IF the data was sketchy at the turn of the century, only 20 years ago, how do you have anything accurate to compare today's "accurate data"?
Twenty years, less than a heartbeat in the history of the earth. Let's see, what part of 6+ billion years is 20 years?
There are far more government agencies, universities, and private research institutes gather data today and there is much more research being done collecting historical data.
It's not just about collecting data. Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.
Effects that scientists had predicted in the past would result from global climate change are now occurring: loss of sea ice, accelerated sea level rise and longer, more intense heat waves.
What percentage of our total atmosphere is CO2?
What percentage of that CO2 is affected by man?
CO2 is a very small percent of our atmosphere. I think it's about .04% if I remember correctly. It is natural to assume that a gas with such as small concentration could not possibly effect the temperature of the earth but it does and here's why. 99% of the atmosphere is made of Nitrogen, Oxygen, and Argon. These gases pass both visible light and infrared without reflecting it back to earth.
That 1% of atmosphere contains neon,
helium,
methane,
krypton hydrogen, and
water vapor in addition to c02. There are of course other gases in minute mounts. The three main greenhouse gases are water vapor, co2, and methane. Without them the earth would be much colder because less heat would be reflected back to earth. As long the average concentration of greenhouses gases are stable over time, their contribution to atmospheric temperature change is minimal. However, when their concentration rises as it has been for many years we start seeing the average temperature of the atmosphere rise which we have been seeing for some time.
It's explained better in the following link.
If carbon dioxide makes up only a minute portion of the atmosphere, how can global warming be traced to it? And how can such a tiny amount of change produce such large effects?
It's a rather simplistic take on the situation. In addition, this author appears to make some rather bold assumptions.and claims. For instance,
"the total heating produced by the increases of all long-lived greenhouse gases (excluding water" vapor) since preindustrial times is equal to about 1 percent of all solar radiation absorbed at the surface."
I'd be interested to see how they came to that conclusion.
Another,
"the ice ages during the last several million years--and the warmer periods in between--appear to have been triggered by no more than a different seasonal and latitudinal distribution of the solar energy absorbed by the Earth"
I would venture he's rather alone on this view as everyone I've heard speak on the subject has flatly stated that we have no idea of what caused the ice ages. There is much conjecture and speculation.
I also find it interesting that they make the point to "exclude water vapor". Even the most strident global warming advocates have admitted long ago that GHGs cannot have the effect which was originally claimed. The models rely on the water vapor feedback to attain the warming. I've yet to hear anyone claim that said feedback can be measured or observed for that matter.
In addition, there are others who point out that increased water vapor would likely lead to increased cloud cover. Clouds are efficient at trapping heat, they are also very good at reflecting sunlight.
However, none of this speaks to the main issue. How much warming can be expected from a doubling of CO2. The estimates vary wildly. I've seen estimates from ranging from .4 to 10 deg. All from "scholarly" sources. James Hansen in 1988 estimated the US would see a 4 C rise by 2020. How's that going?
I've listened to people that can name hundreds of factors that could likely influence climate. The models I've seen described use at most 10 or 12.
Just one time I'd like the warmists admit that they truly do not know.