There was warming due to increased GHG emissions until the early forties, after which air pollution, particularly sulfate particles from burning coal, built up in the atmosphere, reflecting sunlight and resulting in a couple of decades of net cooling until envionmental regulation reduced this pollution in the early seventies, after which warming resumed.

The satellite data shows warming at lower altitudes and cooling at higher altitudes (as increasing concentrations of GHG's insulate higher altitudes from heat coming from sunlight being absorbed at the surface). If warming were due to increased solar radiation, we would expect warming at all altitudes.

The temperatures at the poles have been increasing much faster than those at moderate lattitudes. While average temperature increase for the whole planet has been about one degree centigrade over the last century, the poles have increased by more like 2.5 degrees C.

This is very problematic. As Arctic ice retreats, it exposes bare water, which reflects much less sunlight (ie, absorbs more heat) than the ice did, causing a positive feedback loop. In addition, there are vast quantitites of methane trapped in Arctic permafrost, and as that permafrost melts, that methane, which is a much, much more powerful GHG (heat-trapping GreenHouse Gas) than CO2, is released, causing another potential runaway feeback loop.

Another problematic factor is that one of the chief determinants of wind patterns is the rate of temperature change as you travel from the equator toward the poles. As the poles warm, this rate of temperature change decreases and jet streams and wind patterns change, leading to changes of the weather and precipitation patterns upon which agriculture depends.

While the people advocating that CO2 emissions be curbed are generally all telling the same story, the opposition is all over the map:

• Some say warming has occurred because of varying solar activity, but we know that's not it.
• Some say that satellite temperature data shows that warming has stopped. Not true, it started again.
• others say no warming has occurred and there has been a conspiracy to fake the temperature record which doesn't really hold up to scrutiny
• Some say it's because the tilt of the Earth's axis has changed. But the change hasn't been anywhere near enough.
• Some say it's volcanoes. Wrong.
• Some say it's because the Earth is getting closer to the sun. Wrong, we're getting further from the sun, but just barely.
• others say something about cosmic rays
• Patrick Michaels, formerly of the Libertarian CATO Institute (which has disbanded their climate skeptic efforts as a lost cause), says warming has occurred and will occur, just not enough to justify curbing emissions
• Oren Cass, of the conservative Manhattan Institute, says the predictions of warming by the climate activists are accurate, but we'll just adapt and there will be no catastrophic outcomes
• Jordan Peterson agrees that global warming is real, but he doesn't have a solution, and (modestly) concludes that if he can't think of a solution, no one can. Video.
• Neither Jordan Peterson nor Bjorn Lomborg disagree with the IPCC climate science, but they both agree that the most constructive way to spend money is on health and nutrition for the poorest people in the third world, and therefore nothing else, including decarbonizing the economy, is worth doing. See detail.

Yet even though all these sources agree about almost nothing, they consider themselves "brothers in arms", because they agree on one important point: that we should not reduce the rate of combustion of fossil fuels.

Doesn't it undermine the credibility of one side of the debate when they can't even get their story straight among themselves?

Another tactic frequently pursued by climate skeptics is to say "we don't know". They think that if they create doubt, they win. But if they want to tell society to just forget about climate change and continue burning fossil fuels to our heart's content, it is incumbent upon them to arrive at a consensus around a consistent narrative of what is going on and establish with a high degree of certainty that little harm will come of radically elevated levels of CO2. And they haven't come close to achieving that.

Much of our CO2 emissions wind up dissolving in the ocean and forming acid, so the oceans have been becoming more acidic, which will have a significant impact on marine ecosystems. The oceans are naturally slightly alkaline, but from 1751 to 1996 the pH has declined from roughly 8.25 to 8.14, which translates to a 28% increase in the concentration of H+ ions in the water. Changing the acidity of the ocean will have a profound impact on many of the fundamental chemical reactions upon which life is based. The acidity of the ocean is currently changing faster than it has at any time in the last 55 million years. Ocean fishing is one of the human race's primary food sources.

People frequently bring up change of the Earth's axis as being the cause of the warming we've observed in recent decades.

This just doesn't fly, the Earth changes its axis very gradually in a regular cycle, currently changing at a rate of about 0.012 degrees (meaning the north pole moves less than 2000 ft) per century. During major earthquakes like the 2011 earthquake that caused the massive tsunami in Japan, it moves something like a foot, usually less.

This is nowhere near enough change to cause the significant changes in temperature over a short time that we have observed.

Many people attribute the warming that we have observed to an increase in solar radiation.

This is a view that does not stand up to the slightest scrutiny. Click on the image at left and you see temperature in red and solar radiation in blue. Solar radiation has changed less that 0.1% in the last century, and the observed temperature has not been moving in sync with it.

Furthermore, if warming were due to an increase in solar radiation, we would observe:

Warming due to increased carbon dioxide predicts:

What we observe is C and D, not A and B.

This is covered in more detail at Skeptical Science: Solar Radiation

No. Tidal forces are propelling the Earth further from the sun with time, so the effect from the change of the distance from the Sun to the Earth is cooling, not warming.

The Earth is moving 1/1,000,000th of a meter further from the sun every year. So the earth is 2 millimeters further from the sun than it was when Julius Caesar will killed.