But sceptics needn't be bound by such convention and are free to consider other possibilities.
If you have a look at the annual rate of atmospheric carbon dioxide rise and compare it to human emissions there's a disconnect.
In fact there's a better correlation of the HadCru surface temperature of the southern hemisphere to the rate of rise of CO2.CO2 rise more closely matches air temp than human emissions. The Revelle Factor vs Henry’s law http://t.co/bCLS6R4b8V pic.twitter.com/imb1HQ18DH— Paul Clark (@cbfool) August 25, 2015
CO2 derivitive vs SH temps. Perhaps it correlates well because air temperatures follow closely the sea surface temperature, and the southern hemisphere has a lot of ocean.
And here's ∂CO2 compared to SH Sea Surface Temp's.
Jamal Munshi shows that there is less correlation of rising CO2 to human direct emissions, and more with air temperature in this paper:
Responsiveness of Atmospheric CO2 to Anthropogenic Emissions: A Note
As this graph shows:
.@chaamjamal Between temp rise & deforestation..explains most of the CO2 rise. Very little rise from direct emissions pic.twitter.com/diEJfzhBsq— Paul Clark (@cbfool) August 13, 2015
The oceans have a huge capacity to both absorb and emit CO2, and oceans outgassing could play a role [1, 2], but oceans are probably uptaking CO2 the last few decades.
During this more recent time, a bigger contribution to rising CO2 could be, not from human direct emissions or ocean outgassing, but deforestation.
Tropical deforestation in particular has increased a lot the last few decades:
suggests deforestation makes a larger contribution to the CO2 rise, with direct combustion emissions just contributing 20% by his estimate.
Even the IPCC admitted in AR4 in 2007 that deforestation probably contributed 20% to the CO2 rise depicted in the Keeling Curve:
.@CountCarbon Direct emissions 100% of CO2 rise tho? Even IPCC AR4 concedes 20% from deforestation. Search '20%' here:http://t.co/RictTKtyaA— Paul Clark (@cbfool) August 25, 2015
This was later revised downward to 12% by Team Consensus™, as the 20% figure quoted in IPCC AR4 2007 was not alarmist enough for their liking -- climate action not justified enough .
If it is true that deforestation is the bigger cause of atmospheric CO2 rise, this means that action to reduce direct emissions (also known as "action on climate change") is even more non-sensical and ineffective.
If you point this out to Greenies they'll simply shift the climate argument to include stopping deforestation as well; remember any and all change to the natural order is bad, whether in fact it's actually good or bad.
In this case, with regard to the carbon dioxide increase, the change is good. Carbon dioxide is good in every way for all life on the planet [1, 2].
To demonise as a pollutant the plant gas that greens the earth and sustains all life rather undercuts environmentalists claims to being "green".
Furthermore, if CO2 causes any warming, a bit of warmth is good for earth [1, 2, 3], past colder times having more troubles than warmer times:
Little Ice Age Shrank Europeans, Sparked Wars
The ice age had much more erratic climate, precipitation and temperature swings, as in evidence in this Greenland ice core:
Looks like Google Earth has updated its map images again recently and I see deforestation all around the periphery of the Amazon: in Venezuela, Colombia, Peru, Bolivia and especially Brazil where they're really going gangbusters. Brazil's going to be one big pasture at this rate.
The area in the circle above is expanded below:
It's worthwhile protecting what's left of the Amazon, though in terms of the extra carbon dioxide that's produced, this can only be good for humans and the planet.