The Messenger’s Opinion Exchange column is a valuable way to learn about important issues. Steven Clark and Alison Anderson do a marvelous job of explaining their different policy viewpoints.
We are disappointed, however, that last week’s Exchange posed questions that are now matters of well-established scientific fact rather than matters of opinion:
Is recent climate change real and, if so, is it human-caused? Pre-eminent scientific organizations in the U.S. and the world have definitely answered those questions: yes and yes.
The U.S. organizations include the National Academy of Science’s National Research Council and the U.S. Global Change Research Program established by Congress. Both scientific groups have repeatedly looked at the available evidence in writing their reports, most recently in 2020 (NRC) and 2018 (USGCRP).
The leaders of virtually every country in the world have accepted the fact of human-caused climate change, as shown by the international climate agreement just reached in Glasgow.
In that pact, the U.S., its allies and its adversaries express “alarm and the utmost concern that human activities” have already warmed the Earth and recognize the need for deep and fast reductions in greenhouse gases to avoid even more dangerous warming.
It is not the height of arrogance to think that humans can affect climate; it is scientific fact. CO2 and other greenhouse gases absorb and emit heat, warming the Earth’s surface and lower atmosphere.
These gases naturally exist in very small quantities, but since the Industrial Revolution, humans have released enough CO2 to increase its atmospheric concentration by over 40 percent.
Peer-reviewed scientific studies show that as humans have added CO2 and other greenhouse gases to the atmosphere, temperatures have risen and climate change impacts—like severe storms, droughts, wildfires and floods—have grown worse.
The NRC and USGCRP have concluded that natural factors like solar variations can’t account for the magnitude of the post-Industrial warming we’ve seen, and that human emissions are responsible for the vast majority of it.
While it is true that glaciers existed long ago when CO2 levels were much higher than they are now, the fact that CO2 causes warming is not in scientific dispute, and recent studies have suggested that a combination of factors can explain the ancient phenomenon without calling into question CO2’s role in today’s warming.
As for volcanoes, the U.S. Geological Survey says that present-day volcanoes emit less than 1% of the CO2 now released by human activities. In fact, USGS says, the most significant impact of contemporary volcanoes on global climate is cooling as a result of their sulfur dioxide emissions. The 1991 eruption of Mt. Pinatubo, for example, cooled the Earth’s surface for three years.
If we do not accept the fact of human-caused climate change, we cannot make the changes needed to avoid even more dangerous warming.
The last question posed by the Messenger is the one we need to be urgently debating now: What should we do about it?