Climate Change
Perspectives from a farmer and an environmentalist
IN the 1970s, I was a geography student at Flinders University, learning about cycles of global warming and cooling. In the last 650,000 years, there have been seven cycles of advance and retreat of glaciers, and the last ice age ended only around 7,000 years ago.
Most people will be surprised to know that these climate variations are attributed to very small variations in Earth’s orbit that change the amount of incoming solar energy, and the temperature changes are also quite small.
In the last glaciation, the coldest parts of the earth were only about six degrees Celsius lower than today.
In the 1970s I was also attending organic conferences where one of the major themes was the need for soil remineralisation to stave off the coming ice age.
One of the major protagonists of the predicted ice age was John Hamaker, and a review of organic literature of that decade reveals many references to his ‘rock dust’ strategy.
Hamaker was heavily influenced by books such as Bread from Stones by Julius Hensel and studies of the longevity of the Hunza tribe and others who lived in glaciated areas, where soils were enriched by minerals ground up by encroaching glaciers.
I was drawn to ‘prescription’ fertilisers based upon soil testing rather than generalised spreading of ‘rock dusts’, which didn’t earn me many brownie points with some of my organic colleagues.
But Hamaker’s concept of a cooling world was consistent with the science I was learning about in my studies.
Then something significant happened. Slowly at first, and then with increasing frequency, I started to come across
papers that warned of global warming (the term was first used by Dr Wallace Broeker in 1975).
Predictions in the popular press
In the 1980s, despite my concerns, I used my TAFE Horticulture lecturer position to convene a conference on ‘remineralisation’, although my own contribution was to advocate soil testing and prescription fertilisers.
Some of the contributions to that conference appeared as the main feature in the very first Acres Australia, in the spring of 1988. By that time, however, predictions of global warming had escaped the academic literature and were appearing in the popular press.
The next decade saw intense argument about whether the world was cooling and warming. The conventional wisdom that we were approaching something like the 40th ice age in the 4.5 billion year history of the world was challenged by evidence of warming. Even more controversially, we heard that human activity was responsible.
Understandably, many people found this notion hard to accept. Prior to that era, we tended to believe that the great geological cycles of change were unassailable by human action and we were still treating the atmosphere and the oceans as the great garbage cans of the earth, seemingly able to endlessly accept our rubbish, including carbon emissions, with complete impunity.
Evidence continues to build
Another decade further on, as we entered the new millennium, something changed again. Evidence that we were entering a new period of cooling completely disappeared; something had reversed the eon-long geological cycle.
Evidence of warming continued to build, not just from measurement of temperature, but also from observed effects. Evidence that the change is due to human burning of fossil fuels and the destruction of forests, resulting in increased carbon dioxide (CO2) concentration in the atmosphere, also continued to build.
The issue intensified in many ways, it became a significant part of the political debate and the term global warming gradually gave way to another concept, ‘Climate Change’, and there arose a global response, including the formation of the International Panel on Climate Change (IPCC).
Some doubters started to get more press and encouraged common disbelief that the climate could be so dramatically sensitive to small perturbations, especially on a short timescale.
Some of the seemingly contrary evidence raised by the doubters was responsible for the change in terminology from ‘warming’ to ‘change’, and it is useful to explore why this happened.
At the same time that we were accumulating an impressive list of warmest days, months or years in the climate record, we also encountered apparently contradictory evidence with coldest winters, long freezes and significant storms.
Doubters made good use of this contrary evidence, but we should be very cautious before accepting that occasional record-breaking cold spells are in fact contradictory.
Natural and biological systems try to maintain homeostasis, or a balanced ‘norm’, but when they change, it always results in a period of perturbation, before settling on a new norm.
This is the case with every measurement we can make. Take for instance blood sugar levels in your body. It is not possible to move from one level immediately to a new level. There is a period of ‘wobble’ where blood sugar may go up, and the body tries to rectify the change, so it may go down again, in a repeating pattern, before stabilising again around a new normal.
Think about what is happening to our planetary climate system as the concentration of so-called ‘greenhouse’ gases in the atmosphere change. These gases include carbon dioxide, which is now at the highest level for 55 million years, but also methane and nitrous oxide (which are less abundant than CO2, but more effective at creating the greenhouse effect).
Record temperatures
They are called greenhouse gases because they work in the same way as your glass or poly greenhouse. They permit the incoming long-wave radiation from the sun to enter the atmosphere, but they trap the reflected (short wave) radiation, preventing it from leaving the atmosphere. With the same amount of energy coming in, but less energy able to leave the system, the extra heat has to be distributed around the globe.
