On Being Skeptical of Human Made Climate Change
I am not convinced by the IPCC 2013 report, or NASA very informative site, or current scientific consensus (pdf), that our CO2 levels drive warming of the planet. I accept our current data. I accept that current high levels of CO2 are anthropogenic (have human causes). I agree the earth is warming. I agree a component of that might be CO2 as a greenhouse gas. (I even agree we should trust our experts more than people like me.)
But in the past earth clearly had other drivers for climate change. And those drivers need to be known, understood and scaled against the anthropogenic driver. The IPCC report assumes greenhouse gasses are the main driver today, by showing their anthropogenic origins, and by showing the earth is warming, and by showing strong forcing by CO2.
Claiming for instance this
there is high confidence that the effects of
solar activity within the range of grand solar maxima and minima will be much
smaller than the changes due to anthropogenic effects. And elsewhere this
Currently, water vapour has the largest greenhouse effect in the Earth's
atmosphere. However, other greenhouse gases, primarily CO2, are necessary to
sustain the presence of water vapour in the atmosphere. But any other
driver would also sustain water vapor, amplifying its effect, and
potentially dwarfing CO2s effect. This warrants more discussion.
Only focusing on CO2 goes against our historic understanding of past climate changes. In the past we have had much colder periods and even warmer periods. Moreover CO2 seems to follow temperature, and maybe even with a delay of hundreds of years. Historic records seem to exclude CO2 as the initial driver to warming, it does not even seem to have the ability to maintain warm periods. (See Greenhouse gas, (pdf) CO2 lagging warming, (pdf) CO2 preceding warming, (pdf) role of the sun)
Our most recent ice age ended and was followed by the holocene optimum, a slightly warmer period than today. This cannot be understood by CO2. (See Holocene climatic optimum and the image above)
And very recently we had the little ice age, ending around 1800, from which point our current warming trend begins. It is unlikely that humans caused the little ice age, or that humans ended it. Idem for CO2. (See Little Ice Age, Glacier Bay melting since 1780, on CO2 levels around 1800)
What was the driver to warming of our last ice age. How could temperatures get so high without a CO2 maximum? And what brought them back down. What was the driver to warming 200 years ago. And why are we so confident it plays no role in todays trend?
This is the discussion I am missing. Perhaps this is so obvious to experts that they forget to explain it?
If CO2 is the strongest driver after an initial driver like Milankovitch cycles, how come it has not run away in the past? What caused it to be curbed below 300 ppm in the past? And wouldn't we expect that the rise in temperature would look substantially different from the drop? Especially in speed and CO2 delay, even from an Antarctic ice core perspective?
No Free Pass; The Environment is Important
Personally I am very environmentally aware. I think it is important that we keep our ecological footprint in check. Both locally and globally. We live in a thin fragile layer on a rocky planet hurling through hostile space. We must work our way to an environment neutral society.
Moreover I am confident our scientists are not chasing their own tail or mass hallucinating or controlled by the government. But there can be multiple drivers, each with their own scale and influence. And past data warrants more explanation before we can wave other factors away as irrelevant.