Climate change was affecting Earth long before there were humans around to call it climate change and it will probably still be affecting the Earth long after humans are gone. It is only fairly recently in recorded human history that climate change has been recognized. The Vikings who settled Iceland and Greenland and even established a brief foothold in Newfoundland near the end of the first millenium did not know they were benefiting from a preceding warm spell that was starting to cool. Their descendants who starved in place or abandoned their colonies several hundred years later also did not know they were the victims of climate change in a cooling now called the Little Ice Age and it took several hundred years more before the idea that climate might vary started to enter into human knowledge. Now the warnings of CLIMATE CHANGE are ubiquitous as are the exhortations TO DO SOMETHING ABOUT IT. But when did it all start...human knowledge of climate change that is...what is causing climate change and can something be done about it?
Probably the first Climate Scientist, although this title was not used, was William Herschel around 1801 when he documented a connection between sunspot activity and wheat prices going back a couple of centuries. He speculated that changes in the sun's output with different levels of sunspot activity caused temperature differences affecting wheat yields: He was ridiculed. However, neither the wheat price/sunspot activity correlation nor additional observations that the coldest period in recorded history, the Little Ice Age, also coincided with an extended period of low sun spot activity known as the Maunder Minimum could be ridiculed away. But finding a convincing mechanism that could cause the global climate to change with sunspot activity was difficult; solar output does change with sunspot activity but by an amount that is so small it was not credible that it could cause a temperature swing on the earth of a maybe degree Celsius.
So climate change was observed but not recognised; in particular the biggest climate changes of all, Ice Ages in which vast areas of the world were glaciated had not even been conceived of. It was not until around 1837 that Louis Agassiz postulated that in the not too distant past, geologically speaking, vast icefields had covered Northern Europe. Agassiz was lucker than Herschel, he was not ridiculed, and the idea of significant climate change arose, however there were complications. Once the evidence for ice ages was recognised it became clear that they had occurred on a regular cycle going back millions of years. This presented a problem because the known variation in solar output was (supposedly) too small to realistically account for even little ice ages never mind the real thing. It was almost a hundred years before a mathematician proposed that cyclic changes in the Earth's orbital path, which varied its distance from the sun matching the glacial cycles, were responsible for the ice ages. These 'Milankovich cycles' are the best explanation currently available for Ice Ages.
But the problem of smaller shorter changes still existed; what causes them? Through the early to a bit past mid 20th century THE EARTH WAS COOLING! Then things changed and it seemed to be getting warmer and suddenly a CULPRIT WAS IDENTIFIED. Various gases or vapors in the Earth's atmosphere act to retain heat energy; the so called greenhouse effect. The most significant is water vapor H2O, the next carbon dioxide CO2 and the third methane CH4; of these three both CO2 and CH4 were increasing at the same time as global temperatures were increasing. OBVIOUSLY the cause of global warming was the increasing level of CO2, oh... and CH4 and these are produced by human activity; to paraphrase Pogo 'the culprit is us'. The complication that H2O is a much more significant greenhouse gas than either of the others was glossed over. Water is too difficult to deal with because if it is a vapor it is a green house gas but water droplets, when they are above a certain size, form clouds which can act like a sun shade and cause cooling. So ignore the water, ignore clouds, make nice simple climate models that show temperature rising in synchrony with CO2 levels and THE PROBLEM IS IDENTIFIED. Actually it is more a case of nice complicated climate models so nobody can figure out what you did so of course they cannot pick things apart.
But the sun is still there, still getting sunspots and interestingly enough for the last three or four decades has been very active sunspotwise; much more active than in the first half of the 20th century and throughout recorded history high sun spot activity has always correlated with higher global temperature. However, the direct change in solar output due to sunspot activity was simply not large enough to account for the temperature changes but in recent years other avenues of investigation have opened up. High sunspot activity increases the solar wind, the flow of charged particles emitted by the sun past the earth, causing enhanced aurora, sometimes power outages in northern latitudes and damage to communication satellites. And also interacting with another flow of charged particles that strike the earth and that are know as cosmic rays. Cosmic rays are very high energy particles and occasionally interact with other atoms transmuting them into unstable isotopes. Two such isotopes are Carbon 14 of carbon dating fame and Beryllium 10 of very little fame at all: Except to the scientists looking at ice cores and tree rings, dating them, doing analyses for Beryllium 10 and finding that back through history when sunspot activity was high beryllium 10 was low. And as an aside showing that sunspot activity does not always follow a nice regular cycle and shows variation over and above the long recognized 11 year cycle; with one of the periods of variation apparently being the past four or so decades.
So the climate story over the past three or four decades has been increasing temperature, the exact amount of the increase being debated and re-adjusted but still an increase, with rising CO2 levels the only accepted mechanism. While above everyones' heads the sun's enhanced sunspot activity, which in the historic record has always correlated with increasing temperature IN THE ABSENCE OF INCREASING CO2, this time is not responsible at all. The reduced cosmic ray flux is not causing a reduction in high level atmospheric haze or cloud because it it impossible to prove that cosmic rays, when present, cause clouds.
So the surreal conclusion is that a cause, human generated CO2, that did not exist during earlier periods of global warming is now the only cause of the current global warming, while a mechanism that did cause earlier periods of global warming, even though it may not be fully understood, now does not exist. This would make me just shake my head except that sunspot activity can go down. When it goes down temperatures will stabilize or fall slightly; past experience predicts that. If the envirofreaks and their tame politicians do push through MEASURES AGAINST GLOBAL WARMING they will take the credit!!!
P.S. I deliberately did not provide links. There are plenty of words to put into Google if someone wants to dig deeper.