Saying that GHG's trap the radiation is misleading and the information here is ambiguous.
First the GHG's absorb and re-radiate IR radiation from the earth as a black body that absorbs and re-radiates solar incoming light energy as heat (IR) energy. The GHGs act like a blanket that impedes the escape of the IR energy to space thereby effecting the Earth's heat budget or average temperature.
And the temperature can be affected by clouds, aerosols and particulates in the atmosphere as they can effect the amount of incoming solar energy. So the increase in GHGs my not be a linear effect.
Some research indicates that the heat forcing of CO2 is limited and decreases with increasing levels as a logarithmic effect.
Past historical data suggests that solar energy has a major effect on the Earth's heat budget. About 95 percent of CO2 emissions are natural and much coming from the oceans when they are heated. This explains past CO2 increases. Furthermore ice core data shows CO2 following temperature rises over the course of past climate changes. Also the resident time of methane is only several days as it oxidizes with oxygen. Methane is a fuel.
Water vapor has the greatest effect on the warming of the atmosphere as it is much more abundant then CO2 in the atmosphere by a factor on average of 56x. It also has a broader IR absorption footprint.
Anthropogenic global warming advocates have failed to establish an unquestionable link to the recent rise in temperatures and CO2 emissions. Human land use may have a greater effect. There is currently a heated argument over the reliability of surface temperatures acquired as evidence of unprecedented warming due to leaked emails from a major climate research center in England- East Anglia CRU.
There have also been several past warming bubbles in the current climate optimum cycle between ice age cycles.