The rocks that make up the land are slow to heat, and so is water of the oceans. This results in a greater differential between the hottest and coldest parts of the globe. The heat needs to be redistributed, therefore one of the effects of global warming is more chaotic atmospheric circulation and more damaging winds and hurricanes.
This effect is compounded by water vapour (H2O is the most effective ‘greenhouse’ component of the atmosphere, and the water-holding capacity of warm air is greater, leading to a compounding effect). One of the results of this redistribution can be significant ‘wobble’ in wind and water currents which is capable of producing record cool temperatures in certain locations as well as warming, as the great global systems attempt to stabilise again.
As time goes by, so more evidence of these effects is collected, including more evidence that the fundamental underlying change is the amount of carbon dioxide and
other greenhouse gases that humans have released into the atmosphere, caused by burning fossil fuels, land clearing and adoption of modern industrial agriculture.
Agriculture effects come from land use change (loss and fragmentation of tree cover), ploughing and fertiliser use destroying soil carbon and releasing nitrous oxide, and more concentrated livestock management increasing methane production.
Is there room for doubt?
Scepticism is an important aspect of how science should work. It refers to doubt about the truth of claims, and in philosophy, it refers to a claim that it is ultimately impossible to have complete and certain knowledge about anything.
Scientists are always sceptics because they believe that all claims require evidence, and very few things are ‘certain beyond doubt’.
Evidence of warming itself is now unequivocal, based upon hundreds of thousands of measurements all over the globe, on land, seas and all levels of the atmosphere.
Of course, there remains some doubt about how much warming will occur and the resilience of natural systems to adapt or be overwhelmed, causing more floods, droughts, wildfire and loss of biodiversity.
Scientific institutions such as the IPCC publish the confidence values of their predictions, and it is very high, and 97-98 per cent of climate scientists support their predictions. In a simple analogy of whether we should believe in predictions, if 97 per cent of arborists suggested that a tree had a 95 per cent chance of losing a limb, would you pitch your tent under that tree?
Climate change deniers
Unfortunately, some ‘climate change deniers’ have hijacked reasonable scepticism. Their position is better described as denialism or contrarianism. It has more to do with the wholesale rejection of ideas, whether scientifically valid or not, in favour of opinion.
Sadly, some of the main climate change deniers, when subjected to scientific scepticism, turn out to be paid agents of the coal industry.
Some of them are the same so-called scientists that were engaged by the tobacco industry to fudge evidence that smoking is bad for your health.
Some evidence of climate change
Land surface temperatures are much higher (0.9 degrees C since the mid-nineteenth century), mainly in the last 35 years. Nine out of the ten hottest years occurred in the last decade (global and Australian) and maximum temperatures for specific locations continue to be broken.
Because of delayed response times to carbon already released into the atmosphere, it is predicted that we cannot avoid a temperature increase of 1.5 degrees. If we do nothing, temperatures will continue to rise four degrees or more, with catastrophic effects.
Sea surface temperatures (in the top 700 metres) are the warmest since records began in about 1850 (about 0.4C), and the last decade is the warmest (more than 90 per cent of increased heat from global warming is going into the oceans).
Air temperatures over the oceans and in the troposphere (measured by satellites for 50 years) have steadily risen in the last four decades and the last decade showed a greater rate of increase.
Permafrost (frozen land, especially in Siberia) is melting, releasing more greenhouse gas from organic matter stuck in the frost. Ice is shrinking across the globe. Greenland has lost nearly 300 billion tons (US) since 1993, the Antarctic ice mass is reducing, and glaciers are receding in Europe, the Himalayas, the Andes and Africa, sea ice is retreating, and the thickness of Arctic sea ice has been reducing for three to four decades (35 per cent since 1979).
There is decreasing snow cover and snowmelt is occurring earlier. Sea levels are rising as a result of increased temperatures and melting of ice and the rate of increase is accelerating.
There are more extreme weather events including frequency and intensity of floods, intense rainfall and hurricanes.
Oceans are acidifying (30 per cent increase in surface layers) as a result of two billion tonnes per annum of extra carbon absorbed into the seas, challenging the ability of shellfish to make shells.
There are increased measurements of ‘phenomenological’ effects, example: warm water fish species are migrating further down the east coast of Australia; some are even found around Tasmania.
• Next issue: How should we respond to climate change: amelioration and adaptation?