Problem
Note that all numbers in the table above are given with 90% confidence intervals, which is an indication of the uncertainty on the sources and sinks. For example, fossil fuel and cement production cause the emissions of 8.3 ± 0.4 PgC/year, which means that there is only a 10% chance that emissions from these sources are greater than 8.7 PgC/year or less than 7.9 PgC/year.
Name two ways scientists can reduce uncertainty in these estimates (i.e. what changes to the individual and total measurements used for these estimates would reduce the statistical uncertainty?)