Sulphate from volcanoes can have a catastrophic effect, but water vapour is far more important. Water vapour (0.4% overall by volume in air, but 1 – 4 % near the surface) is the most effective green house blanket followed by methane (0.0001745%). The third ranking gas is CO2 (0.0383%), and it does not correlate well with global warming or cooling either; in fact, CO2 in the atmosphere trails warming which is clear natural evidence for its well-studied inverse solubility in water: CO2 dissolves rapidly in cold water and bubbles rapidly out of warm water. The equilibrium in seawater is very high; making seawater a great ’sink’; CO2 is 34 times more soluble in water than air is soluble in water.
CO2 has been rising and Earth and her oceans have been warming. However, the correlation trails. Correlation, moreover, is not causation. The causation is under scientific review, however, and while the radiation from the sun varies only in the fourth decimal place, the magnetism is awesome.
“Using a box of air in a Copenhagen lab, physicists traced the growth of clusters of molecules of the kind that build cloud condensation nuclei. These are specks of sulphuric acid on which cloud droplets form. High-energy particles driven through the laboratory ceiling by exploded stars far away in the Galaxy – the cosmic rays – liberate electrons in the air, which help the molecular clusters to form much faster than climate scientists have modeled in the atmosphere. That may explain the link between cosmic rays, cloudiness and climate change.”

The change in cloud cover is only a small percentage, and the ultimate cause of the solar magnetic cycle may be cyclicity in the Sun-Jupiter centre of gravity. We await more on that.
Although the post 60s warming period appears to be over, it has allowed the principal green house gas, water vapour, to kick in with more humidity, clouds, rain and snow depending on where you live to provide the negative feedback that scientists use to explain the existence of complex life on Earth for 550 million years. Ancient sedimentary rocks and paleontological evidence indicate the planet has had abundant liquid water over the entire span. The planet heats and cools naturally and our gasses are the thermostat. Nothing unusual is going on except for the Orwellian politics.

As a geologist I am very comfortable with the multiple working hypothesis - I would like someone to start publicizing the other ideas out there. Here is mine. The Danes have been on the case for a long while, studying the sun; who would have thought? The first paper to get is Friis-Christensen and Lassen (Science; 1991) If you can find the entire issue in the reference library, you will see the editors comment referred to this paper as hitting the ball into the anthropogenic court. George Monbiot debunked Friis -Christensen and Lassen (1991) in a Guardian article a few years ago wherein Monbiot stated the results BACKWARDS. I cannot find that article on the Guardian website.
An important correlation between warming and cooling is the sunspot peak frequency, not the actual number of spots. However, correlation is not causation. Cosmic radiation, however, is currently at its highest ever measured. This is happening because the earth’s magnetic shield is down; therefore, climate is changing (and it always will). The climate celebrities, however, are linking climate and the economy. We can likely kick much of the carbon economy sometime late the twenty-first century, but we must not rush to judgement for the wrong reason. Yes, there has been warming to end the Ice Age. Climate is a chaotic system; the facts, however, do not support CO2 as a serious ‘pollutant’. In fact, it is plant fertilizer and seriously important to all life on the planet. It is the red herring used to unwind our economy. That issue makes the science relevant.