Snot catches some of the 50 million particles inhaled with every breath. These particles are one hundredth the size of a human hair and comprise mineral dust, industrial and traffic dust, microorganisms and extraterrestrial particles. Some 40,000 tonnes of extraterrestrial dust falls to Earth each year and, if you are really lucky, your snot may contain a particle that came from the asteroid belt between Jupiter and Mars. Check it out in the privacy of your home and give snot the scientific respect it deserves.

Every now and then, our planet passes through a cometary cloud (e.g. 730-740 AD) which produces cold times because dust reflects light and heat and hundreds of years of cold times follow if this coincides with a weak sun and explosive volcanism (735-737 AD). This happened in the Dark Ages (400-900 AD).

Most desertification occurs during periods of glaciation when winds are stronger, rainfall is lower and vegetation is sparse. There is a good geological record of sand dunes, salt lakes and dust storms during long periods of aridity. A mate of mine who used to live in my Broken Hill house opened all doors and windows when billowing clouds of fine red dust approached on the assumption that the dust would blow right through the house. It didn’t. My place never passed the white glove test but at least it was clean dust from inland Australia. The normal rain after a dust storm covered cars in a desert-red patina.

Red bed copper deposits formed in mid-latitude glacial wind-blown sand dune sediments because of changes in groundwater chemistry, sea level and sedimentation. The major deposits formed in snowball earth times 650 million years ago (e.g. Copperbelt of Central Africa), when Gondwana drifted over the South Pole (e.g. Kupferschiefer of Europe) and the modern ice age (e.g. salt pans in Texas and Saudi). If we want electric cars, then ironically an understanding of ancient climate is one of the tools used to find the copper needed for the cars.

Explosive volcanic eruptions add huge amounts of dust to the atmosphere. Most of these volcanoes are in the circum-Pacific and Mediterranean-trans Asiatic belts. The dust, incorrectly called ash, comprises minute sharp needles of glass from lava supercooled by the instantaneous release of expanding gas when supercritical water flashes to steam. Breathing volcanic dust near an explosive eruption cuts lung tissue, reduces lung capacity and lungs can be lithified. Humans drown in their own blood which fills the cut lungs.

Volcanic dust rises 25 to 60 km into the atmosphere, does a few laps high in the atmosphere as it falls to earth and creates lightning storms, spectacular sunsets and heavy rain by nucleating droplets. Combined with La Niña, this was the reason for heavy rains in eastern Australia after the Hunga Tonga eruption of 15th January 2022. Notwithstanding, the normal suspects brayed that the heavy rain and flooding were due to climate change and how it was all the Prime Minister’s fault.

Hunga Tonga was a small submarine eruption. Previous past large terrestrial eruptions such as Tambora in 1815 led to years of cooling and 1816 was a year without a summer. The 1783-1784 eruption of Iceland’s Laki covered Europe with dust and choking toxic sulphurous fumes – thousands died from respiratory problems, torrential rainfall and cooling destroyed crops and famine followed. Empire-changing eruptions such as the Minoan eruption of Santorini about 1600 BC are recorded in ice drill cores. The Indonesian supervolcano Toba erupted some 72,000 years ago covering much of the planet with thick volcanic dust which is still preserved in India and Alaska. The tropics were devegetated and soils were removed by torrential rainfall, the surviving population migrated north and south, the orbital-driven cooling cycle of the planet accelerated and sea level rapidly dropped.

Airborne dust is precipitated in restricted lakes where there is neither turbulence nor a massive input of sediments, in deep ocean sediments where there are no strong currents and in polar ice. Dust shows us that there are cycles of climate unrelated to human activity. At times the atmosphere has a higher dust content due to impacting, dusty comet tails, desertification, drought, overgrazing, industry and volcanism. Pollen, spores and charred fragments in dust layers show the history of forest fires and evolution of plants. The chemistry of dust and acid layers in polar ice can be used to show when and where an explosive volcano occurred. Iron-rich dust from deserts stimulates carbon dioxide-consuming algal blooms in oceans.

Closed-minded climate activists claim that every natural event is due to climate change and that human emissions of carbon dioxide are to blame. The joy of integrated interdisciplinary science with all of its exciting uncertainties and detective work should be used to stimulate young people rather than trying to fill their minds with guilt, fear, hopelessness, depression and ignorance.