A Dec. 23 letter asserts, “emissions into the atmosphere … are not the main cause of climate change.”
Most of the factors mentioned, however, bolster rather than undermine the consensus among 97 percent of climate scientists that the current climate change is caused mainly by humans’ greenhouse gas emissions.
As the writer says, the climate has changed throughout earth’s history. In almost every case, it changed primarily in response to variations in atmospheric concentrations of greenhouse gases (GHGs: principally, water vapor, carbon dioxide, methane, ozone). Those variations constitute the same climate-warming mechanism humans have activated in the past 200 years, primarily by burning coal, oil and natural gas.
The writer seems to argue that, because natural processes increased GHG concentrations and changed the climate in the past, principally natural processes, rather than humans, too, drive 21st century climate change.
That argument exemplifies the logical fallacy known as “affirming the consequent.” An analogous argument would be: People survived disease in the past; therefore, modern medicine has no impact on survival rates.
In other words, the fact that natural processes caused previous climate changes does not imply the climate is currently changing mainly because of natural processes.
For at least 160 years, scientists have known that increasing atmospheric GHG concentrations would warm the planet. Now, as explained in the White House’s National Climate Assessment, human activity has caused that to occur, leading to widespread human suffering that promises to worsen.
The time has come for all nations to reduce GHG emissions, and the United States should lead the way in doing so, by adopting the Energy Innovation and Carbon Dividend Act (H.R. 7173) and its companion bill in the U.S. Senate.