Thank you for all those who have contributed. I’ve read all the comments and have tried to take account of what everyone is saying. Comments have ranged from “broadly agree” to “there is no sceptic view” to “the whole theory is wrong”. Where comments indicate a consensus to change I’ve tried to address these with amendments. I have tried not to exclude any less well supported view but the focus has to be on those that seem to have the most support here and in the general discussion on places like WUWT.
The Sceptic View (revision 0.5)
Sceptics value diversity of views and there are many strands. As one contributor said:
Climate scepticism isn’t necessarily about what we agree upon, it’s based upon how many questions go unanswered. More, it’s about how many lies that have been told, whether directly or by omission. The greatest liberator of mankind so far – fossil fuel – has been tried, found guilty and condemned without ever being allowed to publicly mount a defence. (TinyCO2 )
Many have passionate views based on the evidence:
As far as I’m concerned I see absolutely no unambiguous empirical evidence that CO2 has any discernible effect on climate whatsoever. It may possibly have an influence but I’m damned if I see it anywhere. (cerberus)
Although there is no single sceptic view, most** sceptics broadly agree with the following:
- Carbon Dioxide (CO2) has been increasing. In 1960 it was 0.032% of the atmosphere, today it is 0.039%.
- There has very probably been warming of average global temperatures in the last 150 years.
- There is a greenhouse effect and CO2 is a greenhouse gas. The best scientific estimate of this effect (for doubling CO2) is about 1C warming.
- People think there are mechanisms that could increase warming further than the direct effect of CO2. This is not supported by the evidence.
- Current estimates of about 0.8 C temperature rise in the past 150 years are very likely too high. There is compelling evidence of malpractice, urban heating and poor instruments & siting. A figure of 0.5-0.6C warming appears more likely.
- Man-made sources have increased global levels of CO2, however scientific analysis shows part of the increase is natural and no one is certain how much or little of this rise is man-made.
- Water in the atmosphere is far more important than CO2 in determining global temperature.
- The harmful effects of warming have been exaggerated as shown e.g. by the absence of substantial evidence for increasing weather extremes.
- Known benefits have been hidden. It is estimated there are more than 20,000 extra winter deaths each year in the UK and increasing fuel costs will make this worse. CO2 is essential for plant growth and increasing levels are beneficial to plants.
- Even under the worst case scenario warming, when the usual method of comparing the cost and benefit of policy is used, it is more cost effective to deal with any problems that occur than to pay to try to stop them.
- Climate proxies are not reliable. If we consider all the evidence including historical records, the evidence suggests the world was warmer during the “medieval warm period” as well as being cooler during the “little ice age”.
- Climate varies naturally. Most of the CO2 rise occurred in the latter half of the 20th century. If this change were man-made the global temperature change for the early and latter 20th century should be very different. They are not. This suggests a natural cause for much of the 20th century warming.
- In 2001 the IPCC stated with a high degree of confidence that global temperature would warm. It has not. In science a theory is not valid unless the data supports it. Climate scientists must accept this theory is not validated and acknowledge that the IPCC confidence in warming was greatly overstated.
- We condemn the many instances of malpractice seen in climate science and those who condone them.
**We encourage debate based on scientific evidence. We particularly abhor any dismissal of potentially good science based on the preconceived prejudice that has dominated climate science and prevented debate. Those who did not agree with the above seemed to do so for the following reasons:
- Some sceptics reject any interpretation of the data beyond a minimal assertion of the facts.
- Others question the validity of isolated surface stations as representing a global temperature.
- A vocal group of sceptics look to other planets as a model of the earth’s climate and argue that the temperatures seen on these planet contradict the theory on which greenhouse warming is based. We think such ideas and theories deserve consideration and require effort to substantiate or refute them based on the evidence.
Revision 0.5 notes on changes
- In response to those saying there is no single view, I’ve moved up the comments about diversity and valuing different views to the top with an explicit statement that there is no single sceptic view. I’ve also added some quotes which seemed to sum up the posts.
- I’ve tried to briefly summarise the views of those who disagree. I think it is important they are represented, just as the average also needs the standard deviation.
- I’ve changed the paras:
There is a greenhouse effect, and CO2 is a greenhouse gas.Increasing CO2 alone should cause warming of about 1C for a doubling of CO2.into one:There is a greenhouse effect and CO2 is a greenhouse gas. The best scientific estimate of this effect (for doubling CO2) is about 1C warming.
- The para:“There has very probably been warming of average global temperatures (about 0.8 C in the past 150 years).”
Has been changed to:“There has very probably been warming of average global temperatures in the last 150 years.”And a new para has been added:“Current estimates of about 0.8 C temperature rise in the past 150 years are very likely too high. There is compelling evidence of malpractice, urban heating and poor instruments & siting. A figure of 0.5-0.6C warming appears more likely.”We had a discussion on this on WUWT (which I cannot find!!) where the consensus was around 0.5-0.6C from memory!! I felt if we said “the 0.8 figure is wrong”, I had to give a sense of what kind of warming we felt could be realistic.
- I’ve added this para:Water in the atmosphere is far more important than CO2 in determining global temperature.This after reading the blog of GlobalWarmingDenier, looking for a short succinct summary of his position. It was also mentioned by others.
- This para changed as indicated:Climate proxies are not reliable. If we consider all the evidence including historical records, the evidence
shows climate has always varied and itsuggests the world was warmer during the “medieval warm period” ( and before 5,000BC)as well as being cooler during the “little ice age”.Note climate varies in next para.
- Other minor changes like a smelling mistake.