Though it’s an established fact that humans are a significant cause of global warming, the issue has been clouded by misunderstanding, misinformation, favoritism, prejudice and a simple refusal to believe it’s happening. To clear the air, it might be useful to take a look at the evidence.

Solving the problem is basically a matter of counting atoms, namely carbon atoms, and counting particles even as small as an atom is something scientists are good at.

Carbon dioxide has a unique ability to absorb solar radiation in the atmosphere, making it the main culprit in global warming. Charles Keeling made the first measurements of CO2 in 1958, and those measurements have continued up to the present.

What Keeling found was the CO2 fluctuated annually around 315 parts per million (ppm). This fluctuation, called the Keeling curve, is caused by plants absorbing CO2 in summer and releasing it in the winter. The process is not offset in the Southern Hemisphere because the dominant plant-covered land is located in the Northern Hemisphere.

But Keeling noticed something else in his data. His curve trended steadily upward year after year, and it has continued to rise during the past 58 years.

The CO2 level now stands at more than 400 ppm. The question is, where is all the carbon dioxide coming from?

Here the scientists had to do a bit of sleuthing, using the three isotopes of carbon, C-12, C-13 and C-14. The isotopes are chemically identical, but the heavier ones move more slowly in chemical reactions, including photosynthesis. This explains why plants contain less C-13 and C14 than the air.

The C-14 also happens to be radioactive, half of it decaying into nitrogen every 5,730 years.

The ratios of C-13 and C-14 to C-12 come from direct measurements of the atmosphere and from tree rings going back many centuries. These data show a gradual decline in the C-13 to C-12 ratio beginning around 1800, the start of the industrial revolution.

The declining ratios rule out volcanoes and ocean-air dynamics, because both have a higher C-13 to C-12 ratio. Since other sources of CO2 are not enough to account for the falling ratio, that means most of it must come from burning fossil fuels.

In recent decades, the C-14 to C-12 ratio also has been rapidly declining. The falling C-14 values means the CO2 being added to the air is highly deficient in C-14. Again, that means the CO2 must be coming from burning fossil fuels, in which all the C-14 has decayed away.

Thus, science has demonstrated the flood of carbon dioxide into the air bears the unmistakable sign of human activity.

On one hand, we have science, the most powerful tool for generating facts that mankind has yet invented, and on the other we have opinionated science illiterates, like the U.S. senator who brought a snowball to the floor of Congress on a cold day in winter as proof there is no such thing as global warming. Which one would you trust?

Global warming produces a host of devastating effects: melting glaciers, shrinking polar ice, rising sea levels, acidification of the oceans, extreme weather events, intense hurricanes, shifting weather patterns, increasing desertification, disruption of ecosystems, species extinction and loss of biodiversity.

Many of these predicted changes are happening now, but the worst is apparently yet to come. “What makes climate experts lying awake at night,” writes Thomas Friedman, “is the scary stuff that they know could happen but that is impossible to predict.”

For example, we know little about how the various feedback mechanisms of climate change might interact with each other. The polar ice already is melting much faster than predicted, and in 20 years the Arctic Ocean might be completely ice free.

In any case, we are performing a mad experiment with the earth’s climate, the ultimate results of which no one can predict. Except that it’s all going to be bad, bad for the biosphere and bad for our own economic, social and physical well-being.

Climatologists say there is a “tipping point,” a threshold beyond which global warming becomes irreversible. The tipping point is hard to predict. Some say we will get there by mid-century, others say we’ve reached that point already. Even if we stop dumping carbon dioxide into the air now, the temperature would keep going up for decades to come.

But there still is hope. There are ways to slow down the rise in temperature, and some of them are being implemented on a small scale across the globe. For example, the carbon cap-and-trade program in California seems to be working well. It just needs to be expanded.

We know the human cause of global warming, and we know some of the effects. What we don’t know yet is whether enough humans will recognize the danger in time to save our planet.

 Richard Weber is a nature enthusiast living in Ellis County.