Scientists have been seeking answers to two questions about global warming: Is it for real? and is mankind’s burning of fossil fuels the cause? (Both the burning of these fuels and global warming have been increasing during just the last 200 years).
Scientists propound theories based on the science of physics, and then collect and analyze evidence to determine whether it substantiates their theories. Conversely, deniers have made up their minds, and search for any argument they can find that agrees with what they believe.
Is global warming real? All the evidence indicates that it is. Worldwide atmospheric temperatures have been on the rise at an increasing rate since 1970 and are 1.5 degrees warmer than they were 100 years ago. And high temperature records have been broken at record rates during the past decade.
But atmospheric temperature is a less reliable measure and is more subject to variability than ocean temperature, which is a better indicator of long-term effects. Furthermore, 90 percent of Earth’s heat gain is stored in the upper 6,500 feet of the oceans, compared to only 2 percent that is stored in the atmosphere. Ocean temperature has also increased 1.5 degrees in the past 100 years, and is also rising more rapidly than in the past. The amount of energy stored in the world’s oceans since 1980 is equivalent to a Hiroshima atomic explosion every second. Further evidence that global warming is real is the worldwide retreat of glaciers, and the rapid shrinking of the Greenland ice cap and Arctic Ocean sea ice to minimums never before witnessed.
A vast majority of climate scientists are in agreement that global temperature will rise by 5 degrees or more by 2100, causing a catastrophe of rising ocean levels, more intense storms and flooding, and drought and forest die-offs. Deniers love to point out that in 1972, climate scientists were predicting a cooling trend, and were wrong. But if temperatures rose instead of falling, shouldn’t that be reason to be concerned about what might be occurring that was powerful enough to reverse the predicted cooling?
So what could be the cause of that warming? Fluctuations in global temperature are normal, resulting from volcanic activity, changes in solar activity and variations in Earth’s orbit and tilt. Fluctuations due to extraterrestrial causes have been gradual (over centuries or millennia), but what we are witnessing is a more rapid change than has ever occurred. Therefore, there must be some other cause — and that has been identified as an increase in greenhouse gases in the atmosphere that reduce the amount of solar energy that is reflected back into space. These are carbon dioxide (CO2) and methane. Atmospheric CO2 has risen from 300 parts per million (ppm) to 400 ppm since 1860 and is now at the highest level in half a million years. There is only 10 percent as much methane in the atmosphere as CO2, but methane is twice as potent as a greenhouse gas, and its release is growing due to increasing fossil fuel extraction, greater numbers of cattle, and permafrost melting induced by global warming.
Some deniers of the global-warming impact of greenhouse gases argue that such a small concentration of CO2 as 400 ppm (0.04 percent) could not have an effect anywhere near comparable to the heat-blanket effect of clouds. Clouds do reduce heat loss at night, but they reflect away many times as much solar energy during the day.
Just where has the unprecedented increase in atmospheric CO2 since 1860 come from? The only logical source is the explosive growth in the burning of fossil fuels. One quarter of that CO2 is fixed in plants by photosynthesis, one quarter is absorbed in the oceans, and the remaining half accumulates in the atmosphere. The increase in atmospheric CO2 since the start of the Industrial Revolution is consistent with the amount of fossil fuels that have been burned during that time. And the decrease in the proportion that is radioactive carbon 14 confirms that fossil fuels (which are devoid of carbon 14 because of their age) are the source of the increase in the observed CO2 in the atmosphere.
More than 95 percent of bona-fide scientists find this evidence convincing — most of the rest are hacks hired by the energy industry. The scientists on the International Panel on Climate Change are 95 percent certain that fossil fuels are the cause of global warming. Deniers, would you board a plane that was given a 95 percent chance of crashing?
“As I See It” appears on the first and third Thursdays of the month. Hal Sundin lives in Glenwood Springs and is a retired environmental and structural engineer. Contact him at firstname.lastname@example.org.