The Old Saw on Global Warming

We're back to the old saw on climate change (previously called global warming)! Cheryl Hogue has another article "Affirming Impacts of Climate Change" in the April 7 issue of Chemical and Engineering News.
It starts out by quoting a new United Nations report as follows: "Around the globe human-caused climate change has affected farming, water supplies and echo systems on land and in water."
Climate is only a long-term manifestation of weather. We all know that weather changes on a regular basis. For example, it may be sunny the next two days and then it may rain, or we might have a tornado thrown in. Similarly, long-term weather (climate) also changes. We may have 50 years of a cold snap or 100 years of a heat spell. These climate changes have been going on for millennia, even before man burned any fossil fuel other than a little wood for his cooking fire. Therefore, how can the UN or anyone say there such a thing as "human induced climate change"? There's no obvious connection. Why not "cattle induced climate change", or "fish induced climate change"? Cattle and fish are living organisms. They move around. Have digestive capacities, which liberate gases, solid and liquid waste, and generate heat.
Christopher Field, who cochaired the IPC working group that prepared UN report, said, "with high levels of warming that result from continued growth in greenhouse gas emissions, risks will be challenging to manage." Sen. Barbara Boxer says the IPCC report "adds a tremendous sense of urgency for Congress to wake up and do everything in its power to reduce dangerous carbon pollution".
Where do they get this idea that carbon dioxide is a bugaboo? The best that I can find in the scientific literature is articles which assume that carbon dioxide in the atmosphere will absorb heat from the earth, thereby not allowing it to pass through the stratosphere, and thus contributing to global warming.
There is never any mention about the heat capacity of a carbon dioxide molecule, or how many molecules it would take to have any real effect. Let's also remember that carbon dioxide concentration in the atmosphere is only 0.05%. The idea also is that the major atmospheric gas constituents (nitrogen and oxygen) do not absorb heat in the same way that carbon dioxide does. May I have some laboratory proof confirming these theories? Federal agencies dole out billions of dollars to university professors for research and development. How about a little research and development on the questions I'm asking?