Why projections of climate change keep being wrong?

Terence Winters:

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• Why does the minute 100-parts-per-million (ppm) increase in CO2 have such an impact on warming?  CO2 concentrations in our air have increased over the last century from 0.03% to 0.04%, a rise of about 0.01%, or 100 ppm — that is, one part in 10,000.  It is the impact of this tiny increase that needs to be explained by advocates of human-induced warming.  Over geological time, CO2 has reached atmospheric levels up to about 8,000 ppm, cycling with various geological events.  The current 400 ppm is at the low end of the average over millions of years.
• Why is CO2 currently the cause of warming when there have been cooling and warming cycles before, not related to CO2?
• Why is the minute effect of CO2 significant when the impact of water as a greenhouse gas is about 250 times greater?  CO2 is a greenhouse gas, but, due to its low concentration and potency, its contribution is insignificant compared to water, the major greenhouse gas in our atmosphere.  Adjusting for water's four times greater greenhouse gas potency than CO2 and taking its average concentration in our air as 2.5%, or 25,000 ppm, increases its influence on warming to about 250 times more than the 400-ppm CO2 and about 1,000 times more than the 100-ppm increase in CO2.  Don't the natural fluctuations in water levels swamp the minute contribution of CO2 to warming? 
• Are the models of climate scientists credible when they treat water as a feedback and not as a forcing in their models?  Their rationale is that water forms clouds above the surface of the Earth that have a different effect on warming.  Clouds actually increase warming due to their insulation effect.
• Are we better off with higher CO2 levels since they accelerate plant growth?  CO2 has a vital role as the raw material for the growth of all green plants by photosynthesis, which we depend on for our nutrition and our oxygen.  This acts as a natural regulator of CO2 levels in the air.  Plants grow faster in higher CO2 concentrations, which would help to feed the world, and they also produce more oxygen, which we need to live.  To call CO2 a pollutant is disingenuous.
• Finally, are warnings of the effect of warming on serious weather events and rising sea levels credible?  Data do not support substantial increases in unusual weather events like hurricanes and storms in recent times. Further, warming would probably not significantly raise sea levels.  Water expands about 10% on freezing and shrinks on melting (this is why water pipes burst on freezing/melting), and it expands slightly on warming when liquid.  There will be a rise in sea levels only if most of the melting ice is above sea level and the water warming is much more than a few degrees, an unlikely scenario.  Warming is unlikely to cause the rising sea calamities that are threatened.

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I think most projections of climate change exaggerate the impact of CO2 on the temperature.  That is the reason that predictions of ice-free poles and New York being underwater have not been met.