It's unfortunate that some climate realists will not accept some, or all, of the most basic climate science that follows:
20,000 years ago, Canada was covered by ice. The ice had melted by about 10,000 years ago. From 100% natural causes of climate change.
The climate from 9,000 to 5,000 years ago was believed to be slightly warmer than today, with a much lower CO2 level. The period was called the Holocene Climate Optimum.
Since then, the climate has varied, but not very much.
Some centuries were warmer, and other were colder.
The coldest period was the 1690s. during a period of low solar energy called the Maunder Minimum (a minimum of sunspots).
Since then, the average temperature has been increasing.
To a level that people living in the cold 1690s would have loved.
Starting in the late 1800's. there have been new manmade causes of global warming added to the natural causes that have changed the climate for 4.5 billion years.
It is impossible to know the percentage of climate change with manmade causes, usually called AGW. My list of likely causes of climate change follows. It is impossible to know the exact effect of each cause.
Unfortunately, a political organization called the IPCC was set up by the UN to "prove" climate change was manmade and dangerous. They started by declaring that all natural causes of climate change were "noise" -- too small to matter. They started with an arbitrary conclusion. That's not science.
Not only does the IPCC promote AGW, but they also predict AGW will be rapid and dangerous (CAGW). This prediction has been wrong since 1988, but it never stops.
CAGW actually has been predicted since the 1970s, before the IPCC existed.
CAGW does not exist -- it is only a prediction.
What does exist is a greenhouse effect that impedes Earth's ability to cool itself.
The greenhouse effect has become stronger since 1975, caused by more water vapor and CO2 in the atmosphere -- both are greenhouse gases.
The actual temperature change from increased CO2 can not be directly measured, but that does not mean CO2 had no effect. It certainly does not mean CO2 caused all the global warming since 1975.
Climate science has devolved into meaningless arguments over what caused the post-1975 global warming. The correct answer is "no one knows". The right answer is probably a variety of natural and manmade causes of climate change.
Unfortunately, the junk science of always wrong predictions of a coming global warming catastrophe (CAGW) has never ended. The predictions are climate astrology, not climate science.
The following variables are likely to influence Earth's climate:
4) Greenhouse gas emissions
6) Unknown causes of variations of a
complex, non-linear system
