Recent temperature rises have been caused by solar activity, not increases in CO2. Fact: Solar radiation reaching the Earth (known as insolation) can only result in minor temperature changes. The sun’s energy fluctuates on an 11-year cycle. It only changes by about 0.1 percent each cycle, so its impact is very small. Scientists estimate that solar activity has contributed about 0.1°C to temperature increases since 1870. For the last three decades solar activity has actually been decreasing, yet the planet isn’t cooling. If CO2 levels had no impact on global temperatures, as climate sceptics claim, then you would expect this not to be the case. What is actually happening is that the impact of CO2 emissions is overwhelming any cooling effect from decreased insolation. Of course, when solar activity starts to increase again, it will exacerbate the impact of greenhouse gas emissions. Another important factor is that if solar activity were causing recent temperature increases, the atmosphere would warm uniformly. In fact, the upper atmosphere (above 20 kms) is cooling, while the lower atmosphere is warming. This is not consistent with solar activity. It is consistent with increases in CO2, however. In addition, if solar activity were the cause of recent warming, summers would be warming more than winters, and days more than nights. In actuality, neither of these things is happening. Hence, all the evidence suggests that CO2 is the cause of the warming we are currently experiencing. Graph showing the disconnect between solar activity and global temperatures over the past half century. [Source: Sceptical Science
Myth: We don’t know what temperatures were like in the past
We can’t possibly know what temperatures were like centuries ago, let alone millions of years ago. They might actually have been hotter during the Medieval Warm Period (900-1150 AD) than now, so we can’t say the Earth is heating up unnaturally. Fact: Scientists use ‘proxies’ to calculate past temperatures. These include tree rings, ice cores, coral sediments and sea levels. [The study of past climates is called paleoclimatology.] The data produced by these proxies is not perfectly accurate but does provide a good picture of the past. That data suggests that the Medieval Warm Period was not warmer than today, although temperatures may have been this warm in parts of the northern hemisphere. [Interestingly, climate sceptics are happy to use evidence from proxies when they confirm their views, but not when they contradict them.] For more detail on the Medieval Warm Period, see the previous two myths.
Myth: The Medieval Warm Period was warmer than today
The Medieval Warm Period (MWP) was warmer than today, as evidenced by the fact that the Vikings were able to cross the north Atlantic and settle in Iceland and Greenland due to the reduced ice cover. This is proof that global temperature changes are natural, and that current warming is nothing to worry about. Fact: The MWP (900-1150 AD) was not warmer than today, although in northern Europe and the North Atlantic temperatures were similar to today’s. In some parts of the world, however, temperatures actually got colder during the MWP. Scientists estimate that on average, global temperatures were similar to those in the mid-20th century. Interestingly, sea levels then were nowhere near as high as they are today. (They rose by 24 cm over a period of 400 years but never got to 20th century levels.) If we only look at the natural factors that generated the MWP (changes in solar and volcanic activity, changes in oceanic currents and small changes in the Earth’s orbit), there should have been global cooling over the past 50 years, not warming. Yet we are experiencing the opposite. The current warming trend is unprecedented – 1.2°C in just over a century. We have not seen such rapid warming in the past two million years, and maybe not for 55 million years. During thaws from ice ages, it took between 1,000 and 2,000 years for the atmosphere to warm by 1°C. It should also be noted that while the MWP improved living conditions in places like Greenland, it devastated regions like the southwest of the United States, which experienced severe and prolonged droughts. Communities in the latter regions were forced to move, while the Vikings were forced to abandon Greenland when the MWP ended. [Had the Vikings discarded their European farming practices and adopted the Inuit lifestyle, they would not have had to leave Greenland.] A final point of interest is that Iceland was settled before the Medieval Warm period began – evidence that reduced ice cover was not the reason the Vikings were able to cross the North Atlantic.
