Hypothetical global warming: scepticism needed

We are constantly told that man-made carbon dioxide has caused global warming that will bring doom and disaster in a few years.

These predictions are largely based on the output of computer models, rather than observations of what is happening in the real world. Always remember the parental advice: "Believe nothing of what you hear and half of what you see". One should always be sceptical and, in science, nothing is more important.

READ MORE: Human role in climate change is clear

Here are 10 reasons why the public should be cautious of the hypothesis that man-made carbon dioxide causes dangerous global warming.

1) The five internationally accepted temperature records - three surface and two satellite - show that the world has not experienced any significant warning over the last 18 years even though atmospheric carbon dioxide increased by 10 per cent.

Claims that 2014 was the warmest year don't mention that the increase in temperature was a minuscule 0.02 degrees and the more accurate satellite records show that it was not the warmest year. Of the Intergovernmental Panel on Climate Change's (IPCC) 114 climate model runs 111 failed to predict this lack of warming. In most branches of science, when the theoretical predictions do not line up with the observations, the hypothesis is abandoned.

In climate science, the observations are discounted or ignored. We can now be confident that man-made carbon dioxide does not cause dangerous global warming and that the predictions of computer models of the climate are worthless.

2) Global sea ice area is well above the 1979-2013 average. In the Arctic it is close to average extent and in the Antarctic it is at the highest level since 1979. Once again, there is a large disparity between the computer based predictions of ever increasing loss of sea ice and reality.

3) Sea levels are rising steadily at between 1 and 3 millimetres a year as they have done for the last 100 years. According to satellite measurements it rose at 4.1mm a year from 1996 to 2006 but only 2.75mm a year from 2006 to 2014. In New Zealand, tectonic movements have a far greater influence on sea levels.

4) Polar bear populations have increased from about 5000 to 25,000 since hunting was restricted in 1970. A population that can recover that quickly in spite of 700 a year still being hunted can hardly be threatened. Various experts claim that the population is now increasing, steady, or decreasing. Take your pick.

5) Coral atolls are not disappearing beneath rising oceans. The highly accurate tide gauge at Tuvalu shows that sea level rise is minimal. Tuvalu certainly does have problems, but they are not caused by rapidly rising sea levels. About 15,000 years ago sea levels were rising at 3 metres a century and coral atolls and the Great Barrier reef survived this rapid rise thus proving that they can cope with rapid sea level rise.

6) Glaciers are retreating in some areas and advancing in others but we do know that 5000 years ago the European Alps had less ice than now and the Canadian tree line lay further north. It has all happened before.

7) Historical records show that the world was warmer during the Middle Ages Warm Period. This is supported by many peer-reviewed papers and recent records from fossil giant clams in the Pacific Ocean. Warming in the Bronze, Roman and Middle Ages Warm periods led to prosperity and progress.

8) Ocean "acidification" is supposed to be a dire threat to marine life. In fact, the ocean is alkaline and is at no more risk of becoming acidic than you would get from putting a teaspoonful of sulphuric acid into a bucket of caustic soda. Recent analysis indicates that the ocean has become more alkaline since 1910 and that there are quite large fluctuations in the short term.

9) Plants cannot grow without carbon dioxide and the increased levels of carbon dioxide have boosted plant growth worldwide by 11 per cent without the need for additional water. The agricultural benefit to the world is valued at trillions of dollars. Modern greenhouses burn natural gas to double the carbon dioxide concentration and hence increase production by 40 per cent.

10) Droughts, floods and cyclones are often claimed to have increased because of global warming. But an IPCC study shows that the frequency of droughts has hardly changed and cyclones have declined.

What can we expect in the future? The only honest answer is that nobody knows. The British Meteorological Office has predicted that the current lack of warming will continue until 2018 at least.

Scientists who study natural climate cycles and the effect of the sun and sunspot cycles on the climate believe that there is a high probability that the world has - or soon will - enter a cooling cycle. If this happens and history repeats itself, we will be faced with famine, disease and war. Most mainstream climate scientists agree that 2 degrees C extra of warming would not be harmful, so let us hope that temperatures stay constant - which is most unlikely - or warm enough to get us back into the situation during the Middle Ages Warm Period. The obvious conclusion is that the science is not settled. As Dr Pachauri, chairman of the IPCC, stated in a recent interview, open debate is needed.

Professor Bob Carter is an honorary fellow of the Royal Society of New Zealand. His expertise is in geology and palaeoclimatology - deducing past climates from geological records. He has written several books on climate change.

Bryan Leyland is an engineer specialising in renewable energy. He is an accredited reviewer for the IPCC and has contributed several articles on renewable energy technologies to overseas publications.

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