Many people say:
“The scale of the negative effects of climate change is often overstated and there is no need for urgent action.”
Under one of its mid range estimates, the Inter Governmental Panel on Climate Change (IPCC) – the world’s leading authority on climate change – has projected a global average temperature increase this century of two to three degrees centigrade. This would mean that the earth will experience a larger climate change than it has experienced for at least 10,000 years. The impact and pace of this change would be difficult for many people and the ecosystems to adapt to.
However, the IPCC has pointed out that as climate change progresses it is likely that negative effects wold begin to dominate almost everywhere. Increasing temperatures are likely, for example to increase the frequency and severity of weather events such as heatwaves, storms and flooding.
Furthermore there are real concerns that, in the longterm, rising levels of greenhouse gases in the atmosphere could set in motion large scale and potentially abrupt changes in our planet’s natural systems and some of these could be irreversible. Increasing temperatures could, for example, lead to the melting of large ice sheets with major consequences for low lying areas throughout the world.
And the impact of climate change will fall disproportionately upon developing countries and the poor – those who could can least afford to adapt. Thus a changing climate will exacerbate inequalities in, for example, health and access to adequate food and water.
“The climate is actually affected by cosmic rays.”
Cosmic rays are fast moving particles which come from space, and release electric charge in the atmosphere. Any effect that cosmic rays could have on the climate is not yet very well understood, but if there is one, it is likely to be small.
Experiments done in a laboratory hint that cosmic rays could play a role in the development of tiny particles that could in turn play a part in the formation of clouds. If this happens in the same way in the atmosphere – which isn’t proven – it might lead to more clouds, which generally have a cooling effect by reflecting the sun’s rays back into space. Whether the whole chain of processes actually occurs in the atmosphere is speculative, but some of the individual steps are plausible.
It has been proposed that this process would act to enhance the influences of the sun on the climate. We know that when the sun is more active it’s magnetic field is stronger and this deflects cosmic rays away from the earth. So the argument is that a more active sun would lead to fewer cosmic rays reaching the earth, resulting in fewer clouds and therefore a warmer earth.
However, observations of clouds and galactic cosmic rays show that, at most, the possible link between cosmic rays and clouds only produces a small effect. Even if cosmic rays were shown to have a more substantial impact, the level of solar activity has changed to little over the last few decades the process could not explain the recent rises in temperature that we have seen.
Below are two further responses.
What people argue:
“Carbon dioxide only makes up a small part of the atmosphere and so cannot be responsible for global warming.”
What the science says
Carbon dioxide only makes up a small amount of the atmosphere but even in tiny concentrations it has a large influence on our climate.
The properties of greenhouse gases such as carbon dioxide mean that they strongly absorb heat-a fact that can easily be demonstrated in a simple laboratory experiment. While there are larger concentrations of other gases in the atmosphere, such as nitrogen, because they do not have these heat trapping qualities they have no effect on warming the climate whatsoever.
Water vapour is the most significant greenhouse gas. It occurs naturally although global warming caused by human activity will indirectly affect how much is in the atmosphere through, for example, increased evaporation from oceans and rivers. This will, in turn, cause either cooling or warming depending on what form the water vapour occurs in, such as different types of clouds or increased humidity.
Humans have been adding to the effect of water vapour and other naturally occurring greenhouse gases by pumping greenhouse gases such as carbon dioxide into the atmosphere through, for example, the burning of fossil fuels and deforestation. Before industrialisation carbon dioxide made up about 280 parts per million of the atmosphere. Today, due to human influence it is about 385ppm. Even these tiny amounts have resulted in an increase in global temperatures of 0.74c.
What people argue:
“Rises in the levels of carbon dioxide in the atmosphere are the result of increased temperatures, not the other way round.”
What the science says
It is true that the fluctuations in temperatures that caused the ice ages were initiated by changes in the Earth’s orbit around the Sun which, in turn, drove changes in levels of carbon dioxide in the atmosphere. This is backed up by data from the ice cores which show that rises in temperature came first, and then were followed by rises in levels of carbon dioxide up to several hundred years later. The reasons for this, although not yet fully understood, are partly because the oceans emit carbon dioxide as they heat up and absorb it when they cool down and also because soil releases greenhouse gases as it warms up. These increased levels of greenhouse gases in the atmosphere then further enhance warming, creating a ‘positive feedback’.
In contrast to this natural process, we know that the recent steep increase in the level of carbon dioxide-some 30% in the last 100 years- is not the result of natural factors. This is because, by chemical analysis, we can tell that the majority of this carbon dioxide has come from the burning of fossil fuels. And, as set out in ‘misleading argument 1’, carbon dioxide from human sources is almost certainly responsible for most of the warming over the last 50 years. There is much evidence that backs up this explanation and none that conflicts with it.