Dear All,
The evidence for global warming is basically the following. You can disagree on individual data sources or the validity of various models, but the following points are well established and are not controversial in any way:
i) The presence of greenhouse gases like water vapour and carbon dioxide in the atmosphere indisputably raises average global temperatures.
ii) In the past there has been a significant degree of correlation between atmospheric greenhouse gas concentrations and average temperatures/climate patterns.
iii) Recently there has been both an unnaturally fast climb in average temperature, and an unnaturally fast climb in atmospheric greenhouse gas concentrations. The correlation between these rises is similar in degree to many historical events.
iv) An unnaturally fast climb in atmospheric greenhouse gas concentrations would cause undesirable effects like increased frequency of natural disasters, rising sea levels, habitat loss, loss of diversity, food production losses and reduced fresh water availability. Most climate models suggest these effects will become severe within the average lifetime and will last for a long time.
Therefore: human activity (large increases in greenhouse gas output mainly due to the use of non-renewable hydrocarbon fuels) is causing average temperatures to rise unnaturally fast.
Therefore: to avoid this change in the climate and thereby avoid the effects in iv), humans need to reduce their emissions of greenhouse gases.
