Most of the last 500,000 years have seen Earth gripped by snow and ice, with short warm periods of about 10,000 years long every 100,000 years. We live in this continuing glacial era but are lucky to exist in one of the regular short warm periods.
There is nothing at all unusual about the current warm period, except maybe that it is the period during which modern human civilisation developed.
Within our warm era, we live in a time that is not unusual either – there have been periods warmer and cooler than today, with no real evidence that mankind has caused global warming (apart from minor urban heat bubbles around mega cities).
There is evidence of a correlation between sunspots and Earth temperature, as well as suggested mechanisms to explain this link. The sun clearly has an effect on Earth temperature, and the evidence tends to suggest we could expect global cooling in the near future.
Even within historical times, the Central England Temperature Record, which goes back to 1659, shows a general rising trend since the depths of the Little Ice age, rising to a peak with the solar cycles, and now signalling a falling trend.
Statistics on human usage of carbon fuels show that it is the undeveloped world not the developed world where usage is rising most sharply. Even in emissions per head of population, it is countries like China where the significant growth is occurring. Carbon taxes and targets are costly and futile.
However when we look at how carbon dioxide affects global temperature, the effect is so small as to be insignificant. It is the behaviour of the sun we should be watching.
Ed Hoskins has looked at all of the above factors in a short but revealing essay.
To read more see:http://carbon-sense.com/wp-content/uploads/2013/12/hoskins-global-warming-climate-change.pdf [PDF, 1.8MB]
Alley, R.B 2000 The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19: pp 213-226.