What was the percent of atmospheric CO2 if it was 280 ppm?

Jim

208 PM × (1% / 10000ppm) = 0.028% Next question What is Verne Troyer's height in miles? 0.0006 miles

Dirac

About 0.028%, which makes it an atmospheric trace gas, just like the other major greenhouse gas, water vapor, which is about 0.4%

JimZ

It was 0.028% if it was 280 ppm but that is based entirely on ice core data that is subject to interpretation and is contradicted by other proxies such as plant stomatas. At 0.028% plants begin to become adversely affected.

Solar Wind

The atmosphere is composed of a mix of several different gases in differing amounts. The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon. Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of one percent of the atmosphere. Water vapor is unique in that its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is. In the cold, dry arctic regions water vapor usually accounts for less than 1% of the atmosphere, while in humid, tropical regions water vapor can account for almost 4% of the atmosphere. Water vapor content is very important in predicting weather.

Dale-E

.000280= .028% it is a rare atmospheric gas and very friendly to human gas as well.