Answer to Question 1
Vostok results showed that atmospheric CO2 and CH4 concentrations have varied in concert with surface temperature. As levels of the greenhouse gases CO2 and CH4 increased, the magnitude of the greenhouse effect also increased, and the climate became warmer. But the temperature curve actually leads the CO2 curve slightly, indicating that cause and effect are mixed up in this record. This is a prime example of why we need to consider the entire coupled system,
Answer to Question 2
Iridium is a metal in the platinum group of elements, which are very scarce in rocks of Earth's crust, because they are mostly dissolved in its molten iron core. These elements are always raining down on Earth as small particles of debris from asteroids or comets. The rate at which such debris hits Earth is known fairly accurately from measurements of the iridium abundance in cores drilled into the ocean floor.
Some red squirrels adopt the offspring of related individuals, a likely example of kin selection pro
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