Answers to some climate change objections
Despite the evidence that has been amassed over recent decades that shows conclusively that man-made climate change is a reality, there are still people who seek to deny that this is so. However, their arguments are specious as will be explained below. Here are six such arguments that are regularly put forward but which cannot be accepted, for the reasons given.
1. Climate change is not caused by humans
It is certainly true that the average temperature of Planet Earth can rise or fall without human intervention, but this is simply not the whole story when it comes to the current rise in global temperature.
There are many factors that must be taken into account when assessing why the temperature is rising, but those that can be deemed “natural” are insufficient to produce the observed rise. There is no logical alternative to the conclusion that human activity must be a major cause.
This activity relates to the action of certain gases in the atmosphere that trap the sun’s rays and cause the land and sea to get warmer. The protective layer of the atmosphere is what makes life on Earth possible at all, because without these “greenhouse gases” the surface would be 30⁰C cooler than it is. However, if the temperature gets too high the consequences could be disastrous for most lifeforms on the planet.
The main greenhouse gases are water vapour, methane and carbon dioxide. Human activity increases the amounts of these gases in the atmosphere, which in turn leads to increased warming. There are no natural processes that could possibly cause these amounts to rise to the levels that are currently observed.
2. Carbon dioxide is not responsible for global warming
It can be shown experimentally that CO₂ (carbon dioxide) is a very efficient molecule in terms of trapping heat, so it has a disproportionate effect on global warming despite being relatively rare in terms of its presence in the atmosphere when compared with other gases.
It is true that water vapour is more significant than carbon dioxide in terms of its direct effect on atmospheric temperature, because it condenses to form clouds that may warm or cool depending on their type and location. However, any warming due to carbon dioxide will lead to increased evaporation and therefore a more humid atmosphere.
Carbon dioxide levels have risen from pre-industrialisation levels of around 280 ppm (parts per million) to 380 ppm, due partly to the burning of fossil fuels but also due to other causes such as deforestation (forests absorb CO₂ that would otherwise remain in the atmosphere).
CO₂ is both directly and indirectly implicated in the increase in global warming noted since mankind starting burning fossil fuels on an industrial scale.
3. The rise in CO₂ levels came after global warming and not before
The reason for this statement is that observed levels of CO₂ in ice cores show that these rose after the onset of the Ice Ages, which were caused by fluctuations in Earth’s orbit around the Sun. From this, it is argued that CO₂ cannot be implicated in causing global warming.
The answer to this is that greenhouse gases are released from both land and oceans as they warm, which they would have done as the Ice Ages reached their end. These gases would then have caused further warming in a form of “positive feedback”.
However, these were purely natural processes that have no relation to what is happening in the modern world of human activity. It can be shown, from chemical analysis, that most of the CO₂ produced in recent years is the result of fossil fuel burning and has not derived from natural sources.
In other words, it is not possible to extrapolate modern conditions from relying on ancient ice core data.
4. The theory is not supported by temperature observations
The reasoning behind this claim is that readings taken during the early 1990s by instruments carried by satellites and weather balloons, of temperatures in the lower atmosphere, did not accord with what was observed at the surface. There was therefore a mismatch between the climate models that were based on the atmospheric data and what was actually experienced at ground level. In other words, the scientists had got it all hopelessly wrong and could not be trusted to tell the truth. From this arose all sorts of accusations about how climate scientists were part of a conspiracy to defraud the world’s population into taking expensive measures to prevent a catastrophe that would never happen.
However, the truth was soon appreciated when it was realised that the data had been wrongly gathered and/or interpreted. There were problems with some of these early measurements caused by, for example, satellites changing their orbit and giving inconsistent readings, and by simple mathematical errors. Once these discrepancies were sorted out, data from these sources has proved to be highly reliable.
It has also been objected that temperatures in the upper atmosphere – the stratosphere – show cooling rather than warming. However, this is due to ozone depletion, which has a knock-on effect on other parts of the atmosphere but which is quite independent of any effect caused by greenhouse gases.
5. The computer models of global warming are unreliable for predicting future climate change
Climate change deniers seem to expect scientists to know exactly what will happen in the future and regard any adjustment in computer models to be an admission that scientists are unable to make accurate forecasts.
However, it has to be appreciated that many factors are at play in terms of climate change, and all a model can do is take these factors on board, based on past and present conditions, and suggest where the trends will take us in future.
Although it is possible to include past data and refine the models as more such data is obtained, there will always be uncertainties in terms of what will happen in future. For example, population growth is a known factor in terms of the past, but what of the future? It is only possible to make assumptions that may not prove to wholly accurate.
A model can only predict the future in terms of “if X and Y happen, then the result will be Z”, but there can be no certainty that X and Y will actually happen.
The important thing about these models is that they can give clear indications of general trends. The degree to which the climate will change in future will depend on the extent to which certain factors come into play, but this uncertainty does not invalidate these trend indications.
6. The negative effects of climate change have been overstated
It is often objected that climate scientists are unduly pessimistic about the effect that a modest rise in global temperatures will have. Even if it is accepted that average global temperatures will rise by 2-3⁰C during the current century, will that really make a heap of difference?
The answer, in short, is – yes, it will. Such a rise is unprecedented during the past 10,000 years, and for it to happen in such a relatively short period of time could have very serious consequences both for people and ecosystems.
There might indeed be some benefits for some parts of the world from temperatures being generally higher, such as increased growing seasons in northern latitudes coupled with the fertilising effect on plants of increased atmospheric carbon dioxide.
However, it would not be long before the negatives started to outweigh the positives. Warmer oceans will generate more severe weather events such as tropical storms, not to mention generally increased rainfall caused by greater evaporation, leading to more incidences of flooding.
Some inhabited parts of the world rely on snowmelt for their water supply, but if the mountains receive their precipitation as liquid rain – which runs off quickly into the sea – as opposed to snow that melts gradually and fills reservoirs, then water supply will be a real problem. This is something that places such as California on the west coast of the United States are already facing.
Rising sea levels, due both to melting icecaps and the overall expansion of ocean water, will have a disproportionate effect on the world’s low-lying countries and islands, many of which are in regions where the population is generally under-developed and therefore least able to adapt.
The negative effects of climate change have not, therefore, been overstated.