Myth: Temperature changes are natural
Changes in global temperature are natural. They happen in cycles, and the current warming is no different. The Earth has passed though countless ice ages and thaws. More recently we have seen the Medieval Warm Period (900-1150 AD) and the Little Ice Age (1450-1850 AD), both of which occurred without any significant CO2 emissions by humans. Fact: Large temperature changes are natural over many millennia (ice ages and thaws), as are small changes over many centuries. We know what causes these changes, and those factors do not apply at present. The current level of warming is unprecedented – 1.2°C in a century and 0.65°C in the past 30 years! During a thaw from an ice age, it takes between 1,000 and 2,000 years for the atmosphere to warm by 1.0°C. This means the Earth is currently warming at 33 times the natural rate. There is absolutely nothing natural about this! As far as the Medieval Warm Period and the Little Ice Age are concerned, they involved significant temperature changes in northern Europe and the Atlantic, but not in other parts of the planet. Scientists estimate that the average global temperature changed by between 0.2°C and 0.6°C from the height of the Medieval Warm Period to the lowest point of the Little Ice Age. During the latter period, winters in Europe were colder than today, but summers were not significantly so. There is little evidence of a widespread breakdown of food production. It should also be noted that the Little Ice Age was not actually an ice age, or anything like it. Many climate sceptics are obsessed with it simply because of its name. They seem to think that because it’s been dubbed an ‘ice age’, it actually was one. The temperature variance between the Medieval Warm Period and the Little Ice Age [Source: Wikimedia Commons]
Myth: Governments are not taking climate change seriously
If global warming really were a problem, governments would be taking it more seriously. The fact that they are not suggests that there is nothing to worry about. Fact: This myth is based on the idea that governments always act rationally and in the best interests of society. Were that the case, the Second World War would never have happened, as the British and French governments would have recognised Hitler as a threat and put an end to his ambitions before they got out of hand. Instead, they believed what they wanted to believe, which was that the Hitler had only limited objectives and was not a threat to world peace. This was strange, given that he had never made a secret of his intentions. [They were published in Mein Kampf in 1925, fourteen years before the start of the war.] Another problem is that politicians often do realise that action is needed but would rather postpone it until a later time – preferably when they are no longer in office. A good analogy would be with smokers. Most know that cigarettes are bad for them, and that it would be better if they quit, but they cannot bring themselves to do it just yet. The benefits they gain now by continuing their habit are greater than the dangers they may face in the future. Besides, they tell themselves, that danger may never eventuate. After all, doesn’t everyone know someone who spent a lifetime smoking and lived into old age? And isn’t a cure for cancer just around the corner? Finally, it should be pointed out that in recent years, governments have been taking climate change more seriously and have begun introducing policies to combat it. This is particularly so in Europe, the United States and China.
Myth: Climate scientists are only in it for the money
Scientists are propagating the notions of climate change and global warming just to make money and become famous. Fact: This myth is simply ridiculous. If anyone could prove definitively that global warming was not happening or was not a problem, he or she would become the most famous and decorated scientist since Einstein. Scientists become famous by overturning paradigms, not by reinforcing them. Besides, if you want to make a lot of money, you don’t go into science as a profession.
Myth: Carbon saturation will stop any further global warming
The Earth’s atmosphere is becoming ‘carbon-saturated’, meaning that as the level of CO2 increases, its impact on global temperature will decrease. (In mathematics, this is known as the ‘logarithmic effect’.) As a result, we can happily go on emitting CO2 without causing significant increases in temperature. Fact: This view has been propounded by two of the most famous sceptics in the scientific community – Professor William van Wijngaarden and Professor William Happer. They claim that a doubling of CO2 levels from 400 ppm to 800 ppm will only increase global temperatures by 1°C. [We are currently at 427 ppm, up from 270 ppm prior to the industrial revolution.] To get an additional 1°C warming, CO2 would have to increase to 1,600 ppm, according to Wijngaarden and Happer. It would be nice to believe that the Earth has a built-in stabiliser to save us from catastrophic climate change. However, the science doesn’t bear that out. Although it is true that the warming impact of CO2 decreases as its prevalence in the atmosphere increases, this effect is nowhere near as strong as Wijngaarden and Happer claim. The main reason for this is that as the concentration of CO2 increases, there is a corresponding reduction in the capacity of the Earth’s carbon sinks (mainly its forests and oceans) to absorb CO2. This means that more of our emissions finish up in the atmosphere than would otherwise have been the case. Another reason is that higher concentrations of CO2 result in feedback effects that increase global temperature. These include a reduction in snow and ice cover (which reduce albedo) and the melting of permafrost (which increases CO2 and methane emissions). So no, ‘carbon saturation’ will not save us from ourselves. Professor William Happer [Wikimedia Commons]
