In addition to the changes within each year, what changes in CO2 concentration occurred between 1990 and 2010? Calculate the average CO2 concentration for the 12 months of each year. By what percentage did this average change from 1990 to 2000 and from 1990 to 2010?

An average is a single number representing a large set of numbers. It represents all numbers available in the data. It is calculated by dividing the total values of data by the number of data.The average value represents quantities that change their values. Thus it is helpful in quickly summarizing the data.

Percent change is a mathematical concept that explains the degree of change during the time duration. It can be calculated by the formula:

\[percent{\rm{ }}change = \frac{{(Final\,value - Initial\,value)*100}}{{Initial\,value}}\]

According to the given data, in all the months, CO₂ concentrations were more in 2010 than in 1990. After adding all the concentrations of CO₂ in 1990, the average will be:

\[average = \frac{{Total{\rm{ }}of{\rm{ }}all\,concentration}}{{number{\rm{ }}of\;months}}\]

\(average(1990) = \frac{{4,254}}{{12}}\)

\(average = 354.51\)

\(average\;(2000) = \frac{{4,433.23}}{{12}}\)

\(average\;(2000) = 369.40\)

\(average\;(2000) = \frac{{4,677.35}}{{12}}\)

\(average\;(2000) = 389.77\)

Percentage change of CO2 concentration in 1990 to 2000-

\[percent\;change = \frac{{(Final\;value - Initial\;value)*100}}{{Initial\;value}}\]

\[percent{\rm{ }}change = \frac{{(369.40 - 354.51)*100}}{{354.51}}\]

\(Percent\,change = 4.2\% \)

Percentage change of CO2 concentration in 2000 to 2010-

\[percent\;change = \frac{{(389.77 - 369.40)*100}}{{369.40}}\]

\(Percent\;change = 5.51\% \)