#macalpine

However, the industry has been very effective at marginalizing scientific evidence that coal is a major cause of global warming and climate change, along with associated weather extremes. Most people seem to believe there isn’t broad consensus among scientists regarding climate change and its causes.

That couldn’t be farther from the truth. The predominant scientific opinion is that Earth’s climate system is unequivocally warming and that humans are causing the problem through activities such as burning fossil fuels. That includes 97 percent of scientific experts polled by the U.S. National Academy of Sciences as well as the national science academies of 32 countries.

This remarkable consensus results from strong and consistent evidence.

First, we know our planet is undergoing a dangerous warming trend based on data assembled by NASA, the National Oceanic and Atmospheric Administration, Berkeley University, and other respected organizations.

From several corroborating studies, we also recognize that carbon dioxide (CO2) produced from burning fossil fuels is the most important “greenhouse gas” in terms of causing global warming.

Light from the Sun passes readily through Earth’s atmosphere and is absorbed at the surface. Then the surface re-emits this energy as infrared heat, which may be trapped by increasing greenhouse gases in the atmosphere and radiated back down again, causing enhanced warming of the Earth.

We’re generating roughly 30 billion tons of CO2 annually, and the CO2 content of Earth’s atmosphere has subsequently risen about 40 percent during the coal-burning era. Fossil-fuel burning and atmospheric CO2 levels have increased together in lock-step, but does a direct correlation necessarily imply a causal relationship?

In this case, we can examine atomic isotopes of carbon (with differing numbers of neutrons) in the atmospheric CO2. The measured isotopic ratios (involving C-12, C-13, and C-14) over time and their relative distributions above the Earth’s hemispheres are fully understandable, but only if the increasing atmospheric CO2 is coming from fossil fuels. This method of “fingerprinting” provides convincing evidence that our burning of fossil fuels is the primary source for increasing CO2 in the atmosphere.

Furthermore, it has been demonstrated that the increased atmospheric CO2 is actually driving the observed global warming. Satellite measurements show the temperature of the lower atmosphere to be rising as Earth’s surface warms, while the upper atmosphere is undergoing a simultaneous temperature decline.

Therefore, excess CO2 in the lower atmosphere must be trapping more infrared radiation from the surface and radiating increasingly more heat back down, while the cooling upper atmosphere consequently radiates less energy back to space (so Earth is heating up and no longer in thermal balance). These atmospheric characteristics are required if increasing CO2 is causing global warming, and global warming must be taking place in view of these temperature trends.

In summary, scientific evidence indicates that global warming is occurring and is largely caused by our burning of fossil fuels, primarily coal. Will Earth be destroyed, and will humankind cease to exist?

Across the planet, temperatures, droughts, fires, floods, and extreme storms will continue to increase, but Earth will survive.

Regarding the future of life as we know it, several studies suggest that more than 90 percent of global-warming-related deaths are in countries that rely heavily on their ecosystems and contribute less than 1 percent to the problem. Conversely, people in developed countries causing most of the problem will probably have the resources to adapt and survive.

I believe this is a major responsibility and justice issue that is particularly appropriate for open discussion in the thoughtful environment of a special place like Earlham.