PROFESSOR IAN R. PLIMER: Climate always changes. Evidence of past climate changes are all around us. It has for 4,567 million years. Ice on Earth is rare. Planet Earth has been warmer and wetter than at present >80 per cent of time. Not one past climate change was driven by carbon dioxide even though atmospheric carbon dioxide was far higher than now for most of time. Climate cycles are of galactic (143 my), orbital (100,000, ~41,000 and ~21,000 yr), solar (1,500, 210, 87, 22 and 11 yr), oceanic decadal (~30 yr) and lunar tidal (~18.6 yr) origin. Sporadic climate changes are caused by supervolcanoes, supernoval eruptions and the pulling apart and stitching back together of continents. Since the earliest times in the Solar System, Earth has been degassing carbon dioxide from igneous activity and metamorphism, before, during and after volcanic eruptions from gas vents, hot springs and craters. The same occurs today on the Moon and the rocky planets.
Over the last 2,500 million years, atmospheric carbon dioxide has decreased from ~30 per cent to 0.039 per cent. The decrease in CO2 results from the long-term biota-assisted sequestration into carbonate rocks and altered rocks. In former times of high atmospheric carbon dioxide oceans were not acid, there was no runaway greenhouse and the rate of change of temperature, sea level and ice waxing and waning was no different from the present. Doubling or quadrupling of carbon dioxide in the past has had very little effect on temperature. To argue that temperature and sea level are increasing depends on when measurements first started. Since 1842, it has been known that coral atolls rise with rising sea level. Coastal planning based on ‘global sea level rise’ ignores compaction, sedimentation and tectonism because not only does sea level rise and fall but the land level also rises and falls hence to talk about sea level rise without referring to land level change is misleading. Some areas in inland Australia are currently sinking (e.g. Lakes Eyre and Frome) whereas other areas are rising (e.g. Flinders Ranges, Barrier Ranges, and the east coast of Australia).
The six major ice ages over the history of time were all initiated when atmospheric carbon dioxide was higher than now. During ice ages, there are glaciations and interglacials (such as now) when ice waxes and wanes. Carbon dioxide increases follow temperature rises by 800-2,000 years during deglaciation. Temperature increases (1860-1880, 1910-1940, 1977-1998) and the rate of these three temperature rises is the same, hence no human signal has been measured. Furthermore, temperature has been decreasing (1890-1910, 1940-1977 and 1998-present) when carbon dioxide has been increasing, hence without a correlation of temperature with carbon dioxide increase, there can be no causation. Much of outback Australia was settled in warm wet times (1860-1880) and the cool dry windy times (1880-1910) led to heartbreak, depopulation and a financial depression. The ongoing Milankovitch, solar and PDO cycles will lead to another glaciation as part of the present ice age that started 34 million years ago.
Humans have adapted to live on ice, in mountains, in the desert, in the tropics and at sea level and can adapt to future changes. During very slight warmings which could not possibly related to human emissions of carbon dioxide (e.g. Minoan, Roman and Medieval Warmings), humans have created wealth and populations grew. Cooler times (e.g. Dark Ages, Little Ice Age) are heralded by famine, starvation, disease and depopulation. During the last glaciation in the current ice age, there have been alternating periods of cool, dry, windy weather when sand dunes formed and warmer, wetter weather when inland lakes (now salt lakes) formed. Humans, although not the dominant biomass of Earth, have changed the surface of the planet. Pollution kills, carbon dioxide is plant food, water vapour is the main greenhouse gas and, because climate models can not be run backwards to show what has happened, it is unlikely that climate models can throw no new light on climate processes and the future. At present, 97 per cent of annual carbon dioxide emissions are natural and it has yet to be shown that the 3 per cent of human emissions change climate.
*Professor Ian R. Plimer, School of Earth and Environmental Sciences, The University of Adelaide
What affects us most is a change that occurs within our lifetime; next-most, a change that occurs in a few lifetimes. After that, any change that occurs faster than living creatures can adapt to it - say, a timescale of a few centuries. Anything beyond a million years has nothing to do with us - we didn't live under those conditions.
And what is the timescale of Anthropogenic Global Warming? A century or two.
And what is the rate of change in CO2? Far, far, faster than any other time in the last million years.
This animated chart from NOAA (America's equivalent of BoM with a bit of CSIRO thrown in) shows both the timescale and the size of the change. There are no captions, so you may need to watch it a couple of times to work out what is going on, but it summarises a lot of information.
Here it is: http://www.esrl.noaa.gov/gmd/ccgg/trends/history.html
Congrats