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•• Types of Skeptics
Deniers
• Paid corporate PR stooges. They will respond to newspapers etc.
• Head in the sand type
Skeptics
• Can come from any walk of life and can be intelligent, educated.
• Mostly do not know or understand the scientific process.
• Have been convinced by the often equal time in the media given to climate change deniers compared to those proposing that climate change is happening. This gives the impression that there is significant doubt within the scientific literature that human induced climate change is happening.
•• The Arguments
Prove to me climate change is happening. You can't because there is no proof?
This argument is based on a lack of understanding of the scientific process, you only have theories, not proofs. In science you can never prove a theory or law but you can disprove. A theories can become laws if the confidence in the theory becomes good enough. But you can still disprove a scientific law in the same way you disprove a theory. You devise a repeatable experiment whose results conflict with the predictions of the theory or law. Sometimes the theory is not discarded but is instead modified to take into account the new data.
Like anything in science we cannot prove that human induced climate change is happening and the best we can do is increase our confidence that it is happening or demonstrate that it is not happening. By now all but a few of the world's climate scientists and meteorologists have become confident enough that to put it in layman's terms they believe human induced climate change is happening, it is serious and reductions in greenhouse gas emissions are essential to minimize the dangerous effects of climate change.
How can a gas like Carbon dioxide (CO2) which makes up such a small fraction of the Earth's atmosphere (around 0.04%) have such a big impact on the Earth's temperature?
Even at this percentage the number of molecules of CO2 in one litre of the atmosphere is still so many that the numbers are impossible to grasp. One litre of the atmosphere at sea level contains approximately 1000000000000000000 molecules of CO2. The Earth emits infra-red radiation over a large range of energies. Carbon dioxide absorbs infra-red radiation over some of the range of energies that the Earth emits, but not all. The Earth emits infra-red radiation because it is warm. Without any greenhouse gases this radiation would escape directly to space. Instead this radiation is absorbed by greenhouse gas molecules and then re-emitted in any direction including straight back to Earth. Other re-emitted radiation will be absorbed by other greenhouse gas molecules and the more greenhouse gas molecules there are the more absorption and re-emission occurs. For the Earth's surface temperature to remain constant the net radiation emitted by the Earth's surface must equal the amount of radiation received from the sun, when this is the case the Earth's surface is in thermal equilibrium. When the levels of carbon dioxide and other greenhouse gases are increased the amount of radiation escaping is reduced and warming occurs until the surface returns to thermal equilibrium at a new higher surface temperature.
Surely the sun which is the source of all warmth on Earth must be the cause of any climate variability. Why don't the climatologists include the effects of the sun in their modelling?
The effects of the variations in the incoming solar radiation (insolation) are fully taken into account in the computer simulations of the climate. It is just that during the second half of the 20th century there has been very little change in insolation and that it is necessary to include the effects of the increase in greenhouse gas concentrations to explain the temperature rise during this time. You can see a plot of the variation in insolation and temperature here.
Scientists told us during the 1970's that we were heading for a new ice age. How many times do they think they can cry wolf to get research funding before we ignore them?
There were some scientists during the 1970s who thought that a new ice age was possible. There was nothing like the current scientific consensus on the issue but it proved to be an exciting story for the media. The reason for the belief that an ice age was coming was because the geological evidence of the timing of past ice ages and interglacials suggested that the current interglacial would soon be coming to an end. Scientists were also aware that the emissions of aerosols like sulphur dioxide from coal fired power stations increased the amount of reflected sunlight. But even at this time other scientists were concerned that warming due to the emissions of carbon dioxide would dominate over the combination of possible natural cooling and aerosol emissions.
If any climate scientist had a proposal for a research project based on decent science that would significantly damage the case for human induced climate change and it was rejected then I am sure the media and political storm that would happen would be huge. I am sure all of us who believe climate change is happening would welcome quality peer-reviewed research that could demonstrate that anthropogenic climate change is not happening. Instead we get fanciful ideas like cosmic rays, cherry picking of data, and even changing data to give different conclusions. Why don't they go and do some real research, I'm sure they could get funding if they had a decent research proposal instead of using the tactics of the tobacco lobby.
