10 reasons for being cautious about global warming

Global warming: 10 reasons to be sceptical

By Bryan Leyland and Professor Bob Carter

We are constantly told that man-made carbon dioxide has caused global warming that, in a few years, will bring doom and disaster. These predictions are largely based on the output of computer models, rather than observation of what is happening in the real world. My father always told me: “believe nothing of what you hear and half of what you see”. It was good advice. One should always be sceptical and, in science, nothing is more important.


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. At the same time atmospheric carbon dioxide increased by 10%.

111 of the IPCCs 114 climate model runs 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 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 increasing loss of sea ice and reality.(2)


3.      Sea levels are rising steadily at between 1 and 3 mm per year as they have done for the last 100 years. According to[ satellite measurements it rose at 4.1 mm per year from 1996 to 2006 but only 2.75 mm per 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 per year still being killed by hunting 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 due to rapidly rising sea levels.

15,000 years ago sea levels were rising at 3 m per 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 and 2000 years ago the Alps had less ice than now and the Canadian tree line lay further north 5000 years ago. 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. It has all happened before.


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. It has all happened before.


9.      Plants cannot grow without carbon dioxide and the increased levels of carbon dioxide have boosted plant growth worldwide by 11%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%.


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 present 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° of warming would not be harmful so let us hope that temperatures stay constant – which is most unlikely – or warm sufficiently 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.


The media needs to start encouraging intelligent, evidence-based debate between all those with an interest in current and future climate trends.


Prof Bob Carter is a marine geologist and an honorary Fellow of the Royal Society of New Zealand.

Bryan Leyland is an engineer specialising in renewable energy and hydropower and with an interest in climate change.