If we do not understand the cause or causes for the biggest climate change of all time, what hope have we of understanding modern climate change?

I believe the earth gets warmer, and I also believe the earth gets cooler, and I think history points out that it does that and that the idea that man through the production of CO₂ which is a trace gas in the atmosphere and the manmade part of that trace gas is itself a trace gas is somehow responsible for climate change is, I think, just patently absurd when you consider all of the other factors, El Niño, La Niña, sunspots, you know, moisture in the air. There's a variety of factors that contribute to the earth warming and cooling, and to me, this is an opportunity for the left to create — it's really a beautifully concocted scheme because they know that the earth is gonna cool and warm. And so it's been on a warming trend so they said, "Oh, let's take advantage of that and say that we need the government to come in and regulate your life some more because it's getting warmer." Just like they did in the '70s when it was getting cooler. They needed the government to come in and regulate your life because it's getting cooler. It's just an excuse for more government control of your life. And I've never been for any scheme or even accepted the junk science behind the whole narrative.

It's been warmer than today's climate in the past, much warmer. It has been colder than this climate in the past, much colder. We know this for a fact. We know that this happens with or without our activities. ... So why do we insist that we are the ones causing it when for over half a million years it happened several times and we’ve only had this supposedly evil earth killing CO2 belching technology a mere speck of that time? Because, many believe global warming is real and there are people in our political world who want the masses to hand over power over their lives to them, so they say "let us handle it". To make that transition easier, they trot out this false premise, that we are totally responsible for natural occurrences in the long span of our planetary history.

If CO2 derived from modern industrialisation is the culprit for global warming, then why did the global temperature increase from 1918 to 1940, decrease from 1940 to 1976, increase from 1976 to 1998 and decrease from 1998 to the present?

I'm betting on the sun's increased activity in the last century, and that CO2 doesn't matter much because its effect is overwhelmed by everything else in our atmosphere that also acts as a greenhouse gas, mostly water vapor.

Temperatures have not risen very much, and most of the temperature rise is probably completely natural, and has nothing to do with increasing CO2. Industrialization probably played a small role, but I think it's very hard to tell how much.

The hypothesis that human emissions of CO2 can create global warming can be tested by measurement. … No warming has occured since 1998. … During that time atmospheric CO2 has increased. … The test of the hypothesis above shows that there is no relationship between measured temperature and CO2 emissions. The hypothesis fails.

To me, the fact that the suns magnetic field is linked more closely to earth now lends credence to theories like that of Henrik Svensmark, which points to an extraterrestrial driver of climate change, cosmic rays which form cloud nuclei in our atmosphere, modulated by solar variance.

What, then, of human activities? Is humankind itself hastening its own end? Man has, for instance, been burning carbon-containing fuel — wood, coal, oil, gas — at a steadily accelerating rate. All these fuels form carbon dioxide. Some is absorbed by plants and the oceans but not as fast as it is produced. This means the carbon dioxide content of the air is going up — slightly but nevertheless up. Carbon dioxide retains heat, and even a small rise means a warming of the Earth's atmosphere. This may result in the melting of the polar ice caps with unusual speed, flooding the world before we have learned climate control. In reverse, our industrial civilization is making our atmosphere dustier so that it reflects more sunlight away and cools the Earth slightly — thus making possible a glacial advance in a few centuries, also before we have learned climate control.

The last numbers in 2011 indicated that climate change was 90% linked to our emissions of greenhouse gases – 90% directly linked to petrol usage and the rest to deforestation.

As I've always said, the sun is the "Big Kahuna" of climate change on Earth. Everything else is secondary, even though man's opinion of his own self importance in the scheme of things often dictates otherwise.

So, whether or not how dramatic this change will be, or is, what it’s caused by, are things that honest people, I think, can disagree with, and I really personally, having been a journalist, the first thing I was always cautioned by when someone was claiming, well, everybody is on my side, or everybody says this, or there is a total consensus, almost always when people said that to me over my years as a journalist, it wasn’t true. It was that there were honest people who disagreed and significant disagreement on such issues. We don’t know what those other cycles were caused by in the past. Could be dinosaur flatulence, you know, or who knows? We do know the CO2 in the past had its time when it was greater as well. And what happened when the CO2 was greater since then and now? There have been many cycles of up and down warming. So with that said, I think that we’ve had a great discussion today.

An overwhelming majority of scientists who have looked into the matter agree that global warming is underway and is... caused by people burning fossil fuels. This is the meta-fact hovering over all the details. [...] In [mining and] burning so much [hydrocarbons in the form of] coal, oil, and gas [as fossil fuels] we've released [a fraction of] 460 million years of sequestered carbon into the atmosphere in a mere two hundred years. There are consequences for doing this. The trajectory of climate problems has gotten only more severe since I discussed the issue in The Long Emergency in 2005. Greenhouse gas emissions have exceeded predictions. The IPCC report expects a sea level rise of at least three feet [91 cm] […]; of NASA says... seventeen feet [5.18 m]. If that is the case, there would be no need to argue over the finer points of how many square miles in the Netherlands would be underwater... along with Bangladesh, many Pacific islands, most of Florida, and the Mississippi River Delta, Houston, Jacksonville, Key West, and thousands of other places.

75% of the greenhouse effect is attributed to <chem>CO2</chem>. This is the biggest problem, 14% to methane and the rest nitrous oxide and F-gases. ...F-gases are 3,000 times more impactful than <chem>CO2</chem>. There's just a lot less of it.