Why do we still listen to the climate scientist James Hansen when testimony to the US Congress by Patrick Michaels in 1998 demonstrated that his predictions of future climate change in 1988 were so wrong?
Because Patrick Michaels removed two of the three predictions that James Hansen had made in 1988 leaving only the worst case scenario. The scenario which James Hansen in 1988 described as the most plausible was one of the scenarios removed. Michaels then went on to discuss how Hansen got it wrong and should be ignored. Hansen's most plausible prediction in 1988 has proved to be a good prediction to this point in time. Hansen who is a NASA employee is required by NASA to only do interviews with a NASA PR person by his side. Michaels managed to discredit for a time the reputation of one of the world's most respected climate scientists. See reports of NASA interference with Hansen interviews here , here, and here.
Water vapour is a much more potent greenhouse gas than carbon dioxide. Why don't the climatologists include the effects of water vapour in their modelling??
Water vapour is a more potent greenhouse gas than carbon dioxide and its effects are fully included in the computer simulations of the climate. Water vapour however behaves as a feedback effect rather than a driver. For example if we removed all of the carbon dioxide from the atmosphere but kept all the water vapour in the atmosphere the world would cool by 6 degrees. But an atmosphere 6 degrees cooler could not hold anything like the same amount of water vapour and the atmosphere would lose water vapour in the form of rain and snow and this reduction in water vapour would drop by the temperature by another 12 degrees. The amount of water vapour in the atmosphere very quickly reaches equilibrium via evaporation and precipitation.
The increase in carbon dioxide is a result of increasing temperatures and not because of human emissions. The increase in the level of carbon dioxide in the paleoclimatological record always follows the temperature rise rather than preceeds it. Increasing carbon dioxide levels in the atmosphere are caused by the world getting warmer not the other way round?
The uncertainties in the correlation between the changes in temperature during the ice ages and the changes in the level of carbon dioxide in the atmosphere are too high to be of real significance either way, it is impossible to say from the record exactly when the carbon dioxide starts rising compared to when temperatures start to rise. It is likely that the the main driver of the ice ages temperature cycle is not carbon dioxide but most probably variation in insolation (Milankovitch cycles). But whether the change in the level of carbon dioxide behaves as a feedback effect or is just an effect of the temperature change cannot be demonstrated from this record. The variation in incoming solar radiation as proposed by the Milankovitch cycle is not enough by itself to explain the full temperature change so a feedback is required. We know the absorbtion behaviour of infra-red radiation by greenhouse gases in the atmosphere and from this we can calculate the impact on temperature and it seems reasonable that the increase in greenhouse gases is the required feedback and not just an effect. The timing of the temperature record versus the timing of the variation in concentrations of greenhouse gases does not clearly demonstrate whether the variation in greenhouse gases is a feedback or an effect. The data is not good enough to add to the evidence either way. It certainly does not disprove that increasing concentrations of greenhouse gases results in global warming. The scale
Human emissions of carbon dioxide are tiny compared to the amount of carbon dioxide in the natural carbon cycle. Surely any increase in carbon dioxide is due to rising temperatures and not human emissions?
The natural carbon cycle involves the transfer of carbon dioxide between the plants, the soil, the oceans and the atmosphere. Around 120 Gigatons of carbon dioxide (GtC) move in and out of the atmosphere each year. Human emissions of carbon dioxide are around 7 GtC of carbon dioxide per year (2006) of which about 3GtC remains in the atmosphere and the rest is absorbed by plants and the oceans. The 3 GtC of carbon dioxide added to the atmosphere every year is equal to the increase in the concentration of carbon dioxide in the atmosphere -- i.e. the entire increase in concentration is due to the extra carbon dioxide produced by human activities. The natural systems are soaking up more than 50% of the carbon dioxide that we emit, demonstrating that the increase in carbon dioxide is due to human emissions not natural causes. This may not last for much longer and that as global temperatures increase it is likely that emission of greenhouse gases from natural sources will increase, for example the rate of decomposition of plant matter in soils will increase releasing more carbon dioxide, or an increase in the emissions of methane from peat that was formerly locked up in the perma-frost. When these feedback effects get going we will be in the realm of runaway climate change.
