To the editor:
One of your readers, whom I shall call “Skeptic,” thinks the “climate crisis” is a “fraud.”
Skeptic is concerned that some atmospheric heating is due to conduction at the Earth’s surface, independent of greenhouse gases. NASA’s Earth Observatory offers a good primer on this subject (https://earthobservatory.nasa.gov/features/EnergyBalance/page1.php), and it also offers satellite measurements. These show that conduction (followed by convection) accounts for only about 3% of the heat carried upward into the atmosphere from the Earth’s surface. Evaporation (17%) and direct absorption of heat radiation by greenhouse gases (80%) account for the rest.
Skeptic would like credit to be given to another 19th-century scientist, Scottish physicist, Balfour Stewart, who first demonstrated that hot bodies radiate in all directions. Correct! Stewart’s observation helped Svante Arrhenius, at the end of the century, to fairly accurately calculate the consequence of doubling atmospheric CO2. But the fact that 50% of the radiation goes upward does not mean that 50% of it escapes into space. Most is absorbed by greenhouse gases in higher layers, then re-radiated. Consequently about 85% of the heat energy leaving the Earth’s surface as radiation is returned due to re-radiation.
Skeptic points out that water vapor is a more potent greenhouse gas than CO2. But water vapor is concentrated near the ground, while CO2 is distributed uniformly. Thus heat absorption and radiation in the upper atmosphere are primarily due to CO2.
It’s difficult to understand how Skeptic can view the climate crisis as a fraud, even if skeptical about greenhouse gases. Perhaps if Skeptic were a victim of one of the record heat waves, droughts, floods or fires of recent decades, Skeptic might agree with “crisis,” and might think twice about “fraud.”
Joel Huberman
Peterborough