The IPCC takes the sensible position that establishing a «business - as - usual» (BAU) baseline for making long - term global climate projections is a pretty tricky endeavor because it means figuring out how the population and economy of the entire world is going to develop over the next century or more. (cato-unbound.org)
Measuring the planet's mass was a somewhat trickier endeavor. (sciencedaily.com)