

The errors in the dangerous human-caused global-warming hypothesis are twofold. First, nowhere is there local radiation balance. As we learn in school geography lessons, solar absorption exceeds emission to space over the tropics (thus it is hotter) and emission to space exceeds solar absorption over middle and higher latitudes (where it is colder). There is no natural law that requires Earth to be in radiation balance.

Second, the greenhouse gases of the atmosphere (mainly water vapour and carbon dioxide) emit more radiation than they absorb and thus tend to cool the atmosphere. The loss of radiation energy by the greenhouse gases is offset by exchange of heat and latent energy from the land and ocean surfaces. It is necessary to warm the Earth’s surface before the atmosphere will warm.

Climate models are constructed on the false assumption that adding carbon dioxide will warm the atmosphere. Moreover, the models were tuned to the 20th-century global temperature record on the basis that all warming was a result of the additional carbon dioxide in the atmosphere.

Computer model projections of global temperature have consistently exceeded the observed temperatures. This failure points to deficiencies in the models.

The extreme activists of Extinction Rebellion draw on warnings from climate modellers, such as Hansen and Schellnhuber, reporting their climate projections. The view of activists is that the computer model projections are too “conservative”, suggesting they do not account for “likely tipping points”, possibly leading to Venus-like conditions on Earth.

The possibility of a climate tipping point can be dismissed as fantasy. Despite millions of years of heating by the Sun, the warmth of the tropical oceans remains confined to a thin lens that overlays several thousand metres of very cold ocean interior. The small perturbation of radiant energy from changing carbon dioxide is insignificant compared with the energy required to heat the ocean interior.

Extinction Rebellion activists draw on community fears that legitimately arise from damaging climate extremes, including heatwaves, tropical cyclones, flooding rains, and so on, to make a range of claims that blame such extremes and their impacts on human activity. There is little basis in science for such links and they are not supported by evidence.

The potential for ocean acidification takes no account of the observation that the most acidic regions of the ocean surface are where there is upwelling to bring naturally carbon-dioxide rich interior water to the surface.

Droughts are not a manifestation of heat but the natural variability of weather. Weather patterns become locked for seasons and sometimes years, and do give regions either an excess or deficit of rainfall. The El Niño pattern of equatorial Pacific Ocean temperature is a major contributor to Australia’s droughts.

There is a broad link between global temperature and desertification but not the one given by the alarmists. Desertification was much more extensive during the cold of the last glacial event than during the current warmth. Deserts contract as temperature rises because of the increasing rate of evaporation from the oceans, the source of rainfall.

A more realistic view of the climate and its variability, though still simplistic, is constructed around the essential transport of heat by the atmosphere and oceans from the tropics to the polar regions. There are major differences in properties of the oceans and atmosphere.

The mass of the atmosphere is equivalent to the surface 10 metres of the ocean and the heat content of the atmosphere is equivalent to the surface four metres of the ocean. The atmosphere provides a fast response to seasonally changing solar heating, with most of the transport during winter months. The ocean circulations change more slowly but their much greater heat capacity and mass means they are the thermal and inertial flywheels of the climate system and regulate climate.

To conclude on an optimistic note, the observed warming of recent decades has been very beneficial. The main warming (from whatever cause) has been experienced over middle and high latitudes of the northern hemisphere during autumn, winter and spring and with little change in summer temperature.

Over the higher latitudes, spring thaw has commenced earlier, autumn frosts and freezing have occurred later, and there is a longer growing season. The observed recent greening of the planet, an ecological benefit, is readily observed in satellite imagery.

William Kininmonth is a former head of Australia’s National Climate Centre. He is author of Climate Change: A Natural Hazard and contributor to Taxing Air.