Earth is growing greener. Carbon dioxide that increased from 0.03 % to 0.04 % by air volume since the beginning of the industrial era has helped boost green foliage, plankton, nutritive plants and crops yields. The benefit for mankind has been estimated to $3,000 billions. Why then IPCC AR5 and COP21 proclaim carbon Public Enemy No. 1? Why cutting CO2 emissions, gas essential and irreplaceable of plant life? Why fighting Earth greening? Climate does change with alternating periods of warming and cooling every 30 years as probed by climate sentinels: sea ice, sea level, ARGO buoys, global mean temperature measured since 1880 and more accurately by satellites since 1979. Once natural cycles are subtracted from observations, the anthropogenic contribution to climate change appears well below dangerous levels consistent with infrared studies of greenhouse gas absorption and latest published climate sensitivity. The balance tilts in favor of the gas of life since moderate warming favors human wellbeing, growth and progress. The tentative change of paradigm is an open question addressed to citizens, to taxpayers, to the industrial, agricultural and economic world.