I recently heard someone express that idea that the campaign to try to do something about climate change had been let slide too much, and that the banner should be taken up again. That may be dangerous talk, because it might be possible to make things quite unpleasant, and the idea that human activity has caused climate change is not supported by science. I followed the matter of climate change closely in the 1970's and '80's, but during the '90's I let it slide. When I started paying attention again within the past ten years things had changed, and there were many sincere people who had come to believe that human activity was causing global warming. I was inclined to go along, but I could remember a few decades earlier that there were many people who expect that an ice age was about to begin, and their facts looked good, so I decided to look at the facts, and I entered a quagmire.
There are many pieces of interlocking data that have been put together to "show" that human activity was causing climate change, and most of those items were being taken on faith by reporters and most of the people how talked about the matter. I decided that I wanted to know more than was reported in the general press. The general assertion is that carbon dioxide (CO2) that has been produced by humans was acting as a greenhouse gas that was making the world warmer. There are several items that had to be checked. The first one was whether the surface temperatures were rising, and that one may be unanswerable.
People have only been using thermometers and recording temperatures for a few hundred years, and during that period it is pretty clear that the average temperature has risen, but the end of the "Little Ice Age' was in the middle of that period, so one would expect that temperatures would have risen. For evidence of temperatures in earlier times I had to look at secondary evidence.
From history we know that the Romans grew wine grapes in Great Britain when they occupied that island from 59 BCE to about 450 CE, but wine grapes hadn't been successful there since then, until the late 1990’s; the growing season was not long enough. We also know that there was a Norse settlement on Greenland that fed itself from 1000 CE until sometime in the thirteenth century, and that agriculture there has been extremely limited since then. Greenland hasn't has a harvest of barely to ripen for about eight hundred years, but there are hopes. Thus, it would appear that the temperatures are now about what they were two thousand years ago but not up to levels of eight hundred to a thousand years ago. Other secondary evidence from tree rings, etc. has been ambiguous. From this I concluded that global warming is within the same range as in the last few millennia.
I also looked into whether sea level had changed significantly. The evidence there is ambiguous, because there have been subsidence and land rising in many places around the world. On the Mediterranean Sea, where there have been human made docks for thousands of years, the evidence is ambiguous, but the sea level is around the same as it was when Rome ruled the region. It is higher in some places and lower in other. It is clear that sea level was much lower before 5,000 BCE, but since then it has barely moved.
The next thing that I looked at was CO2 as a greenhouse gas. The news reports never go into the details of what greenhouse gas is and why some gasses are and some are not. It turns out that a greenhouse gas is one that will absorb solar energy and either hold it or re-emit it as infrared energy. The characteristic of a greenhouse gas is that it is a molecular dipole, which means that one side of it has a positive charge and the other side has a negative charge. Most gases are not dipoles, except ones that have asymmetrical shapes. Water is quite asymmetrical, and it is a strong dipole. CO2 is perfectly symmetrical, so it is not a dipole, and it emits very little in the infrared part of the spectrum. Then I looked for how the people who claim that human activity is causing global warming got by that. They are claiming that CO2 stays in the atmosphere for a very long time, so its tiny addition to greenhouse effect is magnified by the time factor. That might be a good explanation, if it weren't for the fact that CO2 cycles through the atmosphere within two years, which still doesn't add up for a gas that has a greenhouse effect that is less than one percent of water vapor's.
Then there is the matter of how much CO2 humans put into the atmosphere. The calculations vary but are in the same range, and it happens to be less than the typical year to year variation of CO2, so it is impossible to say whether there actually is any net additive by human activity.
When I got this far I decided that anthropogenic global warming was a hoax. I have no doubt that the Earth has varied in temperature over time, but the Sun is a variable star; its output varies. The Earth's orbit around the Sun also varies, so there is more or less energy from the Sun getting to the Earth. And there probably are other cosmic facets of the earth's travel that vary, so one should expect the earth's surface temperature to vary. But there is no evidence that human activity has altered climate; although agriculture has altered local weather in some places.
Now I have to figure out a way to get the general media to look at the actual evidence on global warming.
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