The question in my previous post "Where is all the warming?" seems to have a possible explanation. In a blog by Willis Eschenbach it was concluded:
While my results are far below the canonical IPCC values, they are not without precedent in the scientific literature. In CO2-induced global warming: a skeptic’s view of potential climate change, Sherwood Idso gives the results of eight “natural experiments”. These are measurements of changes in temperature and corresponding forcing in various areas of the earth’s surface. The results of his experiments was a sensitivity of 0.3°C per doubling. This is still larger than my result of 0.05°C per doubling, but is much smaller than the IPCC results.
This is a huge difference compared to what IPCC says. Thus the result implies that the extra forcing of 1.5W/m2 has essentially no effect on the climate. This also makes sense given that we have seen close to no measurable global warming.
But as always, you really have to be "skeptic" about this kind of new results that are considerably different compared to current knowledge about the climate. The energy must still be there somewhere, or is the 1.5W/m2 simply wrong?