The general theme of my columns has been that a fatal contradiction runs through these modern times. On the one hand, our economy is based primarily on science and rational thought, while on the other hand our beliefs remain mired in primitive instincts and medieval superstitions. We see all around us, most obviously in places such as Syria and more subtly in American anti-intellectualism and materialism, the consequences of this clash between evidence-based conclusions and traditional beliefs.

Nowhere is this clearer than in the case of climate change.

Last month two leading scientific organizations, the British Royal Society and the U.S. National Academy of Sciences, issued a summary for the general public titled "Climate Change: Evidence & Causes." It's brief, easy to read, written for nonscientists, and free on the Web. It's written in a Q&A format, providing answers with evidence to 20 questions such as "Is the climate warming?" "What role does the sun play in climate change?" "Why are human emissions significant?" and "How fast is sea level rising?" The report was authored by 12 leading climate scientists and reviewed prior to publication by 13 others.

Science is never certain. In fact, this is one of its great strengths for only fools can be absolutely certain. But I've read lots of science in my life, and it doesn't get much better than this report and the work that backs it up. Here are a few highlights:

How do we know climate change is caused by humans? We've known since 1850 carbon dioxide is central to Earth's energy balance. It has increased by 40 percent since 1800. Analysis of different carbon isotopes shows long-buried carbon from biological organisms -- i.e. fossil fuels -- are the source of this increase. The observed 1.4 Fahrenheit degree increase in Earth's temperature since 1900 is consistent with calculations of the impacts of this carbon dioxide increase. The many observed patterns of warming also match the patterns expected from rising carbon dioxide levels. Finally, calculations using models that simulate what would have happened if only natural factors were influencing the climate yield no warming over the 20th century, while models that include the 40 percent rise in carbon dioxide yield the observed temperature changes.

The warming isn't due to the sun. There's no evidence for long-term changes in the sun's output over the past century, although temperatures have increased significantly. Furthermore, computer models show increases in solar output would warm the troposphere and the full vertical range of the stratosphere equally, whereas CO2-induced warming should warm the troposphere but cool the stratosphere. According to the evidence, the stratosphere has cooled while the troposphere has warmed.

The present rate of planetary warming is more than 10 times that at end of the last ice age and is faster than any known warming trend in the planet's history.

Does the recent slowdown of warming mean climate change is no longer happening? Not at all. Each of the last three decades was warmer than any other decade since measurements began about 1850. Warming trends continue in ocean heat content, sea level and melting ice.

How confident are scientists that warming will continue during this century? "Very confident." Continuation of present emissions trends will cause temperatures to increase by another five to eight degrees by 2100. Even if emissions stopped today, temperatures wouldn't return to pre-industrial levels for thousands of years. The current warming is irreversible on human time scales.

The rational response to all this is to put the brakes on fossil fuel use as rapidly as possible. Yet not only do emissions continue, they actually increase every year. It's a world problem, with America -- which should be a leader -- the chief offender both in terms of per-capita emissions and foolish public attitudes. There is a relatively painless solution: A tax on carbon emissions that would be returned to every American as an income tax reduction. The tax would of course raise the price of gasoline and other fossil fuels and would be opposed by many Americans who should know better. We need to start talking about this.

As one indication of public attitudes, the Pew Research Center found last October that 67 percent of Americans believe there is solid evidence Earth has been getting warmer. Breaking this figure down politically, 84 percent of Democrats and 46 percent of Republicans agreed. But only 25 percent of Tea Party Republicans agreed. Such figures say a lot about America's cultural divide and its corrosive influence on the planet's well-being.

Commentary on 03/16/2014