What affects Earth’s climate?

When I arrived at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, in the 1970s, I started hearing the debate about whether the global climate was getting warmer or cooler. From the “warming” graph in the previous blog, there wasn’t much of a trend at that time.

On our bulletin board, we posted two articles next to each other. One was about an NCAR scientist who said that Earth’s climate was getting warmer because of more carbon dioxide in the atmosphere. The second was about a scientist who said it was getting cooler because of changes in Earth’s orbit and tilt. The changes, he argued, could mean the beginning of a new Ice Age in a few hundreds of years or so. Beneath the two articles, we posted Robert Frost’s Poem “Fire and Ice,” because it starts as

“Some say the world will end in fire,
Some say in ice.”

Surrounded by talk about climate, I retreated into the library and found a wonderful book that was published in the early 1900s, and I realized I hadn’t heard much new about the factors that affect Earth’s climate – the ingredients were:

• How much sunlight is available to heat Earth
• How much heat escapes to space

Which are related to:

• What gases are in the atmosphere (especially carbon dioxide and water vapor)
• How much dust there is in the atmosphere (including that resulting from volcanoes)
• How much ice there is on Earth’s surface (since ice reflects light back to space)
• Where the continents are

And, as I mentioned earlier under “regional climate”

• Properties of the rest of Earth’s surface (other than ice cover)

And of course stuff going on in the atmosphere:

• Amount and height of clouds
• Winds, etc.

And

• What the ocean is doing

Finally, Walter Orr Roberts, the head of NCAR at the time, was interested in the effects of:

• The changing sun

And, as noted in the article about the scientist who thought an ice age was coming:

• Changes in Earth’s orbit and tilt