Sometimes you will hear it said that the evidence is ambiguous. It is not. More than one hundred years of study, on perhaps the most pressing issue in science, points to a clear correlation between rising CO2 levels, rising temperatures, and the explosion of the human population in the last 150 years or so, coinciding with the industrial revolution. For the entire history of humanity -- hundreds of thousands of years or so since the dawn of what we typically call a human -- the population was very low. It was not until the mid-19th century that the population reached 1 billion people. Today, it is more than 7 billion.
This exponential rise in the human populations begins at the beginning of the industrial revolution. And as our lives improve, our population swells, and our technology enjoys an exponential growth. In short order we are able to produce millions upon millions of machines that spew obscene amounts of carbon into the air. This carbon remained below the Earth's surface for millions of years -- deposited over millions of years -- but today we are devouring it at an insatiable rate, dumping our waste products into the air and into the ocean. There is no natural mechanism that could have released such enormous amounts of carbon into the environment all at once. It required the human catalyst for rapid change.