Myth: The emails hacked in 2009 discredited climate science
In 2009, a series of emails between two prominent climate scientists were hacked. These showed a conspiracy on the part of the pair to fudge the climate data. This completely discredited climate science. Fact: The hacked emails didn’t discredit anything. Climate sceptics totally misrepresented what the scientists were discussing in those emails. They were talking about the so-called ‘divergence problem’, which was a minor issue in climate science. [It referred to the relationship between temperature and the width of tree rings in Arctic regions. That relationship changed after 1960, and at the time the emails were written scientists did not fully understand the reason why. The problem has now been largely resolved.] In one of the hacked emails, Professor Phil Jones (Director of the Climatic Research Unit at the University of East Anglia) said that he had come up with a ‘trick’ to reconcile an aspect of the divergence problem. Climate sceptics used this as evidence that Professor Jones and his fellow correspondent (Professor Michael Mann) were perpetrating fraud. Nothing could be further from the truth. In science, a ‘trick’ is jargon for a solution, not a falsehood. Professor Jones was proposing a solution to an aspect of the divergence problem. His words were taken completely out of context. Professor Michael Mann [Source: Professor Michael Mann]
Myth: We should not act until scientists all agree
We should hold off acting on climate change until every single climate scientist accepts that climate change is real and that human activity is the cause. Fact: The fact that 99.9 percent of climate scientists accept the reality of climate change and that greenhouse gas emissions are the cause suggests that the scientific debate is now over. As for the 0.1 percent who still do not accept the scientific consensus, that is not uncommon in science. For example, after Copernicus, Darwin and Einstein published their theories, there was a lot of scientific resistance. More recently, there are still researchers who don’t accept the link between cigarettes and cancer (many of them working for tobacco companies, it should be noted). But that does not mean we should abandon efforts to discourage smoking. Think of it in terms of aviation. If 99 engineers declared that a plane was unsafe, and one said the opposite, how many people would still make the flight? Probably none. Another analogy relates to insurance. Statistics show that the chance of a house burning down in a particular year is about 1 in 3,000 – i.e. extremely small. Yet most people still insist on having home insurance, even though it is far from cheap. The reason is that they are unwilling to put their major asset at risk, however small that risk might be. Yet some of the very same people will take enormous risks when it comes to the security of their celestial home – the Earth. It doesn’t make sense.
Myth: Some scientists still reject the climate consensus
The fact that some scientists still reject the so-called ‘climate consensus’ shows that there is still debate on the issue. Fact: There is no longer any debate over the reality of global warming. All the prominent sceptics in the scientific community have now accepted that the Earth really is heating up, despite having spent most of their academic careers arguing the opposite. Those sceptics include Patrick Michaels, Robert Balling, John Christy, Steven Koonin, Richard Lindzen, Roy Spencer, William Happer and William van Wijngaarden. Instead of challenging the temperature record, they are now claiming that greenhouse gases are either not primarily responsible for the observed warming or that the warming itself will be benign. Steven Koonin, for example, claims that it is impossible to determine the respective contribution of CO2 emissions and other factors (like solar activity) due to “the deficiencies of climate data”; hence, he says, we would be better off adapting to climate change rather than trying to stop it. Roy Spencer blames the observed warming on “natural factors” like the Pacific Decadal Oscillation, although he provides no evidence for this. He seems genuinely surprised and confused about the fact that his earlier predictions turned out to be wrong. John Christy, by contrast, does attribute most of our current warming to CO2, but does not believe future temperature rises will be hazardous. Patrick Michaels agrees, despite estimating that those temperature rises will be as much as 3°C by 2100. Finally, William Happer believes that increased CO2 levels will be good for the world. In 2014, he famously said that the “demonization of carbon dioxide is just like the demonization of the poor Jews under Hitler.” So, while there is consensus among 99.9 percent of the world’s climate scientists, there is no consensus whatever among the other 0.1 percent. All they can agree on now is that global temperatures really are on the rise.