The only constant... is change.
True.
That's true about life. And it's true about the climate. The climate has been constantly changing since the earth was formed 4.6 billion years ago.
For example, in just the past 2000 years, we have seen the Roman Warm Period, when it was warmer than today...Then came the cooler Dark Ages... Followed by the Medieval Warm period, when it was at least as warm as today... Then we had the Little Ice Age -- that drove the Vikings out of Greenland. And, most recently, a gradual 300-year warming to the present day. That's a lot of changes. And, of course, not one of them was caused by humans.
Also all mostly true, right up until that little bit at the end... One of them was caused by humans. The warming that we have been experiencing since 1850.
During the past 400,000 years there have been four major periods of glaciation -- meaning that vast sheets of ice covered a good part of the globe -- interrupted by brief interglacial periods. We are in one of those periods right now. This is all part of the Pleistocene Ice Age which began in earnest two and a half million years ago. It's still going on, which means that we are still living in an ice age. That's the reason there's so much ice at the poles. Thirty million years ago the earth had no ice on it at all.
Yes the cycle of glacial advance and retreat happens over very long time periods. But we are well out of the Pleistocene, we were in the Holocene, which was the interglacial period which followed the Pleistocene and started roughly 11,700 years ago. However, we are now actually in the Anthropocene, which is an epoch defined by humanity's impact on it. We are living in the era in which us, humans, are the most significant actor on all planetary systems.
So, then, what about carbon dioxide, the great villain of the Global Warming alarmists? Where does that fit in to this picture? Not as neatly as you might think.
Temperatures and carbon dioxide levels do not show a strong correlation. In fact, over very long time spans -- periods of hundreds of millions of years -- they are often completely out of sync with each other.
No. The very concept of global warming was proposed in 1896 by Svante Arrhenius after he noted that carbon dioxide played a very significant role in climatic warming. This theory was proved in the 1940's when infared spectroscopy was invented and showed there was a direct correlation between CO2 (and other greenhouse gases) and the amount of heat that is trapped by the atmosphere.
This fact isn't even disputed by other climate denialists...
Over and over again, within virtually any time frame, we find the climate changing -- for reasons we do not fully understand. But we do know there are many more factors in play than simply the concentration of CO2 in the atmosphere -- factors such as the shape and size of the earth's elliptical orbit around the sun, activity from the sun, and the amount of wobble or tilt in the earth's axis, among many others. Even the relatively short 300-year period from the peak of the Little Ice Age to the present has not been steady. The latest trend has been a warming one, but it began nearly a century before there were significant carbon dioxide emissions from burning fossil fuels. And, there has been no significant warming trend in the 21st century. Contrary to media headlines, the trend over the past couple of decades has been essentially flat.
The climate changes for a whole host of reasons yes. We have a pretty good idea of what changed the climate over very long time periods in the past, as you say, changes in sun output, amount of absorption of CO2 and other gases by vegetation and the oceans, the earth is a dynamic system and there are so many feedback loops that send it one way or another for a multitude of reasons. But the warming trend seen in this century has been the fastest and most rapid rise of temperature at any time in the history we have observed. Not only is it unobserved in the last 900,000 years we have records for but the correlation is almost exactly mirrored by the amount of CO2 which we have been dumping into the atmosphere.
Humans are the main cause. This is undisputed by over 97% of the scientific community.
Do your research my man
